It’s open season on Patagonia’s voracious, disruptive … beavers?

Even furry, seemingly friendly creatures like beavers can become big problems when dropped into an ecosystem with no predators to keep them in balance.

That’s what happened in Patagonia, where the busy dam-builders are profoundly changing the once-pristine region that spans the southern ends of Chile and Argentina.

In 1946, 25 pairs of Canadian beavers were brought to Patagonia to kickstart a fur industry. That business didn’t take off, but the beavers flourished; there are now about 100,000 beavers in Patagonia that don't belong there. 

“They've completely changed the entire ecology of the region,” says Derek Mead, editor-in-chief of Motherboard, a digital magazine and video channel.

The industrious beavers have chewed down trees and diverted rivers, reshaping the area's river system. That's a useful function in their normal habitat, but in Patagonia, they've turned beech forests into barren wastelands. The trees, cut down to stumps by the beavers, can’t regenerate or hold onto the soil. Rains and heavy flooding erode the soil, turning a previously dense forest and tight river into an open pit, Mead says.

“One of the biggest things you'll see is literally just a barren wasteland of all the old beech trees that had been growing nice and tightly just cut down and just left with stumps. Basically mud,” he says.

The vegetation that relies on shade from the trees dies and sun-loving plants take over. That in turn changes the environment for local animals, which have to migrate elsewhere.

Motherboard recently made a documentary, "The Beaver Slayers of Patagonia," that chronicles the devastation and human efforts to respond. Park rangers are trying to manage the invasion and prevent the beavers from moving further north.

“We can’t say the beaver’s arrival is an imminent threat," says a park ranger in the documentary. “It’s different for each region, but more resources are needed.”

That means using the old-fashioned method of pest control: hunting. Beavers were protected for 30 years by laws making it illegal to hunt them; now the law categorizes the animal as a harmful species and allows year-round hunting without restriction.

“Right now there's a big emphasis … from both the Chilean and Argentinian governments to try to get both government people and any old hunter to try and kill them," Mead says. "That's the best way to manage them right now … versus trying to poison them en masse or something like that."

Some trappers are selling their catch for the fur, the original reason for introducing the beavers to the area. There’s now even demand for the meat, and some restaurants are starting to offer beaver on their menus.

Even so, officials acknowledge that complete eradication of will be difficult, if not impossible,

“We shouldn’t hate the beavers for being here. This was a result of what humans did,” says one official. “But as a society we have to take responsibility for controlling them.”

This story is based on an interview from PRI's Living on Earth with Steve Curwood.