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Beavers with Canadian roots are an environmental enemy in South America

Twenty beavers flown from Canada in 1946 have exploded into a population that threatens a rugged yet fragile ecosystem.

Beavers descended from 20 animals imported from Canada have become an environmental nuisance in South America's primeval forest.

Steve Dykes/Getty Images

Beavers descended from 20 animals imported from Canada have become an environmental nuisance in South America's primeval forest.

A Canadian-bred attempt to kick off a South American fur industry has resulted in an environmental calamity.

In 1946, a Canadian pilot named Thomas Lamb flew 20 beavers to Tierra del Fuego, a southern archipelago shared by Argentina and Chile. That number was less than the 50 requested by the Argentine government, but the original order fell victim to timing.

“We only had three or four days of trapping when we got an inch of ice,” Lamb wrote in a letter to a friend. “I would watch the beavers walk over our trap. However, we got to 20 beavers when we could hardly get back to The Pas in October.

Since then, those 20 beavers have exploded into an estimated population of 200,000 that is threatening to spread even further into the continent.

“Patagonian ecosystems are not prepared for the kind of changes that beavers bring,” Chilean biologist Girogia Graells told the L.A. Times. “Magellenic forest regenerates from seed banks kept on the ground. So when an area is flooded, the seeds get covered by mud and water and die.”

That flooding, of course, is a product of the hundreds of dams the beavers have constructed throughout the area, disrupting the ecosystem and threatening the future health of Patagonian forests. And unlike their northern cousins, South American trees did not evolve alongside beavers so they are unable to recover from the all the gnawing required to build those dams.

A beaver dam and its resulting destruction can be seen in a photo taken near Ushuaia, Argentina.

Ilya Haykinson/Wikimedia Commons

A beaver dam and its resulting destruction can be seen in a photo taken near Ushuaia, Argentina.

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The Chilean government has been trying to curb the population’s explosive growth by offering pelt bounties since 2003, but the slippery aquatic creatures are tricky prey in the primeval woods.

“The day’s going to come when they’re going to be the only ones left here and we’re all going to have to leave,” local logger Manuel Berbel told the BBC shortly after the bounty system was introduced.

“I want to tell people in other countries, who say what a cute animal the beaver is, to think before introducing it. It’s only natural predator is the bear, so the should have brought the bear, too.”

Since importing bears (or wolves or coyotes or cougars) to snack on the thriving beavers seems just as likely to backfire, the Chilean government is launching a new $7.8M trapping program instead.

Still, local experts are under no illusion that the alien invaders will be eradicated completely. Their best hope now, they say, is to contain them.