Off the coast of Southern California, amid a literal sea of troubles--warming waters, microplastic pollution, overfishing--is a 96-square-mile conservation success story. Santa Cruz Island once teemed with feral pigs and invasive Argentine ants until the Nature Conservancy unleashed a coordinated campaign of eradication. That's allowed the adorable island fox to bounce back from the brink of extinction. The battle was won, but the war wasn't over, because the Nature Conservancy now has to defend that territory from yet another invader: rats. The scourge of islands everywhere, rats get ashore and breed like crazy, devouring just about everything in their paths--native plant seeds, bird and reptile eggs, local people's crops.

I get the feeling you don't dislike rats enough. Because your struggles with the rodents chewing through your house pale in comparison to the problems wrought by rodents chewing through entire island ecosystems. Release just one pregnant rat on an island and soon enough the invasive predators will have decimated that pristine environment like an atom bomb. Sure, rats on their own are pretty neat, but we've got a nasty habit of transporting them where they don't belong, at which point they transform into menaces. Such is the plight of the Galapagos Island of Seymour Norte, a speck of 455 acres off the coast of Ecuador. In 2007, conservationists succeeded in ridding the island of invasive rats, but a decade later, the fiends had returned, likely by swimming from the neighboring island of Baltra.