Thirty
percent of the Anacostia watershed (approximately 33,400 acres)
remains forested. Deciduous stands constitute the largest
type by area, followed by mixed stands, regenerating scrub/shrub,
and coniferous forest.
The
forests of the Anacostia watershed play a critical role
in improving water quality and stabilizing stream morphology
by infiltrating rainfall, reducing soil erosion, slowing
and reducing stormwater runoff, and filtering out various
harmful pollutants. Forests also provide numerous other
benefits, from improving air quality to creating habitat
for wildlife.
Forests
can be broken into categories based on their function and
place in the watershed. Riparian forests are located closest
to waterbodies and have the most direct impact upon water
quality. Riparian forests should extend a minimum of 35
feet from the edge of the water, but riparian buffers of
100 feet or 200 feet are ideal, as wider buffers provide
additional water quality benefits. Within most Anacostia
subwatersheds, more than 50% of the stream length is buffered
by a riparian forest that is at least 35 feet in width.
Upland forests are those forests that are located futher
away from waterbodies and on tops of hills. COG analysis
results show that 24% of the Anacostia watershed is covered
by upland forests.
The Anacostia watershed experienced
a 7.9% decline in forest cover between 1936 and 2000. This
decline in forest cover was caused by shifts in land use from
agriculture to residential and commercial development. Using
1936 and 1938 black and white aerial photographs, COG staff
has identified forest stands that are likely to be at least
65 years old, and therefore considered mature. Mature hardwood
forest makes up about half of the total forest coverage in
the Anacostia watershed.
