Low-income countries could lose 30% of nutrients like protein and omega-3 from seafood due to climate change

The nutrients available from seafood could drop by 30 per cent for low-income countries by the end of the century due to climate change, suggests new UBC research.

That's in a high carbon emissions and low mitigation scenario, according to the study published today in Nature Climate Change. This could be reduced to a roughly 10 per cent decline if the world were to meet the Paris Agreement targets of limiting global warming to 1.5 to 2 degrees Celsius -- which recent reports have shown we're not on track to achieve.

"Low-income countries and the global south, where seafood is central to diets and has the potential to help address malnutrition, are the hardest hit by the effects of climate change," said first author Dr. William Cheung, professor and director of the UBC Institute for the Oceans and Fisheries (IOF). "For many, seafood is an irreplaceable and affordable source of nutrients."

The researchers examined historical fisheries and seafood farming, or mariculture, databases including data from UBC's Sea Around Us to find out quantities of key nutrients that were available through fisheries and seafood farming in the past, and used predictive climate models to project these into the future. They focused on four nutrients that are plentiful in seafood and important to human health: calcium, iron, protein and omega-3 fatty acids, the latter of which is not readily available in other food sources.

They found that the availability of these nutrients peaked in the 1990s and stagnated to the 2010s, despite increases provided by farming seafood, and from fishing for invertebrates such as shrimp and oysters.

Calcium sees biggest decline

Looking to the future, the availability of all four nutrients from catches is projected to decrease, with calcium the hardest hit at a projected decline of about 15 to 40 per cent by 2100 under a low and high emissions scenario, respectively. Omega-3 would see an approximately five to 25 per cent decrease. These declines are largely driven by decreases in the amounts of pelagic fish available for catch.

"Small pelagic fish are really rich in calcium so in areas of the world where people have intolerances to milk or where other animal-sourced foods, like meat and dairy, are much more expensive, fish is really key to people's diets," said senior author Dr. Christina Hicks, professor at Lancaster University. "In many parts of the world, particularly low-income countries across the tropics, fish supply nutrients that are lacking in people's diets."

While seafood farming will contribute more nutrients in the future compared with current levels, the researchers projected these increases would not be able to compensate for the loss from fisheries. Under a high emissions scenario, any gains in the availability of nutrients from seafood farming before 2050 would be lost by 2100.

"The primary reason for this is climate change, which is also a significant threat to seafood farming, leaving us with a growing nutritional deficit," said co-author Dr. Muhammed Oyinlola, a postdoctoral fellow in the UBC department of zoology and the Institut national de la recherche scientifique. "Seafood farming alone cannot provide a comprehensive solution to this complex issue."

The availability of all four nutrients from tropical waters of generally lower income nations, such as Indonesia, the Solomon Islands and Sierra Leone, is projected to decline steeply by the end of the century under a high emissions scenario, compared with minimal declines in higher income, non-tropical waters, such as those of Canada, the U.S. and the U.K.

Globally, the researchers projected that seafood-sourced nutrient availability would decrease by about four to seven per cent per degree Celsius warming. For lower-income countries across the tropics including Nigeria, Sierra Leone, and the Solomon Islands, the projected decline was two to three times this global average at nearly 10 to 12 per cent per unit of warming.

"This research highlights the impact of every degree of warming," said Dr. Cheung. "The more we can reduce warming, the fewer risks to marine and human life."

Using all of a fish

Certain types of fish such as anchovies and herring are packed with nutrients but often used for fish meal and fish oil because these nutrients also promote fish growth. Similarly, many countries retain only select parts of a fish for sale. The researchers highlighted potential adaptations to increase nutrient availability from seafood, by retaining more of these nutritious fish for local human consumption, as well as reducing food waste in fisheries production and consumption by using all parts of a fish including the head and fins.

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Farmed seafood supply at risk if we don’t act on climate change

The supply of farmed seafood such as salmon and mussels are projected to drop 16 per cent globally by 2090 if no action is taken to mitigate climate change, according to a new UBC study.

Ocean-farmed seafood or mariculture is often seen as a panacea to the problems of depleted stocks of wild fish and growing human demand, and is expected to grow substantially in the coming years, says lead author Dr. Muhammed Oyinlola (he/him), a postdoctoral research fellow at the Institute for the Oceans and Fisheries (IOF). But the new modelling study highlights the industry is as vulnerable to the effects of climate change as any other. "If we continue to burn fossil fuels at our current rate, the amount of seafood such as fish or mussels able to be farmed sustainably will increase by only eight per cent by 2050, and decline by 16 per cent by 2090."

By comparison, in a low emissions scenario where the action is taken to mitigate climate change, mariculture is projected to grow by about 17 per cent by the mid-21st century and by about 33 per cent by the end of the century, relative to the 2000s.

The model takes into account many factors, including changing ocean temperatures, suitable mariculture areas in the future, and the supply of fishmeal and fish oil. It examined approximately 70 per cent of the world's mariculture production as of 2015, focusing on Exclusive Economic Zones, where most of the world's seafood farming occurs.

Climate change will affect mariculture production differently depending on where farms are in the world, and what they produce, says Dr. Oyinlola. The hardest-hit regions in the high-emissions scenario -- Norway, Myanmar, Bangladesh, the Netherlands, and China -- could see their mariculture production decline by as much as 40 to 90 per cent.

Climate effects on mariculture include changes in the area of viable ocean in which to farm fish as well as the stock of food used to feed them. Fish farms tend to use fishmeal and fish oil, which are largely composed of smaller fish such as herring and anchovy -- stocks which are also threatened by climate change.

"Some regions produce more bivalves, such as mussels, oysters and clams, and in these regions, the impact is smaller," Dr. Oyinlola said. "In regions that produce more finfish, such as salmon, the impact will be high due to reduction in the supply of fishmeal and fish oil."

Under current carbon emission rates, finfish farming, such as salmon, is projected to decrease globally by three per cent by 2050, and 14 per cent by 2090. Bivalve farming is projected to increase by 2050 and decrease by 2090 under both climate scenarios.

Countries where mariculture is prominent especially for finfish production, such as Norway, Iceland, Finland, Chile, and Bangladesh, will be hit hardest, according to Dr. Oyinlola, whereas regions that produce more bivalves will be more stable or in Canada's case, will grow.

Vegetarian fish: feeding fish soybeans

The study also found that substituting fishmeal and fish oil for plant-based foods such as soybeans could help alleviate the effects of climate change for fish farms.

When a quarter of the fish food was substituted with alternatives, under a low emissions scenario, mariculture production was projected to increase by 25 per cent by 2050 and 31 per cent by 2090.

With no change to current emissions, when a quarter of the fish food was substituted with alternatives, mariculture production was projected to increase by 15 per cent by 2050 and four per cent by 2090. When half the food was substituted in both climate scenarios, these percentages increased.

"This study highlights the need to diversify mariculture development from the current focus on fish," said senior author Dr. William Cheung (he/him), IOF professor and director. Climate-adapted mariculture would include species that are not dependent on fishmeal and fish oil, such as shellfish or algae, or those that can utilize non-fish-based feed. "Farming these species generally helps to reduce exposure of seafood farming to climate hazards."

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