The Potential Long-Term Impacts of Climate Change on the Hydrologic Regimes of North Carolina’s Coastal Plain Non-Riverine Wetlands

HighlightsBased on current emissions, mean water table decline in these wetlands will likely range from 25 to 65 cm by 2100.Projected changes could lead to a decline or loss of the important ecosystem services that wetlands provide to society.Results indicate a potential need to allocate more resources to developing strategies for managing wetlands.Abstract. Wetlands are especially at risk from climate change because of their intermediate landscape position (i.e., transition between upland and aquatic environments), where small changes in precipitation and/or evapotranspiration can have substantial impacts on wetland hydrology. Because hydrology is the primary factor influencing wetland structure and function, the important ecosystem services that wetlands provide may be altered or lost as a result of climate change. While a great deal of uncertainty is associated with the projected impacts of climate change on wetlands, hydrologic models and downscaled climate model projections provide tools to reduce this uncertainty. DRAINMOD is one such process-based hydrologic model that has been successfully adapted to simulate the daily water level fluctuations in natural wetlands. The objective of this project was to determine the range of possible impacts of climate change on the hydrologic regimes of non-riverine, non-tidal Coastal Plain wetlands in North Carolina. DRAINMOD models were calibrated and validated for two minimally disturbed, natural wetland sites using observed water table and local weather data. Two representative concentration pathway (RCP) scenarios were evaluated: RCP4.5 and RCP8.5. Nine models were selected from an ensemble of 32 climate models to represent the range of possible changes in mean precipitation and temperature. Downscaled climate projections were obtained from the U.S. Bureau of Reclamation. Simulations were run from 1986 to 2099, and results were evaluated by comparing the projected mean water table levels between the base period (1986-2015) and two future evaluation periods: 2040-2069 and 2070-2099. The model simulation results indicated that the projected mean water table level may decline by as much as 25 to 84 cm by the end of this century (2070-2099) for the RCP8.5 scenario and may decline by 4 to 61 cm for the RCP4.5 scenario. In Coastal Plain wetlands, declines in water tables can lead to the subsidence of organic soils, which can lead to the loss of stored carbon and increased risk of peat fires. Lower mean water levels can also lead to shifts in vegetation community composition and loss of habitat functions for wetland-dependent fauna. These results provide an overview of the potential impacts of climate change on North Carolina wetlands, and they provide a range of scenarios to inform and guide possible changes to water management strategies in wetland ecosystems that can be implemented now to limit the loss of ecosystem services over the long term. Keywords: Climate change, DRAINMOD, Hydrology, Modeling, North Carolina, Wetlands.

Limnological features of coastal-plain wetlands on the Gnangara Mound, Perth, Western Australia

The Gnangara Mound is an area of elevated sandy soil on the Swan Coastal Plain to the north of Perth. It constitutes a major groundwater resource for metropolitan Perth. Sixteen wetlands on the Mound had total phosphorus concentrations of 12-462�g L-1, the high values being attributed to agricultural and urban activity. Sediment concentrations of total phosphorus and total nitrogen were 61-954 and 1212-16739 �g g-1, respectively. Conductivities were 505-10270 �S cm-1, and pH values were 3.3-9.3. Only one wetland was highly coloured (79.9 8440 m-1), with an E4/E6 ratio of 4.6. Chlorophyll a concentrations were 0.01-130.8�g L-1; in wetlands with low gilvin concentrations, Myxophyceae dominated, whereas wetlands with higher gilvin concentrations had large numbers of diatoms and Chlorophyceae. The highly coloured wetland had the lowest chlorophyll a concentration despite high nutrient concentrations, supporting the hypothesis that the consequent reduction in light or other associated factors are important in maintaining low phytoplankton biomass in dystrophic wetlands of the region, particularly those on Bassendean sands.