Arabis georgiana

Arabis georgiana was listed as Threatened in 2014 by the U.S. Fish and Wildlife Service. A poor competitor, this species occurs on steep river bluffs and requires sloughing soils or gaps in the canopy that allow increased light to infiltrate the forest floor. Despite fairly extensive searches, this species is currently known from fewer than 25 populations in Alabama and western Georgia. The sites have very few plants and little recruitment. The species is threatened by habitat degradation and habitat loss from river alteration, road building, timbering, and grazing. Disturbances from these activities have created conditions favorable to invasive exotics such as Japanese honeysuckle (Lonicera japonica), which will likely outcompete Arabis georgiana in all but the rockiest, most soilless situations.

Arabis georgiana or Georgia rockcress occurs in 8 counties in Alabama and 7 counties in Georgia. Twelve populations occur in Alabama, of which 6 occur in the Ridge and Valley province, and the other 6 occur in the Coastal Plain province. In Georgia, 3 of the 5 populations occur in the Ridge and Valley province, one in the Piedmont province, and one in the Coastal Plain province. There is one population that crosses the state borders and occurs in the Coastal Plain (USFWS 2014).

Twenty-eight occurrences known (20 in Alabama and 8 in Georgia), including 6 historic sites, however, Schotz (2010) says that the precise number of populations that exist is open to interpretation, and he reports 25. Most of the occurrences of this species occur in the Ridge and Valley province in central Alabama and western Georgia, with the southernmost occurrence in the Red Hills region and fewer in the Black Belt region (Schotz 2010).

Arabis georgiana is a rare species with timber harvesting and invasive species (Lonicera japonica, Japanese honeysuckle and Ligustrum sinense, Chinese privet) as primary threats to nearly all occurrences (Schotz 2010). It is at high risk from land-use conversion and habitat fragmentation; threats include flooding by impoundment, clearcutting/disturbances associated with heavy logging, grazing of bluffs and riverbanks and resultant erosion. Housing development and recreation are threats to several populations. At 6 of the sites road bisect populations causing fragmentation and opening corridors for invasive species to enter, and another 4 populations have bridges in addition to roads that impact the bluff habitat (USFWS 2014). One site in Georgia, has been extensively mined and what exists today is believed to be a remnant of a much larger population (USFWS 2014).