Ending Extinction or Playing God?

Inside a sometimes-violent mission to save endangered animals. An excerpt from Battle at the End of Eden, The Atlantic's first story to be published exclusively as an ebook.


Midway Between the Baja Peninsula and the Mexican mainland, a hunk of volcanic rock named San Pedro Mártir juts out of the warm, productive waters of the Gulf of California. The island spans an area roughly half the size of Central Park and has a beachless shoreline of near-vertical cliffs, some surging as high as 500 feet. No humans live here. Instead, it is a mecca to tens of thousands of land and seabirds. For centuries, more than 80 species, from brown pelicans and frigate birds to warblers and kingfishers, have vied for purchase on its stony outcroppings. As a result, its lower slopes are slathered with a coating of bird guano so thick that the island, when viewed from a distance, appears bone white.

In 1885, prospectors from the Mexican Phosphate and Sulphur Company glimpsed San Pedro Mártir's gleaming white bulk, and saw gold. Guano is rich in nitrogen and phosphorus, elements in constant demand for use in fertilizer and gunpowder.

The miners' impact on the island was severe. As they trampled thousands of nests, the birds abandoned their colonies, and the ridgelines began to erode under the stress of relentless excavation. By 1888, the island had more or less been picked clean, and the operation shut down.

A century passed, and by all appearances, activity on the island proceeded as it had for hundreds of years. In March 1990, a Ph.D. student named Bernie Tershy set up camp there to study the island's seabirds--he was struck by something surprising. All over the island, black rats menaced the birds; they infiltrated the colonies, pilfered the eggs, and preyed on the young. At some point during the guano excavations--likely as one of the many supply ships hugged the rocky coast--the rats had scampered ashore. Now, all these years later, as Tershy tracked the birds, he watched helplessly as the rats ate his data. "The birds get oil for their feathers from a gland above their tails, and rats like that. It's one of the places they like to start," he explained. They also go for the middle of the back, where "they can run up and chew, chew, chew, and the birds have a hard time shaking them off."


The island was never intended to accommodate rats. With no predators to keep them in check, Tershy knew the rats would just keep killing the defenseless seabirds until the colonies ceased to exist--these birds, that bred only on this rock and a handful of others scattered across the ocean, didn't stand a chance. Perceiving the situation as grossly unfair, Tershy began to think of ways he might relieve the toll the rats were taking.

In the back of his mind was a story he'd heard. In 1958, an ornithologist at the National History Museum of Los Angeles County named Kenneth Stager visited Clipperton Island, a tiny desert atoll in the Pacific Ocean. He'd gone expecting to observe what early explorers had described as massive colonies of tropical seabirds, but what he found shocked him. Feral pigs left by a failed human settlement had decimated the flocks, leaving a mere 650 birds by Stager's count. The survivors had crammed themselves onto an abandoned ship and some rocky ledges offshore, the only surfaces safe from the pigs' reach.

Stager was what Tershy calls an "old-school ornithologist," so naturally he'd brought a shotgun with him. He had planned to use it to collect a few of the birds, but instead, shot every last pig he could find. Thirty years later, when Tershy visited Clipperton, it had transformed. The seabirds were back, nearly 140,000 strong, as were millions of large, orange land crabs that the pigs had also done in. Stager, in his thoroughness, had staged a one-man eradication, allowing Tershy to find an ecosystem with no trace that humans had ever been there. Admiring Stager's brazen willingness to take action, Tershy wondered if he might somehow replicate his success.

Presented by

Amanda R. Martinez is a science writer who focuses on conservation, neuroscience, and marine biology. Her work has appeared in Scientific American, in Seed, and on PRI’s Living on Earth.

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