Waterbird numbers in the Murray-Darling Basin have declined by more than 70 per cent in the past 30 years, according to a new study.
But while the University of New South Wales study pointed the finger at the construction of dams and water diversion for irrigation, the Murray-Darling Basin Authority said the basin plan was not to blame.
The three decade-long study collected data through yearly aerial surveys of waterbirds and covered almost a third of Australia, with data showing a 72 per cent drop in populations between 1983 and 2014.
‘‘Our analysis of this unique dataset shows there has been a severe degradation of the rivers and wetlands in the Murray-Darling Basin during this period,’’ lead author and UNSW professor Richard Kingsford said.
‘‘By comparison, we found no signs of degradation in the rivers and wetlands in the undeveloped Lake Eyre Basin.’’
The researchers compared trends in the numbers of waterbirds, including pelicans, black swans, different duck species and shorebirds, across both the Murray-Darling and Lake Eyre basins, as well as separately in their main river systems and key wetlands.
The report found that river flows and waterbird numbers were closely linked, indicating reduced water flow due to dam construction and water diversion for irrigation was the primary reason for the long-term declines in waterbirds in the Murray-Darling Basin.
The study also modelled the effect of the Federal Government buying up water rights and returning this water to the riverine environment, at an expected cost of more than $12billion.
This was projected to ‘‘partly restore’’ waterbird numbers, resulting in an 18 per cent improvement, yet was unlikely to be sustainable.
‘‘Projected climate change effects could reduce these benefits considerably to only a one per cent or four per cent improvement, with respective annual recovery of environmental flows of 2800Gl or 3200Gl,’’ the report said.
‘‘This remains highly contentious, primarily because of socio-economic impacts on irrigation communities; poor understanding of social-ecological impacts; little large-scale evidence for widespread ecological impact; and scepticism that returning water to rivers will redress the problem.’’
The MDBA said it welcomed any new research into the basin and acknowledged waterbird numbers had declined in the past 30 years.
‘‘This is due to the impacts of ongoing development of the basin and the extended dry conditions experienced through the millennium drought,’’ the MDBA said.
‘‘Water recovered through the plan is being actively managed by environmental water holders on behalf of governments.
‘‘There are some encouraging signs, with many environmental water actions supporting successful bird breeding in the basin.’’
The authority said environmental flows for waterbird habitats also needed to be supported by other natural resource management actions, such as the control of pests and foxes.