The problem is that the beavers, hunted in North America by wolverines, bears and other animals, have no natural predators in Tierra del Fuego, The Washington Post reported Friday. As they multiply, they cut down trees and build dams that flood the forests, killing still more trees.
Pablo Kunzle, a trapper with the Argentine parks service, has a love-hate relationship with his prey.
"They're hydraulic engineers," he said, pointing to a dam in a pristine river valley. "They're almost the perfect machine."
The Argentine navy originally brought beavers to Tierra del Fuego, an island split between Argentina and Chile. The goal was to establish a trade in beaver pelts, which never took off.
Now the beavers have moved across the Straits of Magellan and at least one colony is thriving on the Brunswick Peninsula in Chile.
"We think they could occupy all of Patagonia," said Laura Malmierca, a parks service biologist.
Efforts to popularize beaver meat as a human food have fallen flat. The next step may be importing sharpshooters for a massive kill.