Sharks and tuna are carbon stores and should not be fished

What’s happening? Large fish species, including shark and tuna, are carbon stores that should remain in the ocean, according to research led by the University of Montpellier in France. Such fish are 10% to 15% carbon. When they die, their bodies sink to the ocean floor and the carbon they contain is sequestered for millions of years. An estimated 94% of this carbon is released if the fish are removed from the ocean by fishing boats, making the carbon footprint of fisheries 25% higher than industry estimates suggest, the study claims. Around 100 million sharks and five million tonnes of tuna are caught each year.

Why does this matter? While technologies such as carbon capture, utilisation and storage (CCUS) may immediately spring to mind when thinking about methods of removing CO2 from the atmosphere, the natural world could have a larger role than realised to play in aiding carbon sequestration.

Trees and forests are often explored as means of offsetting carbon emissions, and these can also provide other ecosystem services like temperature regulation, air filtration and food security. But extending carbon accounting principles to more complex organisms could be an additional method to account for their ecosystem benefits and bolster the preservation of biodiversity. In the case of oceans, this could mean restoring damaged habitats to allow fish stocks to recover or establishing a greater number of marine protected areas.

Research indicates large marine organisms can be even more effective at storing carbon than trees. Great whales, for instance, are able to absorb an average of 33 imperial tons of CO2 throughout their lifespan in comparison to the maximum 48 pounds of CO2 trees can store annually. Such marine life could also grow to play a relatively more important future role in long-term carbon sequestration, as forests’ carbon storage capacities become negatively impacted by rising global temperatures.

From an economic perspective, more than half the world’s GDP is dependent on high-functioning biodiversity. Valuing species for the ecological services they can provide, including carbon sequestration, is another way of understanding their worth while also encouraging greater efforts toward conservation.

Lateral thought from Curation – Aside from storing carbon, providing food security and filtering air, rich biodiversity could also be providing us with invaluable health-related ecosystem services.

According to the UNEP, zoonotic diseases represent around three-quarters of emerging infectious viruses. Habitat destruction, deforestation and biodiversity loss from human activities remove natural barriers and create ideal conditions for such viruses to spread to humans from wildlife. Accelerating efforts to reverse biodiversity loss and preserve natural ecosystems and species would offer disease protection at a cost 100 times cheaper than that of responding to future disease outbreaks, according to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.