Argentina and Chile are now trying to undo a mistake made 80 years ago

Eighty years after 20 beavers were released into the forests of Tierra del Fuego to start a fur industry, Argentina and Chile are now working together to reverse the damage. The two countries have signed a binational agreement to coordinate beaver management and ultimately pursue eradication across the region, after recognising the growing ecological toll of the animals’ unchecked spread.

The beavers, introduced from northern Manitoba, Canada in 1946, found abundant food, suitable habitat, and no natural predators in Patagonia, allowing them to multiply rapidly over the following decades. Scientists now estimate the population numbers in the tens of thousands, spread across both Argentina and Chile, and researchers say the animals have built thousands of dams, flooded native forests, and transformed entire river valleys.

In their native North America, beaver populations are naturally regulated by wolves, bears and cougars, and native forests have evolved alongside the animals for thousands of years. Patagonia offered no such natural checks, and its native Nothofagus trees were poorly adapted to repeated flooding and tree falling caused by dam construction. Researchers estimate millions of trees have been affected over decades of beaver activity.

Conservationists have pointed out that removing the invasive population offers the best chance of protecting the region’s unique temperate forests, though the task is expected to take many years due to the animals’ widespread distribution and continuous breeding. A 2014 historical analysis by researchers Alejandro G. Pietrek and Laura Fasola confirmed the entire population descended from a single release of 20 beavers, correcting earlier claims of 25 pairs or 50 animals.