In a classic example of ecological shortsightedness, the problem began when fifty North American beavers (Castor canadensis) were introduced by the Argentine government during the 1940s in the hopes of establishing a fur industry. Since then however, without natural predators to trim their numbers, the beaver population has now exploded to 100,000 — invading almost 16 million hectares of unique, native forest. The beavers have damaged the forests so much that "that is absolutely stunning - it looks like bulldozers steamed through," says ecologist Josh Donlan, director of Advanced Conservation Strategies, a non-profit based in Driggs, Idaho.South American trees not co-evolved with beavers
One of the key factors to the extent of the destruction lies in the fact that South American trees do not regenerate back from their roots as North American trees do. The beaver dams here transform once-pristine streams into stagnant bogs, negatively impacting local aquatic wildlife. On top of that, once these ponds are drained out, they become breeding ground for other exotic, non-local species.
"The change in the forested portion of this biome is the largest landscape-level alteration in the Holocene - that is, approximately 10,000 years," says Christopher Anderson of the Institute of Ecology and Biodiversity in Santiago, Chile.
Beaver control to prevent migration
Killing traps are one of the beaver control methods now being tested, in addition to adapting North American beaver control techniques using trappers, dogs, helicopters and boats. "We'll have to move in on the beavers in a rolling front, going from watershed to watershed to remove them, with a massive monitoring program behind it to make sure they have all been eradicated," describes Anderson.
But will a program focused solely on watershed areas be effective? "The beavers only live near the water, so you don't have to go over the whole landscape," explains Anderson. "But you have to make sure you eradicate them all - if you have even two beavers, they could repopulate the whole archipelago."
The team's main priority is to prevent the beavers from migrating north to Chile, where a few have already been sighted. According to forest engineer Guillermo MartÃnez Pastur at the Austral Center for Scientific Investigation in Ushuaia, Argentina, if Chilean forests are to be protected from the beaver threat, they "must be totally eradicated."
Image: hiro008 on Flickr