Headline Science: Assisted Migration

Can scientists save species from extinction by moving them to new habitats?

In 2004, an international team of scientists estimated that up to 37 percent of Earth's species would become extinct by 2050 because of global warming, including the Bay checkerspot butterfly. Although this butterfly was once a common sight in the Bay Area, habitat loss has now reduced the species to half a dozen colonies. The few pockets of checkerspot habitat that do remain may soon disappear because of rapid global climate change.

Faced with such dire circumstances, some scientists have begun to wonder about a radical step to save this species and others: a strategy called assisted migration. According to this plan, scientists would identify endangered species that are being cooked out of their current habitats and move them – up to hundreds of miles away–to cooler places.

The Bay checkerspot butterfly (Euphydryas editha bayensis) is critically endangered. Credit: T.W. Davies

While it may sound like a simple solution, assisted migration is actually quite controversial. Even if, for example, scientists were to move Bay checkerspot butterflies up to cooler terrain in Washington, the butterflies may not be able to find suitable food there. Entire networks of species might have to be moved to achieve a successful transplant. Moreover, it is nearly impossible to predict whether or not an introduced species will become invasive in its new habitat, preying on native species or out-competing them for food.

Academy scientist Jack Dumbacher sees yet another danger to implementing assisted migration. "The Endangered Species Act is currently one of the only tools conservationists can use to protect pristine land," he explains. "If moving a species to another area is accepted as an alternative to saving the original habitat, I'm afraid the land will be lost little by little."

While all scientists would love to prevent future species extinctions, assisted migration may create more problems than it solves.