On the Palmyra Atoll in the central Pacific Ocean, conservation biologists are in the midst of a massive, unprecedented experiment. They are trying to rid this remote island of all but a few coconut palms. The gangly tree is an icon of idyllic tropical islands, but also an aggressive invasive species that crowds out native plants and animals. By removing 99% of Palmyra’s millions of palms, biologists hope to create more room on the atoll’s three dozen islets for indigenous forests and seabirds, including the world’s second largest colony of red-footed boobies…

Ripping out the palms has long been on the list of restoration projects on Palmyra. First, however, managers decided to attack another invader, black rats, which likely arrived on ships during World War II. With no predators, rats multiplied into the tens of thousands. They ate the seeds and gnawed the saplings of native trees and attacked seabird colonies, including those of sooty terns, which nest on the ground. Rats are the key suspects behind the absence on Palmyra of eight other species of ground or burrow-nesting birds, including shearwaters and petrels, all found on central Pacific islands that have remained rat-free. The first attempt to eradicate the rats in 2002 failed, partly because Palmyra’s abundant land crabs out-competed the rodents for the poisonous bait. The crabs’ physiology allowed them to eat the poison—the anticoagulant brodifacoum—without ill effect.

The second effort was successful only after [researchers] radio-collared rats and discovered that the rodents liked to hang out in the crowns of coconut palms. The crowns became a convenient platform for stashing cotton gauze sacks of poison bait, delivered by workers firing slingshots or dangling from helicopters. Crabs do not reach the palm tops.

Once rats were exterminated in 2011, researchers watched with delight as native tree saplings began to spring from the forest floor. There were also happy surprises. Scientists discovered two additional species of land crabs that had likely gone undetected because voracious rats suppressed their numbers. And researchers realized they were no longer being bitten by Asian tiger mosquitoes, a pest that attacks during the day and can carry dengue and yellow fever. It appears the mosquitoes depended on rats rather than humans or birds for blood meals…

Excerpts from Ridding Paradise of Palms, Science, Aug. 28, 2020, at 1047