Unleash the Critters.(International Edition; ENVIRONMENT)(beaver reintroduction)

Byline: Christopher Werth

Conservationists hope to turn back the clock on Europe's wilderness by more than 11,000 years.

The Scottish countryside will soon be home to creatures nearly as strange to Britain as the monster that's said to inhabit the depths of Loch Ness. This spring, 17 beavers will be released into a remote area of rivers and deciduous forest. Hunted to extinction throughout Europe, beavers haven't roamed Britain's wilderness for almost 500 years. Their presence has been dearly missed, at least by some conservationists. Beaver dams create the kind of wetlands that many birds, fish and mammals rely on--and that costly land-management programs in Scotland and elsewhere have striven to re-create, with spotty results. Ecologists would like to invite back other long-lost species to help restore the natural balance. To save the country's vegetation from deer, which have doubled to 2 million since the start of this decade, an Oxford University biologist late last year called for reintroducing the lynx--a wildcat that died out in Britain 1,300 years ago.

Nature has long been a popular cause in Europe. Brits love their countryside of hedgerows and fields, the French their vineyards and the Germans their hiking forests. But in recent years conservationists have set their sights on the more distant past, when Europe's forests and meadows were replete with elephants, hippopotamuses, rhinoceroses and big cats. Some ambitious conservationists are now advocating a return to norms of wilderness that date back to the Pleistocene era, more than 11,000 years ago.

The megafauna from that period, which had a dramatic impact on the environment around them, are a vital, missing part of Europe's ecosystem, argue proponents of Pleistocene rewilding, as the movement is known. Elephants, for example, keep forests from growing too dense. Large predators increase the survival odds of their prey by thinning the weak from the ranks. Importing Asian and African beasts similar to the ones that roamed prehistoric Europe would increase biodiversity and restore a natural equilibrium, with the biggest mammals once again at the top of the food chain.

Nobody is advocating allowing elephants and lions to run amok in this densely populated region. The bigger animals--including water buffalo and Heck cattle, bred to resemble the massive aurochs that died out in the 17th century--would live in enclosed parks. But wilding proponents would give free rein to a long list of lesser mammals, including the beaver and the lynx, which some people fear could be destructive. Some landowners recoil at the thought of beavers gnawing down trees and flooding their property; the Scottish Parliament rejected several earlier efforts to reintroduce the mammal. Proposals to set loose wolves and bears in Britain have also encountered resistance.

The Pleistocene-rewilding effort got its start with a 2005 paper in the journal Nature. It was roundly criticized by many scientists, who argued that reintroducing these animals could have a devastating impact on the environment. Advocates countered that the environment is worse off without the animals. Russian ecologist Sergei Zimov is already testing this ...