Researchers examined the evolutionary trees of 17 families of the major groups of terrestrial vertebrates, including frogs, salamanders, lizards, snakes, crocodilians, birds and mammals. They looked at when species split off into new species in the past, and what was happening climatically in their niche environment when they did so. They compared that, in turn, to the rates of climate change scientists predict through 2100.
“We found that on average, species usually adapt to different climatic conditions at a rate of only by about 1 degree Celsius per million years,” researcher John J. Wiens, an ecology and evolutionary biology professor at the University of Arizona, told the UA News Service. “But if global temperatures are going to rise by about 4 degrees over the next hundred years as predicted by the Intergovernmental Panel of 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.”
Though some of the 540 species studied may be able to change their habitat ranges — moving north as climate warms, for example — or persist as a whole even if several populations die out, extinction is a real threat for many of them. These extinctions could in turn affect other species that may not be directly impacted by changing temperatures themselves. In a previous study, Wiens and co-authors found that declines and extinctions of species are often due to changes in their interactions with other species. Even a certain species moving north could have big consequences for existing native species — the displaced organism could out-compete the native wildlife for food and habitat, leading, ultimately, to population extinction.
It’s a long and widely-held position in science that evolution moves slowly, taking hundreds, thousands or even millions of years, but other previous studies have challenged that belief — a 2008 study found lizards introduced to a remote island in the 1970s underwent dramatic physical changes in just a few decades, and a 2006 study found a species of Galapagos finch species developed a smaller beak in just 20 years.
It’s been unclear so far, however, how exactly the Earth’s wildlife will react to climate change, but the initial findings haven’t been promising. A recent study found that small birds, like the great tit, might have the most chance of adapting to a changing climate, but another report found that migratory birds, which are often dependent on phenology changes — set times for spring bud burst and insect hatchings, for example — are highly threatened by climate change. The IPCC predicts that between 40 and 70 percent of species could go extinct if temperatures rise by more than 3.5 degrees Celsius, and a recent study found that, when CO2 levels doubled towards the end of the Triassic Period, three-quarters of all Earth’s species died off.