Wild ginseng grows in forests ranging from Quebec to Georgia. Prized in Asia for its putative health benefits, this slow-growing perennial is one of the most widely harvested medicinal plants in the U.S. The deer harvest the herb too, munching on the leaves, flowers and berries. To gauge the population viability of American ginseng, James B. McGraw and Mary Ann Furedi of West Virginia University tracked seven populations of the plant in West Virginia for five years. They determined that to have a 95 percent chance of surviving for another century, a population would have to contain a minimum of around 800 individuals. Yet in a second, eight-state survey of 36 ginseng populations, the maximum size was 406 individuals--that is, none were viable.
The team then used simulations to explore how curbing deer browsing rates might affect the ginseng outlook. The researchers found that this snacking would have to be halved in order for any of the 36 censused populations to achieve viability.
"Current deer population densities in central Appalachia jeopardize the future of ginseng, as well as the culture of harvest and trade surrounding this important herb," McGraw and Furedi conclude in their report, published today in Science. And the few comparable demographic studies of other forest-floor-dwelling plants and young trees, the authors note, suggest that the deer pose a threat to them as well.