Sometimes, Poison is the Only Thing That Works

Three percent of Earth’s land mass is comprised of islands, but 95 percent of all bird extinctions have occurred on them. Main cause: Mice and rats introduced by humans.

Only 10 percent of the world’s islands are rodent-free, but a rodenticide called brodifacoum is changing that. On hundreds of treated islands recovery of native plants and wildlife has been swift and spectacular.

Consider rugged, 1,450-square-mile South Georgia Island in the Subantarctic. Before mice and rats disembarked from whaling vessels it had been Earth’s richest seabird rookery. For three years it’s been rodent free tha...