Alister Doyle, PlanetArk 31 Oct 08;
OSLO - Climate change is likely to disrupt food chains by favouring animals with short lifespans over often bigger rivals that are worse at tolerating temperature swings, scientists said on Thursday.
The researchers in Germany and Canada said that studies of the physical characteristics of animals showed that all have widely differing "thermal windows" -- a range of temperatures in which they best feed, grow and reproduce.
That meant that climate change would not affect all equally.
"Climate change will favour species with wide thermal windows, short life spans, and a large gene pool amongst its population," the journal Science said of the findings.
Big fish such as cod, which have narrow thermal windows, were moving north in the Atlantic, for instance, partly because the food chain was disrupted by a shift to smaller plankton, reducing the amount of prey on which large fish can feed.
A shift to smaller plankton meant that juvenile cod in the Atlantic had to use more energy to feed, slowing their growth. Female cod tolerate only a narrow "thermal window" when they produce eggs, part of a strategy evolved to cut energy use.
The study focused on the oceans but the scientists said the findings may also apply to land creatures.
"Each species covers a certain range. The ranges overlap, but their (thermal) windows are not the same," Hans Poertner, of the Alfred Wegener Institute for Polar and Marine Research, who was one of the authors, told Reuters.
Knowledge of the differences could help predict the reactions to climate change, widely blamed on human emissions of greenhouse gases from burning fossil fuels.
In the German Wadden Sea, larger eelpout fish, a long and thin species that grows up to about 500 grammes (1 lb), suffered more quickly than smaller specimens when summer temperatures rose above normal.
"In the Japan Sea, different thermal windows between sardines and anchovies ... caused a regime shift to anchovies in the late 1990s," they wrote.
(Editing by Alison Williams)
