Ecology of Shenandoah National Park
Shenandoah National Park is home to a diverse array of plants and animals. With patience and a bit of luck, they can be observed by visitors.
Virginia’s Shenandoah National Park is located in the Blue Ridge Province of the Appalachian Mountains. It is mostly deciduous forest, with 93% of the parkland being forest. A further 2% is wetland. Three percent represents other vegetative areas such as barrens, and the last 2% of Shenandoah National Park has been developed. Oak is the most common tree, closely followed by hickory. Most of the these are about 60-70 years old. These forests and natural areas are homes to several rare plants, such as American ginseng, formally called Panax quinquefolius. This plant is a perennial herb, meaning that, unlike annual plants, it will return each year after the winter season. It is one of the most valuable non-timber products of Eastern North American forests because it has medicinal properties. Because of this, American ginseng is often the unfortunate target of poachers. However, it is protected in Shenandoah National Park, where it is illegal to harvest the herb.
There are 41 known species of fish found in the park, including the eastern brook trout, blacknose and longnose dace, bluehead chubs, mottled sculpins, and fantail darters. Out of these, brook trout, formally named Salvelinus fontinalis, and eastern blacknose dace, Rhinichthys atratulus, are most common in park waters. In catch assemblages of fish, blacknose dace comprised up to 52% of the total catch, and brook trout comprised up to 77% of the total catch. Brook trout are the most commonly observed fish at stations in the park which monitor aquatic life. They have a lifespan of 2-3 years. Brook trout are a cold-water species of fish which are popular among recreational fishermen.
There are also eels in the park’s waters, like Anguilla rostrate, which is more commonly known as the American eel. These eels travel long distances throughout their lives. When they spawn, they prefer marine habitats, but prefer freshwater otherwise, so they often move between rivers and estuaries along the eastern coast of the United States. However, this movement can be impeded by damming rivers. This makes it difficult for eels to move back upstream, meaning that there is a decreased number of eels upstream of dams, and an increased concentration of these animals below dams. This can throw off the balance of aquatic ecosystems because an increased number of eels means a greater level of competition for resources. Conversely, having a lower number of eels than normal means that species whose numbers are controlled in part by eels that prey on them could get out of control. American eels eat both vertebrate fish and invertebrates like crayfish.
Threats to Aquatic Life
The animals living in the waters of Shenandoah National Park are affected by changes in water levels due to droughts and floods, which can cause disturbances to aquatic life. Another major threat is acid rain which can lead to entire sections of streams becoming too acidic to support healthy life.
Acid rain occurs when sulfur dioxide and nitrogen oxide in the atmosphere converts to sulfuric acid and nitric acid which can then reach the Earth’s surface through precipitation. Sulfur and nitrogen are put into the atmosphere via emissions from the use of fossil fuels, or also from natural reactions like volcanic activity and forest fires. Acidity is measured by pH, which is a scale that tells us how acidic or how basic something is. Seven is perfectly neutral, and numbers below 7 indicate acidity. A 1 on the scale, for example, is the pH of battery acid. Normal rain water has a pH of 5.6, though in the park, rainfall with a pH of 4.6 is common. Each change in a number along the pH scale is 10 times more or less acidic than the previous number, so the numbers recorded in Shenandoah National Park are 10 times more acidic than the average rainfall value.
Water in streams will eventually neutralize the acid from acid rain. This ability is called acid-neutralizing-capacity, or ANC. ANC has to do with the bedrock underneath streams and also how steep or shallow their slope is. Many streams in the park experience 6-168-hour periods of low ANC. Modeling, which helps predict likely events based on past and present occurrences, indicates with over 90% certainty that every 40-100 years, there will be four consecutive years of low acid-neutralizing-capability in streams. This could be detrimental to fish populations.
One of the most notable creatures in the park is the Shenandoah Salamander, which is the only known endangered animal in the park it is named for. It has a very specific habitat requirement. It exists only at high elevation slopes in the park which are covered in talus, or rock debris. This is an area of about 6 km2. Since the Shenandoah Salamander has such a specific niche, there is a lot of worry about the species’ survival. It is threatened by competition from the red-backed salamander and also by changes in climate. This species is carefully monitored, and models are used to better understand risks to this creature.
Though it is the most well-known, the Shenandoah Salamander is not the only salamander in the park at risk. Stream salamanders are affected by land use and habitat loss including the disappearance or redirection or fragmentation of the streams they live in. To some degree, these creatures can migrate between stream habitats, so it is equally important to preserve both their streams and the land between them over which the salamanders travel.
Cliff and Outcropping Communities
There are several endangered or rare plants and animals that live on the outcroppings and cliffs of Shenandoah National Park, including the Shenandoah Salamander. In some of the larger rock outcroppings, there are up to 28 of these species. A notable rare plant community type is the High Elevation Greenstone Outcrop Barren which, as you can probably guess, grows at high elevations on a rock called greenstone- an ancient volcanic rock that is very common in the park. The High Elevation Greenstone Outcrop Barren is believed to be endemic to Shenandoah, meaning that this barren originates from the park and thrives in a very specific environment that the park provides.
These rare plant and animal communities can be seen at the many outcroppings along Skyline Drive, which are popular for their scenic views. However, respect towards these communities is essential, as studies have shown that human disturbance at these sites has negatively impacted plants growing there.
Shenandoah, with its plentitude of forests, provides a wonderful habitat for birds, whether they are in the park temporarily for migratory purposes or they live in the park year-round. About half of the bird species, including year-round birds and transitory ones, breed in the park. There are 196 species of birds in Shenandoah. Of these 196, about 30 are permanent residents. The latter category includes red-tailed hawks, wild turkeys, barred owls, Carolina chickadees, and tufted titmice.
Notable mammals found in Shenandoah National Park include spotted skunks, black bears, bobcats, shrews, moles, voles, coyotes, white-tailed deer, big brown bats, and grey squirrels. Some, like deer and squirrels are more likely to be observed by visitors, while others, such as bobcats, are more elusive. Black bears have made a dramatic comeback from a population of two known individuals in 1937 to several hundred today. These bears are omnivores, meaning they eat a varied diet of both meat and plants. They also have been known to procure food from agricultural areas including orchards, beehives, and even garbage cans. Bears bulk up for winter hibernation and can gain one to two pounds a day while doing so. Challenges facing bears in Shenandoah National Park include habitat destruction and improper disposal of waste, which can result in bears having to be disposed of as a potential threat to humans.
The big brown bat is another notable mammal which inhabits the park, though it is not as well-known as the black bear. It is, however, much easier to observe. They are nocturnal, so they can be seen after the sun sets, and look birds with unique flight patterns. They have a wingspan over a foot, within the range of 13 and 16 inches. These creatures are vital because they consume mass quantities of pests which are threats to forest plants and crops. In fact, full-grown female brown bats can eat the equivalent of their body in insects in one night!
Invasive species are organisms that have been introduced to an ecosystem and which cause disruption. They can pose a threat to the other species that live in the area because they compete for resources and also because they may prey on other species for food. Not all of the species introduced into the ecosystems of Shenandoah National Park are harmful, and some even provide benefits. There are 350 nonnative plants in the park, and about 35 of these are actively harmful to surrounding wildlife. One of these 35 is the kudzu vine, which you have probably heard of if you live in the southeastern United States. This plant was brought to the U.S. in 1876 for decorative purposes. However, it spreads quickly and often out-competes native plants and trees. There is a kudzu infestation on the eastern border of the park. A cuter example of an invasive species is the European starling, which were brought to the country in the late 1880s. They are harmful because they steal resources from native birds like northern flickers and redhead woodpeckers. They are common in the park at Big Meadows. There are many more invasive species in the park, such as hemlock wooly adelgids, gypsy moths, trees of heaven, and mile-a-minute vines. The presence of these species has to be regulated and controlled by the National Park Service if it is possible and if the presence of these creatures is a threat to resources or safety. Though it isn’t feasible to completely eliminate invasive species, the park does take steps to control their presence and mitigate their effects on native species. In order to manage plants which are invasive, park officials eliminate them manually or with herbicides. Insectile species are controlled using insecticides specific to the species that is causing harm. Though small, insects can cause enormous amounts of damage, especially to trees.