Last update: November 2, 2022

The state of our oceans – The damaging effects of ocean pollution

Our oceans are a marvel – alive with color, noise, drama, curious life forms, and fascinating creatures – and that is just what we know about today! Every day, scientists learn more about the wonders beneath the waves.

From space, our planet Earth shines blue amidst the infinite blackness. That is because oceans and seas cover over 70 percent of the Earth’s surface and hold 97 percent of all the water on Earth.

The oceans are responsible for making conditions on Earth suitable for us to live on it. Our rainwater, drinking water, weather systems, and climate are all ultimately provided and kept in balance by the oceans. We rely on them as a major source of the food we eat, and they produce the majority of the oxygen that we breathe.

For hundreds of years, we humans have thought that our oceans were so massive, and the animals in them so infinite in number, that our actions could not possibly harm them. But we now know that this is not the case. The threats that our actions pose are significant, and they can have far-reaching effects.

Recent studies have made startling discoveries. For example, by 2050 there will be more plastics than fish in our oceans by weight.[1] Facts like this have helped to make the public more aware of the harm that our everyday materials can cause.

But among all the bad news, there are some success stories. With sensible management, we can undo some of the damage that has already been done. Some fish species, which had almost disappeared due to overfishing, have been successfully rebuilt, and levels of certain poisonous chemicals have fallen after global action was taken.

This guide looks at the major threats that we humans are placing on our oceans in 2018. It explores how they affect the fish and other marine life that are so vital to a healthy planet. In each chapter, we look at what can be done to protect our oceans, with tips and advice that you can personally follow to make a difference.

There is no one simple fix to these problems, but by having a greater understanding, taking small actions, and making small changes, we can all help to keep our oceans healthier and more sustainable for generations to come.


Topic Summaries

This giant guide is broken down into chapters, to make it easier to find the information you are looking for.

Chapter 1: Overfishing

A fishing boat with net overflowing with fish, meaning overfishing

If fishing boats catch fish from the oceans faster than their populations are able to replace themselves through reproduction, then their numbers will start to fall.

Because fish live hidden beneath the waves and can travel thousands of miles over their lives, it is not very easy to keep track of the sizes of their populations like you can with cattle or sheep on land. To make it even more difficult to manage, the oceans are so vast that it is very hard to make sure everyone is following the fishing laws.

Overfishing does not just harm the species of fish that is being caught. It also knocks the entire local ecosystem off balance, affecting the animals that the fish would normally eat and those that rely on it as their food source.

Chapter 2: Aquaculture

Salmon being farmed in aquaculture net in ocean

Many wild fish populations have fallen, making it harder for fishers to earn enough money from their catch. Because of this and the growth in popularity of fish like salmon and trout in developed countries, there has been an increase in fish farming, or aquaculture.

Raising ‘farmed’ fish is cheaper than catching wild fish, and greater volumes can be produced faster. This allows people to buy fish like salmon for a lower price than they could before.

Although some people see fish farming as a way to provide enough fish to feed the growing human population, there are many problems linked to the industry. From putting pressure on wild fish populations and the spread of parasites and disease to the predator control systems that affect local whale and dolphin behavior, the impacts can be far-reaching.

Chapter 3: Destructive Fishing

Dynamite fishing causing explosion in ocean blasting sea creatures into air

Some fishing methods can cause harm to the ocean environments where the fish are caught. Bottom trawling, where fishing boats drag large, heavy nets along the seafloor, is one of these methods and is practiced on a huge scale all around the world.

The other two fishing methods, cyanide and blast fishing, are mostly illegal. The problem is that the countries where they are practiced have not been able to stop people from doing it. Fishers can make more money and catch a lot more fish using these methods compared to using nets or rods.

Corals, sponges, and other organisms living on the seabed are either broken off, killed, or poisoned by these three fishing methods. This makes the seabed a less safe and healthy environment for the creatures that live on it.

Chapter 4: Climate Change

Polar bear stuck on iceberg in ocean due to climate change

The Earth’s climate is warming on a global scale due to human activity. And as air temperatures increase, so do the ocean temperatures. Although ocean temperatures do not rise as fast or as much, small differences can have big effects for the animals and plants that live in them.

Global temperatures are rising because we are producing higher levels of greenhouse gases than ever before. The oceans absorb the majority of these gases, slowly making them more acidic. This process is threatening the health of many marine creatures and putting fragile ecosystems at risk.

Chapter 5: Rubbish and Other Wastes

Plastic bags, bottles, straws, and other rubbish floating in ocean

Think of all the things you use and consume in an average day. What happens when you have finished with them?

  • The shower gel you washed with?
  • The straw you drank your drink with?
  • The bag you bought your lunch in?
  • The food you ate – where does that go when you are done? (Hint: *flush*)
  • The sunscreen you used the last time you went to the beach?

We humans produce a lot of waste… And no matter where we live in the world, not all of it is managed correctly. Huge quantities of waste find their way (or are actually dumped!) into our oceans where they can be potentially deadly to the plants and creatures living in them.

Chapter 6: Offshore Oil and Gas Drilling

Offshore oil rig leaking oil into ocean

For over a hundred years, we have relied on fossil fuels for almost all our energy needs. And, we still do today! To supply this demand, oil and gas are pumped out from deep beneath the seabed and transported all around the world.

Every oil reserve is limited, and eventually no more can be pumped out. This means that companies must continually search for and dig new oil wells. And as the easier locations have already been drilled, companies are looking in more remote and challenging locations to find new sites.

All the activities linked to oil and gas drilling carry serious threats to our oceans and the plants and creatures that live in them. And an accident can have fatal consequences that spread for hundreds of miles and last for decades.

Chapter 7: Surface Runoff

Surface runoff entering ocean

When it rains, or spring temperatures cause snow to melt, large quantities of water run off the land. The ground and trees absorb a lot of it, but plenty still runs into rivers or storm drains and then out to sea.

As the water runs over the land, it wears down the soil and carries it along for the ride. It can also pick up any nutrients, chemicals, or other wastes that were lying on the surface. All of these polluting materials then end up being transported to our oceans.

Depending on what the water carried with it, surface runoff can have different damaging effects. Sediments can block light from reaching plants on the seabed, fertilizers and sewage can cause algal blooms, and pesticides and chemicals can poison marine plants and creatures.

Chapter 8: Invasive Species

Lionfish invasive species chasing other fish and sea creatures

Every day, thousands of species of plants and creatures manage to catch rides out of their home environments and into new ocean locations. Although most of these species will die because they are unable to cope with their new conditions, some are able to adapt well. Too well.

These species are able to spread rapidly without any natural predators to keep their numbers in check. They can then compete against local species for food and space or even develop a taste for them. This is sometimes devastating for the local habitats and fish populations and for the incomes of the fishers who rely on them.

Chapter 9: Vessel Pollution

Cruise ship dumping sewage into water

There are countless millions of boats and ships in our oceans, ranging in size from small pleasure boats to massive oil tankers. Despite laws designed to prevent them from doing so, many of these vessels still dispose of their waste directly into the water.

These wastes can contain oils, chemicals, sewage, or even foreign organisms. And then, there is the noise of the boat as its propeller forces it through the water. These various forms of pollution affect our oceans in a number of ways.

Chapter 10: Port and Harbor Dredging

Digger dredging harbor sand

For a wide variety of reasons, sections of coastal seabeds are dug out to make the water deeper. Mostly it is done to allow boats and ships to gain access to ports and harbors.

This activity kicks up a lot of dirt and debris into the water and disturbs the plants and animals that have made that part of the seabed their home. The collected sediment then is typically dumped at sea, where it disturbs the organisms that live near the disposal location.

Chapter 11: Live Trade of Fish and Coral for the Aquarium Industry

Aquarium with fish from ocean swimming inside

Although most home aquariums are freshwater, there has been a recent growth in the popularity of marine reef tanks. These tanks create a micro reef ecosystem, including colorful tropical fish, corals, and starfish.

The problem is that most of these organisms are taken from wild tropical reefs and then imported to various countries to fill our tanks. Although the trade is smaller than fishing for food, it can still be a major threat to the delicate reef environments that were the first homes of these incredible life forms.

Chapter 1: Overfishing

A fishing boat with net overflowing with fish, showing overfishing

What is overfishing?

When a species or stock of fish is overfished, it means that the fish have been caught at a faster rate than the population can naturally replace itself through reproduction.

Over time, this reduces the population size. If nothing is done to stop it, then it will reach a point where there are not enough fish left to keep the population going. At this point, we would say that the species had been overfished to extinction.

How has this problem come about?

Commercial fishing has been practiced all over the world for many hundreds of years.

In Northern Europe in the Middle Ages from the 12th century, huge numbers of herring were being caught. At that time, it was said that the herring were so abundant you could almost scoop them up with your hands. Large cod fisheries were established in the seas off Newfoundland in the late 15th century.

Since those times, fishing technology, vessels, and equipment have continued to develop, allowing fishers to venture farther from their home shores to catch more and more fish.

Up until the 1970’s, commercial fishing was almost entirely unregulated, and vessels from all over the world were fishing in the richest oceans. This caused some fish stocks to plummet. So much so that stocks like the Northeast Atlantic Herring and the South Atlantic Pilchard were fished almost to extinction.[2]

Although there are now more laws to protect our oceans from overfishing, about 25 percent of US fish stocks are still overfished, and 90 percent of global fish stocks are overfished or close to being overfished.[3]

One of our most popular fish, cod, has been fished so intensively that the International Union for Conservation of Nature’s IUCN Red List of Threatened Species currently classifies Atlantic cod as vulnerable to extinction.[4]

Why does overfishing happen?

There are many causes of overfishing, but these are some of the main ones:

Catching young fish

Baby fish swimming through ocean

When fish are caught before they reach sexual maturity, they are unable to contribute toward repopulating their species. This makes the population less able to recover from the pressure of fishing.

The age of the fish that fishers catch can be controlled by the size of the holes in the fishing gear. Smaller holes catch smaller, and therefore younger fish, while larger holes let the small fish pass through them.

Overfishing is a particularly serious problem when fish are caught deep in the ocean. Deep-sea fish and animals grow slower and reach sexual maturity later than those that live close to the surface, making them much more vulnerable to overfishing.

Unselective fishing

When large nets are used to catch one species of fish, called the target species, they can also end up catching lots of other fish and marine animals unintentionally.

Fishers often throw these animals, known as bycatch, back into the water before the boat gets into port so that they do not have to record how much bycatch they caught.

Inaccurate catch data

Because lots of nations do not have accurate records of the amount of fish that their fisheries are catching, population estimates are inaccurate.

This stops scientists and policymakers from knowing the full scale of the problem, which means that they do not set as strict regulations as they should to protect the fish stocks.

Lack of enforcement and regulation

The fishing industry suffers from a lack of supervision, regulation, and traceability. Many countries are unable to strictly enforce fishing laws, and the current rules are not managing to keep fishing at a sustainable level.

This is a particular problem in the high seas where there are few international fishing regulations and poor enforcement of those that do exist.

Illegal fishing

Illegal fishing refers to when either:

  • Foreign ships fish in another nation’s waters, or
  • The fishing method used breaks the laws of the fishery.

It happens in national waters and in the high seas, across all sizes of operations. It is such a big problem that it makes up around 20 percent of all the fish caught in the world and up to 50 percent in some fisheries.[5]

Lack of protected areas

Only 1.6 percent of our oceans have been given the status of Marine Protected Areas (MPAs). This status restricts certain activities in order to protect the area’s natural or cultural resources. But the status does not necessarily stop people from fishing there. In fact, up to 90 percent of MPAs are open to fishing![6]

How does overfishing harm our oceans?

Fish food chain in oceans

Healthy, sustainable fish populations are vital to the overall health of our oceans. Their young, called juveniles, make up a large proportion of zooplankton, which is a major source of food for other fish and marine animals.

The adult fish are important prey for larger fish, sharks, and marine mammals like whales, dolphins, seals, otters, and polar bears.

Fish can also be important predators within the food chain, keeping populations of other ocean creatures in check. For example, bluefin tuna are major predators of herring, anchovies, and mackerel. If bluefin tuna are fished to extinction, it could have effects that run through ecosystems in the Mediterranean, North Atlantic, and Gulf of Mexico with serious consequences throughout the food chain.[7]

Overfishing also makes it harder for the billions of people around the world, who rely on fish as their primary source of animal protein, to get enough food.[8]

Facts and Stats

1) The US eats nearly five billion pounds of seafood every year, and 90 percent comes from countries that do not have strong management laws, like China and Vietnam.[9]

2) Illegal fishing is responsible for catching an estimated $10-23.5 billion worth of fish each year.[10]

3) Bluefin tuna can reach speeds of over 40 miles (64 kilometers) per hour when chasing prey and can dive deeper than 3,000 feet (900 meters).[11]

But it is not just overfishing that is a problem. Hunting any marine animal to unsustainable levels can have massive, and often unexpected, impacts on the health of the surrounding ocean habitat.

Sea otters as habitat protectors

Sea otter protecting habitat

From around 1790 until 1840, sea otter fur was the fashion material of choice, and otter pelts sold for a small fortune. Otters in the seas of Alaska were hunted in the tens of thousands, and their population collapsed.

In 1911, they were given a protected species status, which outlawed their hunting and slowly helped the population to grow again.

Scientists recently looked at the relationship of sea otters to their habitat. They found that in areas where there were no sea otters, populations of sea urchins, their natural prey, had exploded. The urchins had then eaten all the sea kelp, a large seaweed, in the area.

In contrast, in areas where lots of sea otters lived, the kelp forests were thick and healthy.

Kelp forests are important nurseries for young fish and are extremely productive, capturing huge amounts of carbon dioxide as they photosynthesize. Losing these forests, therefore, had a severe impact throughout the ecosystem.

The scientists estimated that the difference in annual absorption of carbon dioxide between a world with and without sea otters is somewhere between 14 and 47 million tons.[12] This means that losing otters could even have a small effect on climate change.

The Alaskan sea otter population plummeted again in the 1990s, but this time, killer whales rather than humans were hunting the otters.

The scientists completing the study believe that the killer whales had changed their diet to include otters because their main food source, the great whale, had been almost entirely wiped out by commercial hunting.[13]

This goes to show how complicated the effects can be when you overhunt just one animal.

What can be done to save our oceans from overfishing?

No fishing zone in middle of ocean

Scientists are going to great efforts to understand exactly how many fish are actually caught in our oceans so that policymakers and governments can understand the true scale of the problem.

The United Nations (UN) created the Food and Agriculture Organization (FAO) to help governments make decisions to protect marine ecosystems. All nations have to report their fishing data to this body, and with help from scientists, the data is slowly getting more accurate.

The World Wildlife Fund (WWF) created the Marine Stewardship Council (MSC) to encourage sustainable fishing practices. They independently assess fisheries and certify them with an eco-label, which shows that the fish with this sticker are wild, traceable, and sustainable.

The 27 nations of the World Trade Organization agreed in 2015 to reduce ‘subsidies’ for fishing. They recognized that in many cases, subsidies keep more fishing vessels running than the fisheries can support.

Many nations are working to expand or create new Marine Protected Areas to allow fish stocks to recover from overfishing. In 2017, the US and New Zealand agreed to create a 0.5 million square mile (1.55 million square kilometers) MPA in the Antarctic. This is the largest MPA in the world, and over 70 percent of it is a No-Take Zone (NTZ).[14]

No-Take Zones are areas where no marine life can be removed by any method. In one NTZ in Scotland, surveys showed that after five years the seabed was 40 percent more complex and healthier than the area outside the NTZ. There were greater densities of scallops, crabs, and lobsters and increased numbers of juvenile cod and haddock.[15]

Belize is planning to extend its network of No-Take Zones from 3 to 10 percent of its seas by the end of 2018. These zones are already seeing growing fish populations and more variety of species. The expansion will help to protect the second largest barrier reef in the world, behind the Great Barrier Reef.[16]

We are at the start of a very long journey to protect our oceans from overfishing and to allow fish stocks to recover and build back to sustainable levels. But with measures like these, we are slowly moving in the right direction.

What can I do to help our oceans from overfishing?

There are lots of handy guides that show you which fish are sustainable and are good to eat. This relates not just to the species of fish but also to how and where they were caught.

Check out these guides for more information, some of which you can download as handy apps:

You can also look for fish that have the Marine Stewardship Council (MSC) eco-label on it. This means that the fish you are eating was caught in the wild and is sustainable and traceable, meaning they know exactly where it was caught.

Buy local fish – If you live close to the sea, you could buy fish from your local fishers. This is an excellent way to know exactly where your fish comes from, who caught it, and how.

Plus, small-scale fishers often use less impactful catch methods like hook and line or laying pots and traps to catch their fish. Not only that, but you will be supporting the local economy and increasing the demand for local, sustainable seafood.

Eat a wider range of fish – The oceans off the coast of the US contain hundreds of delicious and sustainable fish species, but only three species make up over half of all the seafood we eat – shrimp, salmon, and canned tuna.[17]

By expanding our fish diets to include a greater variety, we will minimize overfishing of these popular species, as well as limiting habitat destruction and harmful catch methods.[18]

Chapter 2: Aquaculture

Salmon being farmed in aquaculture net in ocean

What is aquaculture?

Aquaculture is basically farming in water. It refers to the farming of fish, shellfish, seaweed, and other marine organisms. More specifically, marine aquaculture, or mariculture, which is the farming of marine organisms in our oceans and seas.

Why do we need to farm fish?

Humans have been farming fish for hundreds of years, but the practice has been growing much faster recently, to the point that farmed fish now makes up half of the fish that we eat worldwide.

Because we cannot catch as many fish from wild fisheries as we could before, aquaculture is often thought to be an effective way to meet the seafood demands of a growing global population.

If fish farming is well-managed, it can provide a sustainable source of seafood to meet our growing appetites. It can also be used to rebuild wild fish stocks and populations of endangered species.

Some types of aquaculture, like mussel farming, can actually have a positive effect on their ocean habitats. That is because mussels are filter feeders, so they act like water purifiers![19]

Facts and Stats

1) In the 1970s, aquaculture only produced about 3 million tons of fish, but by 2015, it had reached nearly 77 million tons and was worth $158 billion![20]

2) Aquaculture provides us with about half the fish we eat.[21]

3) Aquaculture employs 16 million workers directly and 6.5 million indirectly.[22]

4) Wild salmon get their color from eating krill and shrimp. The flesh of farmed salmon would be gray, but they are fed a manufactured copy of the pigment that they eat in the wild, making it pink.[23]

How can aquaculture harm our oceans?

Since the term aquaculture applies to the farming of a wide range of plants and animals, we will just focus on one type of aquaculture: fish farming.

The environmental impact of fish farming varies widely depending on the species being farmed, the methods used, and where the farm is located.

When good practices are carried out, it is possible to farm fish in a way that has very little impact on the environment. These operations make sure to limit habitat damage, disease, escapes of farmed fish, and the use of wild fish as feed.

Unfortunately, much of fish farming is still unsustainably practiced. This puts pressure on the marine habitats and threatens wild stocks of fish.

Let us look at salmon farming as an example.

Salmon farming

Three salmon swimming in aquaculture fish net

Salmon farming is the most valuable aquaculture industry in Europe.[24] Farmed Atlantic salmon represents more than 99 percent of the Atlantic salmon we eat and about two-thirds of all salmon.[25] So, most of the salmon you eat probably comes from a salmon farm!

Threat to other fish stocks

Salmon are piscivorous, which means that they eat other fish. To produce farmed salmon, it takes about three times the weight of wild-caught fish.[26] These wild fish are caught and then dehydrated to make a powder form of food called fishmeal.

Over a quarter of all the fish caught worldwide go to feeding farmed aquatic species. This does not only affect the species that were caught for feed, e.g., anchovies and krill, but also all the animals that depend on those creatures as their food supply.

Because salmon farming relies heavily on fish feed from wild-caught fish, it makes it harder for people in developing countries to have enough fish to eat. The largest fishery in the world is the Peruvian anchovy fishery, and most of the anchovies there are turned into fishmeal rather than being eaten by humans.


Breeding fish in large numbers and with so many animals living close together has led to problems with parasites. Farmed salmon in Scotland, Norway, and Canada are suffering from an infestation of a small creature called the sea louse. The louse attaches to the skin of the salmon, sucks their blood, and eats their flesh.

Sea lice populations have exploded over the past 30 years, and they are now a real threat to the farmed salmon industry, reducing the amount of fish produced by tens of thousands of tons per year.[27]

Unfortunately, the problem does not end there because sea lice transfer into populations of wild salmon and trout when the wild fish swim through the same waters that the salmon are farmed in. This is causing populations of wild salmon and trout to decrease.


Chemicals being poured over salmon in fish farm

Salmon farming industries around the world spend over $1.3 billion every year to try to get rid of sea lice and the diseases they bring. One of the main ways to prevent the salmon from being infected by sea lice is to treat them with chemicals and antibiotics.

Unfortunately, the parasites are becoming increasingly resistant to these chemicals, and farms have to apply more and more. Chemical use has increased by 10 times in less than two years.

In Scotland, 45 sea lochs had been polluted with antibiotics and pesticides used to control sea lice. Studies have found that these anti-lice chemicals may cause harm to crustaceans, like the lobster, and other forms of marine life that live far from the farm cages.[28]

Attracting predators

The large concentration of fish in one place can also lead to another problem. It can attract lots of their natural predators like seals.

The extent of this problem was seen in Australia, where a large farmed salmon producer had to relocate more than 2,000 fur seals in one year.[29] The seals are picked up from in or around the fish cages and then relocated several hundred kilometers away.

Seals can become stressed or die during the relocation, while some swim straight back to the fish farm after release. Individual repeat offenders or aggressive seals may then be killed.[30]

Excess nutrients and waste

Salmon pooping in aquaculture fish farm

As well as attracting wild animals, the excess food from the farms and waste from the fish can also increase nutrient levels in the water. This material settles on the seafloor under the pens, where microbes work to break it down. The process uses up lots of oxygen, reducing the amount of oxygen in the local area.

If the low oxygen water at the bottom of the sea is caught up in a storm or rough seas, it can mix with the water in the fish pens. This sometimes leads to mass fish deaths.

Effects on other marine animals

Acoustic deterrent devices (ADDs) are used in many salmon farms to stop seals and other predators from coming close. The devices create a loud sound under the water to scare the seals away from the fish cages or to hurt their ears.

But the devices also harm whales, dolphins, and porpoises, keeping them away from important habitats. Because salmon farms are generally located in coastal areas, coastal species, like bottlenose dolphins and harbor porpoises, are at the greatest risk.

In the waters of western Scotland, which is one of the most important porpoise habitats in Europe, the conflict between salmon farms and whale and porpoise habitats is particularly serious. Scotland has a high density of salmon farms and more than half of them use ADDs to keep predators away. To make things worse, salmon farm developments are on the rise.

What can be done to prevent the threat of salmon farms to our oceans?

Farmers are starting to use new methods to manage their salmon farms. For example, some companies are experimenting with the use of parasite-eating fish, like wrasse and lumpsuckers, to prevent sea lice infestations in their farms. These fish are put into the cages to eat the sea lice off the salmon, reducing the need for pesticides.

Some environmentalists say that salmon farms should be moved from near the coast into deeper seas. Sea lice are not able to survive in the colder waters of the deep seas, and there are stronger waves and currents to carry waste from the salmon farms away.

A proposed strategy to deal with the excess nutrients and waste from the salmon farms – or even to turn them into something useful – is to farm other marine plants and creatures around the salmon. For example, sea cucumbers could eat huge quantities of waste material from under the cages, mussels or oysters could be bred close to the salmon pens to filter out the smaller waste particles, and seaweed racks could be placed around the cages so that the majority of the waste nutrients could be used for good.[31]

There is also a growing understanding that we need to find different sources for the proteins and oils to make fish food. If we could do this, then the fish farming industry would be able to grow more sustainably. Many salmon farms now use plant oils such as canola oil to reduce their need for fishmeal.

High-quality, tight nets are good alternatives to ADDs. They both prevent fish from escaping and stop seals from being able to get to the fish. Other recommendations are to remove dead fish, put fewer fish in each cage, and make it so that the seals cannot see the fish inside the cages.

What can I do to help?

Happy salmon in fish farm

Before you buy seafood, ask if it is sustainable. Just asking this simple question helps to increase the demand for fish that have been caught or farmed in an environmentally responsible manner. As consumers, we play an important role in shaping our oceans’ health.

Download an app like Seafood Watch to get up-to-date recommendations for ocean-friendly seafood.

Try eliminating farmed salmon from your diet – This is the better choice environmentally and ethically. Farmed salmon are generally bred in overcrowded conditions, which can cause the fish significant stress.

Eat more farmed mussels – They are actually good for their ocean habitats, there are fewer ethical dilemmas compared with farmed salmon, and they do not need to be fed other fish because they get all their nutrients from particles in the water.

If you live near a salmon farm, find out what farming methods they are using and see if there are any local resident’s groups that you can join. Through these groups, you can exert pressure on the companies to improve their practices and make your local waters healthier.

Chapter 3: Destructive Fishing

Destructive fishing boat using drag net

What is destructive fishing?

As well as putting fish populations at harm by overfishing, some fishing practices can be damaging to the habitats where the fish are caught.

There are three fishing methods that are particularly damaging to the marine ecosystems where they operate – bottom trawling, blast fishing, cyanide fishing – which we will look at in more detail.

1. Bottom Trawling

Bottom trawling catching everything at bottom of ocean

What is bottom trawling?

Bottom trawling is an industrial fishing method that uses a large net with heavy weights to catch marine animals that live on the seafloor, like shrimp, cod, sole, and flounder. As the net drags across the seabed, it catches everything in its path, from the creatures they mean to catch to other untargeted species and corals.

How does bottom trawling harm our oceans?

Bottom trawling is completely unselective, meaning the nets catch every animal or object that is in their way as they scrape across the ocean floor. So much so that some scientists estimate that the bycatch can be as high as 90 percent of the total catch of a trawl.[32] These unwanted fish and animals are then thrown back into the water, most of them already dead or dying.

Trawling is also damaging to the ocean floor. The weights that keep the net open can weigh several tons, and the bottom of the net is a thick metal cable, studded with heavy steel or rubber balls. These scrape and crush objects on the seabed as they pass.

According to the National Academy of Sciences, bottom trawling reduces the complexity and variety of species living in seafloor habitats. This damage is most severe in areas with corals and sponges. When damaged by bottom trawling, as much as 90 percent of a coral colony may die and up to two-thirds of sponges are damaged.[33]

Commercial fish and other marine animals rely on these seafloor habitats to release their eggs, as nurseries, and for shelter and food. By damaging their habitats, all these animals are put at risk.

Facts and Stats

1) Some bottom trawling operations catch 20 pounds of bycatch for every pound of targeted species.[34]

2) Bottom trawlers use nets that weigh as much as 30 tons.[35]

3) In recent cold-water coral studies, damaged areas showed no new coral growth even after seven years.[36]

4) Trawling stirs up sediment on the seabed, creating plumes that block sunlight from reaching the seabed, reducing the health of algae and marine plants.[37]

5) Bottom trawl nets can reach depths of 6,000 feet (1,800 meters) to catch creatures living on the seafloor.[38]

What can be done to prevent the threat of bottom trawling to our oceans?

Scientists are carrying out studies to understand the full effect of bottom trawling on ocean floor ecosystems. The results from these studies can then be used to communicate fishing policies and enforce stricter rules for these fishing vessels.

Some countries and regions have created Marine Protection Areas, to restrict certain fishing activity, and No-Take Zones, where bottom trawling and other fishing is forbidden. In 2006, the South Pacific nations agreed to ban bottom trawling in all their waters. This area amounts to 14 percent of the Earth’s surface.[39]

Because deep-sea species are more vulnerable to overfishing than shallow water species, they need much stricter management measures. To help ensure protection for deep-sea ecosystems, in 2016 the European Commission created a new law that includes a ban on bottom trawling below a half mile (2,640 feet / 800 meters) in the North-East Atlantic.

The law also banned trawling in vulnerable marine ecosystems and included tougher checks at sea. Twenty percent of EU fishing boats must now have a scientific observer on board to ensure that data are accurately collected.[40]

2. Blast Fishing

Dynamite fishing causing explosion in ocean blasting sea creatures into air

What is blast fishing?

With blast fishing, otherwise known as dynamite fishing, fishers use explosives to kill or stun schools of fish so that they can easily collect them.

It has been banned in most parts of the world, but it still occurs in Tanzania, Malaysia, the Philippines, and some other developing nations.

How does blast fishing harm our oceans?

Not only does the explosion stun the fish that they are trying to catch, but it also destroys the coral reefs at the bottom of the shallow seas where the fishers work.

These reefs support a wide range of ocean creatures, providing shelter from predators and a feeding habitat for young and adult fish, crustaceans, and other marine species. They also play a crucial role in controlling carbon dioxide levels in the ocean.[41]

Facts and Stats

1) Each blast may catch as much as 880 pounds of fish.[42]

2) In Tanzanian coral reefs, fish densities were 12 times higher on a reef with little dynamite damage versus one nearby that was heavily dynamited.[43]

3) In 2016, researchers from the Wildlife Conservation Society counted more than 300 explosions in 30 days off the coast of Tanzania.[44]

What can be done to stop blast fishing?

There are already laws in Tanzania to prevent blast fishing, but with few resources and confusion over who is meant to enforce the law, it is rare that anyone is charged with anything near the full term of the five-year sentence.

A Task Team was formed in 2015 to try to stop blast fishing and other environmental crimes. Together with the efforts of this team, Tanzania is working to:

  • Make the community more aware of the environmental and economic impacts of blast fishing
  • Build a sense of community ‘ownership’ for their seas and the animals in them
  • Strengthen the local economy by developing alternative jobs like ecotourism and seaweed farming
  • Provide training along the entire law enforcement chain so that they take these crimes more seriously
  • Create laws to target everyone involved: The people who fund the operation, those who provide the explosives, and the people who sell the fish[45]

What can I do to help?

If you are planning a vacation to Tanzania – or any other developing country – look to see if you can book through an ecotourism operator. Or, while you are there, see if you can go on tours that are run by local people rather than through your hotel.

In the evenings, try venturing out of your hotel and ask for a recommendation for a local restaurant. Spending your money in the local community, rather than with a large multinational hotel, boosts the local economy, encourages enterprise, and helps to give local people an opportunity to earn a sustainable income outside of harmful activities like blast fishing.

The organization Stop Illegal Fishing is working in Africa to fight against illegal fishing. They are creating a database of fishing vessels because identity fraud, using another boat’s identifying number, is a large factor in illegal fishing. You can add your photos of fishing vessels in the African region to their database.

You can support organizations like the WWF, Stop Illegal Fishing, and Stop Bomb Fishing to help them in their efforts to change policies, educate, and pressure governments to do more.

3. Cyanide Fishing

Cyanide being used in oceans to catch fish

What is cyanide fishing?

Fishers squirt a poisonous chemical called sodium cyanide at fish to stun them, making them easy to catch without killing them. Although it is illegal, it still happens widely in the Philippines.

Cyanide fishing is mainly used for the live food fish markets in Asia, where diners pay a premium to have their fish cooked for them straight from the tank. It is also used as a way to collect exotic fish for the aquarium industry.[46]

How does cyanide fishing harm our oceans?

The International Marinelife Alliance estimates that for every fish caught with cyanide, 11 square feet (1 square meter) of reef is destroyed.[47]

And because using cyanide massively increases the number of fish caught, fish stocks are overfished. This makes it harder for the people of the Philippines to be able to get enough fish in their diets.

Fish stocks in the Philippines have reduced by 90 percent in the last 50 years. With the population of the Philippines expected to be over 100 million in 30 years, there is concern as to how the population will cope with less fish available to catch and eat.

To make matters worse, Hong Kong diners like their fish to be plate-sized. One of the most popular species, grouper, reaches this size just as it is reaching sexual maturity. As a result, most fish never reproduce before they are caught.

Facts and Stats

1) A Filipino fisher makes fives times as much for selling a live fish than a dead fish.[48]

2) It is estimated that fishers have released more than a thousand tons of cyanide into Philippine waters.[49]

3) Around 20,000 tons of live fish are eaten annually in the restaurants of Hong Kong.[50]

What is being done to stop cyanide fishing?

Very few people are caught and sentenced for cyanide fishing. This is partly because cyanide leaves the fish’s body quickly, making it hard to detect which fish have been caught this way.

A ban on the live reef fish trade was proposed in the Philippines, but the WWF believes that this will lead to fishers catching more fish to make up for the lower price that they earn. They also warned that fishers might instead use even more destructive fishing methods, like blast fishing.

Until recently, scientists needed to take tissue samples to detect cyanide exposure, which meant killing the fish. New methods have now been developed to detect cyanide exposure in the fish’s urine. This is a major breakthrough because scientists do not have to hurt or kill the fish.[51]

In the US, which is one of the largest importers of tropical fish for aquariums, the Lacey Act makes it illegal to import any wildlife caught in a way that breaks another country’s laws. Authorities are now being asked to use this Act to crack down on the import of tropical fish caught with cyanide.[52]

What can I do to help?

When you buy tropical fish for your reef tank aquarium, ask your supplier whether the fish were bred in captivity. The free app Tank Watch helps you identify reef-friendly species.

Speaking to your supplier about this issue shows that it is important to you. If enough of us ask and change our buying decisions, then it will put real pressure on breeders, importers, and suppliers to change their practices.

Unlike freshwater species, it is still quite hard to breed saltwater fish in captivity. But new techniques are being developed all the time, and the list of captive-bred marine fish is growing. So, keep checking to find out what fish you can have in your reef tank!

If you are in a restaurant in Asia that serves live fish, ask your waiter how the fish was caught. If they cannot prove that they were caught sustainably, order something else!

Chapter 4: Climate Change

Polar bear stuck on iceberg in ocean due to climate change

What is climate change?

Climate change represents a huge current threat to our oceans. It can be pretty complex because weather systems and climatic events can span across entire continents (and beyond!), systems are interwoven, and it can be affected by many different factors.

But, what scientists all over the world are almost entirely in agreement about, is that the climate is warming on a global scale as a result of human activity. And, this is placing our oceans at a significant risk from a range of factors.

What human activity in particular?

The single biggest cause of climate change and global warming is the burning of fossil fuels, such as coal and gas.

For over a hundred years, we have burned vast quantities of fossil fuels. This has helped our countries to grow and become rich by fueling our factories and transportation systems, generating electricity, and heating our buildings.

As our countries have developed, more and more people have become able to afford cars, air flights, comfortable houses with heating and cooling systems, and more material goods. All these things need fuel to power them or to make them.

And as large developing countries like China, India, and Brazil become wealthier, there are millions more people who can afford these same things, driving the need to burn more and more fossil fuels.

Before we get into the effects that climate change is having on our oceans, we must understand what is causing it in the first place.

What are fossil fuels?

Car being filled with gas at petrol station with fossils (fossil fuel) from ground

Fossil fuels are called that because they are literally made from the fossils of ancient forests and marine animals.

Coal was formed on land when trees and plants died and formed layers at the bottom of swamps. Thick layers of this dead plant matter were compressed by hundreds of millions of years of additional layers of dead plants and sediments that were put under intense pressure and heat. This changed their chemical and physical properties, creating carbon-rich coal deposits.

Oil and gas were formed when huge quantities of marine organisms fell to the ocean floor over time and were buried under layers of sediment, being put under incredible levels of pressure and heat over millions of years.

What happens when fossil fuels are burned?

Fossil fuels are rich in carbon. When they are burned, a chemical reaction occurs that uses up the fuel and oxygen to create energy, water, and carbon dioxide. This reaction is known as combustion.

Natural gas is the cleanest-burning fossil fuel. Coal and oil are more chemically complicated than natural gas, and when burned, they also release a variety of harmful air pollutants.

How does burning fossil fuels lead to climate change?

One of the products of the combustion reaction is carbon dioxide. This gas is known as a greenhouse gas, or GHG for short.

GHGs collect in the Earth’s atmosphere, where they work like an insulating jacket, preventing heat from effectively escaping the planet. GHGs allow the sun’s energy through but absorb the heat energy that bounces back off the Earth’s surface. This energy gets bounced back in all directions, and some returns to Earth where it heats the surface. This process is known as the greenhouse effect.

If the Earth’s atmosphere did not have any greenhouse gases, it would be a chilly 0°F (-18°C).[53] But if there are too many greenhouse gases, the Earth will get hotter and hotter. The more fossil fuels we burn, the more carbon dioxide is created and the more powerful the greenhouse effect becomes.

What naturally happens to stop carbon dioxide levels from rising?

The Earth is delicately and exquisitely balanced. There has always been carbon dioxide in the atmosphere because almost every living creature produces it as they breathe.

Plants and algae naturally absorb carbon dioxide, and the oceans absorb about 30 percent of all the carbon dioxide we produce. This is part of a process known as the carbon cycle.

So, what is happening now?

Global warming

The problem is that since around 1950, we have been producing more carbon dioxide and other greenhouse gases than the natural environment can absorb.[54] This means that levels of GHGs in our atmosphere are rising.

This is gradually warming our planet. And that, in turn, increases the speed of warming since increasing temperatures reduce the effect of some of the things that used to help cool the planet down.

For example, the heat of the sun can be reflected back into space if it hits surfaces that are very light – or white. Snow and ice reflect between 50 to 70 percent of the sun’s energy. But in comparison, the sea reflects only about 6 percent and absorbs the rest.[55]

Because rising temperatures cause the polar ice caps to shrink, there is less snow and ice to reflect the heat of the sun. Instead, the sun’s energy hits more dark surfaces that absorb it, further warming the planet.

How much are temperatures rising?

Scientists think that global temperatures have risen on average by 1.4°F (0.8°C) since 1880. Two-thirds of that warming has happened since 1975, so it is warming faster than before.

How much more are they predicted to rise?

Future global warming levels are hard to predict because the climate is affected by so many different factors. Scientists have created mathematical models to try to predict how much temperatures might rise under different scenarios of greenhouse gas emissions.

The UN’s climate scientists forecast that by 2100, global temperatures will rise between 0.5-8.6°F (0.3-4.7°C). For every emissions scenario, they predict that temperatures will increase by at least 2.7°F (1.5°C) except if we meet the strictest targets to reduce greenhouse gas emissions.[56]

How do global warming and greenhouse gas emissions harm our oceans?

Global warming and increased greenhouse gas emissions have two broad effects on our oceans. First, they make them warmer, and second, they make them more acidic. We will look at both these and see how they are affecting our oceans and the fish and animals that live in them.

Warming Waters

Fish migrating due to oceans getting warmer

What is happening?

2015 was the warmest year for sea surface temperatures since records began 136 years ago. It was also the fourth year that the record had been broken since 2005.[57] It is estimated that surface water temperatures are increasing by about 0.2°F (0.1°C) every decade.[58]

But it is not just the surface water that is warming. All the way down to the deepest depths, our ocean temperatures are increasing. Scientists have detected rises at depths of 2,300 feet (700 meters), where the majority of marine life flourishes.

And the ocean’s role is vital, absorbing more than 90 percent of the excess heat in the Earth’s system.[59] If they did not absorb the heat energy that they did, scientists have calculated that between 1955 and 2010, global temperatures would have risen by an astronomical 65°F (36°C)![60]

Even if we stop producing greenhouse gases today, the oceans will continue to warm for many more years. This is because oceans slowly absorb the heat from the atmosphere and take a long time to respond to changes in greenhouse gas levels.

How do increased water temperatures harm our oceans?

Warming oceans will have wide-ranging impacts on the fish, plants, and other marine organisms that live in them. Here are some of the main problems that we are already seeing and that are likely to become more severe over the coming years.

1. Less variety of marine plants and animals

Invasive fish spreading

As oceans warm, invasive species that previously lived in warmer regions are able to extend their habitat and establish themselves across wider areas and into deeper waters.

In 2018, rare tropical fish from Australia were found in New Zealand’s waters after sea temperatures rose between 4-7°F (2-4°C) during the summer. One fish was found 1,800 miles (3,000 kilometers) away from its home habitat.[61]

The invasion of these new species can put vulnerable local species under great pressure. Combined with the stress of rising water temperatures, it is possible that this might lead to the local species dying out.

Cold-water fish and animals that are able to move are forced closer and closer to the poles or into deeper waters to try to escape the warmth. This can reduce their habitat size or move them away from their natural food sources.

2. Spread of infectious diseases

Diseases spreading through ocean

Warmer waters help spread marine diseases. Scientists are starting to find diseases in seas that used to be too cold for them, and this can have devastating consequences.

One example is a bacterial disease that affects lobsters. The disease eats in from the shell toward the inner flesh, making the lobster unsuitable for sale. It can even kill the lobster by preventing it from being able to shed its shell, which is what allows its growth.

In the 1990s, after a decade of warming waters, the disease affected so many lobsters in the fisheries of Connecticut, Massachusetts, New York, and Rhode Island that they had to close the fisheries.[62]

Many diseases wait for an organism to become weakened by another factor, and then strike when it is unable to defend itself. So as higher water temperatures stress plants, corals, and marine creatures, this can lead to them becoming infected with diseases that they previously could fight off.

3. Coral bleaching

Coral bleaching

Corals have a special relationship with tiny algae that live in their tissues. The algae provide the coral with essential nutrients that make up their main source of food and also give them their color. In return, the coral provides the algae with shelter and access to sunlight.

When the ocean temperature rises, the relationship between the coral and algae becomes stressed, and the algae are kicked out of the coral. Without the algae, the coral becomes white, loses its main food source, and becomes more vulnerable to disease. This phenomenon is known as coral bleaching.

Coral bleaching, however, is not always fatal. If the water temperatures return to normal quickly, then the algae can return, and the corals can recover. But if the temperature rise is sustained, then the coral will die.

In 2005, water temperatures in the Eastern Caribbean increased and stayed high for several months. This caused a mass coral bleaching event, affecting 90 percent of corals around the Virgin Islands. While they were weakened from the bleaching, diseases including one called White Plague attacked them.[63] Two years later, almost 60 percent of the coral around the Virgin Islands was dead.[64]

4. Increased pressure on ocean food chains

Ocean food chain

Warmer oceans could decrease the abundance of phytoplankton, the tiny plants that are at the bottom of most marine food chains. That is because phytoplankton grow best in cool, nutrient-rich waters.

Another study found that continued ocean warming could reduce the growth habitat of krill by 20 percent.[65] Krill are tiny animals that are found in huge numbers in the Southern oceans. There are so many of them that they provide the primary source of food for a wide range of ocean animals, including fish, seals, penguins, and whales.

Scientists found that krill grew fastest in cold water and that warming waters would slow down their growth, reducing the amount of food available to the huge number of animals that feed on them.[66] This reduces the health and fitness of the larger animals, and the impact moves up the food chain, reducing the amount of food available for each animal in turn.

5. More and larger ocean dead zones

Dead zone in ocean where no fish or plants can live

Ocean dead zones are areas that have such little oxygen that most marine creatures are unable to survive in them. They are normally caused by high concentrations of nutrients running into the seas from land.

The extra nutrients stimulate the growth of huge numbers of algae, which block the sun’s energy from passing through the water to the plants on the seabed. When the algae die in their millions, they break down on the seabed in a process that uses lots of oxygen. This results in the water having too little oxygen for fish and other marine animals to live, creating a dead zone.

Oxygen is less able to dissolve into warm water than it is into cold water. This means that warm water actually holds less oxygen than cold water does. As ocean temperatures increase, this causes dead zones, low oxygen areas, to increase in size and number. The problem is made worse by the fact that as water temperatures rise, so too does the animals’ metabolism rate, meaning that they actually need more oxygen to survive.

Dead zones are generally found in deeper waters, and so they reduce the depth of water that fish can live in, forcing them into shallower waters. Fish and crustaceans are particularly sensitive to lower oxygen levels, and some major fisheries of mussels and fish off the US coast have experienced massive die-offs due to oxygen loss.

6. Rising sea levels

Rising sea levels

Warmer water has a greater volume than colder water. This means that as the oceans warm, their levels will rise. And that is before we consider the effect of any additional water from melting land ice.

When glaciers and land ice melt, they add hundreds of gigatons of water to our seas each year, raising sea levels and putting the lives of the billions of people in low-lying coastal regions at risk of flooding.[67]

Rising water levels also put coastal habitats at risk. Flooding and erosion threaten complex ecosystems like mangroves, salt marshes, and coastal wetlands. These habitats are home to an incredible array of species, providing them with shelter, spawning locations, and nurseries for their young to grow.

7. More extreme weather events

Severe weather: Tidal wave and storm on beach

When the oceans become warmer, there is more available energy that can be converted into cyclone winds. Scientists worry that although this will not increase the number of hurricanes and tropical storms, it might increase their intensity.[68]

These weather events can cause landslides, collapses in fisheries, and damage to reefs and shallow-water habitats. For humans, they can destroy lives and properties and cause malnutrition, forcing people to leave their homes.

Freshwater from melting land ice and extreme rainfall can cause the salt levels in the waters around the coast to fall, potentially disrupting the delicate balance among organisms in salt marshes, mangroves, and coastal wetlands.

Extreme rainfall also increases surface runoff, which causes sediments to run into the shallow waters. This debris smothers coral reefs and blocks sunlight from reaching plants and algae on the seabed.

Facts and Stats

1) Starting in 2001, 17 of the last 18 have been the warmest years on record.[69]

2) Fossil fuels still provide the world with 80 percent of its energy needs.[70]

3) In 2016, the northern sector of the Great Barrier Reef experienced coral bleaching in 91 percent of its reef ecosystem.[71]

4) Globally, seas are predicted to rise between 0.66-6.6 feet (0.2-2.0 meters) by 2100.[72]

Ocean Acidification

Ocean acidification killing sea creatures

What is ocean acidification?

The oceans absorb about 30 percent of the carbon dioxide we emit into the atmosphere. When water and carbon dioxide mix, they combine to form carbonic acid, which makes the water more acidic. Since 1750, there has been a 30 percent increase in ocean acidity.[73]

Also, as carbon dioxide dissolves into the oceans, it binds with carbonate ions, reducing the amount of them that are available for creatures to use to build their shells.

How does ocean acidification harm our oceans?

As acidity levels continue to rise, some species of marine plants and organisms will cope better or worse than others.

1. Corals and shelled organisms

When the ocean’s waters become more acidic, they can start to dissolve the shells of marine organisms like clams, oysters, mussels, snails, and corals, making them weak.[74]

This means the organisms need to use extra energy to try to rebuild their shells, making them less healthy over time. If the shells become too weak, they are no longer able to protect the organism, and they will die.

Studies have also shown that mussels struggle to hold onto their supporting when they are in more acidic water, and the acid can also stop oyster larvae from growing their shells in the first place. This effect has been blamed for major oyster die-offs in the US Pacific Northwest.[75]

Corals and shelled marine organisms also need carbonate ions to build their skeletons and shells. As greater amounts of carbon dioxide are absorbed into the oceans, they bind with the ions, making fewer available for the organisms to build with. The creatures have to use more energy to find enough ions to build their shells and skeletons and end up being smaller and weaker.[76]

In comparison, when scientists studied how crustaceans like lobsters, crabs, and prawns coped with higher acidity levels, they actually found that the animals grew heavier, healthier shells.[77]

2. Fish

When the surrounding water is more acidic, the cells in a fish’s skin will naturally try to balance with the seawater by taking in the weak acid. This changes the acidity levels in the fish’s blood, which is not good for the fish. They then expend a lot of energy to get the extra acid out of their blood.

Even using just a little more energy to get rid of the extra acid reduces the amount of energy that the fish has to digest food and reproduce. It also means that they will not be able to swim quite as fast to catch food or escape predators. All of this can cause the fish to grow slower and be less healthy.[78]

Recent studies have found that increases in the acidity of seawater can also make fish behave differently. Normally, clownfish stay close to the coral or anemone they live in. But as the acidity of the water increases, the fish begin to stray farther from their home. This puts the clownfish at greater risk of being eaten by predators.[79]

3. Plants

Plants and algae receive the nutrition they need by absorbing sunlight and carbon dioxide, so higher levels of carbon dioxide could actually be good for them. Plants like seagrass have been found to grow taller, reproduce better, and grow deeper roots in more acidic conditions.[80]

Facts and Stats

1) Between 30 and 40 percent of the carbon dioxide that we create dissolves into our oceans, rivers, and lakes.[81]

2) By the end of the 21st century, we are likely to make the oceans more acidic than they have been in 20 million years![82]

3) Around 25 percent of all marine life, including over 4,000 species of fish, rely on coral reefs for a part of their life cycle.[83]

What is being done to reduce greenhouse gas emissions and stop temperatures from rising?

Paris climate change agreement

In 2015, global leaders came together in Paris to sign a historic agreement – where they would set targets to keep global warming to well below 4°F (2°C) compared to the pre-industrial average temperature, with a further aim to tighten this target to 2.7°F (1.5°C).

This was a huge deal! Countries have been negotiating globally on climate change for over 20 years but have never quite managed to agree on the details. So, this really was something special.

However, there were still some major problems with the deal. First, the targets were not legally binding. That is to say, the countries that signed the deal are not legally required to make any emissions cuts. Instead, each country had to submit a plan for how they will reduce greenhouse gas emissions and will have to review their plan every five years. However, there are no penalties for failing to meet these pledges.

Second, while there was an agreement for the richest countries to provide financial aid to poorer countries to help them use more renewable energies and adapt to the pressures of climate change, no exact sums were agreed. Accounting for this aid has often been weak in the past, with countries just relabeling existing aid funds as climate aid so that no additional money is provided.

Third, there was no agreement to provide financial compensation to the low-lying nations that will almost certainly be affected by rising sea levels. These nations argued that since the developed countries were largely responsible for the current levels of greenhouse gases, they should be held accountable.

Finally, the Paris Agreement suffered a significant setback in 2017 when the US announced that it would withdraw from the deal.

But the news is not all bad. Mayors of over 400 cities across the US have signed a pledge to uphold the Paris Agreement goals.[84]

These mayors represent a total of 70 million people, so their actions will have a positive effect to counteract the government’s decision.

The most important message that climate scientists want to get across to our world leaders, businesses, and the general public is that we must make significant changes urgently. We cannot afford to wait or make soft decisions.

A key part of that effort will be to increase our use of renewable energy sources and reduce our reliance on fossil fuels.

What are renewable energies?

Renewable energy comes from natural sources, such as the wind, sun, rainfall, waves, tides, and geothermal heat.

Renewable energies are unlimited and can provide continuous, clean power without negatively impacting our environment. Renewable energies can be used to complete all the same functions as traditional fuels.

What can I do to help?

There are so many things you can do, starting today!

Try to use less energy in your everyday life by being more energy-efficient. This could include doing any, or all, of the following:

  • Drive less by walking, cycling, or using public transportation more.
  • At work, try to set up teleconferences rather than traveling to off-site meetings.
  • If you fly, offset the carbon dioxide from your flight by donating money to organizations that use it to plant trees and undertake other activities that capture the same amount of carbon that your part of the flight emitted.

You can make your home more energy-efficient by:

  • Improving wall and roof insulation
  • Keeping the thermostat below 70°F (21°C) in winter and above 75°F (24°C) in summer
  • Blocking draughty windows and doors in winter
  • Using shades to block the sunlight from south-facing windows in summer
  • Purchasing energy-saving appliances
  • Turning lights and equipment off when you are not using them

Check if your electricity supplier has a green-energy tariff that you can switch to. If they do not, try to find a supplier that does. These tariffs guarantee that the electricity you are being provided comes from renewable sources.

You can do the same with your gas supplier so that the gas you are provided comes from renewable sources like biomethane rather than from fossil fuels.

Plant a tree or three! Over 40 years, a tree can absorb one ton of carbon from the atmosphere.[85] With over 7.4 billion people in the world, imagine the impact if everyone planted just one tree.

Chapter 5: Rubbish and Other Wastes

Dump truck emptying rubbish and trash into ocean

We humans produce a lot of waste. The average American throws away four and a half pounds of trash every day.[86] That is 0.8 tons a year, which is about the same weight as a fully grown male grizzly bear!

In developed countries, the majority of the waste we dispose of is managed responsibly and ends up in landfill sites, waste incinerators, or in the best case, is recycled back into a usable material again.

However, lots of trash never makes it into a bin, or it escapes from waste management facilities. These waste materials can cause lots of problems in our marine and land environments.

And in developing countries, waste can be an even bigger problem. Many trash collection companies illegally dump waste or manage it incorrectly in vast open landfill sites. And factories dump thousands of tons of harmful waste chemicals into waterways, where they poison the rivers and pollute our seas.

This section looks at some of the main forms of waste that can have dangerous effects on our oceans and the creatures that live in them.

1. Plastics

Plastic trash

Plastic is the go-to material of the 21st century. The first fully man-made plastic was only invented in 1907,[87] and now over 300 million tons are produced every year to make pretty much anything![88]

And, the growth in its use is startling, which has increased twenty-fold in the past half-century and is predicted to double again in the next 20 years.[89]

Plastic was initially seen as a miracle product because it was light, cheap, could be molded into any shape, and lasted without breaking down for a really long time.

One of the environmental problems with plastic is what initially made it seem so special – it takes a really, really long time to degrade. One study estimates that it would take a regular plastic bottle 450 years to completely break down in a landfill! If you throw a bottle out today, it will still be around in the year 2460![90]

Plastic debris was first observed in the oceans back in the 1960s.[91] This was partly what caused plastic producers to develop recycling facilities. But as of 2017, only 9 percent of the world’s plastics actually get recycled.[92]

How does plastic harm our oceans?

We have seen the effects of large pieces of plastic in our oceans for many years: pictures of marine animals tangled in plastic drink holders and discarded fishing nets, turtles with plastic straws wedged up their nasal canals, or seabirds with their stomachs full of large pieces of plastic.

Loggerhead sea turtles mistake plastic bags for jellyfish, their main food source. Albatrosses mistake plastic pellets for fish eggs and feed them to their chicks, which then die from ruptured organs or starvation.

Seals and other marine mammals become entangled and drown in abandoned plastic fishing nets, which often are discarded because they are so cheap to buy.[93]

When plastic debris collects together, it can block out the sun’s light from the phytoplankton beneath them. These microscopic marine algae get their energy from the sun, absorbing carbon dioxide and producing oxygen. If they cannot get enough sunlight, the oxygen levels of the waters may fall.

Phytoplankton is also at the very bottom of thousands of marine food chains. If the plastics reduce their productivity, this will have an adverse effect on a wide range of sea creatures that rely on them as their food source, from tiny shrimp to giant whales.

With the rate that plastics are entering our seas, combined with how long plastics last, this problem is rapidly becoming a huge threat to ocean health.

It is calculated that 10 to 20 million tons of plastic end up in our oceans every year. A recent study estimated that there are 5.25 trillion plastic particles, weighing over 250,000 tons, currently floating in the world’s oceans.[94]

In some parts of our oceans, currents bring the plastics together into giant ‘garbage patches.’ The largest, the Great Pacific Garbage Patch, is made up of two separate areas: the Western Garbage Patch off the coast of Japan and the Eastern Garbage Patch between Hawaii and California.[95]

The Eastern Garbage Patch covers an estimated surface area of 0.6 million square miles (1.6 million square kilometers), making it twice the size of Texas.[96]

Facts and Stats

1) Scientists estimate that 90 percent of seabirds’ stomachs will contain plastics.[97]

2) Because of bad waste management and illegal dumping, about 1 dumpster-load of plastics enters our oceans every minute![98]

3) By 2050, if significant changes are not made, there will be more plastic in our oceans than fish (by weight).[99]

4) Single-use plastics make up 40 percent of European plastic production.[100]

What is being done to solve this problem?

Plastic bags, bottles, straws, and other rubbish floating in ocean

An organization called The Ocean Cleanup has developed a floating platform to clear out the Great Pacific Garbage Patch. Using floating screens and anchors, the system is designed to gather plastic from the surface of the ocean and hold it until it can be collected.[101]

Many not-for-profit organizations are campaigning for bans and reductions in the production and sale of single-use plastics. Friends of the Earth has created a campaign to pressure supermarkets to find alternatives to single-use plastics for wrapping food.

Some manufacturers are developing biodegradable plastics. There are two types currently on the market: plant-based or oil-based. One of the most common plant-based bioplastics, polylactic acid (PLA), is made from cornstarch.

PLA takes up to 90 days to degrade. This is four times faster than a plastic bag degrades when floating in the ocean.[102] And because it is plant-based, it is fully biodegradable, safely breaking down into water and carbon dioxide.[103]

Some countries have deposit return schemes, giving the consumer a small refund when they return their packaging materials for them to be recycled. However, companies like Coca-Cola have pressured governments not to go ahead with these programs because they think it will make people buy less of their product.[104]

A few governments are working to apply taxes and bans on certain single-use plastics. After the UK added a tax on the sale of single-use plastic bags, usage fell by 90 percent.[105]

What can I do to help?

Try to recycle everything that you can, washing your bottles and containers before putting them in the recycling bins. Make sure to check what you can and cannot recycle in your area so that you do not contaminate the recycling. For example, there are loads of different types of plastics, but only a few are acceptable for most municipal recycling centers.

Take a few canvas or multi-use bags with you when you do your grocery shopping. This way you will not have to pay for single-use plastic bags, and you will help to cut down on one of the most polluting types of plastic.

When you buy food at the grocery store, try to buy loose rather than in plastic shrink-wrap. If you see items that definitely do not belong in plastic wrapping, take a photo and post it to your social media account, tagging the offending company and using the hashtag #PointlessPlastic. What is the craziest thing you can find? Can you beat a shrink-wrapped apple that has been cut into slices?

Ask your shops what they are doing to reduce the amount of plastics they use – consumer power can be an incredibly potent force for making a positive impact!

If you see a coke bottle littering the street, beach, or sea, take a photo of it and tag @cocacola, using the hashtags #CocaCola, #TasteTheFeeling, #EndOceanPlastics, and #DontChokeOurOceans. Then, if you can, pick up the bottle and put it in the nearest recycling bin.

Take part in a beach clean!


A pile of microplastics

What are microplastics?

We have looked at the problems that plastic can cause in its original form, but in the ocean, it can break down a lot faster than it does in landfills.

Sunlight and the movement of the sea break plastic down into tinier and tinier pieces, until they become what we call microplastics.

In addition to coming from broken down pieces of plastic waste, ocean microplastics also come from plastic ‘microbeads’ and ‘microfibers,’ so we will look at both of those as well.

How prolific are microplastics?

Microplastics have been found almost everywhere on the globe.

  • Studies of bottled water found that 93 percent of bottles from the top water brands contained microplastics.[106]
  • Ocean creatures at the bottom of the Mariana Trench, the deepest and most untouched place on the entire planet, were found to have microplastics in their guts. This is at depths of 36,000 feet (11,000 meters)![107]
  • In 2018, record levels of microplastics were found in the Arctic sea ice, as many as 45,000 microplastic particles per gallon (12,000 per liter) of ice.[108]

How do microplastics harm our oceans?

Microplastics floating in ocean

Researchers in Japan found that plastic in warm ocean water can degrade in as little as a year.[109]

These tiny pieces of plastic contain toxic chemicals like bisphenol A (BPA), which is added during the manufacturing process to make them more flexible, durable, and transparent. As they decompose, plastics can release these toxic substances into the water.

As well as actually containing toxic chemicals, scientists are also concerned that microplastics are able to pick up other toxic compounds found in the sea and transfer them to the organisms that eat them.

Zooplankton and other small marine organisms at the bottom of the food chain can mistakenly eat the microplastics. The contaminants then pass up through the food chain becoming more concentrated at each level. This puts large marine predators like dolphins, killer whales, and tuna at risk of high concentrations of toxins.

Researchers investigating the deaths of baby dolphins found high levels of toxins in their tissues, which they believe had been passed to the baby through the mother’s milk. Another study found that a dolphin’s first baby received up to 80 percent of their mother’s toxic contaminants through her breast milk and placental transfer.[110]

It can also be dangerous for humans when we eat large marine species like tuna and swordfish. The toxins present in microplastics, and found in the tissues of these fish, have been linked to reproductive, developmental, and hormonal problems in humans.

A recent study also found that when zooplankton ate microplastics, their feeding rate slowed down, and they became less healthy. Many zooplankton are the young of larger fish, so if their health is impacted, fewer juveniles manage to grow into healthy adults, which in turn reduces the size of fish populations.[111]

Because zooplankton is at the bottom of many marine food chains, a reduction in productivity and numbers could also have a significant effect on other marine creatures that rely on them as their food source.

Why do organisms think these tiny pieces of plastic are good to eat?

Scientists think that zooplankton eat the microplastics because they are the same size as their normal food sources like fish eggs and phytoplankton.[112]

Fish may actively seek out microplastics in the oceans because the microplastics pick up a covering of algae that releases a really similar smell to their natural food.[113]

The study found that the fish ignored clean plastic, suggesting that the fish were responding to what they smelled, not what they saw.[114]

In this way, microplastics and their contaminants enter the food chain. The zooplankton and small fish are eaten by other fish, crustaceans, and marine animals. Larger creatures then eat these animals, and at each stage, the polluting effect of plastic is concentrated in the tissues of the animals.

Plastic Microbeads

Microbeads in bowl

What are plastic microbeads?

Plastic microbeads are used by the cosmetics and personal care industries to give products ranging from toothpaste to shower gel an abrasive or exfoliating effect. They have also been added to gels and lotions to act as a cheap filler material to increase their volume!

How do they end up in our oceans?

Because they are so small, microbeads can pass down our drains when we wash with them, and then through wastewater treatment plants without being caught by their filters. From there, they end up in our waterways, which run out into our seas and oceans.

New York State recently inspected a number of their wastewater treatment plants and found that microbeads were present in the water leaving 73 percent of the plants they sampled.[115]

Facts and Stats

1) 2,400-8,600 tons of microbeads enter the European seas every year. That is almost as heavy as the Eiffel Tower![116]

2) A microbead measures between 0.1μm (1/100,000th of a meter) and 5mm – that means that some are so small that we cannot even see them!

What can be done to protect our oceans from microbeads?

In 2015, the US was the first country to sign a bill, called the Microbeads-Free Waters Act, to ban microbeads. Shortly afterward, Canada signed a nationwide ban on the use of microbeads in personal care products, although it did not actually take effect until January 1, 2018.[117]

At the start of 2018, the UK government banned the manufacture of cosmetics and healthcare products containing plastic microbeads.[118]

Many other countries are planning to ban the manufacture of microplastics, but it needs to happen faster, and there are still lots of other countries that have not made any steps yet.

Some brands have joined the campaign Look for the Zero, which was established by the organization Beat the Microbead. But again, there are lots of brands that need to step up their game. Maybe they need to feel a bit of consumer pressure!

What can I do to help protect our oceans from microbeads?

There are some cool apps that you can download, like Beat the Microbead 3.0 so that you can scan your products to see if they contain microbead ingredients.

Look out for beauty products that have the label “Look for the Zero.” This means that they do not have any microbeads in them.

Plastic Microfibers

Pile of microfibers

What are plastic microfibers?

Plastic microfibers are tiny strands of plastic, measuring 50μm to 15mm in length and around 10μm in width – so they are pretty tiny![119]

They come from man-made materials, like polyester, acrylic, and nylon, which a lot of our clothes are made from.

Where do plastic microfibers come from?

During the washing process, all clothes lose fibers. They break free from the garment’s structure when the clothes are whirled and knocked around in the washing machine.

Because these fibers are so small, they pass through the washing machine’s filters and out into the sewers. Then, when they get to the wastewater treatment facilities, most of the fibers manage to pass through their filters too.

The water containing these microfibers then leaves the treatment plants, running into waterways and then into our oceans.

What makes plastic microfibers more harmful than natural fibers?

All materials release microfibers when they are washed. The difference with plastic microfibers from man-made materials, compared to natural microfibers like cotton and wool, is that the plastics do not biodegrade in the environment.

Instead, just like other microplastics, these fibers can bind with toxic chemicals and pollutants in the wastewater.

Facts and Stats

1) More than half of our clothes are made from man-made (synthetic) materials.[120]

2) An average load of laundry can contain more than 1,900 fibers of microplastics.[121]

3) 1 in 4 fish sampled at a California fish market contained microfibers.[122]

4) A single fleece jacket can shed up to 250,000 microfibers during a single wash.[123]

What is being done to protect our oceans from microfibers?

Microfibers floating in ocean

The clothing industry has recently started to wake up to the threat that man-made fabrics are having on the environment. Outdoor clothing manufacturers are particularly incentivized to act because clothes like fleece jackets are some of the worst culprits for shedding plastic microfibers.

And since their brands are often built around allowing people to enjoy nature and the great outdoors, public awareness of the negative impact that their clothes have on the environment is not good marketing!

Scientists are also carrying out their own studies, independent of the clothing industry. These studies are particularly important to help us understand the scale of the problem and the severity of the potential impact to the ocean environment. The results are not always in the interests of the clothing industry, so their independence is crucial.

Some scientists are studying the conditions and material types that cause the most microfiber shedding so that they can find ways to reduce it. They are also researching new fabrics that create fewer microfibers and that emit fewer toxins.[124]

Entrepreneurial companies are trying to tackle the problem by designing tools to catch the microfibers before they leave your washing machine. One such invention is the GuppyFriend microfiber catching bag, which you stick all your man-made fibers in before washing.[125]

There must also be innovative responses from washing machine manufacturers and wastewater treatment plants to develop filters capable of catching the microfibers. This is fundamental to solving the problem because we cannot rely entirely upon individuals to make changes to the clothes they buy or how they wash them.

What can I do to help protect our oceans from microfibers?

Wash clothes in colder water when possible – the hotter the water, the more damage that is done to your clothes and the more fibers that are released.

Use liquid detergent instead of powder. Liquid detergents are less abrasive, meaning that fewer microfibers are released from your clothes. And try to wash only full loads because this creates less friction between the clothes, also releasing fewer fibers.

Only wash your clothes when they really need it. The less often you wash them, the fewer microfibers will be released into the wastewater.

Try to buy clothes that are made of sustainably produced natural fibers – like cotton, wool, rayon, hemp, and silk.

Try using a washing machine bag to capture the microfibers from your clothes.

When you clean out your washing machine or dryer filter, put the lint in the trash, not down the sink or toilet.

Cigarette Butts

Cigarette butts in ash tray

Cigarette butts are the most common form of litter in the world.[126] After they are stubbed out and flicked onto the street or in the park, around 80 percent of butts find their way into our waterways after it rains or the snow melts, depending on where you live in the world.[127] From there, the next stop is for them to flow into our oceans.

And when people go to the beach, not everyone is considerate enough to put their cigarette butts in the bin.

How do they harm our oceans?

Scientists have found that cigarette butts leach small amounts of toxins that could potentially threaten ocean ecosystems. Cigarette tobacco and filters can introduce as many as 4,000 different toxins into the marine environment.

One study found that when a cigarette was soaked in water, it released enough toxins to be poisonous to both marine and freshwater fish in the water. They found that the cigarettes were most toxic when they still had some tobacco in them.[128]

There are many potential causes for the toxicity, such as:

  • The nicotine that is present in the tobacco,
  • The chemicals and fibers that are used to create the filter, and
  • The pesticides that are used to treat the tobacco plants.

Facts and Stats

1) Two-thirds of the 6 trillion cigarettes smoked worldwide every year are dropped or flicked into the environment – around 750,000 tons in total.[129]

2) Cigarette waste makes up roughly 30 percent of the total litter – by number of items – on US shorelines, waterways, and on land.[130]

What is being done to stop it?

The US company TerraCycle has developed a cigarette recycling process, which is free to join and participate in, if you live in the US, Canada, Australia, or Japan. As well as extinguished cigarettes and filters, they also accept the plastic and foil packaging, rolling paper, and ash.

Once collected, the cigarettes and packaging are separated and melted into hard plastic that can be remolded to make recycled industrial products, like plastic pallets. The ash and tobacco are separated out and composted.[131]

Some cigarette manufacturers are experimenting with biodegradable filters, but many environmentalists recommend that the filter be removed from cigarettes entirely. This is because they are concerned that cigarette butts with biodegradable filters would still leach toxins from the tobacco, while making smokers think that they were protecting the environment.[132]

What can I do to help?

If you smoke, make sure that you always safely dispose of your cigarette butts. If you are on the beach or outside in a place where there are not many bins, a portable ashtray is a really handy solution to be sure that you never have to litter.

Take part in a local beach clean. It can be startling to see how many cigarette butts and other plastics that wash up on our shores, which helps to remind us of the importance of safely disposing of all of our trash.

If you live in one of the countries where TerraCycle works, why not sign your workplace or local community up to a cigarette waste recycling scheme? It is free to participate!

Chewing Gum

Mouth chewing gum

Chewing gum was originally made from a rubbery tree sap, but most modern chewing gums are now made from a synthetic, rubber material.[133] The problem is that this does not biodegrade after you finish chewing it.

And where does the majority of chewing gum end up? Well, it is the second most commonly littered item, so you can safely say it does not always end up in the trash can.

How does it harm our oceans?

If gum is flushed down the toilet or thrown into rivers or the sea, then your used gum could potentially end up being eaten by fish.

Facts and Stats

1) 100,000 tons of gum are chewed every year, and about 80 percent does not get put in a trash can.[134][135]

2)In Singapore, chewing gum is banned unless you have a doctor’s prescription.[136]

What can be done to stop chewing gum from being littered?

A British designer has created the company Gumdrop to recycle used chewing gum.

They have created receptacles for people to drop their old gum into. The gum waste is then collected and combined with other plastics to make a compound called Gum-tec, which can be used to make mobile phone covers and coffee cups.

A few companies are developing biodegradable chewing gum from a natural rubber base. This gum will break down naturally over time.[137]

What can I do to help?

When you have finished with your gum, do not throw it on the street or into waterways. If you are not near a trash can at the time, simply wrap it in some paper and throw it in the next one you pass.

Make the switch to biodegradable chewing gum.


Applying sunscreen lotion to arm on beach before swimming

Although it is not a classic ‘waste’ in the fact that we do not actively throw it away, the sunscreen we apply to our skin to protect ourselves from the sun’s UV rays eventually comes off our bodies and runs into the water. That can be either when we bathe after using it, go for a pee, or when we apply sunscreen and then go for a swim in the sea.

How does sunscreen harm our oceans?

Sunscreen pollution threatens coral reefs around the world, from the Red Sea to the Caribbean. Anywhere humans enter the water around a reef, there is a risk of contamination.

Sunscreen does not just get into the oceans when it washes off swimmers’ skin. Many sunscreen ingredients are also absorbed through the skin. For example, oxybenzone, one of the most common UV-blocking chemicals in sunscreen, can be found in urine 30 minutes after it has been put on the skin.

When you flush the toilet or wash off sunscreen in the shower, chemicals from the lotion run down the drains and into the sewer system. In many tourist areas that lack sophisticated sewage treatment systems, pollution is hard to avoid.

A study found that oxybenzone increased the risk of coral bleaching by lowering the temperature at which corals bleach. It was also found to genetically damage the coral, sometimes causing severe deformities. The study also found that oxybenzone can cause the coral larvae, the young coral, to surround itself in skeleton too early, limiting its ability to grow.[138]

These effects were found to occur even when the concentrations of oxybenzone in the water are lower than those found at many popular reef locations.

And, oxybenzone is toxic to sea urchins, fish, and mammals. It slows down the development of sea urchin embryos, can cause male fish to take on female attributes, and female fish to produce fewer eggs.

In mammals, it has been shown to potentially cause genetic abnormalities and to increase the risk of cancer. Dolphin mothers can transfer oxybenzone to their infants through their breast milk.

Facts and Stats

1) An estimated 4,000-6,000 tons of sunscreen is washed into coral reef areas every year.[139]

2) 90 percent of snorkeling and diving tourists are concentrated on 10 percent of the world’s reefs.[140]

3) The European Chemicals Agency has listed 8 out of the 16 most commonly used sunscreens in Europe as a potential threat to the environment and health.[141]

What can be done to stop sunscreen from harming our oceans?

Some manufacturers are making reef-safe sunscreens that do not contain reef-damaging ingredients. Biodegradable sunscreens are better too because their ingredients do not build up to poisonous levels in marine organisms.

Some eco-reserves where coral reefs are most vulnerable to harm have banned the use of products that contain reef-threatening ingredients. For example, Mexico’s eco-reserves Xcaret and Xel-Há have banned these substances for over 10 years.[142]

The US National Park Service is running an educational campaign to help people understand the risks of sunscreen and what they can do to help, calling for people to “Protect Yourself, Protect the Reef.”[143]

Scientists are carrying out important studies to understand more about the effect of sunscreen on reefs and marine organisms. Typically, the studies that you can trust are those that are not funded by the sunscreen industry!

What can I do to help?

This does not mean to stop using sunscreen! Protecting the skin of you and your family from the sun is incredibly important, and sunscreen plays an important role.

Instead of slathering lotion all over your body, why not try using a UV-protecting swimsuit, rash guard, or long-sleeved shirt. Applying lotion to only the neck, face, feet, and backs of hands can reduce the amount of sunscreen in the water by 90 percent.[144]

Hats, umbrellas, and tents also make great ways to protect your skin from the sun’s powerful rays.

Check out this guide to over 200 reef-safe sunscreens. Spending your money with environmentally conscious companies helps to shift the market toward more sustainable and safe products.

Sign the Environmental Working Group’s petition that demands that manufacturers remove oxybenzone from their sunscreen products by 2020.


Sewage flowing from pipes into ocean

The other waste that humans create, but that we do not like to talk or think about, is our own. When you consider that there are over 7 billion people on the planet, that is an awful lot of urine and feces.

What should happen to sewage?

In developed countries, most people are lucky enough that their homes and workplaces are connected to sewer systems. After you flush the toilet, the water runs into sewer pipes where it joins with other wastewater and often rainwater.

And, this all runs to a wastewater treatment plant. From here, the water is monitored, filtered, treated for dangerous microorganisms. The water is then disinfected before it is ready to be pumped into rivers and then out to sea.

How does raw sewage end up in our oceans?

Developing countries also have sewage facilities, but a larger proportion of their populations are not connected to them, or the sewer networks and plants are unable to cope with the amount of waste produced. Then, the raw sewage passes straight into our waterways and out to our oceans.

Even in developed countries, existing wastewater networks can be old or in poor condition. This can cause untreated wastewater to leak or overflow into waterways during storms and heavy rainfall.

How does raw sewage harm our oceans?

Raw sewage is a major pollutant in our oceans, acting in a number of ways.

1. Nutrient enrichment

Algae floating on surface of ocean

When raw sewage enters our oceans, it makes the nutrient levels in the local environment higher than they should be.

If nutrient levels increase even slightly, it can cause plants and algae to grow faster than normal. On a reef, there is a constant battle between coral and seaweed for space and light. Extra nutrients in these waters can tip the battle in favor of seaweed so that it takes over the reef and suffocates the coral.[145]

When nutrient concentrations become really high, they can cause a phenomenon called an algal bloom. This means that populations of microscopic algae dramatically increase. These blooms generally occur in shallow coastal regions where the untreated sewage enters the sea.

A small percentage of algal blooms can be toxic to marine life, threatening the health of fish and other creatures like dolphins and whales. It can also be potentially harmful to humans when we swim in the water, come into contact with it, or eat contaminated shellfish.

2. Dead zones

Dead zone in ocean where no fish or plants can live

After raw sewage enters our oceans, microbes start to break it down in a process that uses up oxygen from the surrounding water. If the amount of sewage is significant, then this process can take so much oxygen from the water that there is not enough left for fish and other marine animals to survive. This can create an area of water near the seabed where nothing can live, called a dead zone.

Dead zones can also occur after an algal bloom when the algae to start to die off in their billions. As they die, they fall to the seabed, where the same oxygen-consuming microbes break them down.

In the oceans, dead zones caused by untreated sewage are growing rapidly in size and number. It is estimated that they are now affecting 95,000 square miles (246,000 square kilometers) of marine ecosystems, putting food chains, fisheries, and fisher’s livelihoods at risk.[146]

3. Disease

Diseases spreading through ocean

Raw sewage can also contain disease-causing microorganisms, which pose a health risk to swimmers and people who eat contaminated shellfish.

Facts and Stats

1) As of 2017, 2.3 billion people did not have access to a toilet or latrine.[147]

2) Of these, 892 million still go to the toilet in the open, for example in street gutters, behind bushes, or into open bodies of water.[148]

3) Globally, over 80 percent of wastewater runs into the environment without being treated. In developing countries, this can be over 95 percent.[149]

4) A single mature tree can keep 4,600 gallons of water out of the sewer each year.[150]

What can be done to stop raw sewage from entering our oceans?

Sewage pipes with cork preventing waste from flowing into ocean

Because rainwater often mixes with human waste in the sewer systems, facilities can become overwhelmed during storms and heavy rainfall. This then leads to untreated sewage getting into our waterways.

Planting trees and restoring wetlands can increase the capacity of sewer systems because more of the rainwater can be absorbed into the ground and tree roots before reaching the sewers.

One of the UN’s Sustainable Development Goals is to ensure that everyone in the world has access to toilet facilities and clean water by 2030. Governments are working with non-profit organizations to provide better toilet facilities and improve public awareness so that no one has to go to the toilet outside.

Around the world, some forward-thinking entrepreneurs are coming up with ways to turn our human waste into a valuable resource.[151]

Some of these uses include:

  • Making fertilizer
  • Converting it into a fuel
  • Growing plants in the sewage drying beds
  • Breeding catfish in the sludge treatment ponds
  • Drying out sludge and adding it to building materials to make bricks
  • Using fatty acids in sludge as ingredients for bioplastics and industrial chemicals
  • Compressing the larvae that feed on feces to make oil for industrial uses

What can I do to help?

Do you have a roof that you could convert into a green roof? Green roofs capture rainwater, reducing the amount that runs into our drains and putting less pressure on our local sewage systems. Plus they are great environments where bugs and bees thrive.

Plant a tree or two! Trees reduce the impact of heavy rainfall by absorbing water that could otherwise cause flooding.

If you are laying a new driveway, try using permeable paving. This allows water to seep into the ground when it rains, rather than running off the paving and straight down the drains.

If you have a septic tank, have it inspected annually and pumped out every two to five years. Do not plant trees or other plants with deep root systems in the drain fields because they might damage the tank and pipes.

Chapter 6: Offshore Oil and Gas Drilling

Offshore oil rig drilling for oil in ocean

Eighty percent of all the energy we use globally, including for transportation, electricity generation, and heating and cooling, still comes from fossil fuels. While coal is mined on land, oil and gas reserves are often found deep under the seabed.

Finding new oil and gas reserves, drilling for the fuels, and transporting them around the world can all potentially harm our oceans and the plants and creatures that live in them.

Oil and Gas Exploration

Using seismic blasting to search for oil in ocean

What is oil and gas exploration?

To find new sites for oil or gas drilling, exploratory companies have to complete something called a seismic survey to find the reserves, which could be buried deep beneath the seabed.

Towed behind ships, seismic airguns shoot loud blasts of compressed air, creating sound waves that travel through the water and miles into the seabed. The reflected sound provides them with information about the location of oil and gas deposits.[152]

These blasts are repeated continually, and the surveys can last for many days and weeks.[153]

How do seismic surveys harm our oceans?

When marine mammals are exposed to the loud noise of the airguns, they can suffer temporary or permanent hearing damage.[154]

A study found that baleen whales could suffer temporary hearing loss, even when they were several kilometers from the blast.[155]

The noise of the surveys also makes marine mammals leave the survey area. A study of fin whales in their Mediterranean feeding and breeding habitat discovered that they avoided seismic survey areas and stayed away for an extra two weeks after the noise ended.[156] This can reduce their ability to feed or could force them to have their babies in a less safe place.

Airguns also raise the background noise level, drowning out the animals’ communication and navigation signals.[157] This makes them less able to hunt as a group and locate their prey, and it also increases the risk of strandings.

The final risk to whales and dolphins is the stress that the noise puts the animals under. There is evidence of long-term stress from seismic survey activity causing physiological and reproductive problems in these animals.[158]

Fish, squid, and other creatures have been seen to suffer similar effects, as well as suffering from developmental problems and lower hunting success.[159]

Even marine creatures as tiny as zooplankton can be affected by the blasts. A study found that following an airgun explosion, the number of dead zooplankton in the sample area was two to three times higher than before a blast.[160]

Facts and Stats

1 ) The sounds of an airgun can be detected up to 2,500 miles (4,000 kilometers) away.[161]

What can be done to stop the damage of seismic surveys?

By using better technology, noise levels can be dramatically reduced. Instead of using airguns to map the seafloors, some scientists recommend the use of a new technology that is already used on land. This emits a small amount of sound energy over a long period of time rather than a large amount of sound energy over a short period of time. Studies show that in some locations, the noise produced would be much less harmful to marine life.[162]

Bubble curtains are also being tested to see how they can block the sound from leaving the working area, acting as a sound barrier.[163]

Scientists recommend that information about where and when important species are breeding, spawning, and feeding should be used to work out when it is safe to do the seismic surveys.

The European Union has proposed putting limits on overall noise emitted from surveys, and Norway has established a system where when one survey is completed the results are shared with multiple clients. This prevents several companies from conducting their own surveys in the same area, reducing the total impact.[164]

Oil Spills from Pipelines, Rigs, Refineries, and Tankers

Offshore oil rig leaking oil into ocean

How do these oil spills happen?

When we explore for new oil reserves, extract the oil and gas, and then transport it, leaks and spills can occur. Natural catastrophes like hurricanes can also sometimes destroy oil platforms and damage pipelines.[165]

Most oil spills are relatively small, but sometimes they can be huge, coming from blowouts or shipping accidents involving loaded oil tankers.

And because we have already developed oil fields in the easy-to-reach parts of the world, companies now have to explore more remote and challenging places to find new opportunities. To get the oil out from such deep and difficult locations requires new technologies that can carry with them even greater risks.

What is the risk of oil spills to our oceans?

When an oil spill occurs in our oceans, it is almost impossible to completely contain and clean up. The environment can then take decades to fully recover.

Crude oil, the type that is extracted from under the seabed, is thick but not as dense as water. In an oil spill, it floats on the surface, creating a ‘slick’ that spreads quickly with the actions of ocean currents and winds. Some of it evaporates and some dissolves into the water. Some sinks to the seabed, forming sticky tar balls that can wash up onto beaches for years after the spill.

Marine birds can be covered in oil if a spill occurs where they live and feed. Seabirds’ feathers keep them warm, so when these get covered in oil, this can cause the birds to die of hypothermia. When they preen themselves to try to clean the oil off their feathers, they can also swallow the oil, causing illness or death.

Marine mammals that have thick fur coats to keep them warm are also vulnerable. When the fur of an otter or fur seal becomes covered in oil, it can no longer warm the animal, which will then die of hypothermia.

The small percentage of oil that dissolves into the water can affect fish and other creatures, such as zooplankton, that live there. Some creatures are able to avoid the oil by leaving the affected area, but others, like zooplankton, may be hurt or killed by the oil. Studies have also shown that the dissolved oil causes more fish eggs and larvae to die.

Although crude oil itself is not particularly toxic, the chemicals that are sprayed on it to break it down, called dispersants, can make it much more harmful. A recent study found that when the oil and dispersant interacted, the oil became 52 times more poisonous to some zooplankton.[166]

Offshore drilling in the Arctic

Drilling for oil in the Arctic - oil rig surrounded by ice

Conservationists are now concerned about plans to lift government bans on offshore drilling in the Arctic.

Conditions in the seas off the Arctic are particularly harsh, with severe weather conditions and lots of floating ice that could damage rigs and pipelines. Because the Arctic is so large and remote, it would also make it very hard to respond quickly enough if a spill did occur.

There is still no technology that can clean up oil in icy sea conditions. This means that spills late in the season would remain in the ice until the following year.

Cold water also breaks oil down much slower than warm water, meaning that it would remain in the environment for many more years than from an oil spill in warmer waters like the Gulf of Mexico.[167]

The oil tanker Exxon Valdez sank off the coast of Alaska and spilled 11 million gallons of oil, and the effects were still being seen on the shoreline 25 years later.

The previous head of the Arctic Council’s Emergency Prevention, Preparedness, and Response working group believes that it is not a matter of “if” but “when” a spill will occur. In the event of a spill, they predict that any response will be “complicated, slow, and likely, fairly ineffective.”[168]

The Arctic is home to some of the world’s richest fisheries, lots of Ecologically or Biologically Significant Areas (EBSAs), and many of our most sensitive and protected species. Opening it up for drilling would place the entire region at risk.[169]

Facts and Stats

1) There are over 5,600 offshore oil and gas platforms in the US.[170]

2) Each year, US drilling operations spill an average of 880,000 gallons of oil into the ocean.[171]

3) At best, only 10 to 15 percent, and often much less, of the oil spilled at sea can be recovered.[172]

4) Estimates of how many animals died outright from the Exxon Valdez oil spill in Alaska in 1989 are:

  • 250,000 seabirds
  • 2,800 sea otters
  • 300 harbor seals
  • 250 bald eagles
  • Up to 22 killer whales
  • Billions of salmon and herring eggs[173]

The Deepwater Horizon oil spill

Oil spill floating on surface of ocean

In April 2010, the Deepwater Horizon oil well exploded, killing 11 people and releasing 4.9 million barrels of crude oil into the Gulf of Mexico over 87 days. It was the largest oil spill in US history and the second largest ever in the world.

Oil contaminated deep-water habitats and affected over 1,300 miles (2,100 kilometers) of shoreline and coastal habitats. The spill had a wide range of biological effects, although some of the worst-case predictions, fortunately, did not end up happening.

Salt marshes and seabird populations were badly affected, and there are continued concerns for the long-term health risks for large fish species, deep-sea corals, sea turtles, whales, and dolphins.

What can be done to stop the risk of oil spills in our oceans?

The safety record of the oil and gas industry has greatly improved over the last decade. However, accidents like the Deepwater Horizon show that as we drill in deeper and tougher environments, major catastrophes can still occur. There must be further improvements to the technology used and better safety measures to prevent the risk of future spills.

In the US, federal laws are in place to prevent oil spills. Companies that cause spills have to pay severe penalties, and there are rules for safer vessel design to prevent spills after shipping accidents.

The current US administration has overhauled how officials monitor safety procedures on offshore drilling rigs. It changed two rules that were put in place after the Deepwater Horizon spill in 2010, stating that they were “overly burdensome” for the industry. This marks a step back in environmental and human health and safety, which could have deadly consequences.

Environmental groups like the WWF are putting pressure on oil companies and governments to have tighter controls and standards for oil spill response. They are also working to ensure that where oil drilling does occur, it avoids the most environmentally sensitive areas and is done as safely and responsibly as possible.[174]

Greenpeace is calling for the creation of an Arctic Sanctuary to protect significant areas of the Arctic waters from oil drilling. As well as ensuring no exploration or drilling of fuels or minerals, it would also protect the Arctic seas from fishing, military activity, and shipping that use heavy fuels.[175]

Habitat Destruction

Drilling for oil at bottom of ocean

How are ocean habitats put at risk of destruction by oil and gas drilling?

Even before a drilling rig is installed, the marine habitat can be damaged. After the completion of seismic studies, exploratory drills are carried out to check that the oil reserves are worth drilling. This exercise uses a mobile platform to drill several temporary wells over the suspected deposit to look for signs of oil. If successful, additional wells are dug to check their findings.[176]

When a site has been confirmed, the drill rig is installed. The drill platform is fixed directly to the ocean floor using metal and concrete foundations or tethering cables. The drilling infrastructure, the drill rig, and undersea pipelines disturb the seabed and the organisms living on it.

The anchors that support the platform leave large scars on the ocean floor, causing the greatest harm in habitats with corals and sponges. These habitats are sensitive to the physical damage caused by the anchor and the sediments that get kicked up as the anchors scrape over the seabed.[177]

If shipping channels have to be dredged to allow the supply ships to access the site, this also throws sediment up, clouding the water and reducing the amount of sunlight that passes to the seabed. The dredging can also hurt marine animals and plants living on the seabed.

The material dug out from the oil well can be contaminated with a mixture of petroleum and heavy metals. The contaminated materials are discarded onsite and then settle back onto the seabed. Once on the seabed, they can be taken up by microorganisms and enter the food chain. Studies have also shown that these materials can harm cold-water coral communities either by smothering or poisoning the coral.[178]

What is being done to stop habitat destruction?

In 2017, Belize became the first country in the world to put a ban on all offshore oil exploration and drilling.[179] New Zealand followed suit in 2018 by placing a ban on all new permits for offshore oil and gas exploration.[180]

What can I do to help reduce the impact of offshore oil and gas drilling?

One voice alone might not have much impact, but together, we can make a change. If you want your voice heard, join campaigns by groups like the WWF that ask your Senators to sponsor the Stop Arctic Ocean Drilling Act.

Join Greenpeace’s campaign to create an Arctic Sanctuary to protect it from drilling forever.

Because we all rely on fossil fuels, we each share responsibility for the problems associated with oil and gas drilling. More importantly, we are jointly responsible for finding ways to solve the problem. Here are just a few things you can do to contribute to the solution:

  • Change to a renewable energy contract for your electricity and gas.
  • Drive less; walk, cycle, and use public transportation more.
  • At work, try to have more teleconferences rather than driving to external meetings.
  • Consider electric when you upgrade your car.
  • Conserve energy in your home:
    • Improve your wall and roof insulation.
    • Purchase energy-saving appliances.
    • Turn lights and equipment off when you are not using them.
    • Keep the thermostat below 70°F (21°C) in winter and above 75°F (24°C) in summer.
    • Block draughty windows and doors in winter.
    • Use shades to block the sunlight from south-facing windows in summer.
  • Take vacations closer to home or offset the carbon when you fly.
  • Reduce your consumption of things, and when you are finished with them, first try to reuse them then recycle.

Chapter 7: Surface Runoff

Surface runoff entering ocean

What is surface runoff?

Surface runoff is the water from rainfall or snowmelt that the ground does not absorb. Instead, this water flows off the land into rivers and eventually into our oceans.

As the water runs over the land, it picks up nutrients and materials on the surface. In urban areas, it runs into storm drains, where it meets with wastewater from our sewers. When all this water then reaches our oceans, it can threaten its health in a number of ways.

1. Sediments

Rain hitting ground and running off into ocean

How do sediments run off into our oceans?

Just under a third of our world is covered in forests. These natural environments are a web of roots and plant matter that hold the top layer of soil in place, trapping its richness in and protecting it from being eroded when it rains.

As our populations have grown throughout the world, we have chopped down extensive areas of forest. We use the trees to provide us with construction materials and firewood, extend our towns and cities into natural areas, and use the land to grow crops or to raise livestock.

These activities reduce the amount of water that the ground can absorb and increase the amount of sediment that the water picks up as it runs off the land.

When farmers grow crops, they almost always grow a single crop type on each field. This system of roots is not very complex, so the soil is not held in place as firmly as it was when the land was covered in forest.

When the crop is harvested, the soil can be disturbed and left bare, making it very vulnerable to erosion. When it rains, the water can pick up and take away the top layers of soil, transporting the sediments into rivers and then out to sea.

As our towns and cities grow in size, more of our land becomes covered in tarmac and asphalt. Water cannot soak into these surfaces, so when it rains, larger volumes run straight off them and into storm drains.

How do sediments in surface runoff harm our oceans?

When rivers transport large amounts of sediment with them out to sea, this can reduce the quality of water across a large area.

The fine sediments float for some time, clouding the water and blocking some of the sun’s light from passing through to the seabed beneath. This makes it harder for corals, seaweeds, grasses, and algae on the seabed to be able to photosynthesize, impacting the health of the reef or seabed environments.

When sediment levels are particularly high, they can block out so much of the sun’s energy that they kill these plants and algae, which are important sources of food for fish and other marine creatures.

When it finally does settle, the sediment can cover coral reefs, smothering the coral polyps and preventing them from being able to breathe.

Heavy metals and pesticides can attach to the sediment, resulting in them being carried out to sea with it, where their poisonous effects can enter the marine food chain.[181]

Facts and Stats

1) In the last decade, around 32 million acres (13 million hectares) of forest have been lost each year. That is the same size as the state of Louisiana.[182]

2) As a result of re-planting, the net loss of forest from 2000-2010 is about 7 million acres (3 million hectares) less than from 1990-2000.

What can be done to protect our oceans from sediment runoff?

Many countries are carrying out large-scale reforestation operations, re-planting millions of trees. This is significantly reducing the global rate of forest loss, which will help to protect the soil and land from erosion.

In Africa, 20 countries have joined forces to build a Great Green Wall across the continent.[183]

Spanning 5,000 miles (8,000 kilometers), this man-made forest of drought-resistant trees will act as a barrier against the continual spread of the Sahara Desert.

In 2017, India completed a record-breaking environmental achievement by planting 66 million trees in just one day. One and a half million people helped to make it happen![184]

Governments around the world are teaching their farmers how to reduce soil erosion on their land. Practices include planting cover crops after the main crop and reducing the amount of times they plow their fields. These practices help to hold the soil in place, protecting it from erosion.

In Queensland, environmentalists are campaigning for a 5,000-acre (2,000-hectare) area of forest to be prevented from clearing, to protect the Great Barrier Reef from being harmed by the increased sediment runoff.[185]


Plant being covered in fertilizer

Around the mid-1960s, fertilizer use started to grow rapidly as countries worried about how they would be able to produce enough crops to feed their growing populations.

The use of fertilizers, together with improved seeds and the use of artificial watering systems, helped densely populated countries like India and China to support their populations within a short period of time. This was seen as a great success.[186]

However, by the 1990s, scientists were seeing that the high use of fertilizers was causing a range of negative effects on land and coastal marine environments.

How does fertilizer runoff harm our oceans?

After fertilizer has been applied to a field, it should soak into the ground and be absorbed by the root system of the plants that it is designed to feed.

Problems occur if too much fertilizer is used, it is applied close to water sources, or it rains heavily after application. Then, some of the fertilizer may run off the land and into waterways. From there, it is transported downriver and is eventually dumped out at sea.

Fertilizers increase nutrient levels in the oceans, causing a spike in growth of plant life and algae. This sudden growth of algae, known as an algal bloom, blocks the sun’s light from reaching the seabed. This makes it harder for plants to photosynthesize, causing oxygen levels on the ocean floor to fall.

The situation is made worse when the algae die off and their bodies sink to the bottom, where microbes break them down. This further reduces oxygen levels in the local area and makes it hard for fish and other marine animals to breathe. If levels drop far enough, it creates a dead zone where no animals can live.

The number of ocean dead zones has doubled since 1990. One such dead zone appears in the Gulf of Mexico, off the coast of Louisiana each summer. It is caused by excessive amounts of nitrogen fertilizer that run down the Mississippi River.[187]

A small percentage of algal blooms can even be toxic, causing harm to fish and other marine mammals. In some cases, the toxins in these blooms have been linked to whale deaths, as the whales experience concentrated levels of toxins when they eat the fish that ate the algae.[188] Humans can also be at risk if they eat shellfish that have come into contact with toxic algae.

When fertilizers run off into the oceans, they can harm coral reefs. Reefs are delicately balanced ecosystems, with the corals fighting a constant battle for space with the seaweed and algae that grow on them. The corals are protected by fish that eat the seaweed and stop it from taking over.

But if large amounts of fertilizer enter the reef ecosystem, they encourage seaweeds and algae to grow faster. They can then take over the reefs, covering the polyps and eventually suffocating them.

The entire ecosystem then suffers, from the tiny crustaceans and fish that use the reefs for shelter and a source of food all the way up to the larger fish and marine animals that prey on the smaller animals.

Facts and Stats

1) Coastal waters represent only 10-15 percent of total sea area but support almost 50 percent of the oxygen-producing plants.[189]

2) Nitrogen levels in our oceans are still rising. By 2030, it is predicted that levels will be 14 percent higher than in 1995.[190]

3) Scientists have counted 400 dead zones around the world.[191]

4) The Mississippi River basin, the area of land from which water runs into the Mississippi, is 1.15 million square miles (3 million square kilometers).[192]

5) If fertilizer enters a river in the Wyoming Rockies, it can end up running out into the Gulf of Mexico!

What can be done to stop fertilizer pollution from entering our oceans?

The environmental protection agencies in many countries have published guidance and codes of practice for farmers to follow.

Farmers are encouraged to reduce the amount of fertilizer they use and put it on their crops at the correct time of year. Both these strategies are relatively easy for the farmer to do, do not cost them anything more, and reduce the amount of fertilizer that enters our seas.

Other things that farmers can do to reduce the amount of farm nutrients entering the water sources are:

  • Plant cover crops after the main crop has been harvested because these plants use up the extra nutrients left in the soil.
  • Plant trees and grasses on the borders of fields to filter out nutrients before they reach waterways.
  • Keep farm animals out of the waterways so that their manure does not enter the water.

A third of our croplands are used to produce animal feed.[193] If we could all reduce the amount of meat that we eat, this would reduce the amount of cropland that we need, putting less pressure on our remaining forests. It would also make more crops available to feed more people in the world, and that would mean that we would need to use less fertilizer.

What can I do to help?

If you have a garden or vegetable patch, try to follow this simple advice:

  • Only use fertilizers when necessary and at the recommended dosage.
  • Do not apply fertilizer if it is forecast to rain heavily.
  • Do not use fertilizer close to waterways.
  • Do not overwater your lawns and gardens.
  • Try planting trees and plants that are native to your area because they will need less water and fertilizer to thrive.
  • Install a rainwater tank to catch the rain off your roof – you can use it later to water your garden.

In your home, use biodegradable soaps and detergents.

When you are washing your car, use non-toxic, phosphate-free soaps – and not too much of them! Use a spray nozzle to reduce water runoff, and try to wash your car on a surface where the water can drain into the ground rather than down a storm drain.

Better still, give your car a commercial wash – these facilities must dispose of their water properly and many filter and recycle it.

Pollutants and Contaminants

Contaminated river flowing into ocean

Where do pollutants and contaminants come from?

Many human activities produce polluting metals and chemicals, such as:

  • Mining for fuels and minerals
  • Burning fossil fuels to make electricity
  • Driving and other transportation
  • Factories illegally disposing of their wastewater into rivers

These polluting materials either run directly into rivers or fall onto the land where rainwater picks them up and carries them into rivers and then out to sea.

Pesticides are commonly used on cropland to protect the plants from insects and other pests that might reduce their health and growth. However, just like fertilizer, they can also run off the fields into our waterways.

How do these pollutants harm our oceans?

Tiny particles of metals like lead and mercury gradually fall through the water, until they land on the seafloor. There, they are taken up by zooplankton, the creatures at the bottom of the marine food chain. As larger animals eat these small creatures, the metals become concentrated in their tissue. At each stage of the food chain, the concentration increases.

Scientists have found that some species of whales are absorbing such high levels of mercury and cadmium, two poisonous metals, that they are being put under toxic stress. They are trying to understand if that might be one of the causes of whale and dolphin strandings.[194]

Humans are also at the top of many food chains, so they can be at risk from heavy metal poisoning. Pregnant women are advised to limit the amount of seafood, like swordfish and tuna, they eat because of the potentially harmful levels of mercury in the meat.

Other contaminants that run off our land and affect the health of our oceans are pesticides. These are used to kill insects, weeds, or fungi that would otherwise reduce the health and growth rate of the plant that they are protecting. Many of them are not targeted, which means that they can be harmful to more species than the ones they were designed to kill.

Man-made pesticides also contain a range of poisonous materials that do not break down naturally. Like metals, these pollutants can increase in toxicity as they are passed up the food chain, until reaching levels that can cause long-term health effects for top-level predators, like tuna, dolphins, and sharks.

Old pesticides like DDT, which are still used by farmers in some countries despite being banned, are particularly bad for building up in concentration within the food chain. Newer pesticides do not do this as much.

Facts and Stats

1) More than 1,000 different pesticides are used worldwide to protect our foods from pest damage.[195]

2) Lead levels have fallen in our oceans since leaded petrol was globally banned, showing that our oceans can recover if they are given a chance.

What is being done to stop it?

Large actions can be taken to reduce the use of pollutants. In the late 1990s, governments around the world banned the sale of leaded petrol because of its long-term health effects.

Farmers can reduce pesticide use and leaks into the environment by having better pest management programs, rotating their crops to break the pests’ lifecycles, and using organic pest control measures.

What can I do to help?

Try to use organic pesticides on your garden whenever you can. This reduces the amount of harmful toxic compounds that can be released into the environment.

Be really careful not to use pesticides on areas of land that are close to waterways.

Try to use your car less and walk, cycle, or use public transportation more. Our cars burn fossil fuels and produce tiny particles that pollute the air before gradually falling down onto the land.

When you buy your next car, why not consider an electric vehicle? They produce no polluting emissions from the tailpipe, and even if they are powered by electricity from a coal plant, they still produce fewer pollutants than normal vehicles.

Chapter 8: Invasive Species

Lionfish invasive species chasing other fish and sea creatures

What are invasive species?

Invasive species are animals or plants from another region of the world that do not belong in their new environment. Once present, some of these new species can spread so fast that they cause damage to the environment, economy, or human health.

How do they get there?

There are several known explanations as to how invasive species enter a new ocean ecosystem. The most common cause is that the plants or animals are picked up in an oceangoing ship’s ballast water when a ship is in one part of the world. Then, when the ship has traveled a great distance and is unloaded of its cargo, it empties out its ballast water. Any species that were picked up are then deposited in their new home.

There are a whole host of other causes, including:

  • Intentional or accidental releases of farmed species
  • Releases from aquariums
  • The escape of live, non-native bait used to catch other fish
  • Species, like mollusks, attaching to the hulls of boats
  • Sea temperature rises from global warming, allowing invasive species to extend their range into ocean habitats where they could not previously survive
  • Species attaching themselves to plastic waste that floats on the surface of the ocean

How do invasive species harm our oceans?

Once in their new ecosystem, invasive species are able to spread rapidly because they do not have the natural predators that would normally keep their population numbers in control.

Invasive species are capable of causing the extinction of local plants and animals, reducing the variety of species in an ecosystem, and changing entire habitats. This can cause huge economic impacts and massive disruptions of ocean ecosystems.[196]

Lionfish in the Caribbean Sea and Gulf of Mexico

Lionfish invading oceans

Lionfish are native in the western Pacific Ocean and are common aquarium fish. Scientists believe that they entered US seas when people let them out of their aquariums! Because they have no natural predators in the US Southeast and Caribbean, they have spread very quickly through reef ecosystems.[197]

The fish are powerful predators of important species like snapper and grouper, and because there is nothing to kill them, they are having serious impacts on these populations. Scientists also worry that they will kill off species that are beneficial to the reefs, like the algae eating parrotfish that prevents seaweed from taking over the coral.

Facts and Stats

1) The first lionfish was reported in South Florida waters in 1985!

2) Lionfish have a sting that is poisonous to humans, so do not get too close if you see one when you are snorkeling.

Sea walnuts in the Black Sea and Caspian Sea

Sea walnut invading oceans

This stingless, jellyfish-like animal is native to the East Coast of the Americas. In 1982, it was mistakenly brought to the Black Sea in a ship’s ballast water. It then spread into the Caspian Sea.

In both seas, it multiplied and formed huge populations. The sea walnuts were a major reason why anchovy fish stocks collapsed because they fed on the same zooplankton that the anchovies ate. This then led to serious drops in the populations of dolphins and other fish.[198]

Seventeen years after the introduction of the sea walnut into the Black Sea, its predator, another comb jelly, was introduced. This caused some populations of sea walnuts to fall to low enough levels that the ecosystems were able to start to recover.

What is being done to solve this problem?

Some dive companies and local restaurants in the Caribbean and Gulf of Mexico are encouraging divers to catch lionfish and are then serving them on their menus as a local delicacy! The National Ocean and Atmospheric Administration (NOAA) is encouraging this to reduce the impact of the fish on reef communities, with the campaign “If you can’t beat ’em, eat ’em.”

Since 2004, ships have had to exchange their ballast water when they are 200 miles out at sea so that any plants and creatures in their tanks get kicked out, and cleaner water can be taken on. The problem is that a ship is normally only able to release about 90 percent of its ballast water at sea, so some organisms may remain at the bottom of the tanks.

What can I do to help?

As an aquarium owner, you can help protect your local waters from invasive species by following this advice:

  • Before you buy fish or other creatures for your aquarium, make sure to check that they will be a suitable fit for their new home.
  • Check with your shop to see if you can return anything that does not work out.
  • If you end up with an ‘undesirable’ plant or organism, do not release them into the sea, rivers, or lakes – or flush them down your toilet! Most will probably die, but a few may be able to survive and cause problems.
  • If your shop will not take them back, see if you can exchange them with other aquarists or donate them to an aquarium society or business.
  • If you have to throw away aquatic plants, make sure to seal them in a plastic bag and throw them in your trash.
  • Talk to your fellow aquarium hobbyists about the importance of following these steps to protect our waters.

If you enjoy fishing or boating, follow this simple advice:

  • When you are fishing with live bait, make sure that you only use species local to the area, called native species. Check with your local fishing supplier, who should be able to advise you on which species are safe to use.
  • Always clean your fishing gear and boots before leaving a fishing site so that you do not get any hangers-on!
  • Clean and thoroughly dry your boat before you leave the site to make sure you do not have any hitchhikers, checking for weed caught in the motor blades and mud on the bottom of the boat.

Chapter 9: Vessel Pollution

Cruise ship dumping sewage into water

What is vessel pollution?

From giant tankers and cruise ships to jet skis and motorboats, over the years we have made our oceans increasingly noisy and congested. And many of the wastes that a ship generates have been disposed of into the oceans, without much thought as to what happens to them next.

There are various forms of pollution associated with vessels that can cause harm to fish and marine animals. We will look at each of them in turn.

1. Noise Pollution

The number of motorized vessels in our oceans is incredible:

  • Over 52,000 merchant ships move goods and people from one port to the next.[199]
  • On weekends and holidays, millions of people get into their motorboats or onto their jet skis.[200]
  • There is an estimated total of 3 million motorized commercial fishing vessels.[201]
  • Over 300 ocean cruise ships carry a total of half a million passengers.[202]

This all adds up to a cacophony of noise in our oceans, which has roughly doubled every decade and is almost completely unavoidable for fish and other marine life.

The sound energy that one container ship emits into the water can be as much as 190 decibels. That is louder than the sound from a speaker at a rock concert.[203]

And sound can travel great distances in the water. Studies suggest that blue whales can communicate with each other over many hundreds of miles.[204]

How does noise from vessels harm our oceans?

Boat noises disturbing fish in ocean

Sound travels for much greater distances through water than light does. For this reason, a huge number of species of fish and ocean animals use sound to communicate with each other, find food, protect themselves from predation, or keep track of their position as they journey through our oceans.

All these marine animals can be affected by the noises that ships and boats make. As the number of vessels in our oceans increases, so too does the noise that they create. And in some places, this is drowning out the vital noises that animals are listening for.

A study of reef-living clownfish found that when they detected a predator, the younger members of the family made noises to tell their mother that they were safe, and the mother made loud, threatening noises attempting to scare the predator away.[205]

The noise generated by motorboats disrupts this natural chatter. In the case of the clownfish from the study, when a motorboat passed overhead, the noise was too great for the fish to hear each other. They stopped making their calls altogether, which made them more vulnerable to predation.

Many species of whales and dolphins hunt in groups, so the exchange of calls is essential to the success of their hunt. Vessel noise has been shown to drown out these calls, and scientists have detected that some whales are trying to make louder calls to hear each other over the noise – but they have to expend more energy to do so, which means they need to catch even more food.[206]

Noise from the propellers of large ships can also confuse whales and dolphins that use sound to understand their positions in the oceans. It is believed that this might be a reason why at times large numbers of these animals have been stranded on beaches.

Since whales also use sound to find their prey, a rise in background noise can drown out the subtle noises that they are searching for, reducing their hunting effectiveness and the amount of fish that they can catch.

Many species of whales live for over one hundred years, and noise levels have changed so much within their lifetimes that some animals cannot adapt to the changing environment.[207]

When they were born, the oceans were quiet! To protect these animals we must figure out what we can do to make them quieter again, or we risk losing these incredible animals forever.

Facts and Stats

1) A blue whale will hear a ship coming for over 24 hours as it travels toward it.[208]

2) The movement of the ship’s propeller through the water causes most underwater noise.[209]

What can be done to reduce noise pollution from vessels?

The good news is that noise is one of the easiest forms of marine pollution to reduce. That is because unlike other pollutions that remain in the environment, as soon as you stop making noise, it is gone forever.

Scientists are recommending that governments work to create quiet sanctuaries and that shipping operators be forced to avoid whale migration routes and reduce engine noise.[210]

Some shipping companies are beginning to use new technology for quieter ships. Larger propellers spin slower, and this can make as much as a 600 percent reduction in the amount of sound produced.[211]

Ships can also reduce noise just by slowing down. In 2017, The Port of Vancouver ran a trial to see how slowing vessels down would reduce underwater noise. Background noise levels fell by almost 50 percent during the period when the speed limit was reduced to 11 knots (12.7 mph).[212]

And a recent study also found that if the loudest 15 percent of all vessels were taken out of service, it could cut total ship noise in half.[213]

In 2014, the International Maritime Organization (IMO) adopted guidelines for quieter ships, but so far, these guidelines are only voluntary. The big challenge will now be to convince shipping companies and ports to take concrete actions to reduce vessel noise.

As for recreational motorboats and jet skis, some tourist destinations are banning these from parts of their coastlines in an attempt to make the local environment quieter for marine animals.

What can I do to help?

The next time you plan to explore the coastline, whether that is near where you live or when you go on vacation, why not rent a kayak or paddleboard rather than a motorboat or jet ski?

The slower pace will allow you to soak up so much more of the life that is all around you. Without the noise of a motor to scare them away, you might find yourself lucky enough to see some wildlife up close and personal!

If you believe that we should be protecting the creatures in our oceans from noise pollution, make your voice heard! For example, the NOAA said that it received more than 85,000 public comments on their Ocean Noise Strategy Roadmap, which helped them decide what their goals should be.

If you are on vacation where whales visit, why not go on a whale watching excursion? It is incredible to see these beautiful animals up close and personal, and by supporting this industry, you will be helping to show local governments how valuable whales are – not just to our environment but also to their economy.

If you find a stranded whale, dolphin, or porpoise, report it to your local strandings network.

2. Bilge Water

Boat pumping out bilge water into ocean

What exactly is bilge water?

Bilge water is actually a mix of fresh water, seawater, chemicals, oil, sludge, and other fluids from a ship. It is found in the bilge wells of the boat, which are right at the very bottom where the two sides of the hull meet.[214]

Seawater is pumped into large ships to cool their engines. As the water moves through the system, it picks up loose oil and waste from around the engine pipes. Lots of this water collects in the bilge well of the ship. In addition, oil drips from the pipes and machinery fittings and eventually collects in the bilge well.[215] Basically, it is a pretty dirty, oily mess!

Why does bilge water end up in the sea?

Legally, it should not – at least not without having been cleaned first. Back in 1973, the International Maritime Organization (IMO), part of the UN, created a convention to prevent the pollution of the ocean environment by ships. This convention, called MARPOL, came into force in 1983.[216]

The first section of MARPOL focuses on oil pollution and says that:

  • All large ships must keep an accurate Oil Record Book that documents what happens to all oil on board.
  • All waste oil and oily water must pass through an Oily Water Separator that reduces the oil content to less than 15 parts per million (PPM) of water before it can be discharged into the sea.
  • No discharges of oily water can be made within 50 miles (80 kilometers) offshore.[217]

However, across the world, many oceangoing vessels break these international laws and empty their untreated bilge water into the sea.

In 2016, a branch of the Carnival Corporation, Princess Cruises, was fined $40 million for bypassing oil treatment systems on their vessels, deliberately dumping thousands of gallons of oil and wastewater into the sea.

The investigation found that one of their ships had been illegally discharging oily water since 2005. Similar practices had been taking place on four other Princess ships, and on one boat, the crew had been using clean ocean water to trick their onboard sensors.[218]

How is untreated bilge water a threat to our oceans?

A study of the environmental effects of the cruise line industry calculated that a typical cruise ship would generate 1.2 million gallons (4.5 million liters) of bilge water annually. Without treating, that water would contain between 290 and 2,300 gallons (1,100 and 8,700 liters) of oil.[219]

Because bilge water is a mixture of different oils, it can have a wide range of environmental impacts when disposed of into the sea, including:

  • Being toxic to plants and animals
  • Damaging coastlines
  • Covering seabirds and furry marine mammals
  • Contaminating the seabed
  • Affecting the development of fish eggs and larvae
  • Reducing the population size and health of affected fish[220]

Facts and Stats

1) Bilge water is the most common source of oil pollution from cruise ships. [221]

What can be done about it?

Both internationally and nationally, there are many laws and rules to stop vessels from polluting our oceans with oily waste. Internationally, the most important is MARPOL.

These laws have high fines for companies that break them, but the biggest problem is enforcement, which can be exceptionally hard considering the size of the oceans that vessels work in.

When large cruise operators like Princess Cruises are sued and publicly made an example of, this sends a strong message to the industry that these practices will not be accepted.

It was a junior engineer aboard the Caribbean Princess who informed authorities after he noticed that the crew was dumping untreated bilge water and then putting false readings in their records. He took photos of them in action and reported them as soon as the ship arrived at the next port, resigning from the company.

In the US, if a person informs the authorities of illegal practices like this and the company gets fined, the informant can receive up to half the fine. Informants, otherwise known as whistleblowers, are vital to helping law enforcement agencies successfully convict companies. Without them, it can be very hard to catch companies ‘in the act’ when they are carrying out illegal operations.

3. Ballast Water

Boat taking on ballast water

What is ballast water?

Large ships are fitted with ballast tanks to make them more stable and balanced. Ballast water is pumped onboard to give a boat extra stability in bad weather. For cargo vessels, it is also taken up or let out when cargo is unloaded or loaded, to balance out the weight of the cargo.

How does ballast water harm our oceans?

The greatest risk that ballast water poses to our oceans is the transportation of invasive species. In fact, that is how most marine invasive species enter their new habitats.

Ships draw in water at their loading port to balance out the weight of their cargo. When the ship arrives at its destination, it releases the ballast, along with whatever species happen to be inside, from schools of fish all the way down to microscopic organisms.

For example, the North Pacific Seastar is a starfish native to Japan, North China, and Korea. It was picked up as larvae in ballast water and transported with the ship to Australia, where it is now causing damage by eating the eggs of the endangered handfish.[222]

Invasive species can cause a lot of damage because when they are moved to a new ocean habitat, they are taken away from all the natural predators that would normally control their populations. This means that they are sometimes able to multiply at an incredible rate.

What can be done to solve this problem?

In 2017, the IMO’s Ballast Water Management Convention came into force. This convention introduced global rules to reduce the movement of potentially invasive species.

Under the Convention, existing ships will initially have to exchange ballast water at least 200 nautical miles from shore, in water at least 650 feet (200 meters) deep.

Eventually, most ships will need to install ballast water treatment systems, which will disinfect the water and make it safer to discharge.[223]

Facts and Stats

1) Each year, 45,000 cargo ships move more than 10 billion tons of ballast water worldwide.[224]

2) A single ship can draw in more than 20 million gallons (75 million liters) of seawater into its ballast tanks. That is almost the same volume as the Royal Albert Hall in London![225]

3) Seven thousand species are transferred in ballast water every hour of every day.[226]

4. Sewage

Cruise ship dumping sewage into water

Are boats allowed to dump their sewage at sea?

Vessels are legally allowed to discharge untreated sewage if they are more than 12 miles from the coast. In ports and close to shore, this is illegal, and it is unlikely that they would do so for fear of being caught.

Recreational boats are another source of sewage in the marine environment. These boats tend to stay close to the shoreline and group together in large numbers. In these areas, the effects of untreated sewage can be noticeable.

Although recreational boats often now have sewage holding tanks, they are only effective if the owner chooses to use them and if there are onshore waste disposal facilities available.

How does sewage from boats harm our oceans?

Boat sewage is the same threat to our oceans as untreated sewage from land. However, the volume of sewage waste from boats is much less, and the greatest problems are caused when it is released into shallow coastal areas.

When untreated sewage is released in shallow waters, it sinks to the seabed and gets broken down by microbes in a process that uses up large amounts of oxygen from the water.

Because sewage is rich in nutrients, another effect it can have is to encourage the sudden growth of algae in the water, leading to an algal bloom. When all of these algae die, their bodies also sink to the seabed and are decomposed by the same microbes, again using up lots of oxygen.

In small coves and protected bays where there is less wave and tidal activity, the oxygen levels at the seabed can drop so much that fish and other marine animals cannot survive. This low-oxygen area is called a dead zone.

Human sewage can also contain diseases, causing bacteria and viruses like dysentery and rotavirus. If these are detected in the water, then beaches may have to be closed and shellfish bans put in place to protect the public from the risk of disease.

Facts and Stats

1) On a one-week voyage, a large cruise ship can generate 210,000 gallons of human sewage. That is about 10 backyard swimming pools worth![227]

What can be done about it?

Large ships can only discharge sewage that has been disinfected by an onboard treatment plant, at a distance of more than three miles from land. However, they are still allowed to discharge untreated sewage when they are more than 12 nautical miles from land.[228]

In the US, the Clean Water Act requires that all recreational boats with toilets must have a Marine Sanitation Device. This is a system that stores or treats the sewage.[229]

The same Act also allowed states to create No Discharge Zones, where the discharge of both treated and untreated sewage is banned. These are areas that require more protection or have special environmental importance, like shellfish beds or coral reefs.[230]

What can I do to stop boat sewage from harming our oceans?

If you own a boat with a toilet, always use your holding tank, and then dispose of it at port waste disposal facilities (pump-out stations).

When you are in harbor, use shore-side toilet facilities rather than filling up your own tank!

If your tank fills up when you are at sea, it is illegal to discharge raw sewage into US waterways. You must go more than three miles from shore to discharge untreated waste, or you must treat the waste first.

Look out for ‘No Discharge Zones’ – it is illegal to even discharge treated sewage in these areas.

5. Cleaning Waste (Graywater)

Boat taking on water from ocean

Graywater is water from sinks, baths, showers, laundry, and galleys. This water can contain fats, oils, chemicals, bleaches, and germs that can be of harm to marine animal and human health.

How does graywater harm our oceans?

Graywater is a relatively low-level pollutant to ocean water quality, but it can be a greater problem in smaller areas like ports, marinas, and sheltered bays. This is because the concentration of graywater can become quite high, especially if lots of boats are discharging their water.

The biggest problem associated with graywater is that, like sewage waste, it contains additional nutrients. When microbes in the water break down these nutrients, oxygen levels are depleted, making it harder for fish and other marine animals to live.

The additional nutrients also tip the balance of the local ecosystem in favor of algae, allowing their populations to explode and causing algal blooms.

Facts and Stats

1) On a one-week voyage, a large cruise ship is estimated to discharge 1 million gallons (3.8 million liters) of graywater, about one and a half times more than the water in an Olympic swimming pool.[231]

What is being done to stop it?

Many marinas and harbors now have no-discharge policies for graywater, and in some US states, leaving soap bubbles on the surface of the water is a reportable pollution offense.[232]

What can I do about it?

If you have a boat, there are a few things you can do to reduce the amount of graywater you produce:

  • Use water-saving devices such as low-flow showerheads and faucets.
  • Use sink strainers to catch food waste and solid particles from running into your graywater tank.
  • Try to use shore-side shower and laundry services whenever possible.

To reduce the environmental impact of the graywater that you do produce, try to buy only biodegradable, non-toxic cleaning products.

Wherever possible, try to use port pump-out facilities for your graywater. When that is not possible, only discharge it when you are at least three miles offshore.

6. Shipwrecks

Sunken boat at bottom of ocean

How do shipwrecks harm our oceans?

When a ship is wrecked at sea, there are two major environmental risks – the material that they are carrying may spill into the sea, and the ship’s fuel may also spill.

The Sanchi oil tanker in the South China Sea

When an Iranian oil tanker sank off the coast of China in 2017, the oil spill covered an area the size of Paris.[233] The tanker was carrying around one million barrels of oil from Iran to South Korea when it collided with another vessel.

The fuel it was carrying, called condensate, is a very light form of oil that is used to make products like jet fuel.

Unlike crude oil, which can create long-term environmental problems by sinking to the ocean floor and remaining there for years, condensate is much lighter and can very quickly evaporate or dissolve into water. In the Sanchi shipwreck, that meant that the greatest environmental concern for scientists was short-term toxicity to marine life.[234]

It was hard for scientists to manage the spill and predict its effects on marine life because there had never been a spill of this size and oil type before.

Their concerns were that the poisonous chemicals in the condensate could harm plankton, fish, and invertebrate larvae on the sea surface. They predicted that fish could suffer from reproductive problems while the chemicals remained in the water and that birds and marine mammals could be harmed by exposure to the chemicals.[235]

What can I do to help prevent vessel pollution?

If you enjoy going on cruises, ask the cruise company about their environmental policies before you make your booking. Specifically, “What do you do with the waste from your ships?”

By showing businesses that this may affect your purchasing decision, you are using the strength of your money to show that their environmental practices are important to their customers.

Use Friends of the Earth’s Cruise Ship Report Card to help you decide which cruise to take, based on a ship or cruise line’s environmental and human health impacts.

Chapter 10: Port and Harbor Dredging

Digger dredging harbor sand

What is dredging?

Dredging is the removal of sediment and debris from the bottom of ports, harbors, and marinas. The sediment is cut out, dragged and scooped up, and then transferred into a container for disposal.

It is generally carried out to deepen or maintain existing facilities. In some ports and harbors, dredging must be done regularly to keep the water deep enough for boats to use. This is particularly the case where a river or ocean currents drop lots of sediment onto the seabed.

Dredging can also be carried out to:

  • Improve water drainage from a river so that flood risk is reduced
  • Maintain or deepen shipping channels
  • Build new port and harbor facilities
  • Rebuild beaches that have washed away in hurricanes
  • Remove sediments on the seabed if they are contaminated with environmental pollutants

What is the threat of dredging to our oceans?

When a section of seabed is scraped out, the biggest threat to the local marine environment comes from the sediments that this activity kicks up into the water. This occurs at the dredging (in the ports) and also where the collected sediment is dumped (out at sea).

These sediments take time to settle back onto the seafloor, and until they do, they reduce the amount of sunlight that can pass through the water to reach the plants on the seafloor. This reduces the ability of the plants to photosynthesize, which then reduces the oxygen levels in the water. The lower oxygen levels can put a stress on the fish and marine creatures that live on the seabed.

Dredging can also physically damage the seabed habitat, pulling out the seagrasses and seaweeds that were attached to it, or damaging sites where fish have laid their eggs.

A study in the Niger River delta in Nigeria found that after dredging, there was a 93 percent decrease in the populations of invertebrates living on the seafloor. There was also less variety of species than before. The scientists also found that only some of the species returned to the area after the dredging was completed.[236]

If dredging happens close to coral reefs, it can damage the reef. The kicked-up sediments may smother the corals when they settle back down. When the sediment is suspended in the water, it can reduce the water quality, lowering coral survival rates.[237]

What can be done to make dredging less impactful?

Some port authorities now work with environmental consultants to find ways to reduce the number of times they have to dredge, while still keeping the water depth they need.

New technologies to remove sediment are being explored that do not kick up so much material into the water. Some companies have found alternative uses for the sediment on land, which is less environmentally impactful than disposing of it at sea.[238]

Although many ports and harbors in the developed world are improving their dredging management practices, the harder job is to help developing countries to improve their practices. This can be a big challenge since studies have shown that the lower the average income of a country, the less the governments value and protect their environment.[239]

Chapter 11: Live Trade of Fish and Coral for the Aquarium Industry

Aquarium with fish from ocean swimming inside

Live trade of ornamental fish

Most fish kept in aquariums are from fresh water, but many aquarists now enjoy creating mini-marine reef ecosystems. These tanks contain live rock, corals, crustaceans, snails, starfish, and sea urchins, as well as a wide variety of colorful fish.

While most freshwater species are bred in captivity for aquariums, it has been harder to do this for marine species. Instead, the majority of these species are caught in the wild from the tropical seas around Indonesia, the Philippines, Sri Lanka, the Maldives, and the central Pacific Islands including Hawaii.

How does the live trade of ornamental fish threaten our oceans?

Ornamental fish are in high demand and can have a very high market value. This leads to them being caught in larger and larger volumes, threatening the sustainability of the fishery and the habitat from which they were caught.

The Yellow Tang, which currently cannot be bred in captivity, is one of Hawaii’s most targeted fish. Because of this, its population has plunged in recent years. It is estimated that fishers were taking somewhere between 2 and 10 million Yellow Tangs every year.[240]

Some fishers use highly toxic substances such as sodium cyanide to stun the fish without killing them, making them easier to catch. This is harmful not just to the fish but also to the coral habitat where they were caught. Estimates are that for every fish caught with sodium cyanide, 11 square feet (1 square meter) of coral reef is destroyed.[241]

Most of the species currently traded have large populations and can be found over wide geographic areas. This makes them quite safe from overfishing. One exception to this is the Banggai cardinalfish, which naturally occurs only in the waters around Sulawesi, an island in Indonesia.

Once the cardinalfish became popular for marine aquariums, it was quickly and heavily traded and overfished. This made it hard for individual fish to find a mate, with so few potential partners around. As a result of plummeting natural population numbers, the Banggai cardinalfish is now an endangered species. Collectors then moved the cardinalfish to new locations, where it has become an invasive species.[242]

Facts and Stats

1) There are an estimated two million saltwater aquariums throughout the US.[243]

2) The United States imports 11 million tropical fish each year.[244]

3) The Bandit angelfish sells for up to $1,200 each.[245]

4) The Yellow Tang can live for up to 40 years.[246]

5) The longest anyone has been able to raise a Yellow Tang in captivity is around 80 days.[247]

What can be done to stop this?

In 2017, Hawaii passed a bill to ban the capture and trade of wild reef fish from within the archipelago. They hope to protect their reefs from the damaging effects of this practice and to allow their fish stocks to recover.

Captive breeding does not present risks to wild fish stocks and their natural habitats since the fish are raised specifically for the aquarium industry. Because captive breeding can often be carried out closer to where the fish are sold, there are also fewer risks of the fish dying or becoming stressed during transportation.

As of 2017, breeders have managed to successfully breed 330 species of marine aquarium species, and new techniques are allowing more and more species to be added to the list every year.

Coral and Live Rock Extraction

Hand picking coral and live rock from ocean

The use of live rock, corals, and invertebrates for aquariums has greatly increased with the rise in popularity of reef tanks, and most of these are currently collected from the wild.

Live rock is made from the skeletons of dead corals that form most reefs. It is usually covered in algae and a huge variety of microscopic and larger marine organisms that live on and inside the rock. The aquarium industry also uses coral for decoration and as living components of reef fish tanks.

What is the threat of coral and live rock extraction to our oceans?

Fiji and Indonesia used to be the world’s largest suppliers of live rock and coral, with people mining them by wading or snorkeling in the shallow waters of the reef and using a hammer and chisel to break pieces off it.[248]

This practice leads to reef damage, reducing the quality of the habitat for the fish and marine organisms that live among it. Coral reefs are a vital habitat for egg spawning, make a safe nursery for young fish, and play a key role in shoreline protection and the prevention of coastal erosion. Damage to the reefs can, therefore, have serious consequences.

Facts and Stats

1) About 3,000 tons of coral are traded in the ornamental fish industry every year.[249]

What can be done to stop this?

At the end of 2017, Fiji placed an immediate ban on the harvesting, purchasing, sales, and export of coral and live rocks to protect its reefs from damage and habitat loss.[250]

International trade in hard corals is restricted by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).[251]

People are now culturing live rock and corals. To make new live rock, pieces of limestone or similar rocks are placed on the seabed, close to natural live rock. When left in the sea, the new rock slowly becomes covered in a wide variety of the same naturally occurring microorganisms, algae, and small marine creatures until it becomes live rock suitable to be harvested.

Coral can also be cultured by attaching small pieces of coral to certain pieces of rock. These are placed back into the wild or grown in tanks on land. Clippings from the new growth can then be used in the reef tanks, while the original piece of coral can be left at sea to continue to grow and be used to repopulate previously damaged natural reefs.[252]

What can I do to help?

If you are an aquarist or fish hobbyist, talk to your suppliers about where your fish come from. They should all have stickers on their tanks with information about where the fish were sourced. Ask them if they were live caught or captive bred. This way, you can be sure your fish were sustainably sourced, while encouraging your suppliers to also consider it.

Only some species of marine fish can be bred in captivity, although as improvements are made, the list is always growing. Try to only buy these species for your reef tank. Check out this list for 2017.

When you are buying live rock and coral for your tank, ask your supplier how they were grown. If you are unable to find cultured corals and live rocks at your local supplier, speak to them about the damage that extraction places on the reefs, and ask them if they might be able to use another supplier. You could also order it online!

The Importance of Protecting Our Oceans

Our oceans filled with fish, dolphins, turtles, whales, and crabs

We all have a part to play.

Our oceans make it possible for life on Earth to exist. Not only that, but they are also home to millions of fascinating plants and creatures, everything from microscopic plankton to 200-ton blue whales.

But as things stand in 2018, our oceans are under a great threat.

As you read this guide, you might at times have felt overwhelmed by all the ways that we humans are harming our oceans and the creatures that live in them. And when you feel overwhelmed, it can be easy to feel helpless, like there is nothing much you can do.

But by following some of our “What can I do to help?” advice at the end of each chapter, you really can make a difference.

Even when the problem is as big as climate change or drilling for oil and gas, there are still things that we as individuals can do in our own lives to affect change.

One great thing that we can all do is to talk to our friends and family about these issues. By spreading the message of how important our oceans are, and how much they need our help to protect them, your individual action can grow into something much bigger.

You can make your first positive step now by sharing this guide with your friends and family!

Despite all the threats facing our oceans, they have shown us that they can be incredibly resilient. If we can manage to change our practices in time, evidence suggests that our oceans and the creatures living within them may be able to bounce back.

But we have to give them a chance to do so.

Can they count on you?

Great Barrier Reef Education Material

Ian Sterling

Ian Sterling, founder of, began his aquarium journey over 30 years ago, driven by a deep fascination for fish and their diverse personalities. His website,, is dedicated to making fishkeeping accessible and enjoyable, offering beginner-friendly guidance, expert insights, and a community for aquarists to connect and share experiences.

Comments (3)

While this article was well written, it does not leave me with much hope that we can work together as a human race and solve these issues. Too many problems, not enough care.

Hi Nicola,

Yeah, it is a bit depressing. While the world working together does seem improbable, it doesn’t mean that it’s impossible. We may just save our oceans yet. Stay optimistic!

Thank you for this important article.

Kindly stop perpetuating 2 dangerous myths:

1. This planet has one (1) ocean. All “separate” seas and “oceans” are interconnected in one ocean covering most of a planet that would be better and more accurately referred to as OCEANIA. I know, because I have 40,000 sea miles in my trimaran’s wake.

2. This is not “our” ocean to abuse, exploit, kill or “save”. (This is not “our” planet, either.) We are one species among millions – not owners or managers of an intricately interacting biosphere we are just beginning to glimpse, while utterly unable to manage ourselves. (Or at least the corporate elites that rule us for their short-lived profits and control.)

We are custodians of our own choices. For good or ill, we are responsible for the consequences of our individual actions. As the current mass extinction gathers momentum, we will be held accountable.)

In regards to the foundering space colony we call Earth, we are crewmembers – not passengers. It is up to each of us to inform ourselves through articles such as this – and to act. Because the worse sin of all is to know of intolerable injustices ashore and offshore and do nothing.

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