19 Records

Harperella is one of the rarest native plants found in Maryland. According to MD DNR Harperella is restricted to only two mountain streams in Allegany and Washington Counties. NatureServe says, "Approximately 45 [global] occurrences (24 drainages/watersheds) are believed extant in scattered localities in the southeast, mid-Atlantic, and, somewhat disjunctly, in the Ouachita Mountains of Arkansas. The largest population concentration occurs along the West Virginia/Maryland border, with a second large population concentration in Arkansas. The species is dependent on narrow hydrologic conditions and is vulnerable to alterations to the natural hydrologic regime, siltation and erosion, water quality reductions, disturbance and trampling, and, possibly, competition from invasive plants; land-use conversion is also a threat at some sites. Many of the occurrences are at least partially on federal or state lands, under a conservation easement, or managed for conservation, but, particularly for the riverine populations, protection/management of occupied sites alone may be insufficient to ensure persistence in the face of watershed-level threats." NatureServe goes on to say that, "Because population numbers and suitable habitat naturally fluctuate dramatically from year to year in response to hydrological conditions, overall population trends are difficult to assess. However, long-term monitoring data does suggest that the three historically-largest populations in West Virginia and Maryland are declining (Douglas 2008). Specifically, since the early 1990s, the Sleepy Creek, WV sites have declined from approx. 2,000,000 to 400,000 plants, the Cacapon River, WV sites have declined from approx. 72,000 to 400 plants...[and a certain site in MD] has declined from approx. 30,000 to 7,500 plants"