Climate-driven thresholds on cumulative effects of droughts and floods on inland aquatic ecosystems

The impacts of extreme climatic events (prolonged floods, droughts, and hurricanes) are expected to increase in frequency and intensity. The cumulative effects of these events are likely to exceed the adaptive capacity of many species in coastal rivers, lakes and wetlands. Many freshwater ecosystems have thresholds that determine when biotic diversity and natural processes can be lost or sustained. The loss of key species result in shifts that result in a rapid decline in the provisioning of clean, disease-free water supplies and loss of riparian or coastal protection. Studies on variability of rainfall in the Okefenokee Swamp in Georgia provide insights to how past and recent climatic drivers altered species dominance and ecosystem functions.  For example, prolonged droughts have resulted in burning of peat and loss of carbon storage capacities. Hurricanes flood the wetland and alter species distributions and functions. Other examples include how protective levees have been redesigned to meet environmental extremes. These “hard” engineering responses are often insufficient if biotic processes provided by natural wetlands and riparian zones are ignored. Wetland habitats in drainage basins have important economic values that can be compared to derive new concepts needed for adapting to climatic uncertainty and tipping points that define the limits of these processes.