Science 333, 1024–1026 (2011)


Although it is generally accepted that Earth's species are migrating up mountainsides and towards the poles because of global warming, demonstrating this trend in a statistically robust way has not been easy. Now, an analysis that combines all published studies on the subject has revealed a migration rate that is two to three times faster than previous estimates.

Using more than 2,000 measurements of species' movements, Chris Thomas, of the University of York, UK, and his colleagues report that the world's flora and fauna are, on average, shifting their distributions towards higher elevations at a rate of 12.2 metres per decade and to higher latitudes at a rate of 17.6 kilometres per decade. However, they found great variation among taxa. A quarter of all species shifted their ranges downhill, for example, and 22% moved towards the Equator. Birds changed elevation the least, but moved most rapidly away from the Equator.

There is a good correlation, the researchers say, between predicted range shifts for different regions (based on average temperature change over the past 40 years) and how far species in those regions have actually moved.