On a recent afternoon, Laura Shappell followed a slender deer trail into a thicket of invasive Japanese knotweed. The plants towered over her head, and their deer-
trampled stalks crunched under her boots as she vanished into the mass of pale green leaves.
“If I’m not out in 10 minutes, send help,” she called back. A graduate student at Rutgers University, Shappell is a member of a research team exploring the link between biodi-
versity and human disease. Led by Rutgers wetland ecologist Joan Ehrenfeld, the group is looking at plant diversity in a variety of freshwater wetlands in New Jersey. After characterizing each plot, they will compare the diversity of its plant communities with bird diversity and the prevalence ofWest Nile virus within mosquito populations. The research builds on previous studies showing that areas with high bird diversity tend to have lessWest Nile virus, which mosquitoes can transmit from birds to people. The link to plants? “Birds need a variety of plant species and habitats for nesting and foraging,” Shappell explains.
“Reduce plant diversity and you may reduce bird diversity as well.” And across North America, nonnative invasives like Japanese knotweed pose one of the greatest threats to plant diversity. “There’s not much that can grow under this stuff,” Shappell says of the exotics overrunning the Rahway River wetland she is surveying. The Rutgers study is just one of many new investigations into the link between biodiversity and human health. “The
natural world provides so many services vital to our health,” says Eric Chivian, founder and director of Harvard Medical School’s Center for Health and the Global Environment. “But these services depend on an enormous diversity of species about whose interactions we know very little.” Over the past decade, the Harvard center has been working with three United Nations agencies to draw together what scientists do know. In 2008, it published Sustaining Life: How Human Health Depends on Biodiversity. The 542-page tome
IN THE NORTHEAST, a tick hatching in a disturbed forest will probably get its first meal from a white-footed mouse (above left). Because most mice are infected with the bacterium that causes Lyme disease, the tick can pass the disease along to deer and people. In an undisturbed forest, a tick’s first host is likely to be an opossum (above), bird or other animal that rarely carries Lyme disease.
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DAVID VANDRE
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