A profile of the damning legacy of forced species introduction in Patagonia.

The island of Tierra del Fuego has been overrun by invaders: Canadian beavers. The species was introduced in 1946, in what turned out to be one of the most disastrous attempts to change an environment for human advantage. From an original twenty beavers, the population has now surpassed 150,000 and poses a severe threat to local wildlife on the island, and potentially to the rest of continental South America.—Lee McLellan