Environmental problems and threats

Human activity has had a major negative impact on the marine environment, especially in recent decades. The sea and its biodiversity are being affected, especially by the nature and scale of these activities.

For example, the quality of sea water has changed in recent decades, due to marine litter and eutrophication or overfertilisation. Climate change, in turn, is having an effect on the temperature in the sea and increasing the acidity. Fisheries are also a very important problem, due to overfishing and impact on the seabed. In addition, the noise levels in the water are changing owing to work on wind farms, shipping, sand extraction, defence activities, recreation, etc. Finally, indigenous biodiversity is also declining, while invasive alien species are ending up in the North Sea through human intervention, making life even more difficult for its own species.

The Department for the Marine Environment is constantly looking for specific solutions to these problems. However, positive change is also possible at an individual level: everyone can contribute to a healthier sea!

Marine litter

Marine litter is a growing problem for all seas and oceans, and is a considerable threat to our environment. Any fixed material manufactured by humans that has been released into the marine environment, directly or indirectly, deliberately or accidentally, is viewed as marine litter.

Every year, an average of 8 million tonnes of plastic waste ends up in the sea worldwide. This is an entire lorry's worth per minute! 

Origin of the waste

All this comes both from the sea and from land. Shipping, fishing and aquaculture are activities at sea that could be a source of marine litter. Abandoned fishing nets are a major issue in this respect.

© Vilda

Litter from the land ends up in the sea via rivers, sewers, water purification installations, or simply by the wind. A significant proportion of beach waste results from tourist activities. When there are fireworks, festivals, sporting events and beach bars, massive amounts of rubbish are left on the beach. The popularity of such events is increasing, as is the amount of waste left behind.

© Vilda

Plastic litter

The North Sea is struggling with the issue of marine litter. About 90% of the litter in our North Sea consists of plastic waste. Plastics are polymer-based synthetic substances that are known for their durability and long lifespan, which means they remain in the environment for a very long time. Some substances only degrade after 450 years and small fragments such as micro or nano-plastics will never even disappear at all. Along with a continuous stream of additional plastic litter, this will create an accumulation in the marine environment that will be around for decades and even millennia to come.

Marine litter poses a major threat to the marine ecosystem and biodiversity. Fish, birds, sea turtles or marine mammals regularly get entangled in abandoned nets. Many animals see the litter as food, which fills their stomachs with rubbish. This leaves less room for food and the animals are weakened.

© Unsplash and Vilda

In addition, various toxic substances, persistent organic pollutants in jargon, easily bind to micro-plastics. The more plastic the animals eat, the more of these toxins accumulate in the animal. This process is called bioaccumulation. This problem worsens the higher up the food chain you move. After all, plastics and toxic substances bound to them do not disappear when eaten. This process of accumulation within a food chain is called biomagnification. It is an important process for humans, as we are resolutely at the top of the food chain and therefore unconsciously absorb plastic and toxic substances during the consumption of a fish fillet. Fish species higher up in the food chain, such as tuna or salmon, account for this in particular.

What is the government doing?

The federal government is going toe to toe with marine litter through the Federal Marine Litter Action Plan. This action plan aims for a broad support base and focuses on the prevention of macro and micro litter, both from land and from the sea. The action plan is intended to raise public awareness of and alertness to the problem of marine litter. It includes measures for the prevention of marine litter at source, for cleaning up the plastic soup at sea and for monitoring compliance with legislation. The action plan also emphasises collaboration and invites all the partners involved, whether national, international, governmental or industrial, to take their own responsibility. The Federal Marine Litter Action Plan thus contributes to the achievement of the UN's Sustainable Development Goals.

© European Commission

The Department for the Marine Environment has been supporting the ‘Fishing for Litter’ project for several years. Fishermen take the waste they encounter during the catch back to land in ‘big bags’ and hand it over for processing free of charge. The action raises their awareness and ensures that the waste does not end up in their nets over and over again. Moreover, they are also contributing to the protection of fish stocks through the project – an aspect on which their profession is highly dependent.

In addition, the Marine Environment Service  takes care of cleaning up waste in and around wrecks.  In 2019, it was the West-Hinder's turn. The clean-up operation brought up 4.5 tonnes of waste. In 2021, divers started removing waste from a second wreck: the SS Kilmore. 

What can you do?

On our website The sea starts with you, you can find a whole series of tips and inspiration to help you make a difference.

Overfishing and bycatch

Better fishing techniques, larger vessels and an increasing demand for fish mean that fishermen are bringing in more and more fish. When ships catch so many fish that there are not enough fish stocks left to conserve the species, this is called overfishing.

Overfishing is one of the main problems facing the European Union's Common Fisheries Policy. They therefore determine the quotas that can be fished per country per species and are also responsible for the sustainable management of the fishing fleet and the pursuit of a sustainable transition in the sector. After all, overfishing is not only an ecological problem. It is also an economic problem for the fishing industry. Fish stocks of commercial species such as cod, sole and plaice, for example, have declined sharply in recent decades. Once the fish stocks are exhausted, many fishermen will be out of a job.

© C. Ortiz Rojas and WWF (Rudolf Svensen)

In addition to overfishing, there is also unwanted bycatch in skippers' nets. These are usually specimens that are too small, but could also be other species such as crustaceans, molluscs, starfish, and even marine mammals and seabirds. At present, bycatch usually ends up back overboard. However, animals that are thrown back often die as a result of the injuries sustained. However, in the case of marine mammals, in practice mainly harbour porpoises, fishermen must report bycatches to MUMM (the Management Unit of the North Sea Mathematical Model), the competent authority. They monitor the evolution of these figures.

Since 1 January 2016, discards of bycatches and undersized fish have been prohibited throughout the European Union by the discard ban. The small fish are not yet fit for consumption but do need to be reported, in order to get a correct estimate of the fish stocks. The European Commission determines which fish species are covered by these regulations, what exceptions there are and for how long these provisions apply.

When fishing with beam trawls, 40 to 75% of the total catch is bycatch. In shrimp fishery, this can be as much as 85 to 90%. This is causing certain species to deteriorate enormously, such as the flat oyster, the bottlenose dolphin and the thornback ray.

What is the government doing?

By taking fisheries measures, Belgium, in consultation with other Member States, plays an active role in protecting the marine environment from the impact of fishing in sensitive areas. In 2015, for example, a new law was introduced by the Flemish Government prohibiting the use of tangle-nets. On the coast, these posed a risk of suffocation for harbour porpoises and seabirds.

What can you do?

  • Choose sustainably caught or farmed fish from labels such as MSC and ASC. These labels guarantee that the fish you eat come from a sustainable source.
  • Use fish calendars and fish guides to make ecologically sound choices. These indicate when it is best to buy fish and from which areas, so that the impact on fish stocks remains minimal. During the mating season, it is best to disturb fish as little as possible so they can reproduce optimally.
  • If you do see setups of illegal tangle-nets on the beach, you can report this to the coastguard so they can be removed and no animals unnecessarily entangled in them.


Habitat and species loss

It is getting busier and busier in the North Sea and the space for nature is under increasing pressure. Habitat loss occurs when the necessary habitat for animals and plants significantly deteriorates or even disappears. The majority of the oceans are under pressure, especially around the coastal areas. These are densely populated and there is a lot of human activity: tourism, industry, ports, transport and habitation cause a lot of pressure on these places. 

© Vilda

Precious coastal areas often host important habitats. Dunes, marshes, estuaries, mudflats and salt marshes often serve as spawning, breeding or foraging grounds. They therefore play a key role in the life cycle of many species. Habitat loss or the disappearance of a key species from a habitat often has a major impact on biodiversity. Indeed, a loss of biodiversity can lead to a reduction in ecosystem services. This, in turn, leads to less of a buffer against the human pressure on the ecosystem.

Human influence can also be felt at sea. As a result of seabed-disturbing activities, such as fishing, the construction of wind farms and sand extraction, the oyster beds that once existed off the Belgian coast have disappeared completely. The gravel beds have also been severely disrupted. As a result, the presence of biodiversity has decreased. Due to the turmoil in the gravel, some species present were destroyed and were not given the chance to develop again. At the moment, we can only find relics (remnants) in places that are naturally protected against disturbance due to their location. For some vulnerable species, such as the European flat oyster and the dead man's thumb, all our help comes too late. They are only rarely observed now.

© Depositphotos

Human impact also indirectly disturbs the habitat and the species that live in it. Climate change, for example, is also having a major effect at sea. The water temperature is rising and the acidity is increasing. Nitrogen pollution and invasive alien species are significantly altering the characteristics and species composition of our North Sea.

More information on the protection of habitats and species can be found in the conservation objectives of the Department for the Marine Environment and the Royal Decrees on procedures and species protection.

What is the government doing?

A sustainable balance between a healthy marine environment and human activities at sea is crucial. Only this way can we protect and, where necessary, restore the biodiversity present. An Environmental Impact Assessment (EIA) should therefore be drawn up for any significant human activity at sea. This EIA maps out the potential environmental consequences of a plan, activity or project and may form the basis for a permit.

Through the Belgian Nature Integrated Project (BNIP), the various Flemish, Walloon and Federal authorities have joined forces to achieve the Natura 2000 objectives on land and at sea via Prioritised Action Frameworks (PAF). The Agency for Nature and Forests is co-ordinating this project and creating an operational framework for providing expertise and support for Natura 2000 projects on the ground. For more information about the BNIP project, please visit the website.

What can you do?

  • Learn more about nature in and around the sea, as well as in your neighbourhood. You can find a great deal of information at the local nature association, at nature centres, in books or online.
  • Help inform others about the importance of nature.
  • Visit nature reserves! Nature education centres, bird sanctuaries and nature reserves will teach you a lot about nature. Need any tips? Head out to the Zwin, the Duinpanne, the Doornpanne, etc.
  • Help prevent pollution. 


Invasive alien species

Alien species occur regularly in our sea. That in itself is not a problem. Sometimes, however, they begin to multiply uncontrollably. When ecological or economic interests or public health are threatened, this is what we call an invasive alien species.

American jackknife clam and Japanese oyster © Misjel Decleer and Oscar Bos

Invasive alien species are the second-largest cause of species extinction. As a result, they pose one of the greatest threats to indigenous biodiversity on land, freshwater and saltwater. There are 73 non-indigenous species in the Belgian part of the North Sea. Some can even be found on the beach: the American jackknife clam, the Philippine carpet shell and the Japanese oyster. They were introduced via ‘vectors’. In the marine environment, this is primarily shipping, via attachment to the hull or in the ballast water. Other vectors include offshore aquaculture and the release of aquarium animals or plants into the wild. In some places, such as seaports, more than 60% of the species are non-indigenous!

What is the government doing?

A management plan to protect our indigenous biodiversity is crucial. Belgium is committed to allowing non-indigenous species to have only a positive impact on marine ecosystems.
Several concrete measures are covered by the Marine Environment Protection Act. For example, it is forbidden to import non-indigenous species into the Belgian part of the North Sea. In addition, a procedure is needed to authorise the cultivation of non-indigenous species within offshore aquaculture.

The presence of invasive alien species is explicitly included within the Marine Strategy Framework Directive. The Ballast Water Convention is another tool. This international agreement prevents, limits and prohibits the movement and introduction of harmful aquatic organisms and pathogens into the marine environment. This takes place through inspection and management of ships' ballast water when they sail from one port to another. The FPS Mobility monitors the application of this Convention.

What can you do?

  • Do not dump fish bait into the water after a fishing session. It often contains worms, small roaches (a kind of carp) or crayfish that do not occur naturally in the North Sea and may turn into an invasive species.
  • Never release animals from an aquarium or pond into the wild. Throw your aquarium plants in the bin with a plastic bag.
  • Clean your hiking boots when you go from one nature reserve to another. You could be spreading plant seeds, microorganisms or pathogens from one area to another.
  • As a consumer, give preference to native species and eat locally. 


Underwater noise

For many marine organisms, marine mammals, fish species and even invertebrates, hearing is one of the most important senses for performing necessary actions. Sound waves allow them to move and orient themselves, to communicate, to feed and to reproduce, etc. After all, underwater, light is quickly absorbed. Developing a strong sense of hearing is, in light of their evolution, above all a good survival strategy. Sound is all the more amplified under water and sound waves are also a very powerful medium there: they are barely dampened and travel five times faster underwater than above water.


A great many human activities (shipping, pile-driving for the installation of wind turbines, military exercises, seismic surveys, etc.) cause a lot of underwater noise and can therefore affect all these vital processes. The consequences of this vary from masking biologically relevant signals, altered behaviour, damage to hearing organs or to injuries or even death at very high noise levels. In addition, marine mammals (cetaceans, dolphins, harbour porpoises) and fish (because of their gas-filled swim bladder) are particularly sensitive to sound waves from explosions. Most invertebrates suffer little damage because they do not have organs filled with gas.

What is the government doing?

The management of acoustic disturbance is one of the objectives of the Marine Strategy Framework Directive. When assessing the environmental impact of projects at sea, noise is an environmental pressure that is evaluated within the environmental permits.
The Department for the Marine Environment is therefore consulting with the military sector in order to apply some non-technical measures, such as the destruction of explosives on land rather than at sea, the provision of a deterrent system, the postponement of the destruction of mines when marine mammals are sighted and a temporary ban on explosions during periods of high harbour porpoise densities. Along with the FPS Mobility, the Department for the Marine Environment is also raising awareness among the shipping industry in order to limit the effect of underwater noise on cetaceans.

Ocean acidification

Carbon dioxide (CO2) can dissolve in water to a limited extent, causing oceans to absorb CO2 from the atmosphere. As the concentration of CO2 in the atmosphere increases, so does the concentration of CO2 in the oceans. One quarter of the CO2 emitted into the atmosphere (by burning fossil fuels) is absorbed by the oceans. This makes them an important buffer in our battle against global warming. But every buffer has its limits, and here too, humanity is putting the marine environment to the test. When an ocean absorbs CO2, it reacts with seawater to form carbonic acid (H2Co3). This carbonic acid decays naturally into bicarbonate and carbonate molecules. This chemical process, in which H+ ions are released, acidifies seawater.


Acidification, or an increase in the concentration of CO2 in the oceans, complicates the production of calcium carbonate (CaCO3) by organisms. This substance is the main constituent of shellfish shells, but is also important for e.g. diatoms, corals, and starfish. They build their skeleton with this material. A lack of calcium carbonate results in a brittle skeleton, which in turn results in reduced chances of survival. The acidic ocean dissolves the limestone skeletons, as it were.

Because diatoms form the basis of the food pyramid at sea, there is a danger that ocean acidification could have a major impact on human food supply. The pH of seawater has already dropped by 0.11 since the 18th century. This might sound small, but it involves an increase in acidity of more than 25%. The estimated drop of 0.3 or 0.4 pH by 2100 could thus have a disastrous outcome for the marine environment.

What is the government doing?

Belgium has an active climate policy with regard to the CO2 issue. The specific problem of acidification is being tackled internationally within various international forums such as the London Convention and the Convention on Biological Diversity. The Department for the Marine Environment ensures that Belgian positions are co-ordinated within these different forums. For example, a representative of the Marine Environment Department is invariably present at the annual major climate meetings (the climate COPs) in order to put the interests of the oceans in the picture.

What can you do?

Ocean acidification is a consequence of CO2 emissions. That is why climate action is a good way to stop the acidification of the oceans. There are several ways to reduce your CO2 emissions. As an individual, it is mainly about how we eat, how we travel, how we live and what we buy. As a rule, it is always more efficient to avoid an activity. For example, it is better to insulate your home properly than to heat it using a heat pump, just as working from home is better than driving an electric car to work.

More detailed tips can be found at the Department for Climate Change or at klimaat.be.


Eutrophication or overfertilisation occurs when too many nutrients, such as phosphates and nitrates, are present in the water. This is usually due to human activities such as agriculture and industry. At first sight, this does not seem to be a problem: plants in rivers, lakes and oceans can primarily benefit from this increased supply of nutrients.

In water, algae are the first to use this extra influx of nutrients, which can cause an explosive algal bloom. When the algae then die, they are broken down by bacteria in an aerobic process. As a result, oxygen is gradually extracted from the water. This can ultimately lead to fish mortality and food scarcity for birds. An additional danger is that some algae species produce a range of toxins that can be absorbed by animals or humans, resulting in symptoms such as muscle cramp, fever, diarrhoea or eye irritation.

The colour of the algae is important for identifying the species and the type of toxins they produce. On our coast, this algal bloom may occur in the form of green tide or foam on the beach.

© Vilda

What is the government doing?

The problem of eutrophication of the marine environment is mainly being addressed through the implementation of the Water Framework Directive. In collaboration with the OSPAR countries, river basin management plans for the Belgian coastal waters are being monitored and drawn up. This way, more targeted measures can subsequently be taken to tackle eutrophication at the source. 

What can you do?

  • Be aware of the fertilisers and chemicals you are using. Use them wisely, to be sure they are not simply swept away to a nearby waterway during a thunderstorm.

  • Reduce water pollution by using ecological cleaning, (dish) washing, care products and paints (e.g. with the EU Ecolabel. Only use disinfectants, pesticides and other chemical products such as bleach, descalers and unblockers when necessary, safely and properly.


Climate change

The role of oceans in the battle against climate change has thus far been underestimated. They provide us with most of the oxygen we breathe and form a protective CO2 buffer against global warming. For example, the oceans have absorbed more than 90% of the added heat since the 1970s. This is a direct consequence of human activities. But there is a limit to that capacity to absorb heat and the ocean is gradually becoming saturated with CO2. This has repercussions, not only for life in the ocean but for us too.

Ice caps melting

One of the best known images of global warming is the melting of the ice caps at the poles. This is dramatic and could trigger a domino effect. The ice caps contain a very large amount of methane, which may be released faster when the ice caps melt. Since the effect on methane warming is 25 times higher than that of CO2, this could cause a waterfall of effects, causing nature to take over the process of climate change from us. Human efforts will then no longer be of any use in halting climate change.

© Givingcompass

Consequences for biodiversity

In terms of biodiversity, iconic species such as polar bears, walruses, penguins and whales are losing precious habitats. But organisms in warmer waters, such as corals, are also having difficulty adapting to the increased temperature. They are dying en masse, leaving only faded coral.

Aquatic organisms will migrate en masse in search of the right living and mating conditions. The warmer water temperature will shift the habitat of more southern species further and further north. New species, including certain species of barnacles, will appear off our coast and other species, such as herring, will just disappear. The altered species composition could lead to disturbances in ecological relationships within the marine food web and affect our food chain.

© Reuters

Impact on sea currents and sea level

Climate change will also have an effect on sea currents. These currents are caused by temperature differences in the water, between the tropics and the poles. As the water gets colder, it becomes heavier and sinks to deeper parts of the oceans to rise again elsewhere. Changing the temperature of the water can thus affect the direction and speed of sea currents. Migratory species that depend on this current for the supply of food or the spreading of their larvae to reproduce will be the first to be affected. Afterwards, the local weather climate and precipitation will also be affected.

© Jonathan Webb

The melting of the ice caps also causes a rapid rise in sea level. By 2050, a rise of 30cm is estimated and, by 2100, even a rise of 80cm. Small island states in the Atlantic Ocean and lower, densely populated coastal areas (e.g. Bangladesh) will give rise to the first climate refugees. If we do not stop the rise in sea level, several island states will be swallowed up by the ocean by the end of the 21st century.

What is the government doing?

As climate issues are global in nature, collaboration and solutions for the protection of oceans against climate change are being sought across borders. This is why the United Nations decided to dedicate the 2021-2030 period to marine research in support of sustainable ocean management worldwide.

Along with the Department for Climate Change, the Department for the Marine Environment organised a climate conference on 19 February 2019 at which the ‘Brussels Declaration on climate change & ocean preservation was signed by representatives from more than 30 countries. This text brings together numerous political actions around the themes of oceans and climate change. It also stresses the crucial importance of science-based policy-making and encourages ocean and climate research.

Furthermore, the Department for the Marine Environment is contributing to the efforts to reduce CO2 emissions within the shipping sector, as proposed in the Paris Agreement.

What can you do?

The threat of climate change may seem overwhelming. An initial step is therefore to inform yourself correctly about how the ocean works and the impact of your daily habits. Learn about tips that can help you protect the seas in everyday life and keep your ecological footprint as small as possible. Pay attention to how you travel, what you eat, what you buy and how you live. Be sure to share your knowledge with friends and family. Here are a few handy tips to get started:

  • Travel: by avoiding travel, you can reduce your emissions. If you have to go outdoors, then ideally go on foot or by bike, followed by public transport. People who cannot live without a car should choose an economical model: hybrid or electric. Carpooling is also a great option, keeping more cars off the road.

  • Living: our homes also make a substantial contribution to greenhouse gas emissions. Living in a city centre or just in a smaller house or apartment reduces this contribution at a stroke. Insulating well, installing heat pumps, installing solar boilers and installing solar panels are even more advantageous. Take a look at your home's EPC certificate, which will give you some useful tips for reducing your home's emissions.

  • Purchasing: every product, from a sheet of paper to a computer, came at a CO2 cost during its production. Thinking about your consumption behaviour is therefore part of a climate-friendly life. Borrowing items or buying second-hand is a great alternative to new purchases, but correct recycling is also important. That way, raw materials will not be lost. The fewer raw materials needed to run your life, the better for the climate and the environment.

  • Food: a sector receiving a lot of attention within the climate debate is the agricultural sector. A low-meat diet is in the picture in particular. You do not need to lead a meatless existence (although that is obviously the most effective way); eating vegetarian food a few days a week is already a step in the right direction. A second point for consideration is local nutrition. This way, you avoid transport and limit the impact. Seasonal food completes the picture. Do you eat vegetables out of season? Then energy-consuming greenhouses or cold stores were needed for their production. By opting for food during the natural harvesting months, you can keep this to a minimum too. Vegetable calendars will help you on your way!

    More info at www.klimaat.be.

Seabed disturbance

Damage to the seabed is mainly expressed in the composition of and services provided by the seabed habitats and the species living there. The damage may be caused by disturbances, such as scraping off the seabed, disturbing the sediment or extracting sand or gravel.

Beam trawling, for example, is a technique in which a large net with heavy weights is dragged across the seabed. It takes everything in its path, destroying fragile seabed ecosystems and leaving the seabed disturbed. When pile-driving for wind turbines, a hammer is also often used that punches piles into the ground with enormous force. The shock wave that travels through the soil can potentially damage the internal organs of invertebrates located in the soil.

© Brian Skerry and NOAA

When extracting sand, entire communities are sucked up from the seabed along with it and removed from the marine environment. Sand extraction can also create a plume of sand that makes the water turbid, which also has an impact on the marine life present. It can form a barrier to corals that need sunlight to function and thus result in fish mortality due to a lack of food and oxygen.

Deep-sea mining will cause similar problems: both the extraction of minerals and the return of the residue will result in enormous sediment plumes. The damage to the seabed from all these activities has a major impact on biodiversity and the food web in marine systems.

What is the government doing?

One activity is obviously more harmful than another. All activities differ in size, degree of impact or degradation of other types of habitat. For this reason, each activity has been given a separate Environmental Impact Assessment and a separate permit must be applied for each activity, with its own period of validity. 

What can you do?

It is not easy to see how an individual can have a direct effect on seabed disturbance. Raising awareness about the cost of some fishing techniques and sand extraction for the environment is a good start. After all, these are activities that are driven by consumer demand. A concrete example of this process is deep-sea mining, where companies are starting to look at the unexplored mineral deposits in the deep sea. Due to the high demand for smartphones, tablets, etc., an additional source of valuable raw materials is attractive. Being aware of your purchasing behaviour is therefore already a step in the right direction.