Deer population threatens the survival of the widely harvested medicinal plant, Ginseng

Feb 13 2005

An abundant deer population with a hearty appetite for American ginseng threatens the survival of the widely harvested medicinal plant, a study by West Virginia University biologists suggests.

Ginseng, a wild herb that inhabits eastern deciduous forests from Maine to Georgia, faces extinction within 100 years if foraging by deer continues at its current rate, James McGraw and Mary Ann Furedi report in Friday's (Feb. 11) issue of Science, the flagship journal of the American Association for the Advancement of Science.

"Without more effective deer population control, ginseng and many other valuable understory herbs are likely to become extinct in the coming century," the authors conclude.

American ginseng, or Panax quinquefolius, grows under forest canopies in well-drained, nutrient-rich soils. The plant consists of green leaves, red berries and gnarly roots whose touted medicinal qualities range from improving mental performance to being a cure-all.

Asians have sworn by these medicinal qualities for centuries, and the high demand for ginseng in that corner of the world has made it a cash crop in Appalachia. More than 10,000 West Virginians go into the woods each fall to find ginseng to sell; for some, the harvests provide an important income supplement. In 2002, more than 6,400 pounds of ginseng with a value exceeding $2 million were harvested in West Virginia, according to the state Division of Forestry's Web site.

Past studies have shown a drop in ginseng populations, and concern over its rarity led to the plant being added to an international treaty's list of protected species.

In the WVU study, McGraw, an Eberly Family Professor in WVU's Department of Biology, and Furedi, his research associate, conducted a census of about 800 ginseng plants in seven different locations in West Virginia from 2000-04.

Furedi examined each plant every three weeks during the five-year period, collecting detailed information ranging from the height and number of leaves to whether deer had browsed the plants.

The amount of deer browsing ranged from 11 percent to 100 percent, depending on deer and plant populations and plant locations, she said.

The lowest rate, McGraw noted, is more than double the amount of ginseng harvested, which is less than 5 percent.

Next, McGraw designed a computer program that took Furedi's field data and manipulated it to determine the effects of deer foraging of ginseng at various rates over 100 years.

Their simulations included browsing based on various deer populations, ranging from the present herd count studied to no deer.

"We found that at current deer browsing rates, virtually all ginseng populations are likely to go extinct," McGraw said. "As you reduce the browsing rates, the ability of ginseng to survive increases dramatically."

McGraw said he is concerned that ginseng could be the ecological equivalent of the canary in the coal mine, noting that deer eat many other forest plants such as trilliums and wild orchids.

"We don't think it's just ginseng we have to worry about," he said. So what can be done?

McGraw said there are three options: Do nothing and watch ginseng likely disappear from the landscape; reintroduce deer predators such as mountain lions and wolves; or change hunting regulations that would lead to a reduction in deer populations.

"This has a potential impact not only on plant biodiversity in the region, but also on the economy and culture of the people who harvest ginseng," he said. "Reversing this impact will require a joint effort of all stakeholders whose lives are negatively affected by increased deer populations -- from farmers and foresters to landscapers and motorists."

The National Science Foundation supported the study.