Natural climate variability over the past century has emerged as the main trigger of soil salinity problems in south-eastern Australia, according to the surprise outcome of a major new groundwater study.
The finding overturns decades of accepted wisdom by revealing that land-clearing - which has long been attributed with the major role - has only a secondary part to play in the development of dryland salinity.
"We got the dryland salinity concept distorted because we did not take account of rainfall variation," says one of the study's authors, Professor Ian Acworth, who holds the Gary Johnston Chair of Water Management at the UNSW Connected Waters Initiative.
"Cutting down trees turns out to be a secondary factor to rainfall, which we now know has followed a 100-year cycle.
"The good news, for the salinity issue at least, is that the balance has now shifted back again. That extended wet period ended about 2000 and we have returned to dry conditions since 2001 and groundwater levels are now falling. If the same pattern is followed over the next 40 years or so there would seem to be little to worry about until mid-century when salinity could return as a major problem," Professor Acworth said.
Professor Acworth and Aleksandra RanÄiÄ‡, of the NSW Department of Environment and Climate Change, developed this new insight by examining thousands of records of groundwater levels in bores sunk in many parts of NSW, going back more than 100 years.
The Federal Government has recently given a substantial funding boost to groundwater studies through the new $30 million National Centre for Groundwater Research and Training, co-funded through the Australian Research Council and the National Water Commission.
Read the full story on the Faculty of Science website.