To reach Nihoa, an uninhabited 171-acre piece of land in the northwestern Hawaiian Islands, scientists must take a 30-hour boat ride, leap ashore from an inflatable dinghy amid violent waves and then scale a cliff. Until recently, the critically endangered millerbird lived nowhere else on earth but Nihoa. But in 2011 and 2012 Sheldon Plentovich led a team that brought 50 of the tiny songbirds on a three-day voyage to Laysan, a sister island where introduced rabbits had driven a different millerbird subspecies to extinction roughly a century ago. At one point, “I thought [a few of] the birds were going to drown,” says Plentovich, a U.S. Fish and Wildlife Service (FWS) biologist and former professional kiteboarder. “But somehow we were able to pull it off.” As documented in July in Biological Conservation, the Laysan population has since swelled to about 164, providing a bulwark should disaster ever strike Nihoa's birds.

For Plentovich and other researchers focused on remote U.S. Pacific islands—most of which have no permanent residents and are off-limits to the public—such adventures are par for the course. All their conservation projects share a common theme: undoing damage caused by careless humans (such as the ones who transported rabbits to Laysan). “It is so humbling and disconcerting to see the obvious effects of humans—even in the middle of nowhere,” Plentovich says.

U.S. Pacific Island Conservation Projects

Palmyra Atoll: Some 30,000 rats (52 per acre) overran this former military base until the FWS and two nonprofit organizations wiped them out five years ago in an operation involving helicopters, slingshots and poisoned bait. Stefan Kropidlowski, who manages the atoll's wildlife refuge and spends half the year there in near-complete isolation, has since turned his attention to similarly destructive coconut palms, which crowd out the native trees on which many seabird and crab species depend.

Johnston Atoll: A one-time nuclear weapons testing site, this four-island cluster serves as a seabird haven despite being highly contaminated with plutonium, asbestos and other toxic substances. The arrival of yellow crazy ants, however, threatened to devastate nesting populations. The invasive insect sprays acid as it swarms its prey—a tactic that frequently deforms chicks. Over the past six years FWS volunteers on six-month tours of duty have managed to beat back the infestation with poison-laced cat food and corn syrup. The latest strike team, which arrived in June, had uncovered only one small crazy ant nest as of press time.

Midway Atoll: Last winter FWS scientists on the three-island chain discovered that mice were eating albatross alive (the birds resist leaving their nests during incubation for any reason). The agency has initiated a program to remove the nonnative rodents from this location, best known for a World War II naval battle.

Kure Atoll: Strewn with garbage carried by ocean currents, this northernmost Hawaiian landmass hosts researchers as well as year-round volunteers who pick up the debris that is most likely to entangle wildlife. Cynthia Vanderlip, Kure's field camp manager, and her team are also working to demolish an unused airplane runway, eradicate invasive big-headed ants and golden crownbeard (a type of daisy), and plant native grasses and shrubs with an eye toward bolstering seabird populations. Meanwhile endangered Laysan ducks have been reintroduced, and the U.S. Coast Guard plans on cleaning up toxic PCBs it left behind decades ago.