A fishy problem

Global Warming's Fish-Sex Effect - TIME

"We found that in fish that do have temperature-dependent sex determination [TSD], a rise in water temperature of just 1.5 degrees Celsius can change the male-to-female ratio from 1:1 to 3:1," says Piferrer, the study's co-author. In especially sensitive fish, a greater increase can throw the balance even more out of whack. Ospina-Alvarez and Piferrer have found that in the South American pejerrey, for example, an increase of 4 degrees Celsius can result in a population that is 98% male.

What makes these findings especially troubling, of course, is that the International Panel on Climate Change (IPCC) predicts that ocean-water temperatures are likely to rise by 1.5 degrees over the course of this century — and they may even go up a few degrees more. "If climate change really does result in a rise of 4 degrees, which is the maximum the IPCC predicts, and if species can't adapt in time or migrate, then in the most sensitive cases of TSD, we're looking at extinction," says Piferrer.