Ocean heating causing 'staggering' decline in marine life: Study
What's the story
A new study has revealed that chronic ocean heating is driving a "staggering and deeply concerning" decline in marine life. The research found that fish populations have decreased by 7.2% for every 0.1 degree Celsius of warming per decade. The study, published in the journal Nature Ecology & Evolution, looked at year-to-year changes in 33,000 Northern Hemisphere populations between 1993 and 2021.
Research methodology
Loss of biomass due to chronic heating
The researchers isolated the effect of chronic seabed warming from short-term changes like marine heatwaves. They found that biomass loss due to chronic heating can be as high as 19.8% in a single year. "To put it simply, the faster the ocean floor warms, the faster we lose fish," said Shahar Chaikin, a marine ecologist at Spain's National Museum of Natural Sciences and lead author of the study.
Long-term effects
Marine heatwaves can cause temporary population booms
Chaikin explained that while a 7.2% decline for every 0.1 degree Celsius of warming per decade may seem small, it represents a "staggering and deeply concerning loss of marine life" when compounded over time across entire ocean basins. The study also found that marine heatwaves can cause temporary population booms but mask long-term harm from climate breakdown.
Variable impact
Responding differently to ocean warming depending on location
The study found that ocean warming affects fish populations differently depending on their location. For instance, a heatwave could cause a decline in sprat populations in the Mediterranean Sea but lead to a boom in the North Sea. This is because fish in cold areas are better able to capitalize on these shifts than those in warm areas.
Governance concerns
Implications for ocean governance and management strategies
Carlos Garcia-Soto, a scientist at the Spanish National Research Council, said the study reveals a "concerning" dynamic for ocean governance. He explained that while overall warming lowers fish biomass, the heatwaves can generate temporary increases that mask the underlying trend. This combination poses a clear risk of poor interpretation when making decisions about marine conservation and management strategies.
Perspectives
Overfishing exacerbating effects of climate change on marine life
Guillermo Ortuno Crespo, a marine biologist who is co-directing a high seas specialist group with the International Union for Conservation of Nature, cautioned against terming climate breakdown the main explanation for biomass changes in marine species. He emphasized that overfishing has historically been the main driver of biomass declines in many fisheries and is now being further exacerbated by ocean warming and deoxygenation.