Scientific American, 17th July
As San Diego and Los Angeles have grown, the scrub land of southern California has been paved and built over. That has squeezed out the Quino checkerspot butterfly’s habitat, and with the climate changes coming as a result of human greenhouse gas emissions, its listing as an endangered species by the U.S. government may not be enough to save the pretty little butterfly from extinction.
But a group of biologists suggest in this week’s Science that simply moving the butterfly into similar habitat in nearby mountain ranges might solve the problem by overcoming the unnatural barriers humans have erected in the path of any potential shift in its natural range to follow such changing conditions. They call the idea "assisted colonization."
"Humans have dominated the landscape to such an extent that natural dispersal cannot take place in many areas," says biologist Camille Parmesan of the University of Texas at Austin, who helped craft the proposal. "It is in those cases that assisted colonization makes the most sense—use it on species that would have been able to do it on their own, if not for humans."
Specifically, Parmesan and an international group of biologists are proposing moving certain carefully selected species, such as the Quino checkerspot butterfly, as their historic habitats change rapidly because of global warming. They aren’t calling for drastic moves, though. "We are not recommending placing rhino herds in Arizona or polar bears in Antarctica," the group writes, as, for example, the polar bear would then devastate Antarctic penguin and seal populations that have never encountered such a predator. "We are, however, advocating serious consideration of moving populations from areas where species are seriously threatened by climate change to other parts of the same broad biogeographic region," meaning in nearby locations sharing similar ecosystems.
The cost of such an effort is unknown, but could range from nearly free for a small-scale effort such as shifting the Quino a few 100 miles (kilometers) north to multimillion dollar projects such as, for example, moving a monkey species from one cloud forest to another, according to marine biologist Ove Hoegh-Guldberg, of the University of Queensland in Brisbane, Australia, and lead author of the proposal. Not every potential project makes sense: The researchers offer a list of conditions under which such assisted colonization would be appropriate, including imminent extinction, feasibility and a favorable cost–benefit analysis.