Introduction

Bottom trawling is a long-standing fishing practice in European waters, targeting species such as crustaceans, bivalves, and bottom-dwelling fish. However, the practice is increasingly contentious due to well-documented ecological damages, including habitat complexity reduction, permanent changes in seabed community composition, and reduced productivity. High levels of non-selective bycatch—ranging from 31% to 55%—and significant discarding of non-target species further complicate the industry’s profile. Research indicates that 60% of global discards originate from trawl fisheries, leading to biodiversity concerns and economic losses. This study provides a comprehensive assessment of the net value of bottom trawling to society in Europe, exploring the trade-offs between private economic benefits and broader public costs, particularly regarding climate impacts and marine protection.

Materials and methods

The research focuses on the European bottom trawling fleet, defined as vessels flagged to the 27 EU Member states, the United Kingdom, Norway, Iceland, the Faroe Islands, and Svalbard and Jan Mayen. Using Automatic Identification System (AIS) data from Global Fishing Watch, the study estimated fishing effort between 2016 and 2021. The methodology involved calculating private profits by subtracting total operating costs (fuel, labour, and other overheads) from revenues derived from Sea Around Us (SAU) landed value data. Societal costs and benefits were then estimated, encompassing direct employment value, the replacement value of protein for human consumption, the cost of discarded catch, government subsidies, and carbon emissions.

A critical component of the analysis involved modelling carbon costs. These include emissions from fuel combustion and the remineralisation of organic carbon stored in seabed sediments. The study utilised a regionalised version of previous models to estimate how much disturbed sedimentary carbon is released as aqueous CO2 and subsequently transferred to the atmosphere. Recognising the uncertainty in parameterising carbon remineralisation, the researchers explored multiple scenarios, including a conservative approach where degradation rates were reduced by a factor of ten. The analysis also examined the spatial overlap between trawling activity and Marine Protected Areas (MPAs) using the World Database of Protected Areas.

Results and discussion

The study found that the average annual net value associated with bottom trawling in Europe is negative, ranging between –€15.97 billion and –€2.07 billion. A significant disparity exists between private and public beneficiaries; while a net benefit of approximately €0.18 billion per year accrues to the private sector, the public bears a net cost between –€16.15 billion and –€2.25 billion. Key public benefits include annual fishing revenues of €4.41 billion, protein production valued at €2.46 billion, and direct employment worth €1.78 billion. However, these are outweighed by substantial costs. Annual government subsidies total €1.17 billion, and the lost value from discarded catches is estimated at €220 million.

The largest societal cost is atmospheric CO2 emissions resulting from disturbed sedimentary carbon, which ranges between –€18.15 billion and –€4.87 billion annually, depending on the social cost of carbon used in the valuation. The researchers estimate that trawl-induced emissions from sediment averaged 112.4 million metric tonnes annually. Furthermore, the footprint of bottom trawling is extensive, encompassing 25.6% (approximately 1.87 million square kilometres) of the European Exclusive Economic Zone (EEZ). Notably, 13.04% of all trawling effort (kWh) occurred within MPAs. In certain countries, such as Belgium, France, and Spain, more than 25% of annual trawling effort takes place inside protected areas, where intensities are often similar to or higher than in unprotected zones.

Conclusions

The analysis demonstrates that bottom trawling generates substantial net costs to society, primarily through climate impacts. Even under conservative modelling scenarios, the value of carbon emissions remains comparable to total fishing revenues. The report suggests that reducing bottom trawling effort by more than 50% could maximise net societal benefits. Eliminating the practice within MPAs is identified as a promising pathway to achieve immediate conservation and climate goals without significantly disrupting food security, as bottom trawling provides only 2% of Europe’s animal protein. Policy recommendations include redirecting the €1.17 billion in annual subsidies toward transition support, such as licence buyouts, vessel decommissioning, and fisher retraining programmes, to align fisheries policy with Europe’s broader environmental commitments for 2030 and 2050.