Conservation planning for environmental water to climate refugia in the manageable Murray-Darling Basin

One mechanism for improving the resilience of freshwater systems affected by climate change is to use environmental water to support refugial habitats which allow species, ecosystems and functions to persist and recover after severe droughts. We applied systematic conservation planning (SCP) to prioritise wetlands and lakes with the aim of informing the delivery of environmental water for the creation and protection of refugia habitat in the Murray-Darling Basin, Australia. SCP uses a complimentary algorithm to generate planning solutions that protect all target ecological assets for the lowest "cost" of the management constraints considered. Here the ecological assets were 294 wetland dependant taxa including species of fish, frogs, dragonflies, crustacea, molluscs, and plants, 42 different ecosystem types and ecosystem productivity. Managements constraints included resistance to drying, condition and connectivity and the ease of environmental water delivery. Conservation inundation targets were aligned with the approximate annual delivery of environmental water by the Commonwealth Environmental Water Holder. We found that prioritisation of sites for enivronmental water was sensitive to the choice of target ecological assets and less so but to some extent the cost of management. We found environmental water delivery in the Basin is reaching refugial wetlands that support the majority of ecosystem and species diversity. However, certain taxonomic groups, such as invertebrates, are comparatively poorly represented. To effectively manage taxa, more data on ecological and life history traits is needed to better identify the spatial and temporal location of their refugia. This case study demonstrates that the SCP approach offers an objective and repeatable process for informing environmental water allocation and delivery, that could be applied to other basins globally.