Natural World

Natural Features & Ecosystems

National Parks are widely recognized for their inspiring scenery. At Gettysburg National Military Park the visitor is offered a step back in time to 1863. A walk down a historic lane or park avenue invites the visitor to reflect on the events that occurred here and reflect on events that are occurring in their present day lives. The park’s 5,989 acres provide opportunities for both naturalist and historian to learn and reflect upon the various components of the cultural landscape.

Gettysburg National Military Park comprises a mosaic of pastoral landscapes and forested knolls, with pockets of dispersed wetland and intermittent streams. Over 2,300 acres of the park’s landscape are planted in crops, pasture, or meadows providing the visitor with a glimpse of the local agrarian lifestyle. Over 1,600 acres of woodlots and forested habitat comprise several successional communities, from mature oak/hickory to early scrub-shrub. Wetlands dot the landscape roughly totaling 148 acres of palustrine wetland and over 26 miles of associated riparian habitat.

The natural landscape offers a respite to the ever increasingly busy schedule of the modern day visitor. The historic landscape is interwoven into the fabric of existing natural features, such as woodlots, wetlands and geology. These features provide visual stimulation as well as academic stimulation. Ongoing studies to understand forest regeneration in woodlots at Gettysburg has been a continuing study since 1985. Wetlands and their functional values in terms of ecological niches and filters have been important factors in rethinking the agricultural special use program. Granite rock outcroppings at Devil's Den are recognized for more than strategic positions; they are records of processes that have occurred throughout the earth's natural history.

In 1999, the Gettysburg National Military Park GMP/EIS was approved, outlining goals for rehabilitating the1863 features that impacted the battle. Components of the plan included replanting missing historic woodlots, orchards and thickets and removal of non-historic vegetation. These landscape changes were designed and proposed to aid interpretation of the battle story. In addition, the methods of landscape change where thoughtfully considered to create the least amount of impact, in context with park objectives, on species known to use the park.

Nature & Science

Gettysburg National Military Park is the site of the American Civil War Battle of Gettysburg, the Soldiers’ National Cemetery and the commemoration of the great battle of Civil War veterans. Significant sites on the battlefield began to be preserved almost immediately after the 1863 battle, and the park came under federal ownership in 1895. Administered by the National Park Service (NPS) since 1933, the park now incorporates a significant portion of land across which the battle, its aftermath and the commemoration occurred. The park attracts 1.8 million visitors each year and is open year-round. It offers visitors hiking trails, scenic car tours on over 40 miles of roads, and beautiful vistas overlooking the battlefield and nearby town. There are also over 1,400 monuments and 400 cannons, which dot the landscape.

The park is situated in the Piedmont Province east of Appalachian Mountains in south central Pennsylvania, encompasses over 5,989 acres of land. The park is fifteen miles east of South Mountain, which rises to 2,000 feet above sea level. Within the park are gently rolling hills and valleys with elevations averaging between 500 to 580 feet above sea level. The landscape is a mosaic of mature and maturing woodlands and woodlots, agricultural fields, pasturelands and intermittent streams which provide habitat for 187 bird, 34 mammal, 17 reptile and 15 amphibian species documented to date. Floral inventories have recorded 553 species of vascular plants, of which 410 are native.

Since 1863, natural succession and human development has changed the natural appearance of the landscape and historic battlefields. While some vegetation features (thickets, woodlots and woodlands) were removed by man over the years, others were overgrown by nature, becoming dense and containing many non-native species. In addition, some historic fields, pastures, and other open areas are covered by non-historic vegetation. In 1999, the Gettysburg National Military Park General Management Plan /Environmental Impact Statement (GMP/EIS) was approved, outlining goals for rehabilitating the1863 cultural and natural features that impacted the battle. The plan includes such projects as the replanting of historic woodlots, orchards, and also the removal of non-historic vegetation. Work is also underway to re-establish original fencelines, lanes and trails, recreate historic view sheds, as well as maintain the integrity of the historic farmsteads. The management plan included an Environmental Impact Statement, which considers courses of action that would have the least amount of impact on species in the park.

Prairies and Grasslands

Grasslands are considered by many as one of the most endangered ecosystems globally. Grasslands were once abundant in the 1800’s when settlers had cleared much land for hayfields and pastures.  Today grasslands face danger from fires, human development, and changes in agriculture technology.

Grasslands are important because they protect large amounts of open space and provide wildlife and nesting habitat for specialized species.  The ecosystem is especially important to birds such as the Bobolink, Savannah sparrow, and the Eastern meadowlark. Grassland birds require large contiguous patches of grassland habitat for successful breeding. Many grassland birds will only nest in this type of open grassland habitat and decline in grasslands causes decline in breeding birds.

Much of Gettysburg NMP is considered grassland habitat. The park was designated one of several Important Bird Areas in Pennsylvania set aside to protect birds and grassland habitat. In efforts to maintain the characteristics of an 1863 landscape much of the main battle action resource areas are being converted from large agricultural fields to smaller contiguous patches of native grasses. The restored field patterns will better reflect historic 1863 conditions and provide valuable grassland habitat.

Nonnative Species

Most non-native species of the park are in the form of plants in which 143 of the 553 plant species are non-native. Non-native invasive plant species can be threats to natural ecosystems and native flora of the park. These species often grow quickly and crowd out native plant species while providing limited habitat worth to park wildlife.

The Gettysburg NMP Natural Resources staff works to control non-native invasive vegetation to restore native vegetative communities.    Plants species that provide the biggest challenge to park staff are multiflora rose, Japanese barberry, Ailanthus, and Mile-a-minute weed. With the help from the Mid-Atlantic Plant Management Team, based out of Shenandoah National Park, efforts are combined to treat these exotic species by chemical methods, mechanical methods, and hand pulling.

There are also several non-native insects in the park that put stresses on the park’s native vegetation. An insect of concern is the Hemlock wooly adelgids, Adelges tsugae, a pest species that negatively impacts the growth of the Eastern Hemlock. “Hemlock wooly adelgids (HWA) is the single greatest threat to Hemlock health and sustainability…” USDA. HWA is believed to be an introduced species from Asia, first documented in the States around 1924. Currently there are no effective natural enemies known to keep the pests in balance. However, park staff annually monitors infestations on both the battleground and the Soldiers’ National Cemetery. When HWA populations are high approved chemical methods are used to protect the trees.

Wildflowers

Springtime in the park brings from the ground ephemeral wildflowers that cover the landscape with a mosaic of colors like paint on a canvas. Many of these flowers cover stream banks and woodland areas before the trees spread their leaves and block the sunlight. Virginia bluebells and violets are a few of the many wildflowers to bloom in the spring.

From summer to fall, the field and forest floors will come to life with the many species of aster and goldenrod found in the park. Their relative, the black-eyed susan is one of the most common wildflowers in America and is abundant throughout the park. Visitors can also be treated by the sight of the cardinal flower, a favorite to hummingbirds and distinguishable by its bright scarlet flower.

Grasses

The variety of habitats within the park ranging from forests to wetlands provides home to 553 species of vascular plants, 410 of which are native. The Pennsylvania Natural Diversity Inventory has also listed 23 of these plants as endangered, threatened, or species of special concern.

In the forested areas of the park, the dominant overstory species documented in woodlots and woodlands are white oak, white ash, and northern red oak. A mixture of black cherry, spicebush and white ash saplings dominates the understory. Beside woody plant species there are an abundant variety of herbaceous plants and wildflowers that occupy both forested and open areas.

Open fields and field edges boast a diverse mixture of vegetation for both the visitor to observe and for wildlife to utilize as either cover or feed. Currently the park is transitioning portions of agricultural lands into warm season grasses to encourage a more diverse plant community for open-upland bird species.

Vegetation management is an important responsibility of the park's natural resource staff. The primary goals of Natural Resource Planning at Gettysburg and Eisenhower are to (1) restore and perpetuate the battlefield as it appeared at the time of the Battle of Gettysburg in July 1863 and to (2) preserve resident fauna and flora that are compatible with the goal of historic accuracy. With these goals, park personnel conduct floral inventories, monitor seedling recruitment, and map vegetative cover types. Vegetation management is also a critical part of the park's landscape rehabilitation plan.

National Park Service staff also work to combat several invasive plant species such as the multifloral rose, Japanese barberry, ailanthus, and mile-a-minute. Six weeks each year, staff with the help of the Mid-Atlantic Plant Management Team treats these exotic species by chemical methods, mechanical methods, hand pulling and sprays.

Trees and Shrubs

Settlers cleared most of the original forest of the Gettysburg area for farming in the 18^th and 19^th centuries. Today wooded areas are in patches scattered across agricultural land. Penn State University surveyed six woodlots for species composition and community structure.Typical tree species of the forest include oaks, hickory, and poplar, which are common to the Appalachian area. The predominant overstory species of the wooded areas are white oak, white ash, and northern red oak. Common seedlings and saplings include spicebush, black cherry, and white ash. Also the state endangered shrub, the Missouri gooseberry, occurs through the northern section of the park.

Birds

One hundred and eighty-seven species of birds have been identified within the boundaries of the park making Gettysburg NMP a great place for birdwatchers and nature lovers alike.  The park contains many acres of open grasslands, wet meadows, hay fields, and pasture lands which provide homes to birds such as the Eastern bluebird or Northern bobwhite.  Because the grasslands provide critical habitat to a variety of bird species, a western portion of the park has been designated an Important Bird Area by the state.  This designation is important because it protects some of the vanishing grassland habitat in Pennsylvania while also protecting the species of birds that reside there including the state-endangered Loggerhead shrike and Short-eared owl.

Other bird species that rely on grassland habitat for survival include many songbirds, which can by found in the park through the different seasons. With a careful ear one will be able to detect the cheerful tunes of the American robin or Yellow warbler. Also, a visitor may cross paths with such game birds as the ring-necked pheasant or wild turkey, although hunting is strictly prohibited within the park.

Within the forested canopy layers, bird species range from the gregarious Red-headed woodpecker to the inconspicuous Ruby-crowned kinglet. On forest edges visitors can observe a Red-tailed hawk or a Cooper's hawk keeping a watchful eye on the field below for prey of the park's large small-mammal population.

Streams in the park provide habitat to waterfowl such as ring-necked ducks and Canada geese. One may also be fortunate enough to catch sight of a majestic great blue heron walking slowly through one of the park's streams or tributaries while hunting for fish.

Many species of endangered and threatened birds are also migrants or visitors to the park. Of significance is the recent observation of Peregrine falcon within the park. The species is endangered within Pennsylvania but its population has been slowly growing since the early 1990's due to state reintroduction efforts.

Amphibians

Inventory and monitoring surveys in 2000 and 2001 identified fifteen species of amphibians in Gettysburg NMP.  Of these fifteen species, eight were frogs, four were salamanders, two were toads, and one newt.  Most of these species occupy wetland and pond habitat within the park.

One can not mistake the low "a-ruumm a-ruumm" call of the bullfrog on a late summer afternoon. These calls and the sound of splashes as they plunk into the water are distinctive identifications of the presence of the large green frogs. Park visitors may also recognize the swift "peep peep peep" of the spring peeper's chorus on a warm evening.

The silent salamanders of the park are not as easy to find. They are typically inactive during the day so it is not common for visitors to come upon them. But the lifting of a log may reveal a moist home abundant with the smooth-skinned, lizard-like creatures.

An amphibian survey is planned for the summer of 2004 to identify and record breeding frogs within the park. Wood frog and spotted salamander egg mass count projects are also planned for the summer of 2004 to determine available habitat.

Animals

Gettysburg NMP is more than just battlefields and monuments.  Its large size and variety of habitats allow many species of birds, mammals, reptiles and amphibians to call the park home.  While walking through the 1,900 acres of maturing woodlands and woodlots visitors have the potential to observe a variety of species ranging from the common white-tailed deer to the less prominent black-throated blue warbler.

The 2,300 acres of pasturelands and farmlands provide an open-upland habitat.  The open landscapes host many of the same species found in the forested areas, however the open fields provide a specialized niche for many birds and insects.  Visitors may observe a red-winged blackbird resting on a fence post or butterflies such as the monarch and the painted lady drifting from flower to flower feeding on nectar plants.  While maintaining the speed limit it is also possible to observe a red fox in the open fields.

Through studies conducted in cooperation with the Pennsylvania State University, a complete inventory of amphibian and reptile species has been documented.  If patient a visitor may have the opportunity to observe a northern two-lined salamander in one of the riparian areas or a spotted turtle in the shallow areas of one of the park’s streams.

Gettysburg NMP is also a home or stopover point for several federally and state-listed endangered, threatened, or candidate species.  Threatened bird species such as ospreys and federally endangered bald eagles have been observed soaring in the skies over the battlefields.  National Park Service staff mist netting has confirmed the presence of a candidate species of bat, Northern myotis, within the park.

Reptiles

Seventeen species of reptiles including nine snakes, six turtles and two skinks are found within Gettysburg National Military Park.  Visitors touring some of the parks wetland habitat may often spot wetland turtle species such as the painted turtle basking on a log or the head of a snapping turtle peeking up through some water grasses.  It is also common to cross paths with the slow-moving terrestrial Eastern box turtle.

The large population of small mammals in the park provides adequate prey for the nine species of snakes within the park. Most of the snakes such as the common garter snake and black rat snake are nonvenomous, however the park does contain two species of venomous snakes, the copperhead and timber rattlesnake. The Northern water snake is not venomous and is common in the streams of the park. Its dark color and stout body often cause it to be mistakenly identified with the venomous water moccasin, which is not found in the park.

Mammals

Invertebrates are the most numerous and diverse animals on Earth of whose species comprise about 98 percent of the animals in the animal kingdom. Invertebrates occupy important places in the food web as primary and secondary consumers and also decomposers. Invertebrates also have value ranging from the role of earthworms in the fertilizing and aerating of soil to the task of pollinating flowers undertaken by honeybees, butterflies, and moths. Considering all these facts, it is hard to understand why such insects and spiders are so underrated and feared by many people.

In 1999, butterfly and arthropod inventories at Gettysburg NMP were conducted in cooperation with Penn State University. For butterfly collection, suitable habitat was determined and collection sites were based on the availability of nectar sources and shelter. The park provides important habitat to butterflies in the form of mixed farmland and forest landscape. Butterfly specimens were collected and identified by taxonomists who identified a total of 38 butterfly species in the park. On a warm day, visitors to the park will be able to observe some of these species such as tiger swallowtails, spring azures, or monarchs drifting among the flowers and grasses.

For the 1999 study, terrestrial arthropods were collected at wooded sites of Big Round Top, Plum Run area, and Codori-Trostle Thicket. Samples contained much insect biodiversity but flies, ants, bees, mites, and beetles were the most prominent specimens. Through the study seven new species known to science and at least one new genus of Diptera (flies) were also discovered.

Geologic Formations

Although the park does not contain volcanoes, canyons, or other such grandiose geologic formations, its topography and geologic features are equally important in the influence that they had on the historic Civil War battle. Approximately 180 million years ago during the late Triassic Period, the Gettysburg Formation comprising sandstones, siltstones, and shales was deposited in a large carved out basin in the Gettysburg area. These lowlands were broken by hills and ridges that were formed as a result of geologic activity when a dense 2000-foot thick slab of igneous (molten) rock called the Gettysburg Sill and also two 50-foot dikes were thrust into the Gettysburg Formation. One of the dikes underlies Seminary Ridge in a north to south orientation while the other parallels the ridge to the west. Sills are responsible for the topographically high areas of the Round Tops, Culp’s Hill, and Cemetery Ridge and Hill.

The intrusion dikes are composed of very fine-grained, dense diabase rock very resistant to weathering. The composition of these rocks indicates that the molten masses cooled very rapidly. The Gettysburg sill is coarse-grained diabase, an igneous rock otherwise known as granite. The sill also contains a large amount of feldspar, which is prone to weathering. The forces of weathering are evident when observing the large round boulders of Devil’s Den formed from diabase outcrops. 

Geology was important in the outcome of the battle of Gettysburg in many ways. Union troops positioned themselves along the park’s ridges and hills, which provided excellent vantage points. In turn, Confederate troops moved across the cleared valleys and lowlands in an effort to drive the Union troops off Cemetery Ridge, Culp’s Hill, Little Round Top, and Big Round Top.

The boulders scattered across the landscape and also the rocks of Devil’s Den, provided cover and strategic defensive positions for the soldiers. Thin soil on many of the sides and tops of hills also made it almost impossible for Union soldiers to entrench themselves. The resistant diabase bedrock was so close to the surface on these hills that the troops were unable to “dig in.” They had to rely on existing stonewalls, scattered boulders, and outcrops of rock for protection. Because of the Union army’s inability to entrench its position, it suffered heavy losses of 23,000 men, while the attacking Confederates lost a little more than 28,000.