Impounded Freshwater Emergent Marsh Habitat Description. Site Stressors Summary

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1 Impounded Freshwater Emergent Marsh Habitat Description This area consists of freshwater marshes in former rice impoundments. The area is currently managed by S.C. Department of Natural Resources for waterfowl habitat. It is mapped by the NWI as palustrine, emergent, persistent, regularly flooded habitat. Managed wetland impoundments provide excellent foraging and open water habitat for wildlife especially waterfowl species. The historic ricefield impoundment edges and dikes are often vegetated with plants such as Chinese tallow tree (Sapium sebiferum), Rubus sp., red maple (Acer rubrum), sweetgum, and salt bush (Baccharis sp.), and various nonnative sod grasses. Management regimes dictate the species composition within the impoundments. Managed and unmanaged former rice impoundments cover a widespread area within the Winyah Bay watershed. Currently, many are actively managed to provide essential habitat for migrating waterfowl, an important economic resource for the area. Many historic rice plantations are also permanently protected via conservation easement. The potential to change management regimes in order to reduce climate vulnerability may exist for many of these areas. Site Stressors Summary Sedimentation and erosion issues are currently the greatest stressors, and the habitat may be severely impacted by the interaction with an increase in frequency or intensity of storms. Storms represent the greatest exposure threat with the potential to completely remove the habitat. Invasive species are currently a moderate threat, and may be exacerbated by predicted changes in temperature and precipitation, although an increase in sea level may have a positive affect for the habitat. Nutrients and chemical contaminants are not perceived as current issues, and are not anticipated to be worsened by climate change impacts. The habitat may have a high degree of adaptive capacity due to its dispersal/ movement and recovery/regeneration characteristics. There is also a potential for management actions to offset climate effects, but the institutional capacity and human response potential may be lower.

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4 Climate Forecast Temperature Data from National Climate Change Viewer, USGS, for Waccamaw watershed Current min ( 0 C) Predicted min ( 0 C) Current max ( 0 C) Predicted max ( 0 C) Winter Spring Summer Fall Mean annual Precipitation Current P (mm/day) Predicted P (mm/day) Change in Evap. Deficit (mm/mo) Winter Spring Summer Fall Mean annual Change in runoff (mm/mo) Sea Level Current marsh Predicted marsh with 1 FT SLR

5 Current Conditions Direct Climate Effects Plant community composition is based on drought and flood Soil subsidence and rise in sea level are concerns Tropical cyclones impact management actions Access is needed to river water for flooding management. There has been no change over the long run A dynamic system adapted to changes in environmental conditions Invasive Species Current invasives species water hyacinth, alligator weed, Phragmites, Arundo donax, possibly Hydrilla, feral hogs Boat traffic brings in invasives Salinity (through flooding management) can be used to kill invasives Soil management - Disturbances increase invasives Changes in soil fertility from management of some local impoundments using agricultural practices allow invasives to colonize more rapidly and create downstream nutrient effects. Nutrients Nutrient import and export was one of the factors used to justify impoundments There is no good assessment of this particular reserve, so information was assumed from other reserves. Inputs are dependent on up-river inputs from surrounding agriculture River (boat) traffic may affect flows into and out of the habitat. Impoundments may be a source of nutrients to the river system. Potential legacy issue- The previous land owner had corn agriculture, but that was many years ago There is an assumption that there sufficient sources of nutrients from water inflow to support the system Sedimentation Dike system maintenance creates a sediment disturbance, dike maintenance is non-stop (100 miles of dike) Upstream impacts of increased sediment loads from development

6 Erosion Erosion from storms, river traffic is constant Drought results in plant loss, results in erosion Erosion and subsidence occurs every time a dike is built, part of a natural process Contamination Fecal coliform may be present from ducks Sewage outfall location are unknown Herbicide have been used to control invasives Old fuel spills on Waccamaw River No mosquito control is allowed in the area. Flushing nature of the management system removes contaminants Impoundments may be a trap for heavy metals from the river system (mercury) but levels are not higher than the rest of the river. The contribution of biosides in boat paints that wear off and go into water is unknown. Creosote has been used on water control structures over many years, treated lumber chemicals

7 Climate Change Vulnerability Assessment Tool for Coastal Habitats Ta b le D - 2 : W o r ks ho p W o r ks he e t f o r I n va s i ve / N u i s a nc e S p e c ie s INVASIVE / NUISANCE SPECIES Current Conditions Notes/Considerations Score Certainty Current invasives species water hyacinth, alligator weed, Phragmites, Arundo donax, possibly Hydrilla, feral hogs Boat traffic brings in invasives Soil management - Disturbances increase invasives CO 2 Phragmites has been shown to be more competitive at higher CO 2 Temperature Lengthening of growing season would benefit water hyacinth, water lettuce may re-occur in blooms 2 degrees change may not be enough to open the door to new invasives More blooms have a negative impact on native flora Change in Precipitation Change in Sea Level Extreme Climate Events Flooding spreads invasives through seeds and propagules A few months of good rainfall can have a great effect on growth One big rain event in summer will boil the soil and kill off plants, which can get rid of invasives but can also hinder natural plant communities Change in salinity up to 5 ppt will start to affect plants salinity will help hyacinth and possible water lettuce problems- may benefit system Diversity is stability- it is good to maintain both fresh and brackish communities There will be an immediate effect but the habitat naturally regenerates after about 3 years. Recovery from Hugo was seen within a couple of years An increase in the periodicity of extreme events would have an adverse effect- if hurricane were every year it would have an impact. Page 88

8 Climate Change Vulnerability Assessment Tool for Coastal Habitats Ta b le D - 4 : W o r ks ho p W o r ks he e t f o r S e d i me nt a t io n SEDIMENTATION Current Conditions Notes/Considerations Score Certainty Sediment loads may be increasing due to upstream development CO 2 Increased plant growth may trap more sediment, cause infilling of canals needed for drainage Temperature Longer growing season, increased plant growth may trap more sediments Change in Precipitation Heavy rain can cause ditches to fill in, increase sediment loading Prolonged flooding without drainage may increase sediment settling Change in Sea Level Draining of fields may not occur at appropriate times or at slower rates, increasing sediment settling Extreme Climate Events Impoundments are generally well protected from wind and storm surge, unless the dikes are breached. If there is a breach, the impoundment could be in filled with sediment from storm surge or increased river flow. Page 90

9 Climate Change Vulnerability Assessment Tool for Coastal Habitats Ta b le D - 5 : W o r ks ho p W o r ks he e t f o r Er o s io n EROSION Current Conditions Notes/Considerations Score Certainty River traffic (boat wake) is a source of erosion along dike edges CO 2 Increased growth of plants may reduce erosion along edges Temperature Increased growing season length for plants may reduce winter storm erosion along edges Change in Precipitation Drought followed by heavy rain increases erosion Change in Sea Level More erosion likely, dikes can only be built to a certain height salinity will remove plant buffer which will increase erosion from wave action Flooding around dikes will have an effect Extreme Climate Events Dike loss- breaching may occur, but currently the resources are available for repairs. Page 91

10 Climate Change Vulnerability Assessment Tool for Coastal Habitats Ta b le D - 7 : W o r ks ho p W o r ks he e t f o r A d a p t i ve C a p a c it y ADAPTIVE CAPACITY Fragmentation Barriers to Migration Y Recovery / Regeneration Notes/Considerations Score Certainty There is some fragmentation by internal dikes and the Middleton cut, but the habitat is not fragmented by disturbance from point of view of ducks. Compare to another unit it is less fragmented. As a waterfowl management unit, the study area is more effective because of size ( acres) and would be less valuable if fragmented Barrier to migration is the law. Permitting process does not allow the unit to go anywhere. It can only migrate inward and get smaller. Another impoundment cannot be built. Geologic record suggests species assemblages could migrate with sea level rise if new impoundments were built Recovery is imminent, although there might be a slightly different species composition after a disturbance. The forested portion (cypress) may take years, but there would be a shorter recovery time for non-forested areas. Diversity of Functional Groups 8 Management Actions ù Institutional / Human Response This habitat essentially starts with a blank slate every year, and there will always be something in the seed bed that can survive whatever the conditions are. This particular site is well situated because of its location and previous management history, many management tools Inability to manage- can t pump fresh water into the impoundments. Management with salt water flooding can increase diversity Managers have already been planning for what if scenarios. Tools, equipment are available. A general permit was established for emergency repairs to flood gates and impoundments demonstrated the ability to adapt to new situations. Several attempts to re-impound have nearly gone through. Most of dike system is maintained by private land owners for hunting. Some landowners will do anything they can do to maintain their land This site has the habitat component and the historical component that people will want to maintain