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Waterbird populations in the Murray-Darling Basin keep dropping. Why?

A new study has found dam construction and water diversions in the Murray-Darling Basin are responsible for a dramatic drop in waterbird numbers across eastern Australia.

The study, published in Global Change Biology, found a 72% decline in waterbird populations between 1983 and 2014.

River flows and waterbird numbers were closely linked, indicating reduced flows from dam construction and water diversion were the main reason for long-term declines, said the study’s lead author University of New South Wales Professor Richard Kingsford.

Kingsford and his team found a reduction in dozens of waterbird species, including ibis, swans, egrets and pelicans.

“We separated that group into all of the birds that eat fish, all of the birds that eat invertebrates and vegetation, and what we’re seeing is that all of those groups are also declining, which tells you the whole of the ecosystem is in decline,” he said.

Researchers compared the Murray-Darling Basin with the less developed Lake Eyre Basin and found that Lake Eyre waterbird populations were thriving.

The Murray-Darling Basin contains 240 dams that store almost 30,000GL of water, in contrast to the Lake Eyre Basin, which contains only one dam that stores 14GL.

Researchers compared trends in the numbers of waterbirds across both basins as well as separately in their main river systems and wetlands.

They found that over the same time, waterbird numbers in the Lake Eyre Basin showed no significant change.

“We can’t see any sort of changes in any sorts of waterbirds,” Kingsford said.

This has finding has major implications for river management on a national and international scale, he added, and could exacerbate the long-term impacts of water resource development.

However, Kingsford’s research also found that through water buy-backs and increased environmental flows, waterbird populations could recover by as much as 20% in coming years.

A representative from the Murray-Darling Basin Authority (MDBA) said the organisation was keen to look into this issue and collaborate with others to reach a solution.

“Over the coming years, we will continue to work with governments, local communities and researchers to work towards a healthy and productive basin,” the spokesperson said.

“This year, the MDBA is releasing multi-year environmental priorities that identify specific sites, ecological communities and species including birds that require support over the next three to five years.”