Crow's Nest Natural Area Preserve is a large wilderness area located on the southern border of Stafford County, Virginia, United States, between Potomac Creek and Accokeek Creek. The greater portion of the Crow's Nest Peninsula is approximately and lies within the coastal plain of Virginia. About of the peninsula is protected as part of the Virginia Natural Area Preserve System. Funding for the original two tracts came from a number of sources including DCR, Stafford County, Virginia Department of Environmental Quality and a number other sources.
Virtually the entire Crow's Nest Peninsula is forested with an impressive, mature stand of mixed hardwoods. Hardwood forests of this extent are becoming increasingly rare in the Virginia and Chesapeake Bay coastal plain due to prevalent forestry practices and fragmentation of natural areas for development and agriculture. The size and continuity of this hardwood stand enhance its viability and its value in providing a large, unfragmented natural area for diverse organisms. Within a relatively short time (50–100 years), this forest will also comprise a substantial occurrence of old-growth forest with inestimable scientific, biological, and aesthetic values. Currently, trees greater than diameter at breast height (dbh) are common, and very large relict tree specimens are scattered throughout the site.
The entire Crow's Nest Peninsula is undeveloped and is primarily forested with mature stands of hardwood trees such as oaks and hickories. This is especially true in the eastern half of the peninsula and the northern slopes facing Accokeek Creek. The coastal plain landscape in this region of Virginia was formed beginning in the late Triassic period, approximately 230 million years ago, through the rise and fall of the sea. Crow's Nest is approximately in length from east to west, across and rises above the surrounding Accokeek and Potomac creeks. The peninsula is highly dissected on its north and south sides by steep ravines flowing into these two fresh-water tidal creeks. In contrast, most landscapes in the coastal plain of Virginia are relatively flat and/or gently rolling. Crow's Nest's dramatic rise to above Potomac and Accokeek creeks is startling compared to the adjacent peninsulas in Stafford County, such as Marlborough Point and Widewater Peninsula, which are relatively flat.
A large portion of Crow's Nest is composed of calcareous, or calcium-rich, soil layers from ocean or marine animals that once lived at the bottom of a vast inland sea. Most soils in the Piedmont and coastal plain of Virginia are not calcareous or limey and thus tend to be acidic. This calcareous soil strata within Potomac Creek is referred to as the Aquia Formation, which is 60 million years old. The Aquia Formation is found within a larger outcrop belt known as the Pamunkey Group, a sequence of Lower Tertiary (Paleocene-Eocene) sands and clays that formed in shallow marine environments beneath the western margin of the Atlantic Ocean. The Aquia Formation is composed of marine sediments that are dark green to gray-green, argillaceous, highly glauconitic, well sorted fine-to medium grained sand with shell beds up to in depth.
Today, shell-marl/calcareous ravine forests such as those at Crow's Nest are not common anywhere in the mid-Atlantic region. These plant communities are rare to this coastal plain ecosystem. There are two nutrient-rich plant communities associated with lime sands and localized shell concretions at Crow's Nest. One can be broadly classified as Basic Mesic Forests (G2, globally imperiled). Another rare community found at Crow's Nest that is typically associated with the shell-marl/calcareous environments is the Basic Oak-Hickory Forest (G2, globally imperiled). These are found on two very steep slopes facing Potomac Creek and represent this plant community.
Much of the shell-marl/calcareous ravine forests that do still exist on the east coast of the United States have since been heavily logged. In assessing natural communities in need of protection, the Virginia Department of Conservation and Recreation listed the state's few remaining calcareous ravine forests to be conservation priorities. The Crow's Nest site is perhaps Virginia's best remaining example of this rare forest community.
Due to the unusual subsurface calcareous soil formations underlying most of the peninsula, the unusual soils are basic (alkaline) and give rise to rare plants and plant communities. This is due to the ability of the limey soils at Crow's Nest to neutralize and buffer soil pH within the range 6.3 to 6.8. Elements such as calcium (Ca) and magnesium (Mg) create conditions in the soil that raise the pH of the soil and increase nutrient availability for plants. This results in the establishment of more robust and diverse vegetation at Crow's Nest. Additionally, disjunct plant communities at Crow's Nest are found that are not common in the Piedmont and coastal plain of Virginia, as these areas generally have lower pH soils. These rare or "disjunct" plants and plant communities include small-flower baby-blue-eyes (Nemophila aphylla) and glade fern (Athyrium pycnocarpon).
After assisting and conducting field surveys for rare plant species and plant communities, the Virginia Department of Conservation and Recreation, Division of Natural Heritage determined in 1999 that "Crow's Nest is considered one of the finest, if not the finest example of mature forests remaining in the Coastal Plain of Virginia." These forest communities on the peninsula consist of several distinct community types. The peninsula supports several regionally and globally rare plants and plant communities, two of which are ranked Globally Imperiled (G2) by NatureServe.
Geologic history
The mid-Atlantic Ridge started to form in the early Jurassic period (175 million years ago), breaking apart the super continent Pangaea and beginning the expansion of the modern Atlantic Ocean. It has widened steadily to its present size. This rifting event separated North America from Africa, and the area known today as Virginia became the trailing edge of the newly formed North American continent. The Jurassic Period is found in the Mesozoic Era, or the Age of the Dinosaurs. The Mesozoic Era spanned a length of time from 251 million years ago to 66 million years ago.
In the early Eocene Epoch (55.8 million years ago) the Coastal Plain of Virginia was completely underwater. Sediment accumulating beneath this sea eventually would become the Crow's Nest of today. The Paleocene and the Eocene epochs are found in the Cenozoic Era, or the age of the mammals. The Cenozoic Era spanned a length of time from 66 million years ago to the present.
During the Eocene, the Atlantic Ocean was considerably narrower than it is today, making migration relatively easy for marine animals. The climate of Virginia during this period was considerably warmer than it is today. According to extensive records, the Earth experienced its warmest interval of the past 66 million years during the early Eocene, and Virginia was probably much warmer than central and southern Florida today. The remains of large alligators and turtles have been found at this latitude in Virginia.
The calcareous soil strata within Potomac Creek, the Aquia Formation, is 60 million years old. This formation is found within a larger outcrop belt known as the Pamunkey Group, a sequence of Lower Tertiary (Paleocene-Eocene, 55.8 million years ago) sands and clays that formed in shallow marine environments beneath the western margin of the Atlantic Ocean. The Aquia Formation is composed of marine sediments that are dark green to gray-green, argillaceous, highly glauconitic, well sorted, fine-to medium-grained sand with shell beds up to in depth.
Biology
Crow's Nest has been referred to as a "biological gem". There have been few formal surveys for rare plant and animal species, however, mostly conducted by the Virginia Department of Conservation and Recreation in the late 1990s.
Virtually the entire Crow's Nest Peninsula is forested with mature stands of mixed hardwoods. In the words of Gary Fleming, Natural Heritage Program ecologist, "Overall, Crow's Nest supports one of the finest—if not the finest—upland hardwood forests remaining in the Virginia Coastal Plain."Gary Fleming, Virginia Department of Conservation & Recreation, Division of Natural Heritage Report, October 1999. Surveys documented two state-listed species and the potential habitat for two other federal listed species and several state-listed species. Several Stafford County records for plants and two state-listed endangered plant species were found, including ginseng (Panax quinquefolius) in rich ravines and river bulrush (Scirpus fluviatilis) in adjacent tidal marshes. Suitable habitat was found for small whorled pogonia (Isotria medeoloides), although it does not grow there.
The peninsula is forested with huge trees, some over in diameter, including chinkapin oak (Quercus muhlenbergii) and tulip poplar (Liriodendron tulipifera). Other trees include bitternut hickory (Carya cordiformis), pignut hickory (Carya glabra), black walnut (Juglans nigra), and black locust (Robinia pseudoacacia).
In addition to the high-quality forests found at Crow's Nest, there are approximately of freshwater tidal marshes surrounding the peninsula that account for 60% of all marshes in Stafford County. The marshes are in nearly pristine condition and represent some of the best examples found in the state.Final Environmental Assessment for Proposed Accokeek Creek National Wildlife Refuge, December 2000
Several environmental factors exert important influences on vegetation on the Crow's Nest Peninsula. First, the steep terrain made most of the site unsuitable for agriculture, so it was never fragmented or plowed. It is one of the largest unfragmented patches of hardwood forests in Virginia's coastal plain. The steepness also limited logging to a substantial degree. Secondly, the mix of freshwater tidal wetlands, ravine bottoms, steep slopes of various aspect, and high ridge crests has led to a high biodiversity, including sites important in neotropical bird migration. Lastly, the Lower Tertiary deposits in this part of the mid-Atlantic Coastal Plain consist largely of glauconitic sand, shelly clay-silt, and some sandy limestone and calcium-rich sands. These contribute to the development of relatively basic, nutrient-rich soils. Basic or calcareous soil environments are uncommon to rare on the Virginia coastal plain and can support vegetation unusual for the region.Virginia Department of Conservation & Recreation, Division of Natural Heritage Report, October 1999
Crow's Nest is surrounded on three sides by a freshwater-tidal estuary, and a multitude of resident and spawning fish thrive in these waters. Local fishermen captured the shortnose sturgeon (Acipenser brevirostrum), a federally listed endangered fish, twice in 2002.
A variety of marine fossils have been found on the shores of Crow's Nest. These include Paleocene-epoch shark teeth, as well as ancient parts of rays, turtles, and numerous mollusks of genus Turritella. Turritella has an elongated, highly coiled corkscrew shape. The internal molds and casts of these gastropods can be found in these waters and are especially plentiful at nearby Bull Bluff on Potomac Creek.