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Species Simply Can't Adapt Fast Enough to Keep Up with the Changing Climate

New research shows rising temperatures require many animals to evolve 10,000 times faster than they have in the past.
Photo: USFWS/Flickr

Among people that say climate change isn't a big deal, a fairly common refrain is that animals can just adapt to deal with warmer temperatures. But new research coming out of the University of Arizona shows that global temperatures are rising so quickly—with 4°C higher temperatures looking increasingly assured within the next 100 years—that many vertebrate species will be unable to evolve to these new conditions quickly enough.

The research, published in Ecology, shows that many animals would have to evolve 10,000 times more quickly than they have in the past just to keep up with the changing environment.

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"We found that on average species usually adapt to different climatic conditions at a rate of only about 1°C per million years," University of Arizona professor John Weins, a co-author of the study, said in a release. "What that suggests overall is that simply evolving to match [the conditions expected by the end of this century] may not be an option for many species."

To figure out how much change species could handle in general, the researchers looked at what types of changes species could survive in the past.

"Basically, we figured out how much species changed in their climatic niche on a given [evolutionary tree] branch, and if we know how old a species is, we can estimate how quickly the climatic niche changes over time," Weins said. "For most sister species, we found that they evolved to live in habitats with an average temperature difference of only about 1-2°C over the course of one to a few million years."

So if a couple degrees of temperature rise spread over a few million years was survivable, what happens when you compress that time frame immensely?

"We then compared the rates of change over time in the past to projections for what climatic conditions are going to be like in 2100 and looked at how different these rates are," Weins said. "If the rates were similar it would suggest there is a potential for species to evolved quickly enough t to be able to survive, but in most cases, we found those rates to be different by about 10,000-fold or more. Almost all groups have at least some species that are potentially endangered, particularly in tropical areas."

Of course, some species may be able to adapt to new climatic conditions by moving to nearby areas, but that requires, at least in most cases, unimpeded access to nearby areas with newly suitable climatic conditions. Considering the amount of habitat fragmentation that has occurred with the expansion of human population and land use, that's not always an option available to animals. And, it doesn't apply to animals that already live in high elevations, with nowhere higher to migrate.

In a wider view, recent analysis by the International Union for Conservation of Nature shows that 24-50 percent of bird species are highly vulnerable to extinction due to climate change, with 24-44 percent of amphibians vulnerable. Looking the effect of climate change on extinction at the broadest level, research published in Nature shows that by 2050 15-37 percent of all species on the planet will be "committed to extinction."