A study has shown that the speed of evolutionary change is far outstripped by the rate of global warming, meaning many creatures will face extinction
by Robin McKie
Among the many strange mantras repeated by climate change deniers is the claim that even in an overheated, climate-altered planet, animals and plants will still survive by adapting to global warming. Corals, trees, birds, mammals and butterflies are already changing to the routine reality of global warming, it is argued.
Certainly, countless species have adapted to past climate fluctuations. However, their rate of change turns out to be painfully slow, according to a study by Professor John Wiens of the University of Arizona. Using data from 540 living species, including amphibians, reptiles, birds and mammals, Wiens and colleagues compared their rates of evolution with the rates of climate change projected for the end of this century. The results, published online in the journal Ecology Letters, show that most land animals will not be able to evolve quickly enough to adapt to the dramatically warmer climate expected by 2100. Many species face extinction, as a result.
“We found that, on average, species usually adapt to different climatic conditions at a rate of only by about 1C per million years,” Wiens explained. “But if global temperatures are going to rise by about four degrees over the next 100 years as predicted by the Intergovernmental Panel on Climate Change, that is where you get a huge difference in rates. What that suggests overall is that simply evolving to match these conditions may not be an option for many species.”
The study indicates there is simply not enough time for species to change their morphologies – for example, by altering their bodies’ shapes so they hold less heat – to compensate for rising heat levels. Too many generations of evolutionary change are required. Nor is moving habitat an option for many creatures. “Consider a species living on the top of a mountain,” says Wiens. “If it gets too warm or dry up there, they can’t go anywhere.”
The crucial point of the study is that it stresses a fact that is often conveniently ignored by climate change deniers. It is not just the dramatic nature of the changes that lie ahead – melting icecaps, rising sea levels and soaring temperatures – but the extraordinary speed at which they are occurring. Past transformations that saw planetary temperatures soar took millions of years to occur. The one we are creating will take only a few generations to take place. Either evolution speeds up 10,000-fold, which is an unlikely occurrence, or there will be widespread extinctions.
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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.”