What is bottom trawling? How it works and environmental impact

How ClientEarth is using the law to put an end to bottom trawling

In the Mediterranean, France currently allows bottom trawling in its so-called ‘protected’ marine areas.

In May 2024, BLOOM and ClientEarth, who are members of the Med Sea Alliance, filed an administrative request to demand that France repeal three decrees authorising trawling in certain French MPAs where it should be banned.

They have received no response, so they took the issue to court, by filing a legal challenge against the French government in September 2024.

According to our legal expert Nils Courcy: “These areas are meant to be protected as they’re essential for biodiversity and climate protection. That’s why this protection is enshrined in law. But in spite of these commitments, and global commitments to protect nature, we’re seeing countries like France constantly bend the rules. We’re taking the issue to court to make sure that protected truly means protected.”

Then, in October 2024, we took action with our partner Oceana against the Spanish government for allowing bottom trawling in its MPAs. The Spanish government is flouting the rules by systematically allowing it in these waters so we took them to court.

We are also advocating for stronger fisheries control systems and regulations on fish imports. This will help to ensure the seafood in Europe is sourced responsibly without harming human rights or the environment. We also urge the rapid implementation of CATCH, the EU-wide digital system that makes seafood fully traceable.

What is the environmental impact of bottom trawling? And how is it linked to the biodiversity crisis and climate change?

Bottom trawling emits around 40% of annual U.S. transportation emissions.

While it's responsible for the largest share of global catch compared to any other fishing methods, bottom trawling is notorious for its destructive environmental impact on the most delicate marine habitats. The heavy nets drag on the seabed to catch marine species that live there. In doing so, they harm reefs and clear-cut seagrasses, one of the ecosystems that absorbs the most carbon - 35 times faster than tropical rainforests do. By destroying seagrass meadows, bottom trawling releases around 40% of annual U.S. transportation emissions.

Among the top 10 countries in the world that emit the most carbon emissions through bottom trawling, 8 are in Europe: UK, Italy, Denmark, France, the Netherlands, Norway, Croatia and Spain.

Bottom trawls are also unselective in what species they fish. That means that they unintentionally capture a lot of non-target species, which can make up to 60% of the total catches. Unwanted fish and endangered animals such as dolphins, sea turtles, and sharks, get stuck in the nets, get badly injured or killed, and are then thrown back to the sea.

By damaging seafloor ecosystems and harming marine life with bottom trawls, the fishing industry is effectively removing one of the most important natural mitigation tools we have against the climate crisis, while contributing to a decline in biodiversity.

Is bottom trawling banned in Europe?

Bottom trawling is astonishingly not always banned in Marine Protected Areas (MPAs). EU law bans trawling in some Marine Protected Areas (MPAs) hosting certain vulnerable habitats such as seagrass meadows and coral reefs. These habitats are protected because of the vital ecosystem and climate roles they play. Seagrass, for example, is one of the biggest carbon sinks on the planet, while coral reefs and algae beds house many species that are the basis of marine food chains.

The European Commission itself defined bottom trawling as one of "the most widespread and damaging activities to the seabed and its associated habitats” and advocated for a transformation of the fishing industry to reduce its impact on the environment.

With just 0.23% of the Mediterranean fully or highly protected, its marine ecosystems are in serious trouble. This makes the European Commission's call to ban bottom trawling all MPAs by 2030 even more important.

But this bottom trawling ban in some MPAs has not yet turned the tide for marine conservation, almost 20 years after its entry into force. That is because some EU countries don’t play by the rules and still refuse to implement it.

Meanwhile, there are also good news: trawlers are effectively banned from fishing in deep-sea areas around the Canary Islands, Azores and Madeira, as well as some parts of the Baltic Sea and the Mediterranean that host fragile habitats and vulnerable marine species.

In April 2024, Greece set an example in terms of safeguarding MPAs by announcing a ban on bottom trawling in all its marine protected areas by 2030.

What are the sustainable alternatives to bottom trawling?

Fishing more sustainably is possible and alternatives to bottom trawling do exist: adopting different and more sustainable fishing gear, or using artisanal, small-scale fishing techniques that are more selective and less energy intensive. These are only a few examples of how we could reduce unwanted by-catch and slow down the depletion of our seas and oceans, while also reducing climate emissions.

Restoring oceans is not only important for safeguarding marine life. It is also urgently needed if we want to tackle global hunger and food security. As a matter of fact, MPAs can help fish come back, replenish fish stock and boost seafood catch to eight million tonnes.