Study: Ocean Warming Has Already Affected the World's Fisheries
In a new paper published this week in Science, a group of researchers led by Dr. Chris Free of UC Santa Barbara and Prof. Malin Pinsky of Rutgers found that worldwide fishery productivity has already declined due to warming seas. According to the authors, the maximum sustainable yield of the world's fisheries fell by four percent between 1930-2010 due to warming, with some ecoregions experiencing larger declines of 15-35 percent.
While the percentage decline seems small, it represents about 1.4 million tonnes per year of lost animal protein for human consumption, or about 0.7 percent of the global total from all animal species. It also represents an additional cause of fish population pressure in an era characterized by widespread overfishing and illegal, unreported and unregulated harvests.
The scientists combined global data on fisheries with ocean temperature maps to estimate temperature-driven changes in the sustainable catch (or maximum sustainable yield) from 1930 to 2010. Their analysis covered about one third of the reported global catch, and losing species outweighed the winners as the oceans warmed.
Notably, the study is a hindcast: it evaluates apparent environmental damage that occurred years ago. “We were stunned to find that fisheries around the world have already responded to ocean warming,” said Prof. Malin Pinsky, a co-author and associate professor at Rutgers. “These aren’t hypothetical changes sometime in the future.”
In addition to net worldwide effects, different regions and species are responding differently to the effects of global climate trends. The UN's Food and Agriculture Organization (FAO) projects a warming-driven decline in maximum sustainable yield in Asia and an increase in Europe, but Free et al. observed somewhat different patterns in past data: the greatest losses identified were in the Sea of Japan, the North Sea, the coast of the Iberian Peninsula, the Kuroshio Current and the Celtic-Biscay Shelf regions. The greatest gains occurred in the Labrador-Newfoundland region, the Baltic Sea, the Indian Ocean and the Northeast U.S. Shelf.