Modern Global Warming More Damaging Than In Past

by Lara Magouirk

"Some people will tell you that the planet has warmed in the past and that species always managed to adapt, so there's no cause for alarm. Unfortunately that's not the case," said Johannes Foufopoulos, assistant professor at the University of Michigan School of Natural Resources and Environment. Foufopoulos says new research illustrates major differences between global warming today and past natural climate fluctuations as they relate to species extinctions.

Generally, each species requires specific habitat and climate conditions to survive. In the past when climate changed, populations of a species would die out on one edge of their habitat range and expand into newly available habitat at the other edge. This colonization process was crucial for the survival of species during the unstable climate of the last ice ages.

However this broad movement of species, which has prevented large-scale extinctions in the past, is not likely to operate effectively in the modern world, he said.

Today, human activity has reduced previously continuous ecosystems to small fragments of natural habitat. As a result, it is becoming increasingly difficult for species to colonize areas that become habitable under a changing climate.

"Humankind has fragmented natural habitats to such a degree that many species will not be able to track a warming climate," Foufopoulos said. "There might be buildings, suburban sprawl or miles of roads in the way now."

Foufopoulos says that mobile species such as birds or butterflies, which can colonize new habitats with relative ease, stand the best chance of survival as temperatures increase. Sessile species, such as reptiles and amphibians, are at the greatest risk for extinction.

Foufopolous' findings are based on research conducted in conjunction with Anthony Ives and Marm Kilpatrick at the University of Wisconsin-Madison Department of Zoology, on reptile populations in the Mediterranean at the end of the last ice age. Because of the fragmentation of the islands, the reptiles were stuck in their individual habitats. As temperatures increased, more heat-tolerant reptiles were not able to replace those that died out on the island, and whole populations were lost. These areas experienced a net lost of diversity in marked contrast to the more typical continuous neighboring mainland areas.

Foufopolous says this process of species impoverishment foreshadows what is likely to happen with state parks and protected natural areas in the future, and directly contradict statements that downplay the dangers of global warming. "Human activity has made it very hard for some species to compensate for habitat lost to a changing climate," he says.