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cross-posted from: https://beehaw.org/post/18695339

A new study finds that even as mariculture expands globally, the industry could actually decrease its current biodiversity impact by 30%—if they get smarter about where they farm. But the same study also cautions that seafood farming in the wrong locations could just as easily ramp up current marine biodiversity impacts by over 400%.

One-fifth of the fish we consume is provided by farmed seafood, and that figure is only projected to rise as global demand for protein grows. The new research, published in Nature Ecology & Evolution, calculated that mariculture—the controlled production of shellfish, bivalves, and finfish in coastal areas and in the open ocean—will need to increase by 40.5% from 108,729 hectares to 152,785, to meet this growing demand by 2050.

Under a worst-case future scenario, where mariculture expansion occurred only in biodiversity-rich regions such as these, the effects could be profound: the cumulative biodiversity impact of seafood farming would increase by an average 270% at the country level, and by 420.5% at a global scale, compared to current impacts. Species-wise, the worst affected by mariculture under this extreme scenario would be large marine mammals including whales and seals, because these animals have considerable ranges that would overlap with more open-ocean farms.

But just as there’s a worst-case scenario, the researchers also posit a best-case scenario—one we could achieve, they say, if we take a more strategic approach.

“The best case scenario refers to all mariculture farms in 2050 [being] placed in sea areas with low [impact], including relocating existing farms and the new farms,” says Deqiang Ma, postdoctoral researcher at the University of Michigan School for Environment and Sustainability, and lead author in the new study. The model showed that if farms of the future were almost exclusively sited away from biodiversity hubs, the cumulative effects of mariculture would be on average 27.5% lower at the country level compared to 2020. Taken at the global scale, that equaled an impact reduction of 30.5%. Under this best-case future scenario, almost all marine species considered in the study would experience lower impacts compared to the current-day harms of seafood farms.