One of the questions raised by the prospect of climate change is whether it could cause more species of animals to interbreed. Two species of flying squirrel have already produced mixed offspring and those have somehow been blamed on climate change, along with a hybrid polar bear and grizzly bear cub (known as a grolar bear, or a pizzly).
A paper in Nature Climate Change tallies the potential number of such pairings and across North and South America it estimates that only about 6 percent of closely related species whose ranges do not currently overlap are likely to come into contact by the end of this century.
A 2010 editorial in Nature suggested that northern species may begin to interbreed and create a so-called "Arctic melting pot," and even prompted one artist's rendition of what those new offspring would look like.
Such speculation worried land managers looking at how to prepare for climate change.
"Climate change is causing species' ranges to shift, and that could bring a lot of closely related species into contact," said lead author Meade Krosby, a scholar in the University of Washington's Climate Impacts Group. "People have been concerned that climate change would be bringing all these species into contact, and that this could unleash a wave of interbreeding. What we found is, not so much."
The study attempted to see how much that should be a concern. It looked at 9,577 pairs of closely related species of birds, mammals and amphibians in North and South America. For the 4,796 pairs whose ranges currently do not overlap, computer models show that only 6.4 percent of them will come into contact due to climate change by the year 2100.
The most overlap among species occurred in the tropics, and among birds, likely because more species live in the tropics and birds cover wider ranges, Krosby said.
While the study suggests that climate change is unlikely to result in widespread interbreeding, wildlife biologists still need to consider their particular region and animals of interest to best protect specific populations.
"Managers still need to look case-by-case at species at a local scale, but at a global scale, the big picture is that it's probably not going to be a huge problem," Krosby said.
The study likely overestimates how many species could be at risk of interbreeding because it assumes that all species will be able to access new habitats that become available due to climate change. In fact, natural barriers prevent animals from reaching all potential new habitats, and humans have created new barriers such as highways, farms, and cities that can block migrations to more hospitable places.
"The number one strategy for helping biodiversity respond to climate change is to increase connectivity, to link up habitats that have been fragmented by human activity, so species can move, and track climate as it shifts to stay comfortable," Krosby said. "If people are worried that wildlife corridors and other ways to increase connectivity could bring these species into contact, we're saying: That's probably not going to happen, and allowing species to move is far more important."