Eyes of Paint Branch

Inventory of Biodiversity and Significant Habitats in the Paint Branch Watershed

By John M. Parrish, Field Botanist/Ecologist 2001

3.1 Threats

1. Habitat Loss and Ecosystem Degradation (forest, field, wetland)
   
   Suburban development (roads, housing, schools, and business development) has led to a severe loss of natural habitat within the Paint Branch Watershed, as well as degradation of the streams and tributaries due to impervious surface run-off and other toxic pollution sources (see below). With only 26 percent of its original forest cover remaining, Paint Branch Watershed has lost nearly three-fourths of its forests, and one-third of its historic (pre-colonial) non-tidal wetlands. Forest and wetland acreage continue to decline.
   
   
2. Forest Fragmentation
   
   Suburban development has severed the last remaining forests into isolated tracts. Isolation of flora and fauna populations inevitably leads to reductions in biodiversity. The remaining tracts of forest are often too small to support the ecosystem dynamics that once sustained a complex “web of life.”
   
   
3. Invasive Species
   
   Certain aggressive species of flora and fauna outcompete and displace native species thereby threatening a delicate and complex web of relationships that has resulted over a long history. This threat continues to be one of the most dangerous threats to native ecosystem health.
   
   
4. Off-road Vehicles (ORVs)
   
   Motorbikes (two- and three-wheeled), mountain bikes, SUVs, etc causes extensive destruction of vegetation, floodplain, and wetland areas. They are a source of erosion, sedimentation, soil compaction, vernal pool destruction, noise and pollution.
   
   
5. Sand and Gravel Mining
   
   Existing and historic Sand and Gravel Mining destroys natural habitat and causes increased soil erosion and stream sedimentation.
   
   
6. Storm Water Run-off/Impervious Surfaces
   
   At 18 percent, the impervious surface area in the Paint Branch Watershed is very high. Experts have determined that 10 percent is the maximum amount of development that watershed can have and still maintain suitable trout habitat. The consequences of impervious surfaces are severe. Uncontrolled run-off from impervious surfaces and construction sites causes sharp increases in stream flow velocity. This leads to streambank erosion and stream habitat sedimentation. The run-off also carries with it highly polluting and toxic compounds such as oil, grease, fertilizers, road salt, and other chemical compounds, which are transported directly into the streams resulting in degradation of stream water quality. This runoff also causes dangerous increases in stream water temperature due to the heated impervious surfaces (roofs, roads, parking lots). Impervious surfaces also prevent the natural infiltration (by the forests) of stormwater. This inevitably leads to reductions in stream base flow due to a lack of groundwater recharge. Springs, seepages and wetlands (and their associated biodiversity) rely on infiltrated stormwater to maintain relatively stable hydrological regimes.
   
   
7. Cumulative Impacts
   
   This impact is the most difficult to measure, but it is perhaps the most important impact to acknowledge because it is has by far the largest adverse impact on watersheds and their associated ecosystems. Natural habitat alteration and subsequent degradation over the past few centuries has drastically reduced the habitat diversity and complexity in the Paint Branch Watershed, as well as the surrounding regions. Historically, nearly 100 percent of this watershed was forested. Bogs were once an important component of the wetland biodiversity in the watershed. Scores of species are no longer found within the watershed due to deforestation and wetland destruction. This destructive trend continues into the 21^st century.