Today’s paradox: tropical ectotherms don’t like warming

Ecological damage of climate change is expected to be highest where the changes are most profound. That is, due to albedo feedbacks, at very high latitudes and at very high altitudes. So species loss is expected to be highest in for instance the Arctic tundra ecosystem. The decline of unique species of Alpine flora would also be above average. This is of course amplified because these climate zones often form the local extremes. If you like it chilly, it’s hard to keep finding new habitat once you run out of upward slopes. The same goes for Arctic warming. Your average snowy owl will have a hard time crossing the equator in search of a new life on Antarctica.

However symbolic such species may be, the ecological focus may be wrong. The total biodiversity is much higher in the tropics, forested areas especially. And today a new study in Nature claims tropical species are equally at risk – even at slight warming. This goes for the ectotherms at least, the ‘cold-blooded’ animals, like amfibians, fish, reptiles and insects.

Cold-blooded animals have their metabolisms evolved around certain climatic values, making them dependent. Not only do they need to warm at the right time of day, for instance to start a hunt, they also need to cool, while inactive. If however their core temperature stays elevated, so do their caloric needs.

“Here we show that estimated changes in terrestrial metabolic rates in the tropics are large and equivalent in magnitude to those in the north temperate-zone regions, and are in fact far greater than those in the Arctic, even though tropical temperature change has been relatively small,” concludes author Michael Dillon, Assistant Professor in Zoology at the University of Wyoming.

“Because of temperature’s nonlinear effects on metabolism, tropical organisms, which constitute much of Earth’s biodiversity, should be profoundly affected by recent and projected climate warming.”

© Rolf Schuttenhelm |

Comments are closed.