The Effects of a Warmer World Are Visible in Animals’ Bodies

For humans, adapting to climate change will mostly be a matter of technology. More air conditioning, better-designed houses and bigger flood defences may help mitigate the effects of a warm world.     1     In a paper published in Trends in Ecology & Evolution, a team led by Sara

Ryding, a phd candidate at Deakin University, in Australia, shows that is already happening. Climate change is already altering the bodies of many animal species, giving them bigger beaks, limbs and ears. In some species of Australian parrot, for instance, beak size has increased by between 4 % and 10 % since 1871.

All that dovetails (吻合)nicely with evolutionary theory. “Allen’s rule”, named for Joel Asaph Allen, who suggested it in 1877, holds that warm-blooded-animals in hot places tend to have larger appendages (附属物) than those in less hot regions.    2     For example, Fennec foxes, which are native to the Sahara desert, have strikingly large ears, especially compared with their Arctic cousins.

Ms Ryding examined museum specimens, comparing their bodies to those of their modern counterparts. She is not the first researcher to take that approach.     3     All sorts of other factors, from changes in prey to the evolving reproductive preferences of males or females, might possibly have been driving the changes. Her team combined data from different species in different places.Since they have little in common apart from living on a warming planet, she says, climate change is the most reasonable explanation.

    4     Researchers have already seen changes in the geographical range of many species, from insects to fish. Another evolutionary rule-of-thumb, Bergmann’s rule, holds that animals in hotter places tend to have smaller bodies, another way to boost the ratio between surface area and volume. Other animals may alter their behaviour as well as their bodies, such as by seeking shelter at hot times of the day.

Studying a broader range of animals will help firm up exactly what is happening. Much of Ms Ryding’s data concern birds, with less information available for other taxa (类群). But it seems clear that the world of the future is not just going to be hotter than humans are used to.    5