Climate change threatens global fisheries, say UBC researchers

The oceans have become warmer, more acidic and less oxygenated due to climate change and human activity.

According to a new study involving UBC researchers, global fish stocks cannot recover to sustainable levels without strong action to mitigate climate change.

Scientists from the University of British Columbia, the Stanford Center for Ocean Solutions and the University of Bern projected the impacts that different global temperature increases and ranges of fishing activity would have on biomass, or the amount of fish by weight in a given area, from 1950 to 2100.

What they found suggests that climate change has reduced fish stocks in 103 of 226 marine regions surveyed, including Canada, from historic levels.

They said these stocks will struggle to replenish their numbers below projected levels of global warming in the 21st century.

“More conservation-oriented fisheries management is essential to rebuild overexploited fish stocks in the context of climate change. However, this alone is not enough,” said lead author William Cheung, a professor at UBC’s Institute of Oceans and Fisheries (IOF).

“Climate mitigation is important for our fish stock recovery plans to be effective,” he said.

Fisheries and Oceans Canada spokesperson Kariane Charron said the department is working closely with Environment and Climate Change Canada and other partners to better understand the impacts of climate change and advance a long-term climate strategy. for Canada.

“The Department continues to explore ways to better integrate environmental factors, such as climate, oceanographic and ecological information, into its scientific advice on fish stocks and ecosystems, and into its decisions related to fisheries management, oceans and coastal infrastructure, species conservation, and maritime security,” said Charron.

Global warming

Currently, the world is on track to exceed 1.5 degrees of warming above pre-industrial levels and approach two degrees over the next few decades, Cheung said.

The study predicted that, on average, when fisheries management focuses on the highest sustainable catches per year, the additional climate impacts on fish at a warming of 1.8°C would prevent fish stocks from recovering. .

If people around the world only caught three-quarters of the highest sustainable annual catch, fish stocks would be unable to recover at a higher degree of warming, 4.5°C.

“Tropical ecoregions in Asia, the Pacific, South America and Africa are experiencing declines in fish populations as species move further north to colder waters and are also unable to recover due to fishing demand,” Cheung said. “These regions are the ones that feel the effects of global warming first and our study shows that even a slight increase of 1.5 degrees Celsius could have a catastrophic effect on tropical nations that depend on fisheries for their food and nutrition security, their incomes and jobs. ”

In 2021, G20 countries agreed that limiting global warming to 1.5°C above pre-industrial levels would require “meaningful and effective” action.

worst case scenario

In the worst-case scenario, scientists say, global fish stocks could drop to 36% of current levels. This scenario would result from a case where nothing is done to mitigate global warming, including meeting internationally agreed targets, and where overfishing beyond sustainable targets occurs.

“To rebuild fish stocks, climate change must be fully taken into account,” said study co-author Juliano Palacios-Abrantes, an IOF postdoctoral fellow. “We live in a globalized world, where situations are interconnected. We see this especially in tropical regions, but also in the Arctic, where many exploited species are slow to mature, or in Ireland, Canada and the United States, where fishing mortality rates are high. These climatic effects, even when we have looked at conservation-oriented scenarios, make it too difficult for fish stocks to rebound. »

Charron said the oceans as a whole have become warmer, more acidic and less oxygenated due to climate change and human activity.

These changes have a direct impact on where marine animals live, what they eat and how they grow and develop, Charron said.

Due to climate change, the world is unlikely to return to historic levels of fish stocks, he added.

“We are at a turning point. What we need is a coordinated global effort to develop practical and equitable marine conservation measures to support effective biomass replenishment under climate change,” he said.

“These must recognize the ways in which marine biodiversity contributes to livelihoods and economies, particularly in tropical marine ecoregions, as well as demand stricter limits on fishing activities to achieve greater potential for recovery. biomass,” Cheung said.

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Teresa H. Sadler