Avoiding the heffalump trap

As the climate warms, conservationists might consider looking to the past to protect the future

THE Earth is heating up—and, if a study presented by Britain’s Meteorological Office to a meeting in Oxford this week is anything to go by, it may soon be hotter than it has been for more than a million years. Even if the 4ºC rise this century that the Met Office predicts does not come to pass, climate change is still going to be awkward. Because people are able to adjust their surroundings to meet their needs, Homo sapiens will no doubt survive. Other species, though, cannot make such adjustments. Instead, they deal with changing climates by moving their ranges. Or, at least, they have done so in the past.

Now, with much of the Earth’s surface given over to agriculture, such range-shifts are not so easy, and many species may need a helping human hand. If such “assisted migration” of threatened creatures does take place, however, the question will arise of what to move where. Introductions of new species, both accidental and deliberate, over the past few centuries show the problem. Many fail to thrive. A few thrive too well.

Creating whole new ecosystems that mix natives with transplanted exotics might be risky. But on September 23rd, at the annual meeting of the Society of Vertebrate Palaeontology, held in Bristol, England, Anthony Barnosky of the University of California, Berkeley, and Elizabeth Hadly of Stanford University suggested a way to minimise this risk. Their proposal was to learn from the flora and fauna living in past environments that went through climatic changes similar in scale to those happening today— namely the ones that accompanied the ice ages of the Pleistocene epoch, which ran from 2.6m years ago to 10,000 years ago.


Hot and bothered
The idea of turning parts of the United States into “Pleistocene Park”, by importing endangered African wildlife and releasing it in, say, Texas, was raised in 2005 by Josh Donlan of Amherst College, in Massachusetts. Though the threats he had in mind were hunting and habitat loss rather than climate change, part of his inspiration was, indeed, the fossil record. This shows that, in the recent past, North America had a much more diverse large-mammal fauna than it does now. For example, bones dug out of the tar pits at Rancho La Brea in Los Angeles (illustrated above) show that mammoths, mastodons, sabretoothed cats, jaguars and lions were all present in southern California between 38,000 and 10,000 years ago.

Dr Donlan argues, in light of this, that moving lions, cheetahs and elephants from Africa to America is not a stupid idea. Though they are not the exact same species that disappeared from the Americas 10,000 years ago, they are those species’ ecological equivalents. Better a home in an alien habitat than extinction.

Dr Barnosky is not quite so gung-ho about transcontinental transplants, but he thinks that understanding the ebb and flow of species in response to previous climate change within a continent may help conservationists by pointing out places where species that are endangered in their present ranges have done well in the past. In previous periods of warming, for example, many types of animals have displayed reliable trends. Ground squirrels spread rapidly as the temperature ameliorates. Vole populations contract.

Gophers move west, while simultaneously becoming physically smaller. His work in a place called Porcupine Cave in Colorado, shows that cheetahs, camels, horses and peccaries were present 800,000 years ago, yet none of these species survives there today. Meanwhile, Dr Hadly has been comparing the fossil record with modern-day reality in Yellowstone National Park, where types of amphibian that have thrived for 3,000 years have all but disappeared recently, as their ponds have dried up.

Whether such research really can help conservationists is moot. The fossil climates Dr Barnosky and Dr Hadly have been looking at are, even at their warmest, cooler than the more extreme predictions for the next 100 years. But, by showing what sorts of species have managed to coexist in the ecosystems of the past, palaeontology might indeed help to design those of the future.

Source of Information : The Economist 2009-10-03