12. The River Murray-Darling Basin: Ecosystem Response to Drought and Climate Change

The River Murray-Darling Basin is one of Australia’s largest river basins, and contains highly valued water-dependent ecosystems, including 16 Ramsar-listed wetlands. Through the impact of drought and over-allocation (69 % of the basin’s water is abstracted for irrigation, industrial, and domestic use), these ecosystems are now widely considered to be severely degraded. Future climate scenarios suggest a drier and more variable climate with continued and intensified drought periods. Future water-sharing policies are under consideration to address this degradation by changing the balance between consumptive and environmental water, including the security of environmental water. This chapter outlines the challenges involved in managing ecosystem adaption to a drier climate while maintaining key ecosystem assets. We conclude that it is unlikely that it will ever be possible to return to an ecosystem like what existed pre-irrigation development. While this past ecosystem state has often been used as benchmark in ecological assessment, the great scientific challenge now is to provide rigorous assessment that allows those setting policy to gain a better sense of what is ecologically possible and socially desirable within constraints of water diversion and climate futures that we now face.