Halting overfishing can make a huge difference in tackling climate change, as the practice poses significant threats to the ocean’s ability to store CO2 and preserve ecosystems, a study released on Tuesday has shown.
The research, published in the journal npj Ocean Sustainability and carried out by a group of international scientists from the UK, Canada, USA, and Norway, said overfishing and associated marine habitat degradation reduce the ability of the ocean to buffer the impacts of climate change while threatening marine biodiversity.
In particular, industrial fishing is altering the vital role of marine vertebrates in the ocean carbon cycle – including fish, marine mammals, and seabirds, the authors said. This is causing damage to the carbon-rich seabed and contributing to rising GHG emissions through fuel use.
Fish alone contribute to approximately 16% of organic carbon transferred from the ocean’s surface layers to its depths, and they could be responsible for more than 20% of the carbon stored in the deep sea.
“Moving towards good management that ends overfishing and restores ecosystems would ensure resilient fish populations that are more capable of supporting the delivery of their ecological functions,” the study said.
“This, in turn, will help sustain the contribution of fish to the biological carbon pump and drawdown of atmospheric CO2, and the associated climate change mitigation benefits.”
The global fishing sector accounts for an estimated 1.2% of global oil consumption and experienced a 28% increase in emissions between 1990 and 20115, the authors noted.
According to the figures cited in the study, in 2019, 35.4% of stocks were fished at unsustainable levels, compared to 10% 50 years ago, and an estimated 11% of the global fisheries catch was discarded.
CLIMATE AND BIODIVERSITY
Controversial practices involved in overfishing, such as bottom-contact gears, are widely considered one of the main threats to marine conservation, hugely damaging sea habitats by dragging heavy nets along the seabed.
Notably, a study published in Frontiers in Marine Science early this year found that, between 1996 and 2000, bottom trawling was responsible for up to 370 million tonnes of CO2 emissions annually.
It is estimated to be nearly double the amount of emissions from the entire global fishing fleet of some 4 mln vessels.
“Too often, the climate and nature crises are addressed as separate from one another, but overfishing and marine habitat degradation threaten both ocean biodiversity and reduce the ability of the ocean to buffer the impacts of climate change,” said co-author Natalie Andersen, scientific lead at the International Programme on the State of the Ocean (IPSO).
“Effective fisheries management [is] a key strategy to not only protect ocean carbon stores but also mitigate the impacts of climate change, curb greenhouse gas emissions, and promote marine biodiversity, food security, and community resilience.”
According to scientists, the measures needed to improve fisheries management include:
- Reviewing reference points and stock assessments.
- Accounting for illegal, unreported, and unregulated catches.
- Engaging stakeholders.
- Including economic and social factors in long term management plans.
The authors also called for establishing no-take marine protected areas (MPAs) that cover exploited species habitats, in a bid to restore catch potential under climate change.
During the Our Ocean Conference in April, Greece announced a ban on bottom trawling in its MPAs by 2026, but the controversial practice is still permitted in some of Europe’s most crucial protected underwater ecosystems.
By Giada Ferraglioni – giada@carbon-pulse.com
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