BY JOHN BOWDEN , The Hill, 07/02/20
As many as 60 percent of the world's fish species could struggle to breed and reproduce if climate change causes the Earth to warm by 5 degrees Celsius over the next 80 years, the current projection for what will happen if greenhouse gas emissions continue unchecked, according to a new study. A study released Thursday in the journal Science that examined nearly 700 species of freshwater and saltwater fish found that 6 in 10 species would be affected if bodies of water around the world continue to warm. If global warming was limited to 1.5 degrees Celsius, the study's authors added, that number falls as low as 1 in 10 species.
"Efforts to meet ambitious climate targets (SSP 1–1.9) could therefore benefit many fish species and people who depend on healthy fish stocks," the authors wrote. "Our analysis shows that spawning adults and embryos consistently have narrower tolerance ranges than larvae and nonreproductive adults and are most vulnerable to climate warming. The sequence of stage-specific thermal tolerance corresponds with the oxygen-limitation hypothesis, suggesting a mechanistic link between ontogenetic changes in cardiorespiratory (aerobic) capacity and tolerance to temperature extremes," the study's abstract continued.
Flemming Dahlke, a German researcher and one of the study's co-authors, told CNN in an interview that the finding emphasize the need to cut carbon emissions substantially. Twenty percent of the world's population "derives at least one-fifth of its animal protein intake from fish, and some small island states depend almost exclusively on fish," according to the World Health Organization.
"More than half of the species potentially at risk is quite astonishing, so we really emphasize that it's important to take action and follow the political commitments to reduce climate change and protect marine habitats," said Dahlke, a marine biologist. "If climate change continues unchecked, we will probably see big changes in the species composition of our ecosystems," Dahlke continued. "When species can no longer reproduce in their traditional habitats, they have to either go into deeper water or further North if possible, or become locally extinct if they're unable to do that."