October 31, 2008

Climate Change Expected To Support Short-Lived Species

Researchers in Germany and Canada reported on Thursday that climate change could effect the global food chain by supporting animals with short life spans rather than their larger long-lived predators.

Researchers noted that animals showed widely differing "thermal windows" -- a range of temperatures in which they best feed, grow and reproduce, meaning that global warming would have a varying effect on each species.

"Climate change will favor 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.

"Each species covers a certain range. The ranges overlap, but their (thermal) windows are not the same," said Hans Poertner, of the Alfred Wegener Institute for Polar and Marine Research.

Further analysis of these thermal windows could reveal better predictions for how different species may react to global climate change caused by human emissions of greenhouse gases.

In the German Wadden Sea, larger eelpout fish, a long and thin species that grows up to about 500 grams (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," scientists wrote.


Image 2: Distribution areas of Cod and Eelproud in the Northern Atlantic and the distribution areas of their southern counterparts. Drawing: Sonja Schadwinkel, Alfred Wegener Institute


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