Condition of Selected Natural Resources at Fort Pulaski National Monument: 2023 Assessment

A view of the north side of Cockspur Island in Fort Pulaski National Monument.

NPS/Joel Cadoff

America’s National Parks protect abundant and diverse natural resources. The excitement of seeing wildlife in their natural habitat, hearing birds singing or other natural sounds, or viewing beautiful scenery or historic structures draws millions of visitors to our parks each year. These natural resources are parts of complex ecosystems, and they interact with other plants and animals and their environment.

Park natural resources respond to both natural and man-made drivers and stressors (such as human disturbance and development, water pollution, and sea level rise), which vary by resource. Understanding the condition of park natural resources, as well as how they’re changing over time, is vital for managing and protecting the resources.

Natural Resource Condition Assessment (NRCA) projects, such as the study described here, are designed to provide an efficient, scientifically defensible update on current conditions, and to identify drivers and stressors and critical data gaps, for a subset of park natural resources. Understanding what forces are driving change in conditions can help park managers determine needed management and stewardship activities.

Focusing in on a subset of resources at Fort Pulaski National Monument

Fort Pulaski National Monument (NM) is made up of two islands in coastal Georgia, McQueens and Cockspur, which are separated by the Savannah River near its confluence with the Atlantic Ocean. Cockspur Island, made mostly of dredge material from the Savannah River, contains the 19th century masonry fort, Fort Pulaski, and the monument’s visitor services and facilities. The fort was built, starting in 1829, to protect the port of Savannah. McQueens Island is almost entirely salt marsh habitat, and most of its area is eligible federal wilderness. This island contains one of Georgia’s oyster recreational harvest areas (RHAs), Oyster Creek RHA. Both McQueens and Cockspur islands are designated as a National Oceanic and Atmospheric Administration Marine Protected Area (MPA), which emphasizes the significance of Fort Pulaski NM’s natural resources. Collectively, the natural resources at Fort Pulaski NM are affected by the sea level, which rose by almost 1.2 feet from 1935 to 2022.

Fort Pulaski NM managers selected four resources to study in the NRCA—salt marsh, Eastern oysters, shorebirds, and butterflies. The NRCA team evaluated each of these resources as a gap analysis, which highlights what we know and don’t know about a resource and provides suggestions for collecting needed information for future assessments. If more extensive current data and information had been available for each resource, the team would have conducted a condition assessment in each case. A condition assessment is a more thorough evaluation of a resource’s current condition.

Salt Marsh

Estuarine, freshwater, and riverine wetlands cover most—about 84%—of Fort Pulaski NM, with estuarine wetlands accounting for the majority of the wetland area. The main wetland types are salt marsh (dominated by smooth cordgrass [Spartina spp.]) and unconsolidated shore (muddy, silty, or sandy areas that are primarily unvegetated). Most of the monument’s estuarine wetlands are on McQueens Island.

Salt marsh areas, which dominate the coast of Georgia, are important feeding, breeding, and nursery grounds for a wide variety of marine organisms. For example, Fort Pulaski’s extensive salt marsh habitat and beaches provide critical food resources and habitat for shorebirds, especially during the pre-breeding season. Functioning salt marsh habitats also protect coastal communities/areas from storm surges and sea level rise due to their ability to buffer and stabilize shorelines.

For the NRCA, the NRCA team described the types of wetlands at Fort Pulaski NM and summarized a 2012 study by the Georgia Department of Natural Resources (GADNR) that evaluated the ecological functioning of wetlands in Georgia, including those at McQueens Island. The GADNR evaluation rated the McQueens Island wetlands primarily as high functioning at that time. For example, the unconsolidated shore wetland in the Oyster Creek recreational harvest area (described in this article), was rated as high for all wetland functions expected for that type. However, another wetland (north of Highway 80) received low ratings because the adjacent highway causeway altered the marsh’s ability to function properly. Although data were not yet available for the NRCA, the NPS Southeast Coast Inventory and Monitoring Network is monitoring the wetland surface elevation at two sites in Fort Pulaski NM to gain information about elevation changes in the marshes and whether they are sufficiently accreting (building up vertical elevation) to keep pace with rising sea level.

McQueens Island salt marsh adjacent to Lazaretto Creek in Fort Pulaski National Monument.

NPS photo

Eastern Oyster

The Eastern oyster (Crassostrea virginica) is a vitally important species in estuaries along the Atlantic and Gulf coasts of the United States. Besides being a popular seafood, oysters have significant ecological importance. They filter (and clean) the water, and as they form reefs, they help stabilize salt marshes and provide habitat for a wide variety of other species, such as fish, crabs, and other invertebrates.

The Georgia Department of Natural Resources (GADNR) Coastal Resources Division manages the state’s oysters in five shellfish growing areas (SGAs) along the coast. These SGAs may include recreational harvest areas (RHAs) and/or commercial harvest areas. One of the SGAs includes Oyster Creek RHA, an approximately 1,200-acre area that is entirely within Fort Pulaski NM and comprises almost one-fourth of McQueens Island salt marsh habitat. While oysters occur at other locations in the monument, approximately 70% of Fort Pulaski’s oysters are concentrated within Oyster Creek RHA’s boundary.

For this study, the NRCA team summarized available data for oyster area, oyster density, and spat recruitment for a GADNR 2013 oyster enhancement project in Oyster Creek RHA; the team also addressed important questions about oysters posed by Fort Pulaski managers. Just a few of the NRCA findings are mentioned here. For oyster area, a 2013 oyster mapping effort by GADNR found about 53 acres of oysters in Fort Pulaski NM, with most of this area (about 70%) within the Oyster Creek RHA. For spat recruitment, the team reviewed a successful 2013 reef enhancement project in Oyster Creek RHA that reported a pre-enhancement oyster area of 29 square feet that increased to 9,580 square feet of oysters by 2018.

Eastern oysters (center) in the Oyster Creek Recreational Harvest Area off McQueens Island, where the public can harvest shellfish with a state permit.

NPS Photo

Shorebirds

Fort Pulaski NM’s extensive salt marsh habitat, including mud flats exposed at low tide, and beaches provide critical food sources and habitat for shorebirds that use the Atlantic Flyway, especially during the pre-breeding season. The Atlantic Flyway is a major north-south flight path for birds along the U.S. Eastern Seaboard. The American oystercatcher (Haematopus palliates), whimbrel (Numenius phaeopus), and federally threatened rufa subspecies of red knot (Calidris canutus rufa) have been identified as high priority species in the flyway by the National Fish and Wildlife Foundation. These species/subspecies have been observed on Cockspur Island during shorebird surveys at Fort Pulaski. The monument’s habitat, and the food it provides, including horseshoe crab eggs, fiddler crabs, and bivalves, also supports a variety of other shorebird species, such as ruddy turnstone (Arenaria interpres), sanderling (Calidris alba), black-bellied plover (Pluvialis squatarola), and willet (Tringa semipalmata).

Black-bellied plovers (in non-breeding plumage) observed in early spring during International Shorebird Surveys at Fort Pulaski National Monument.

Photo credit and permission: © PAM SMITH

For this study, the NRCA team summarized available shorebird data using International Shorebird Surveys (ISS) at Forth Pulaski NM, and relative abundance and trend estimates from eBird (see reference at end of this article) for whimbrel, red knot, and American oystercatcher. A sampling of results from the gap analysis are presented here.

The International Shorebird Surveys were conducted in 2019, 2021, and 2022. In total, 22 shorebird species were recorded in Fort Pulaski NM. These species include those already mentioned above. The five most common shorebirds observed throughout the year were dunlin (Calidris alpina), semipalmated plover (Charadrius semipalmatus), ruddy turnstone, least sandpiper (Calidris minutilla), and willet, although the willet was more often observed during the fall (August–November) surveys.

The analyses from eBird data for whimbrel indicate its average estimated relative abundance was highest during the pre-breeding migratory season (1 March–14 June), with the highest abundance estimate occurring just south of McQueens Island. eBird data analyses for red knot indicate average estimated relative abundance was highest during the pre-breeding migratory season (5 April–14 June), especially to the north and south of Fort Pulaski NM. Of these three focal species (whimbrel, red knot, and American oystercatcher), the oystercatcher had the highest year-round average estimated relative abundance. The oystercatcher was estimated to be at its highest abundance at Fort Pulaski during its post-breeding migration (31 August–16 November) and non-breeding (23 November–22 February) seasons. The ISS counts for this species were highest during the non-breeding and pre-breeding seasons.

Butterflies

Upland habitat at Fort Pulaski NM, located primarily on Cockspur Island, supports vegetation that can serve as nectar, host, and/or roost plants for pollinators, especially butterflies. One of the reasons butterflies and other pollinators are important is because they transfer genetic material within flowers and between plants, which is necessary for most flowering plant reproduction. This includes many of the foods we eat! Over 160 butterfly species occur in Georgia, with the state’s coastal region (where the national monument is located) supporting about 118 of these species.

For the NRCA, the NRCA team summarized the available information on butterfly occurrence (such as presence, abundance) and presence of plant species used as host plants, nectar sources, and roost or resting spots. Host plants are plants on which adult butterflies lay eggs and caterpillars feed.

Scientists with the Butterflies of the Atlantic Flyway Alliance (BAFA) started monitoring the fall butterfly migration at three sites at Fort Pulaski NM in 2021. They monitor every year from August to November for three target species—monarch (Danaus plexippus), gulf fritillary (Agraulis vanillae), and cloudless sulphur (Phoebis sennae)—and four additional species (the American lady [Vanessa virginiensis], painted lady [Vanessa cardui], common buckeye [Junonia coenia], and long-tailed skipper [Urbanus proteus]). During the 2021 fall migration survey, BAFA scientists recorded the three target species and a fourth. These initial data reflect a small percentage of the butterfly species that potentially occur at Fort Pulaski based on checklists and other information.

The NRCA team reviewed plant species identified in vegetation monitoring plots at Fort Pulaski and found that 69 of the species may be used as host, nectar, or roost plants, although more probably exist. Two types of habitats in the monument—Cedar-Live Oak-Cabbage Palmetto Marsh Hammock, and Cabbage Palmetto Woodland—contained the greatest number of these 69 plant species, but nearly every habitat type at Fort Pulaski had some beneficial butterfly plants.

A monarch butterfly on a flower (a nectar source). Fort Pulaski NM managers began working with Butterflies of the Atlantic Flyway Alliance (BAFA) scientists in 2021 to record the number of migratory monarchs, as well as additional species, at the monument.

Photo Credit and Permission: © PATRICIA VALENTINE-DARBY

Fort Pulaski NM staff have been working to restore a meadow in the national monument to benefit pollinators. The NRCA team identified additional actions, to benefit butterflies and other pollinators in the monument, and these actions include mowing less of the grassy areas currently mowed to allow them to reach a more natural condition.

Using what we learned to take Action

Knowing the condition of these resources and what information is lacking is only the first step. Study findings also need to be linked to actions park managers can take to better protect the resources. For that purpose, the NRCA team developed management considerations for each focal resource as next steps for furthering science-informed management. Here are a few of the findings for Fort Pulaski NM.

• Promote the significance of the salt marsh habitat’s role in protecting adjacent communities. Incorporating an interpretive message of how Fort Pulaski’s salt marsh habitat is the 21st century’s “fortress,” protecting the surrounding communities from sea level rise and storm surges would raise awareness of this habitat’s significance.

• Continue to improve shorebird habitat on Cockspur Island. Apply the U.S. Army Corps of Engineers’ lessons learned from recent island-building efforts in the region to Cockspur Island’s beach restoration projects, especially by keeping the quality and placement of dredge material relevant to horseshoe crab spawning requirements. This will benefit all shorebirds, and, in particular, the red knot. Eliminate non-native invasive plants that appear on newly placed dredge material.

• Continue to manage visitor (and pet) beach access. Fort Pulaski NM managers have already implemented beach restrictions on Cockspur Island to limit disturbance to shorebirds. This management action has been proven elsewhere to successfully protect shorebirds at breeding, foraging, and roosting sites and may become increasingly important if a greater number of shorebirds nest on Cockspur Island.

• Establish wilderness character measures and goals. Establishing indicators and measures that meet Fort Pulaski NM’s desired wilderness character is necessary to know whether goals are achieved. This will include all aspects of wilderness character (e.g., oysters, soundscape, and viewscape) that are evaluated collectively.

• Conduct a comprehensive butterfly inventory to identify the species at Fort Pulaski NM. There are currently surveys for only migratory species, which make up only a portion of the potential number of species present.

References

Fink, D., T. Auer, A. Johnston, M. Strimas-Mackey, S. Ligocki, O. Robinson, W. Hochachka, L. Jaromczyk, A. Rodewald, C. Wood, I. Davies, and A. Spencer. 2022. eBird Status and Trends, Data Version: 2021; Released: 2022. Cornell Lab of Ornithology, Ithaca, New York. Available at: https://doi.org/10.2173/ebirdst.2021 (accessed 15 February 2023).

Information in this article was summarized from Struthers K. 2023. Natural resource conditions at Fort Pulaski National Monument: Findings and management considerations for selected resources. Natural Resource Report. NPS/FOPU/NRR—2023/2555. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2300064