April 1, 2014 — To anyone on land, climate change can seem subtle. The sea, however, is changing alarmingly. The latest report from the UN’s Intergovernmental Panel on Climate Change (IPCC)—the second of three reports on the impacts of global warming—offers the scary forecast that the hotter the planet, the higher the risk of ”abrupt and irreversible changes” (pdf, p.13) to ecosystems.
We’ve already tipped past some of those ”tipping points” in the oceans, though. By the middle of the century, global warming will have thoroughly reshuffled marine ecosystems (pdf, p.16). That will leave some areas with more sea life to catch, but will thin out the marine populations in more temperate climes. The complex interplay of these and other factors will invite the invasion of a few marine species, driving others to new, less hospitable habitats—and even extinction.
Fish don’t like it hot
Since fish are lousy at adapting to hotter water, they simply move to where it’s cooler. This, says the IPCC report, will hurt commercial fishing in a big way. As fishing populations in the equatorial areas disappear, more fish and marine invertebrates will be pushed toward the poles. That means fishing fleets will have to travel farther, driving up costs. And some species won’t survive these strange new habitats.
The red and yellow areas in the map below show where fish catches will decrease the most. Many of these are close to shore, where commercially valuable species tend to congregate because food is more plentiful. There are lots of blue areas where fish populations are predicted to increase, but they’re smaller to begin with. The IPCC is vague on whether this will reduce the total global fish supply, but catching those fish will certainly be harder.