A new study published in the journal Global Change Biology has found that, without immediate and strong actions to mitigate climate change, global fish supplies will not be able to be recover to sustainable levels. By projecting the impact that various global temperature rises and ranges of fishing activities would have on biomass (the amount of fish by weight in a specific area) from 1950 to 2100, the experts discovered that climate change has reduced fish stocks in 103 out of the 226 marine regions studied, and that these stocks will struggle to recover under most projected global warming levels over the 21st century.
“More conservation-oriented fisheries management is essential to rebuild over-exploited fish stocks under climate change. However, that alone is not enough,” said study lead author William Cheung, an expert in marine ecosystems at the University of British Columbia (UBC). “Climate mitigation is important for our fish stock rebuilding plans to be effective.”
By using computer models to identify the climate change levels at which over-exploited fish stocks cannot rebuild, the scientists found that, if global temperatures exceed 1.8 degrees Celsius above pre-industrial levels, fish stocks will not be able to rebuild themselves. In a worst-case scenario (above 4.5 degrees warming), if people all over the world fished only three quarters of the annual sustainable catch, fish stock will still be unable to rebuild.
“Tropical ecoregions in Asia, the Pacific, South America and Africa are experiencing declining fish populations as species both move further north to cooler waters and are also unable to recover due to fishing demands,” Dr. 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 are dependent on fisheries for food and nutrition security, revenue, and employment.”
In a scenario in which nothing is done to mitigate global warming and overfishing beyond sustainable targets occurs, global fish stocks are estimated to drop to 36 percent of the current levels. Sadly, due to climate change, the world is unlikely to ever return to historical levels of fish stocks.
“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 rebuilding under climate change. These need to recognize the ways that marine biodiversity contributes to livelihood and economies, particularly in tropical marine ecoregions, as well as requiring more stringent limits on fishing activities to achieve greater biomass rebuilding potential,” Dr. Cheng concluded.