A modern ark

ALONG THE BANKS of the Apalachicola river, near the border between Florida and Georgia, lives a rare tree called a stinking cedar. Once common, Torreya taxifolia seems to have got stuck in this tiny pocket as the continent warmed after the last ice age. It cannot migrate northward because the surrounding soils are too poor. Attacked by fungi, just a few hundred stinking cedars remain along the river. Rising temperatures now threaten to kill them off entirely.

Spying a looming extinction, a group of people is engaged in a kind of ecological vigilantism. The self-styled “Torreya Guardians” collect thousands of seeds a year and plant them in likely places across the eastern United States. Stinking cedar turns out to thrive in North Carolina. The Torreya Guardians are now trying to plant it in colder states like Ohio and Michigan as well. By the time the trees are fully grown, they reason, temperatures might be ideal there.

Some are dubious. The Torreya Guardians were at first seen as “eco-terrorists spreading an invasive species”, remembers Connie Barlow, the group’s chief propagandist. She rejects that charge, pointing out that she is only moving the tree within America. She also thinks that drastic action of this kind will soon be widespread: “We are the radical edge of what is going to become a mainstream action.”

Conservation is nearly always backward-looking. It aims to keep plants and animals not just where they are but where they were before humans meddled. The only real debate is over how far to turn back the clock. Scotland and Wales have been heavily grazed for centuries, giving them a bald beauty. Should they now be reforested, or “rewilded”, as the trendy term has it? Should wolves be encouraged to reclaim their ancient territory in America’s Rocky Mountains?

In a rapidly warming world, this attitude is becoming outdated. No part of the Earth can be returned to a natural state that prevailed before human interference, because humans are so rapidly changing the climate. Conservation, as traditionally practised, is being overtaken by fast-moving reality. In future the question will no longer be how to preserve species in particular places but how to move them around to ensure their survival.

A cool move

Global warming has already set off mass migrations. Having crossed the Baltic Sea, purple emperor butterflies (pictured above) are fluttering northward through Scandinavia in search of cooler temperatures. Trees and animals are climbing mountains. The most spectacular migrations have taken place in the oceans, says Elvira Poloczanska of CSIRO, Australia’s national science agency. Many sea creatures can move quickly, which is just as well: in the oceans it is generally necessary to travel farther than on land to find lower temperatures. Phytoplankton populations are moving by up to 400km a decade.

Not all plants and animals can make it to new homes, though. Some will be hemmed in by farmland, cities or coasts. Animals that live in one mountain range might be unable to cross a hot plain to reach higher mountains. And many will find that the species they eat move at a different speed from their own: carnivorous mammals can migrate more quickly than rodents, which in turn migrate faster than trees. The creatures that already inhabit the poles and the highest mountains cannot move to cooler climes and might be done for.

It is not clear that climate change has yet driven any species to extinction. Frogs native to Central and South America have been wiped out by a fungus to which they may or may not have become more vulnerable as a result of changing temperatures. Yet the speed at which species’ habitats are shifting suggests they are already under great pressure—which will only increase in the next few decades. Chris Thomas, an evolutionary biologist at the University of York in England, has estimated that by 2050 between 18% and 35% of species could be on the path to extinction.

A few years ago Mr Thomas helped transport hundreds of butterflies—marbled whites and small skippers—to Durham, at least 50km north of their usual range, and released them into the cooler air. The butterflies fared well. These days he thinks bigger. Why not move creatures farther, he suggests, to places where they have never lived?

He suggests several candidates for “assisted colonisation” to Britain. The Caucasian wingnut tree, which clings on in a few moist parts of Turkey and Iran, could probably be planted widely. De Prunner’s ringlet, an endangered butterfly native to southern Europe, feeds on grasses that are common in Britain. The Iberian lynx, an endangered cat, would find lots of rabbits to eat. Britain is a highly suitable ark for other countries’ endangered species: thanks to the Gulf Stream, its climate is expected to remain broadly constant over the next few decades.

The notion of deliberately moving species a long way from home is starting to look a little less heretical. The International Union for Conservation of Nature, which shapes biodiversity policy, recently revised its guidelines, apparently giving a slight nod to such relocations. It insists upon great caution. But “if you have too much risk assessment, nothing will happen, and these species will go extinct,” says Mr Thomas.