Landscapes change. They always have. Before 1492 A.D., the beginning of European influence in North America, there were plenty of human-caused alterations to the forest, though they were considerably less intensive than what was to follow. Layered on top of human effects on forests, there have always been natural disturbances to the landscape, from fire to tornadoes to hurricanes, that would re-set the forest to an earlier stage.
In terms of scale, transformation of forest to agriculture presents an order of magnitude greater change than what had occurred before in the eastern forest. Clearing for agriculture not only wiped out trees at a site, but the native understory as well. As agriculture spread across the continent from east to west in uneven waves, ginseng habitat became wheat habitat, or sheep habitat, or some other agriculture producing landscape. But it was no longer forest.
Image (right): Hayfield in Tucker Co., WV that exhibits an agricultural field in what would have been forest. Credit: WVDT
At its low point in the early 1900’s, the total mature or re-growing forest comprised less than half the landscape, with the remainder being agricultural land or land permanently transformed to cities, towns, roads, etc. While many farms were abandoned in the early to mid-1900’s, the early successional forests are only slowly re-gaining their previous stature and biodiversity. Understory species are particularly slow to recover in such forests, so the agricultural clearing effect lingers on for centuries.
Image (left): Charleston, WV Skyline in 1891 (Top) and 1941 (Bottom,) Credit: WVU
Example of mountaintop mine site
Ginseng’s natural range overlaps the rich deposits of coal in the eastern United States. Surface mining for coal is a long-standing practice, and is more common than underground mining in this ecologically rich area.(1,2) This process destroys the habitat for the herbaceous understory. At its worst, surface mining converts the landscape, destroys soil composition and profile, alters the hydrology, raises human health concerns, and releases heavy metals into the water system, leaving a rocky landscape in place of a forest, which all but the most vigorous plants are slow to re-colonize.
In this map from Appalachian Voices (2008) the comparison between Mountaintop Removal and Poverty is made. The yellow outline, added by the McGraw lab at WVU, represents the eight counties where ~60% of ginseng harvest from the state of West Virginia occurs (4). Ginseng is an important secondary source of income for these areas, but the habitat for ginseng is being greatly reduced.
Mountaintop removal (and valley fill) refers to one method of coal mining in which the overburden is removed from above the coal seam, and typically discarded in the abutting valley. Between 1992 and 2012, according to estimates by the E.P.A., Mountaintop removal mining was responsible for destroying 816,000 acres of forest in southern Appalachia(3). While it is known that mountaintop removal certainly eliminates ginseng populations located on mine sites, the amount of ginseng affected by mountaintop removal remains un-estimated. Additionally, no research has been conducted on ginseng populations surrounding these mining sites. Altered environmental conditions in mining areas, as well as loss of gene flow from ginseng populations formerly located on mine sites, may negatively affect viability of surrounding ginseng populations.
(1) EIA Coal 2012
(2) McGraw et al. 2013. Ecology and conservation of ginseng (Panax quinquefolius) in a changing world.
(3) Wickham et al. 2007
(4) Bailey PhD Dissertation 1999
Suburban Sprawl & Vacation Home Development
Looking out an airplane window when flying over the eastern portion of the U.S., you can see networks of roadways, housing developments, and strip malls carved out of forested land. Of course their construction consumes local habitat, but the effects of suburban sprawl and other forms of development may affect the area in secondary ways. Along forest edges abutting developed areas, the light, temperature, and moisture regime is altered, affecting populations of understory plants and making the area of ‘interior’ forest even smaller than it appears. Research in our lab has shown that the pollinators servicing ginseng are different, and less effective, near the edges of the forest. Additionally, roadways and housing developments are often corridors for invasive species, (1) particularly when non-native species are planted as ornamentals in yards and lawns. Land conversion from forest to suburban lots is also likely to increase local densities of white-tailed deer, which pose a risk to local American ginseng populations. Fragmentation of forested habitat may also disrupt gene flow among populations, potentially reducing within-population genetic diversity (2).
Mosaic of forests, fields, and edges in suburban-rural interface ~ Photo from Google Earth