As the Earth warms up (2006 was the hottest year on record in America and the hottest in Britain since 1659), ecologists expect many plants and animals to move up, too -- up north and uphill, to locations where temperatures are more to their liking.

UC Davis ecologist Mark Schwartz is one of the first scientists to ask publicly a question that has been a topic of insider conversation for some time: Should people give those migrations a helping hand?

"Global warming is predicted to threaten a large number of our plants and animals with extinction. One obvious solution is to help species at risk move to new environments where they may thrive," said Schwartz, a professor of environmental science and policy and director of the UC Davis Center for Population Biology.

"However, our experience with costly unintended consequences of biological invasions should give us pause before embarking on such a mission."

A good example of an animal already shifting its habitat because of climate change is the Edith's checkerspot butterfly (Euphydryas editha wrighti). Found in the Sierra Nevada, the butterfly has moved in the past 25 years from lower elevations to higher ones, and from southern locations to northern ones.

Schwartz and two assistant professors at the University of Notre Dame have written the first major scientific paper on the subject of "assisted migration." The paper, "A Framework for Debate of Assisted Migration in an Era of Climate Change," is set to be published soon in Conservation Biology, the journal of the Society for Conservation Biology. His co-authors are Jason McLachlan and Jessica Hellmann.

The Jan. 23 New York Times discusses the issues in a story by science writer Carl Zimmer titled "A Radical Step to Preserve a Species: Assisted Migration." In it, an expert on global warming and extinctions calls Schwartz's Conservation Biology paper a "breakthrough" for framing the assisted migration debate.

Schwartz is chair of the UC Davis Graduate Group in Ecology, which helped UC Davis earn U.S. News & World Report magazine's top ranking in 2006 for graduate programs in ecology and evolutionary biology.