Dryland rivers in arid regions of the world support dependant ecosystems under highly variable conditions. The biota of dryland rivers and floodplains has adapted, over time, to the natural cycles of flooding and drying that characterize these environments. Aquatic microinvertebrates form a critical link in the transfer of energy from primary producers to fish and waterbirds that thrive when the rivers rise and floodplains are inundated. Importantly, aquatic microinvertebrates contribute to resiliency of dryland river biota through their ability to form drought-tolerant resting stages during long dry periods. I examined the response of aquatic microinvertebrate communities to changes in environmental conditions, including water regimes, floodplain processes, and habitat availability in the Macquarie Marshes in the arid-zone of western New South Wales, Australia. The Macquarie Marshes are temporary wetlands which have, historically, supported rich and diverse ecological communities such as huge bird colonies of international significance. While these communities have waxed and waned over time with natural flood and drought cycles, anthropogenic changes, in particular modification to the water regime through river regulation and extraction are now altering the normal ecological cycles in the Marshes. ...This study showed that when flooded, the Macquarie Marshes support huge populations of microinvertebrates and correspondingly high numbers of dormant resting stages in dry sediments once the waters have receded. Changes to water regimes that reduce the frequency of flooding and change temporary creeks into semi-permanent water bodies will have a detrimental effect on microinvertebrate communities.

Floodplain wetlands in arid and tropical environments are intermittently or seasonally flooded, drying for months and up to years in arid wetlands between floods. Aquatic food webs in these systems are adapted to this variable water regime; pulsing in productivity and diversity after floods, yet dependent on nutrients generated during dry cycles. In floodplain wetlands, upstream dams and irrigated agriculture have reduced floods and extended drying, leading to changes to natural levels of productivity and diversity. Environmental flows can contribute to the sustainable management and restoration of degraded wetlands in agricultural landscapes. Decisions on the timing, frequency, duration and magnitude of environmental water allocations depend on sound knowledge of ecological thresholds, and indicators to measure success or failure of management interventions. Thresholds are discussed for concentrations of carbon, ecosystem metabolism and microinvertebrates in arid wetlands as indicators of key ecosystem functions. This approach is also relevant to floodplain wetlands in tropical climates where water managers must balance environmental and agricultural needs in the midst of the uncertainty of climate change.

Wetlands in arid and semi-arid areas face intensifying pressure for their water resources yet harbor unique biota and ecological processes that rely on the "boom and bust" regime of alternating flood and drought. Recent research in Australia has revealed that models of ecosystem processes derived from northern temperate zone wetlands are often inapplicable to arid zone wetlands, confounding efforts to manage or protect these threatened habitats. We review four case studies from inland Australia that demonstrate different degrees of successful management, aiming to draw out lessons learned that will improve our sustainable use of these delicate systems. Inappropriate extrapolation across scales that ignores the inherent spatial and temporal variability of arid-zone wetlands, "reactive" rather than "collaborative" research and management, and a reluctance to adopt functional indicators to complement state variable are several common themes. We are optimistic that managers and researchers are collaborating to tackle these issues but warn that a parched future faces some wetlands where jurisdictional boundaries hamper their effective management or entrenched beliefs and community distrust of managers threaten ecologically sustainable resource use. In arid areas where water is so precious, environmental allocations are costly and their long-term effects are difficult to identify against a backdrop of high inherent variability. Preservation of this variability is the key to successful management of these "boom and bust" systems but diametrically opposes the desire for regulated, reliable water supplies for human use. Social and institutional acceptance and change now appear to be greater barriers than limited ecological understanding to effective management of many "parched wetlands" in Australia.