About 3 billion people around the globe rely on seafood for their main source of protein. But as the population grows, wild-caught supply isn’t enough to sustain increasing demand for oysters, clams, salmon, shrimp and other marine delicacies.

So, experts have turned to aquaculture, which is essentially farming in the ocean where fish, shellfish and aquatic plants are bred, raised and harvested. It produces nearly half of the seafood we eat.

But a new study casts doubt on the method’s ability to save the seafood industry from ruin ⁠— at least if we don’t take immediate action to address the climate crisis, researchers with the University of British Columbia in Vancouver, Canada say.

Global farmed seafood supply such as salmon and mussels is projected to drop 16% by 2090 if the world continues to burn fossil fuels such as petroleum, coal and natural gas at its current rate. Regions such as Norway, China, Myanmar, Bangladesh and the Netherlands, where seafood farming is abundant, could see supply decrease by as much as 40% to 90%.

In a hypothetical scenario where action is taken against climate change, farmed seafood supply is expected to grow by about 17% over three decades and by 33% by the end of the century, according to the study published Monday, Dec. 13 in the journal Global Change Biology.

Experts say climate change could affect ocean temperatures and areas deemed suitable for seafood farming in ways that would add to issues surrounding depleted stocks of wild fish. It could also negatively impact the supply of food used to feed these farmed aquatic critters, which consists of fishmeal and fish oil made primarily of ground-up smaller fish like herring and anchovy.

“Climate change affects everything, including aspects of seafood farming we’ve not previously considered,” senior study author William Cheung, director of the Institute for the Oceans and Fisheries at the University of British Columbia, said in a news release. “We need to act, and quickly, to mitigate climate change rather than rely on one solution to solve all our seafood production problems.”

Aquaculture “is the fastest growing food production system in the world,” according to the World Wildlife Fund.

Yet, if we stick with current global greenhouse gas emissions, the supply of farmed seafood will increase only by 8% by 2050, researchers found. It’s not a positive trend given 85% of the world’s marine stocks are already fully depleted or overfished.

Finfish farming, including salmon and sea bass, would be hardest hit in a scenario where no action is taken against climate change, with global supply dropping 3% by 2050 and 14% by 2090. This means the regions that do the most finfish farming will face the biggest supply issues, including Norway, Chile, Finland, Iceland and Bangladesh.

Bivalve farming, on the other hand, which produces mussels, oysters and clams, will experience the least negative impact from climate change.

VEGETARIAN FISH?

Researchers also experimented with the idea of converting farmed fish into vegetarians, feeding them soybeans instead of their friends’ unwanted remains.

Under a low emissions scenario, aquaculture supply was projected to jump 25% by 2050 and 31% by 2090 when a quarter of fish food was replaced with plant-based substitutes.

Even with no change to current fossil fuel activity, farmed seafood supply was still projected to increase 15% by 2050 and 4% by 2090 if fish are fed soybeans.