Australian rangelands and climate change – aquatic refugia

Australian rangelands and climate change – aquatic refugia Report

Climate Change in Australia – Impacts & Adaptation Information for Australia’s NMR Regions

  • Author(s): Davis, J.
  • Published: 2014
  • Publisher: Rangelands NMR Cluster, Ninti One Limited and CSIRO

Abstract: The NRM Rangelands Cluster region is highly water-limited, and all water (surface and groundwater) in the region is environmentally, culturally and economically important. Given that water scarcity is likely to continue under all climate change scenarios, the identification, management and restoration of aquatic refugia is a critical adaptation strategy for rangelands ecosystems and the biota they support. Refugia are defined as habitats that biota retreat to, persist in and potentially expand from under changing environmental conditions. Different types of refugia are important for different species over differing spatial and temporal scales. Two major types of refugial habitats are recognised: evolutionary refugia and ecological refuges. Evolutionary refugia are defined as those waterbodies that contain short-range endemics (species that occur only within a very small area) or vicariant relicts (species with ancestral characteristics that have become geographically isolated over time). Although these species often have very small geographical ranges, their populations are relatively stable and high levels of genetic diversity are present. All aquatic evolutionary refugia in the NRM Rangelands Cluster regions are groundwater-dependent ecosystems. Evolutionary refugia are most likely to persist into the future and should be accorded the highest priority in NRM adaptation planning. Ecological refugia are defined according to the water requirements of the species they protect. Obligate aquatic organisms (fishes and some aquatic invertebrates that can only disperse via water) need perennial (permanent) aquatic habitats, or closely located near-perennial habitats, to ensure persistence. In contrast, important ecological refugia for waterbirds are the large temporary or ephemeral freshwater lakes and salt lakes that hold water after infrequent but large episodic rainfall events. The conservation significance of ecological refugia, and the priority assigned to their conservation, depends on the level of knowledge available for the species they support. Information regarding species characteristics, such as dispersal traits, is particularly important for the determination of the importance of ecological refugia. Highly mobile species are less likely to be dependent on perennial systems. The vulnerability of aquatic refugia to climate change is influenced by their source of water (groundwater or surface water). Those waterholes that depend primarily on rainfall (surface water) for their water supply are highly sensitive, and those that depend primarily on discharge from groundwater (either regional or local) systems are the least sensitive, because of the great buffering capacity of groundwater, both hydrologically and thermally. The climate adaption capacity of aquatic species in the rangelands is influenced by their habitat requirements and their dispersal ability. Short-range endemics and relictual species have limited capacity to recolonise waterbodies that dry out and so these species are at the greatest risk of extinction, particularly from the indirect impacts of climate change. The indirect effects of climate change, particularly an increase in human demands for water (for direct consumption and production of food, fibre and energy) are likely to have greater impacts than direct climatic effects. Excessive groundwater drawdown will destroy spring-based evolutionary refugia, and the construction of surface water impoundments will destroy the aquatic connectivity essential for the persistence of riverine waterholes as ecological refugia. The existing adverse impacts of livestock, feral herbivores, invasive fishes, exotic plants, recreation and tourism must also be managed. Tools for NRM adaptation planning provided in this report include a list of priority aquatic refugia (sites likely to act as future refugia) and a decision support tree. The latter will aid the identification of major types of waterbodies and the refugia they provide, vulnerability assessments and development of management responses to address direct and indirect climate impacts and other stressors. A site register of important rangelands aquatic refugia is provided at Appendix A. This is regarded as a ‘living’ register that should be updated as more information becomes available.

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Suggested Citation
Davis, J., 2014, Australian rangelands and climate change – aquatic refugia, Report, viewed 18 August 2022, https://www.nintione.com.au/?p=2825.

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