Along the United States Gulf of Mexico coast, an extensive network of forested headwater wetlands and low-order creeks drain coastal lands. Maintaining the integrity of these headwater wetlands is critical for the important functions they provide including flood attenuation, carbon cycling, contribution to local biodiversity, and maintenance of water quality. Urbanization and other land use changes continue to be a major stressor on these systems and can change the capacity for wetlands to provide functions. Because of their smaller size, they are often displaced or altered through filling, dredging, and stormwater management practices that alter their natural drainage patterns. Surrounding land use changes can also reduce adjacent habitats and increase the loading of nutrients and other pollutants to wetlands and coastal creeks. Understanding the magnitude of functions provided by headwaters and the potential loss of function due to land use change is important for predicting and managing future environmental conditions along these coastal areas.
Results/Conclusions
We highlight recent findings on the effects of land use on headwater wetland functions (i.e., water quality, nutrient cycling, and habitat) in coastal Alabama, USA. Evaluating 30 wetlands across a range of conditions, urban land use (i.e., watershed impervious surface area, ISA) corresponded to reduced hydroperiod and the loss of hydric soil indicators (e.g., low soil chroma). Urban land use also corresponded to increased surface water flows, increased water level flashiness (based on Richard-Baker Index), and decreased wetland leaf-litter content (g C m-2) on the forest floor. Using a subset of wetlands, amphibian assemblages shifted with land use change with an increased occurrence of more cosmopolitan species and reduced numbers of sensitive species. Most recently, four wetlands were intensely monitored for their capacity to attenuate dissolved nutrients (i.e., nitrate+nitrite). Despite urban land use, where stormwater flows were ameliorated and wetland hydroperiods sustained, wetlands continued to function at a high level and reduced nitrate+nitrite loads (up to 64%). We offer practical suggestions and options on how to maintain the functional capacity of these wetlands in a region facing significant land use change.