Shifting Goalposts: Setting Restoration Targets for Waterbirds in the Murray-Darling Basin Under Climate Change

The Murray-Darling Basin (the Basin) is the largest river system in Australia, supplying about 40% of the country’s irrigated agricultural output. Associated water resource development has come with a heavy price for the Basin’s freshwater ecosystems degrading them over decades. Australian governments are attempting to achieve environmental sustainability by returning water to the environment through buy-back of irrigation licences and improved water efficiencies. To determine effectiveness, basin-wide management objectives were established for key indicators, including waterbird populations and life histories which can effectively indicate ecosystem function and condition, driven by flow and flooding regimes. Ongoing monitoring of waterbird numbers indicates continued declines. We evaluated the feasibility of meeting established waterbird objectives under existing and predicted climates. We modelled long-term waterbird numbers using one of the world’s largest ongoing waterbird surveys (1983–2020), covering about 13.5% of the area of the entire Basin. Our findings suggest that under near future climate change projections, waterbird numbers will likely continue to decline, and remain below restoration targets set for the Basin. We discuss the current policy settings for using environmental water to support waterbird populations, recommending adjustments to restore the Basin’s waterbird populations and their wetlands in order to meet Australia’s conservation targets in relation to the ongoing global crisis of biodiversity loss.

Effects of phosphorus control on primary productivity and deep-water oxygenation: insights from Lake Lugano (Switzerland and Italy)

Attempts to restore Lake Lugano, Switzerland and Italy, from eutrophication have produced weak responses in the target variables (primary productivity and hypolimnetic oxygen concentrations), indicating shortcomings in the underlying eutrophication model. An analysis of monitoring data showed that the decrease in phosphorus concentration, although nearly compliant with restoration targets, produced only slight decreases in primary productivity and no change in hypolimnetic oxygen conditions. These target variables were equally or more sensitive to factors external to trophic state, including plankton structure, which influenced primary productivity, and the depth of mixing during turnovers, which influenced hypolimnetic oxygen. To improve the chance of success, the restoration approach should revise the phosphorus concentration target and explicitly account for the influence of external variation, especially mixing depth.