Credit: Tracy Feldman

Although climate change has driven some species closer to the poles, the range of others has remained unchanged. But as temperatures continue to rise, the southern boundaries of plant species that have so far remained static may shift dramatically.

Daniel Doak at the University of Wyoming in Laramie and William Morris of Duke University, North Carolina measured survival, reproduction and growth in two tundra plants, moss campion and alpine bistort, between 2001 and 2006 (ref 1). The study sampled the plants' entire ranges, from Colorado to Alaska. Plant survival rates in Colorado were lower than in more northerly areas. But owing to longer, warmer growing seasons, plants in Colorado grew more rapidly and produced more fruit than their northern counterparts, preventing declines at southern locations.

During the warmest years of the study, however, southern temperatures exceeded the tipping point for a range shift in both species. Further warming could cause plant populations in Colorado to crash, say the scientists.