Life at the edge: ecological and evolutionary trends in temporary wetlands

Temporary wetlands are ecosystems at the edge, the ecotones between terrestrial and aquatic habitats. Temporary wetlands processes depend on both wet and dry phases yet the dry phase is often ignored by aquatic ecologists and the wet phase by terrestrial ecologists. Although numerically and spatially the most abundant type of aquatic ecosystem in Australia, temporary wetlands have been the poor country cousins of permanent rivers and lakes: human needs for water have focused research and management on permanent waters and in comparison temporary waters have been limnologically neglected. Temporary wetlands have often been drained or dammed to make them more permanently dry or wet, with scant recognition of the essentials of cycling between wet and dry. Climate change predictions of higher temperatures and more extremes of drought and flood suggest that many of our permanent waters will become more temporary and pressure to sacrifice temporary wetlands to enhance water availability for humans will continue. To manage these scenarios understanding how temporary wetland communities survive and maintain their resilience in unpredictable and variable environments is crucial. In this context I will address the question of whether temporary wetlands really can remain resilient in the face of relatively sudden major changes to the timing, duration and frequency of wetting and drying cycles and increases in salinity. What are the limits to their ability to bounce back after disturbance? Using wetland plants and their seed banks in temporary wetlands as examples, I will explore selection pressures, adaptation and opportunism as mechanisms of change in plant communities. Understanding these relationships should help us to set directions for research and management into the future.