Widespread floods and environmental flows have been a boon for waterbirds, with annual surveys in eastern Australia recording more than half a million birds.
But researchers say long-term declines in populations persist and the effects of El Niño and drying across eastern Australia are showing, with the total area of surveyed wetland habitat decreasing over the past year.
Scientists have conducted the eastern Australian waterbird survey annually since 1983 to monitor continental-scale changes in the distribution and abundance of waterbirds and their breeding, as well as change in the extent of wetland habitat over time.
During this year’s survey – the 41st – researchers observed increased numbers of waterbirds, counting 579,641 individuals, the seventh-highest figure in the survey’s history.
The boost in numbers came after three La Niña years and widespread breeding of waterbirds throughout eastern Australia in 2021 and 2022.
The director of UNSW’s Centre for Ecosystem Science, Prof Richard Kingsford, said it showed the “importance of the widespread flooding and environmental flows that we have seen in the last three years”.
But he said three of four major markers of waterbird health – total abundance, number of species breeding and area of wetlands surveyed – continued to show significant long-term decline.
“The results are still showing a long-term decline and so the long-term loss of waterbirds has not been reversed,” Kingsford said.
The scientists found waterbirds were most abundant in the temporary wetlands of the Georgina-Diamantina River system in north-western Queensland, with Lakes Mumbleberry and Torquinnie supporting more than 180,000 waterbirds.
There were also more than 50,000 waterbirds south of the Coorong, in South Australia, in the south-east wetlands.
Kingsford said waterbird numbers in the Lower Lakes and Coorong were higher than in previous years, with breeding of several thousand straw-necked ibis, Australian pelicans and pied cormorants observed in their usual breeding sites.
“This long-term data is critical to identifying trends in the health of rivers and wetlands and it is important that we continue to track these changes so that we can identify the problems and solutions,” he said. “It allows us to work out the extent of human impacts within the natural cycles of our river systems.”
Kingsford said implementation of the Murray-Darling Basin plan, which aims to bring the basin back to a healthy and sustainable level, would be critical.
Legislation that amended and strengthened aspects of the plan passed the federal parliament during the final sitting weeks for the year.
Despite the lift in numbers of waterbirds recorded in the 2023 survey, the researchers observed that the effects of El Niño – which is associated with hotter and drier conditions – were already evident on waterbirds and their habitat.
The scientists recorded little breeding activity overall in 2023 and the area of wetlands surveyed had decreased to 192,083 ha, a significant fall from 326,768 ha in the flood year of 2022 and well below the long term average of 281,209 ha.
The Macquarie Marshes in New South Wales was one area where there had been less flooding than in the previous year. According to the survey report, relatively low numbers of waterbirds were observed at this site and no breeding colonies were recorded.
October rainfall was 65% below the 1961 to 1990 average across Australia and the researchers said many of the large wetlands surveyed in 2023 were drying out.
“Breeding species’ richness and abundance decreased considerably compared to the previous year, with breeding abundance falling by an order of magnitude to slightly below the long-term average,” said Dr John Porter, a senior scientist from the NSW Department of Environment and Planning and the survey’s coordinator.
