The effects of ocean warming are already being felt on crop yields and fishing stocks, according to the most comprehensive report yet on the topic, released by the International Union for Conservation of Nature at the IUCN World Conservation Congress in Hawaii.
“The scale of ocean warming is truly staggering with the numbers so large that it is difficult for most people to comprehend. If the same amount of heat that has gone into the top 2000 [meters] of the ocean between 1955-2010 had gone into the lower 10 [kilometers] of the atmosphere, then the Earth would have seen a warming of 36 degrees [Celsius],” says the report, “Ocean warming: causes, scale, effects and consequences.”
More than 93 percent of the extra heat generated due to greenhouse gases and other human activities since the 1970s has been absorbed by the ocean. But not without consequences. Critical species like plankton are moving farther north by as much as 10 degrees in the northeast Atlantic in order to reach cooler waters, forcing the animals that feed on them to migrate as well if they are to survive. Rising water temperatures are altering the seasonal ebb and flow of plankton populations in certain areas, potentially causing a mismatch between plankton, fish and other marine animals whose own populations respond to plankton numbers.
Fish are also shifting their range, resulting in “species invasions and local extinctions, shifts in community structure and increasing dominance of warm-water species,” says the report. Marine Protected Areas (MPA), like Hawaii’s 580,000 square mile Papahānaumokuākea, may not be as effective if vulnerable fish start to adjust their territory. Even cold-water seaweeds, which offer a vital habitat for marine animals, are losing ground, while warm-water species are expanding their presence. Especially in the Arctic, once complex seaweed forests have been replaced by far simpler and less productive “coralline crusts, filamentous turfs or small fleshy seaweeds,” says IUCN.
Warmer ocean temperatures are having on impact on farms, too, by increasing the rainfall in monsoon-regions and lowering precipitation in several sub-tropical regions. Both situations can dramatically hurt crop yields.
“Ocean warming is one of this generation’s greatest hidden challenges – and one for which we are completely unprepared,” IUCN Director General Inger Andersen said in a press release. The statement emphasizes that the greatest losses will be felt by poor coastal communities who depend on fisheries and aquaculture for their subsistence. Together, the two provide roughly 4.3 billion people with about 15 percent of their protein.