Rising ocean temperatures driven by human-generated greenhouse gases are already damaging the world's fisheries—and that toll is on track to get worse without urgent global action to cut planet-warming emissions.
"We were surprised how strongly fish populations around the world have already been affected by warming, and that, among the populations we studied, the climate 'losers' outweigh the climate 'winners.'"
—Christopher Free, UC Santa Barbara
A pair of new studies published Thursday adds to a growing body of research which warns that anthropogenic global warming poses a mounting threat to both populations of marine fish and the more than 56 million people worldwide who depend on fisheries for survival.
First, a study in the journal Science found that from 1930 to 2010, the maximum sustainable yield—or the amount of fish that can be caught annually without endangering future harvests—fell by about 4.1 percent among the 124 marine species analyzed across 38 ecoregions, with some regions seeings declines as high as 35 percent.
"We were surprised how strongly fish populations around the world have already been affected by warming, and that, among the populations we studied, the climate 'losers' outweigh the climate 'winners,'" Christopher Free, a postdoctoral scholar at UC Santa Barbara who oversaw the research while earning a doctorate at Rutgers University, said in a statement.
Given the impacts Free's team observed—with the most severe losses in productivity seen in the Sea of Japan, North Sea, Iberian Coastal, Kuroshio Current, and Celtic-Biscay Shelf ecoregions—the researchers strongly suggested proactive changes in fisheries management.
"We recommend that fisheries managers eliminate overfishing, rebuild fisheries, and account for climate change in fisheries management decisions," Free said. "Policymakers can prepare for regional disparities in fish catches by establishing trade agreements and partnerships to share seafood between winning and losing regions."
He added that "knowing exactly how fisheries will change under future warming is challenging, but we do know that failing to adapt to changing fisheries productivity will result in less food and fewer profits relative to today."
Adapting to climatic changes is important to the future of fisheries—but so is addressing the root cause of those changes, as was highlighted by another study published in Science Advances.
"Adapting to existing climate change effects and implementing the Paris Agreement is crucial for the future of the planet’s ocean fisheries, while facing the growing challenges of supporting healthy and peaceful societies into the future."
—Rashid Sumaila, UBC
After comparing potential consequences for fisheries if warming hits 1.5°C above pre-industrial levels—the 2015 Paris agreement's end-of-century benchmark—versus the 3.5°C anticipated under a "business as usual" emissions scenario, researchers concluded that pursuing the global climate accord's top goals is "crucial" to safeguarding ocean ecosystems and economies of nations that are highly dependent on the fishing industry.
"Achieving the agreement is projected to increase sustainable global fish catches of the top revenue-generating fish species studied by 7.3 percent per year or 3.3 million metric tons," according to the study—and about 90 percent of that increase would occur in the territorial waters of developing country waters.
"The largest gains will occur in developing country waters, such as Kiribati, the Maldives, and Indonesia, which are at greatest risks due to warming temperatures and rely the most on fish for food security, incomes and employment," explained Rashid Sumaila, lead author of the study and a professor at the University of British Columbia (UBC).
The Science Advances report points out that marine fisheries provide about 260 million full- and part-time jobs worldwide—notably in nations such as India, Indonesia, and Nigeria—and that "seafood products remain a critical export commodity for many developing countries."
"A steady supply of fish is essential to support these jobs, food sovereignty, and human well-being," Sumaila said. "Adapting to existing climate change effects and implementing the Paris Agreement is crucial for the future of the planet's ocean fisheries, while facing the growing challenges of supporting healthy and peaceful societies into the future."