Global warming role reversal.

• Position: Survival

Science has a way of forcing us to reexamine some of our basic assumptions about nature. Consider the following statement: Animals that thrive in high temperatures are more likely to survive global warming than those that are less tolerant to heat. While this conclusion may seem obvious, a Stanford (Calif.) University study finds that the opposite may be true.

An experiment performed by postdoctoral fellow Jonathon H. Stillman examines the effect of climate change on porcelain crabs--inch-long invertebrates that inhabit coastal areas along the Pacific Ocean. The experiment focused on four species: two from the chilly coast off Cape Arago, Ore., and two from Puerto Penasco, Mexico, located on the Gulf of California. He discovered that those in the cool Pacific Northwest have the ability to adjust to larger increases in habitat temperature than crabs living in the warm coastal waters of Mexico.

"This is definitely counterintuitive," he indicates. "You would expect heat-tolerant organisms to be the most resilient to global warming, but it turns out they may have a harder time surviving as their habitat temperatures increase." Moreover, a half-degree jump in the Earth's temperature could be enough to wipe out countless porcelain crabs.

"The results were surprising," Stillman admits. It turned out that coldwater crabs were able to change their upper thermal...