TIDAL SALT MARSH
Nothing is more symbolic of the South Carolina low country than the great expanse of tidal salt marshes . These ecosystems are as dynamic and diverse as they are beautiful . They were also cited as a major driver for moving to Kiawah Island by our property owners in a recent survey ( personal communication , KICA AMP Task Force , 2020 ). Twice a day , they are inundated and drained with salt water due to the ebb and flow of semidiurnal tides . In lower elevations they are dominated by smooth cordgrass ( Spartina alterniflora syn . Sporobolus alterniflorus ), but contain a diversity of other wetland plants in higher elevations . The extensive growth of vegetation in tidal wetlands supports a diversity of wildlife natural processes which greatly benefit human and wildlife communities ( MEA , 2005 ).
Tidal marshlands and adjacent estuarine areas are some of the most biologically productive habitats in the world , providing many ecosystem services to both human and wildlife communities ( MEA , 2005 ; Costanza et al ., 2014 ; Sandifer et al ., 2015 ). Despite wetlands only comprising 4 % of the world ' s total land cover , one third of the world ' s population is dependent on the critical ecosystem services they provide ( Barbier , 2013 ). The services provided by marshes to these populations include nutrient cycling , tertiary nutrient breakdown , carbon sequestration , property protection from storm surge , recreation , wildlife viewing , and erosion control , among many others . This also applies to coastal communities such as Kiawah Island , where tidal salt marshes protect the land from erosion by reducing wave action , buffering storm surges , as well as providing abundant wildlife , recreational , and aesthetic amenities . These services have been estimated to be valued at around $ 6,626 per acre per year ( Purcell et al ., 2020 ).
Although they are one of the most productive ecosystems , coastal wetlands are also the most fragile . Coastal wetlands have historically been declining globally , with future projections suggesting further decline due to sealevel rise ( Blankespoor , 2014 ; Schuerch et al . 2018 ). Human population densities in coastal regions are also nearly three times that of inland areas , with these populations exponentially increasing ( Kummu et al ., 2016 ). With this , there is concern of the long-term stability of coastal populations due to the future impacts to tidal salt marshes . Sea-level rise , major storm frequency and intensity , excess stormwater , and coastal development all have the potential to adversely impact the health of salt marshes and present negative impacts on coastal communities . These negative impacts on tidal marshes are expected to continue , with current projections suggesting 46-78 % will be lost by the year 2100 without significant mitigation efforts ( Spencer et al ., 2016 ).
The degradation of these tidal marshlands will significantly depreciate the ecosystem services provided to residents , leading to adverse effects on their health and well-being . Understanding the impacts to these habitats and monitoring areas to inform mitigation efforts will help protect our wetlands and allow them to continue providing services for human and wildlife communities .
Marsh Hydrology
Marshes are dependent on the hydrologic processes which occur through tidal fluctuations and upland freshwater influences . Flora and fauna within tidal salt marsh habitats have adapted to be tolerant of the high salinity content of seawater . Typically , sea water has a salinity between 30-35 parts per thousand ( ppt ). Inputs of freshwater from upland areas contribute to the survival of marsh species in different ways , mostly through contributions from runoff and groundwater discharge .
In upland areas , rainfall events introduce freshwater to the shallow subsurface aquifer , otherwise referred to as ' groundwater .' This percolation of rainwater into upland soils recharges the groundwater and increases the
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NATURE-BASED SOLUTIONS MANUAL FOR KIAWAH ISLAND