Science 334, 652–655 (2011)

Credit: MEGAN SAUNDERS

To speak of a steady poleward advance of species is to oversimplify how organisms are responding to a warming world, argues a team led by Michael Burrows of the Scottish Marine Institute in Oban. A more accurate approach is to map spatial changes in isotherms, and then to consider the challenges that organisms face in maintaining their thermal niches.

Burrows and colleagues did this, and then compared the results with a calculation of the seasonal timing of temperatures over the past 50 years, measured in days per decade. They report that both methods show a patchy velocity of climate change on land and seasonal shifts at sea. For example, spring advanced 30–40% faster in the oceans in both hemispheres than on land between 1960 and 2009.

The authors say that certain marine zones are particularly at risk from climate change, notably those near the poles where species may lose their thermal niches entirely, and places such as the Mediterranean Sea, where the European land mass prohibits creatures from tracking thermal niches.