TIERRA DEL FUEGO NATIONAL PARK, ARGENTINA—They look so cute and harmless, with their furry bodies, long whiskers and buck teeth. And the tourists who flock to the southern tip of South America rejoice when they see the beavers busily building dams and gnawing through trees.

But it’s exactly that industrious, tireless work ethic that’s fast reducing forests here and alarming authorities, who have tried just about everything to stop the beavers, including a campaign to get locals to acquire a taste for beaver meat.

Now there’s even talk about hiring professional sharpshooters to search and destroy every last one of them, perhaps even from helicopters.

Why the anxiety over Castor canadensis, a web-footed herbivore known for being painfully shy?

It’s because the 25 pairs of Canadian beavers introduced here in 1946 by Argentine officials to generate a commercial fur trade might now number 200,000, a virtual army that is chomping, cutting and flooding forests across this frosty, remote archipelago known as Tierra del Fuego, or Land of Fire. And the beavers are moving north, having swum across the turbulent, freezing waters of the Strait of Magellan.

With a colony firmly established on continental South America, on Chile’s Brunswick Peninsula, some people fear there might be no stopping the ingenious mammals. What lies ahead are lots of big, juicy trees along the Pacific fjords of Chile and in the lush mountains of Argentine Patagonia.

“We think they could occupy all of Patagonia,” said Laura Malmierca, a biologist with Argentina’s parks service.

Of course, none of this is the fault of the beaver.

It’s nature’s engineer, a plodding, purposeful animal instinctively obsessed with building dams, canals and lodges as protection against predators and to easily move and store food. Frontiersmen in North America ranged far to trap beaver, its fur prized for hats and its glands for medicine.

Argentina’s navy, which administered this remote territory in the 1940s, thought the beavers could spur the fur industry here. There were only a few hardy souls on Tierra del Fuego then, and Argentina worried it could lose its half of the island to perennial rival Chile.

The industry, though, never took off.

Instead, the beavers did. With no natural predators — no bears, wolves, wolverines or coyotes, as in North America — the beaver population exploded, spreading to smaller islands.

“At least they didn’t bring bears here,” quipped Malmierca.

Today, the locals have something of a love-hate relationship with beavers.

They might be rodents and cause millions of dollars in damage, often to roads flooded by beaver dams. But they are so beloved by some that a guy in a beaver suit plies the streets of Ushuaia, Tierra del Fuego’s main tourist town, passing out visitor brochures.

Pablo Kunzle, an expert beaver trapper with the parks service, talks about them with a mix of admiration and dread.

“They’re hydraulic engineers!” he said, showing off a dam, perfectly built, along a stretch of valley sandwiched by towering snow-capped peaks. “They’re almost the perfect machine.”

Perhaps such ambivalence has blunted efforts to corral the furry beasts. When the government started paying locals to trap beavers, novice hunters never tried too hard. They mainly trapped beavers by the sides of roads, rarely venturing deep into the forest.

“There is no hunting culture,” said Malmierca, noting that many of the people who settled here were from cosmopolitan Buenos Aires.

Ezequiel Rodriguez, owner of Gustino restaurant in Ushuaia, recounted how chefs were urged to come up with tasty beaver dishes for the city’s 2007 food festival.

“Next, we had to ask, ‘If we put them on the menu, would people eat them?’” said Rodriguez. “And will chefs accept them?”

The chefs did, though the meat was gamey and a little tough, and it needed a long time to cook. As it turned out, the government never gave permission for the harvesting of beaver for food.

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Now, at least on paper, Chile and Argentina have agreed that it is time to get serious.

A 2008 report on the feasibility of eradication makes clear that eliminating the beavers is “of highest priority.” It suggests a variety of tools: traps, explosives, hunting dogs.

The two countries have not decided what step to take next, or how to pay for the expensive endeavor. For the time being, the focus is on simply managing the beaver population.

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