Ecological research and management of intermittent rivers: an historical review and future directions

Rivers and streams that do not flow permanently (herein intermittent rivers; IRs) make up a large proportion of the world's inland waters and are gaining widespread attention. We review the research on IRs from its early focus on natural history through to current application in management and policy. The few early studies of the ecology of IRs were largely descriptive. Nevertheless, in the 1970s, synthesis of this sparse research complemented work on temporary standing waters to found a powerful framework for much of the subsequent research on IRs. Research on the ecology and biogeochemistry of IRs continues to fuel our understanding of resistance and resilience to drying and flooding as disturbances. Syntheses of the growing literature, including cross-continental and cross-climate comparisons, are revealing the generality and individuality of ecological and ecosystem responses to flow cessation and surface water loss. Meanwhile, increasing numbers of experiments test the causality of these responses. Much of the increased consideration of IRs in research, management and policy is driven by the observed and projected shifts in flow regimes from perennial to intermittent associated with changes in land and water use and climate, superimposed on the high incidence of natural intermittency. The need to protect and better manage IRs is prompting researchers to develop new or modified methods to monitor flow status and assess the ecological condition of these systems. Intermittent river research and management will benefit from greater exploration of aquatic-terrestrial linkages, wet-dry cycling and temporal dynamics, more-detailed mapping and predictive modelling of flow intermittency and the application of metapopulation and metacommunity concepts alongside multiple-stressors and novel-ecosystems research. By building on existing knowledge, continuing to develop quantitative models and distribution maps and using experiments to test hypotheses and concepts, we can further ecological understanding and wise management of these ubiquitous ecosystems.