Evolution can be fast, but not fast enough to keep up with the rate of human-caused climate change, say two researchers who have studied the evolution rates of hundreds of species in the past.
In fact, many vertebrate species would have to speed up their evolution rate 10,000 times to match today's pedal-to-the-metal rate of global warming, according to John Wiens, an ecology and evolutionary biology professor at the University of Arizona, and Ignacio Quintero, a postgraduate research assistant at Yale University.
"A big question is 'Can some species adapt quickly enough to survive?'" said Wiens. "So we looked at 17 groups of animals" comprising 540 species that included amphibians, birds, reptile and mammals, to see how they adapted to temperature changes in the past. "We estimated the rate of climate change for these species."
Specifically, they looked at when these species split into new species based on genetic data, which is a measure of their rate of evolution, and compared that to climate changes in the niches where those animals lived at those same times in geological history. What they found was that the species could handle a global temperature change of about one degree centigrade per million years. Their results appear in a paper in the latest issue of the journal Ecology Letters.
The problem, of course, is that humans are un-sequestering and burning millions of years worth of carbon-rich fossil fuels and releasing their heat-retaining gases into the atmosphere at a rate that's causing a temperature rise of perhaps 4 degrees Celsius by the year 2100. So if a species can't move to a nearby cooler habitat, it will be unlikely to evolve out of its predicament and survive.
All this seems to fly in the face of a variety of special cases of rapid evolution that have been documented in birds, reptiles and amphibians. But that's not quite so, explained evolutionary biologist Robert Holt of the University of Florida.
The rate of evolution of a particular group of animals probably has a lot to do with how big a set of genetic tools, or flexibility to develop new traits, a species has to work with. Some species have more than others, Holt said.
"There is a lot of rapid evolution in the world as well as a lot of animals that don't evolve when you thought they would," said Holt. Horseshoe crabs, for instance, haven't changed much in 300 million years, he said. But their ecological niche hasn't changed much either. So evolutionary "stasis" is key to that animal's survival.
But the same talent for not evolving could be a serious liability for a species being directly affected by rapid climate change -- like a bird, reptile or amphibian, for instance. And even those species that are more capable of changing may not always make it.
"Even if they have the genetic variation, it may not be enough," said Holt. "The rate of population decline may still be so much that they can't avoid extinction." This is especially true of species that are already small in numbers, he said.
On the other hand, there are clearly some species that are great at adapting quickly and thrive in a changing world. Unfortunately, said Holt, these are often the same species we call pests and invasive species. If so, there's a chance our 22nd century descendants could be raised on kudzo smoothies and python burgers and learn about rare frogs and birds only from books documenting the casualties of climate change.