Henderson Island, a tiny, unpopulated coral atoll in the South Pacific, could scarcely be more remote. The nearest city of any size lies some 5,000 kilometers away. Yet when Jennifer Lavers, a marine biologist at the Institute for Marine and Antarctic Studies in Tasmania, ventured there two years ago to study invasive rodent-eradication efforts, she found the once pristine UNESCO World Heritage Site inundated with trash—17.6 metric tons of it, she conservatively estimates—pretty much all of it plastic. (The rubbish originates elsewhere but hitches a ride to Henderson on wind or ocean currents.) One particularly spoiled stretch of beach yielded 672 visible pieces of debris per square meter, plus an additional 4,497 items per square meter buried in the sand, Lavers and her colleague reported recently in the Proceedings of the National Academy of Sciences USA.

By comparing the data with a study of the nearby Ducie and Oeno atolls conducted in 1991, the team extrapolated that there is between 200 and 2,000 times more trash on Henderson now than there was on those neighboring islands back then. Unidentifiable plastic fragments, resin pellets and fishing gear make up the bulk of the total (graphic), but the researchers also came across toothbrushes, baby pacifiers, hard hats, bicycle pedals and a sex toy. Thousands of new items wash up daily and make any cleanup attempt impractical, according to Lavers, who specializes in studying plastic pollution. Meanwhile many of the world's other coastlines could face a similar threat. “Regardless of where I go or how far removed from society,” Lavers says, “plastic is what I find.”