How far will species have to travel to escape climate change? Depends on where they live.
As climate changes, species will need to relocate to follow their ideal climate, generally by uphill or to higher latitudes. But how quickly will this change occur?
In a new study, researchers calculate that climates will shift about a third of a mile per year, on average, over the next century.
"When most people think about a rate of climate change, they're thinking about how much climate is changing in time," said study lead author Scott Loarie of the Carnegie Institution for Science at Stanford University.
"But there's also a spatial gradient," he said. "How far do you have to go from a given point to change your climate? On a mountain, it's not very far. But if you're in the middle of the Amazon basin, you have to go very far to change your climate."
The researchers combined these two aspects -- how fast climate is predicted to change over time with how temperatures vary by location -- to create a global map of how climate will move across the landscape over the next 100 years. They published the research today in Nature.
The team found that climate will move fastest over flat areas like flooded grasslands, mangroves or deserts. In these areas, the average shift is about three-quarters of a mile per year, though this could be as much as six miles a year in the most extreme scenarios.
"All of us were quite astonished at that average speed," said study author Healy Hamilton of the California Academy of Sciences. "Of course we're not trying to suggest that every spot on the planet is going to be experiencing a fixed rate of climate change, but the overall rate of temperature increase at any given point on the surface of the earth is really surprisingly high."
In mountainous areas, the velocity is slower, because temperatures change quickly up and down a slope. This means organisms won't need to move as far to track their climate. Mountains may offer refuges for some species by providing a range of climates in a small area, Loarie said.
The researchers, however, can't predict how the estimated climate movement will affect species migration.
"We just looked at climate; the extent that that is going to translate into species is going to vary," Loarie said. "If you have species that have really wide tolerance, those species might be able to absorb changes for a while before they start moving. If you have species on the edge of their range, or with a more narrow tolerance, those will need to move more or less at the speeds we estimate here."
The authors also calculated how quickly climates will sweep through sensitive ecosystems. "Only 8 percent of the world's protected areas are large enough to really hold their climates for the next century," Loarie said.
This means new conservation strategies are needed, Hamilton said.
"Our central conservation strategy is to draw static boundaries around an area we want to protect," she said. "Unless species are far more adaptable than we ever imagined them to be, species are going to try to track their preferred climates, and they're going to track them right out of the areas we've designed to protect them."
"The study nicely illustrates that terrain really can exacerbate or at least modify the potential impacts of climate change," said Jim Clark of Duke University in Durham, N.C.
"The thing we know well is, the less climate change, the better," Clark said. "The less obvious thing is that we can have heterogeneous landscapes represented in protected areas. In terms of planning and designing our reserves, we might want to think about planning and designing them to connect climates."
There are some efforts underway to do this. The Yellowstone to Yukon Conservation Initiative, for instance, aims to create a network of parks and wildlife corridors stretching from Yellowstone National Park to the Yukon in Canada that will allow species to move across this entire region.
Given how quickly climate may move, some species may not be able to move fast enough. The study raises the question of whether humans may have to play a role in helping species to keep up with their climates by transplanting them into new areas.