Assessment of Change in North Carolina Coastal Plain Wetlands
The goal of this project is to compare current wetland condition and function to historical information obtained 5, 10, and in some cases, just over 30 years ago, to understand how and if our Outer Coastal Plain wetlands are being changed by sea level rise and increased inundation, as well as how far inland these changes may be taking place. We have just finished collecting detailed resample data (vegetation, soil, water, and general habitat) from 30 wetland sites scattered across the Outer Coastal Plain of North Carolina. Information gained from detailed data collection, as well as rapid assessments on function and habitat quality, will allow us to comment on ecosystem functions being provided by these wetlands, and if changes have occurred since the last data collection.
Project data collection has occurred over two consecutive sampling seasons (2021 and 2022). The project is focused on vulnerable freshwater wetlands in the Outer Coastal Plain of North Carolina. Vegetation data collection protocols matched those used in previous data collection. Rapid assessments (Ohio Rapid Assessment method [ORAM] [Mack 2001] and North Carolina Wetland Assessment Method [NCWAM] [NC Wetland Functional Assessment Team 2010]) were completed at all sites.
Additionally, we have partnered with a variety of outside entities, such as Duke University, NC State University, and PCS Phosphate, to compile some wetland resample data they have collected to augment our dataset. In the end, we are analyzing data from 85 separate resample sites across the outer Coastal Plain of North Carolina.
Rising sea levels threaten NC’s outer Coastal Plain wetlands, but increased intensity of storms, both in rainfall and wind, are also causing increased freshwater inundation. Drainage ditches can facilitate increased flooding as well as saltwater intrusion into more inland areas (McPherson 2009). The presence of salt promotes rapid decomposition of peat soils by sulfate-reducing bacteria (Hackney and Yelverton 1990). Loss of peat causes soil subsidence and increased inundation. Within wetlands, these changes are expected to result in plant composition shifts and more open water habitat. Even if climate change causes an increase in estuarine wetlands, this may come at the expense of the often more diverse freshwater wetlands. Lost biodiversity comes with a loss in the variety of ecosystem services freshwater wetlands provide (Isbell et al. 2011).
Given the importance of coastal wetland systems to the environment and economy of NC, their priority for wildlife and coastal management agencies, and their vulnerability to water related changes brought about by climate change, it is imperative that we assess their current condition relative to historical condition. Most academics and state and federal agency staff rely on remote sensing or nationally available spatial datasets for change detection, but these only allow detection of substantial plant community shifts and erosion. Earlier, subtler indicators of change require on-the-ground data collection, which is lacking, particularly in freshwater wetlands vulnerable to impacts from salt.
North Carolina’s coastal wetlands provide the state with an array of essential services. Coastal wetlands, especially forested wetlands, stabilize shorelines and serve as buffers against storms and erosion, a service valued at $25.6 billion per year (NCDEQ 2016). They can store water and lessen flooding, which creates value in protection from extreme rain or storm events. Wetlands are needed as natural filters for water supplies, a service vitally important to the Coastal Plain aquifers which supply water for more than half of NC’s population (US EPA 2010). They also are important for sequestering carbon. “Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet, sequestering approximately as much carbon as do global forest ecosystems.”(Moomaw et al. 2018).
Our wetlands serve as refuges for beneficial pollinators and other insects and provide critical habitat for wildlife and plants. Over two-thirds of NC’s rare, threatened, and endangered species of plants and animals live in wetlands (USGS 1996). Coastal wetlands serve as vital breeding and migration stopover points for many migratory birds, as well as key breeding areas for some bird species in decline (DeWan et al. 2010). In particular, Coastal Plain freshwater wetlands are very important habitat for bitterns, rails, and a variety of other wading and shorebirds.
NC has a billion-dollar commercial and recreational fishing industry, ranking it among the nation’s highest seafood producing states (NC DEQ 2016). The state’s estuaries and associated wetlands are an essential economic resource, serving as nursery grounds for many commercially important fish and shellfish, such as crabs, shrimp, and flounder species (DeWan et al. 2010). Tidal freshwater wetlands provide nursery habitat for aquatic species that live in salt waters but rely on fresh and brackish waters for larval recruitment and development. These freshwater swamps and marshes occur along rivers or sounds in areas where flooding is influenced by wind or lunar tides.
Additionally, NC’s wetlands provide value in aesthetics, tourism, and recreation, especially in the Coastal Plain where large national wildlife refuges, game lands, and preserves exist. Lake Mattamuskeet National Wildlife Refuge is a major stopover for huge flocks of migratory and overwintering waterfowl, where more than 130,000 visitors come every year for wildlife observation and other recreation (USFWS 2008).
For all these reasons, wetlands are singled out as priority ecosystems by state agencies. The NC Wildlife Resource Commission 2015 Wildlife Action Plan describes all wetlands statewide as priority habitat for conservation, including coastal wetland habitats such as tidal freshwater wetlands, bottomland and floodplain wetlands, pocosins, bays, isolated depressional wetlands, wet pine savannahs, and brackish marshes (NCWRC 2015). The NC Division of Coastal Management’s Coastal and Estuarine Land Conservation Program lists all coastal wetland habitats as priority for restoration and conservation (NCDCM 2007, 2011).
Coastal wetland provide important functions, like nursery grounds for seafood animals, buffering from storms, water filtering, and floodwater storage.
This work is being funded under EPA Wetland Program Development Grant Cooperative Agreement CD00D98120 and matching funds from the NC Department of Environmental Quality.
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