Climate change could mean less nutrition in the seas

Climate-driven changes in ocean temperature and acidification could make it more challenging for people across the world to find the nutrients they need from seafood.

William Cheung, a fisheries biologist at the University of British Columbia, is the lead author of a new study in the journal Nature Climate Change that models how climate change will affect different types of seafood, and what that means for humans. Experts predict some ocean animals, like herring and anchovies, will struggle in warming waters, while other species like jellyfish will thrive in warming waters. The new research suggests the shift will decrease the amount of nutrients, like calcium and protein, available for humans — especially in lower-income regions.

“It’s devastating,” said Sonia Strobel, chief executive officer of Vancouver-based fishery Skipper Otto. “It's really discouraging to see the ways that climate change is exacerbating existing inequalities and inequities around the world.”

Scientists already know that climate change will make it harder for people to get food. On land, climate-driven heat and extreme weather are expected to put crops in jeopardy. Lower levels of oxygen and increasingly warm and acidic waters are making the world’s oceans less hospitable for some fish, while other species are projected to flee to cooler waters.

Seafood is the largest traded food commodity in the world, according to the World Wildlife Fund, and more than three billion people worldwide rely on seafood for protein. It’s also an important source of iron, needed to make healthy red blood cells, calcium, which can maintain bone strength, and omega-3 fatty acids, which are used in a range of functions in the heart.

Cheung and co-workers found that without strong action to mitigate climate change, by the year 2100, nutrients like protein, calcium, iron and omega-3 fatty acids could become up to 15 per cent less available relative to levels in 2000. Even if world governments do step up to stop emitting planet-altering gases, nutrient levels could drop by up to 10 per cent.

Strobel, whose company links small fisheries with consumers, said climate change already means certain species, like hake and salmon, might not be able to support a fishery every year.

“Seafood is the last great wild protein on the planet, and it's uncertain.” Strobel said, “We don't know what will be abundant any given year. We don't know what we're going to catch.”

The change would hit tropical regions, like Southeast Asia, Pacific Island nations and West Africa, even harder. The study projects that if the planet continues on its current path to 4 C of warming, levels of all four nutrients could drop by as much as 30 per cent near tropical countries like Nigeria or Sierra Leone.

“To consider the way nutrients are going to be further funnelled into the hands of the already privileged by climate change is devastating,” Strobel said.

But Wilf Swartz, an associate professor of marine affairs at Dalhousie University who was not involved in the research, said less availability doesn’t necessarily mean it will be harder for people to get food.

“Who has access to seafood depends on your wealth, your status in the community, and so on,” Swartz said. “So a projection of nutrient availability is the first step, but it's an incomplete picture.”

In the study, researchers said world fisheries should prepare for the risk of climate change by shifting to catch the species that will thrive. Back in Vancouver, Strobel said she wants to see the Canadian government manage fisheries so they harvest species that are abundant.

“With the uncertainty that's created by climate change, it's even more important that we have nimble management,” Strobel said. “People can continue to eat with the ecosystem and we can support fishing families who can pivot to catching what is abundant to take the pressure off of what isn't there.”

But not everyone should have to adapt or lose access to their traditional foods, Swartz said. Some First Nations in Canada have the constitutional right to harvest culturally significant food, like salmon — a species threatened by climate change.

“We need food for more than just to meet our nutritional needs, food is part of our culture. Food is part of what makes many societies,” Swartz said. “Just because the type of fish available in the seas is changing with climate change, we can’t expect societies to change as quickly.”