Extensive clearing of native trees is making Australian droughts hotter and is an under-recognised factor in climate change, research shows.
The study by researchers from the University of Queensland and Queensland's Department of Natural Resources and Water shows that land clearing made the 2002-3 drought in eastern Australia 2°C hotter.
The research, published online in the journal Geophysical Research Letters, also found average summer rainfall has decreased by between 4-12% in eastern Australia and by 4-8% in southwest Western Australia because of land clearing.
These are historically the regions in Australia that have been most extensively cleared of native vegetation.
Dr Clive McAlpine, of the university's Centre for Remote Sensing and Spatial Information Science, says about 13% of the Australian continent has been cleared of native vegetation since European settlement in 1788.
However, in many agricultural areas in eastern Australia and southwest Western Australia more than 90% of native vegetation has been cleared.
"This study is showing Australian climate is sensitive to land clearing," he says.
"And our findings highlight that it is too simplistic to attribute climate change purely to greenhouse gases.
"Protection and restoration of Australia's native vegetation needs to be a critical consideration in mitigating climate change."
What's the impact?
Dr McAlpine says the research used the same modelling system as the UN's Intergovernmental Panel on Climate Change to determine the impact of land clearing.
It simulated climate scenarios for the country using data on pre-European settlement vegetation coverage and 1990 vegetation coverage for Australia.
This showed more than 150 years of land clearing had added significantly to the warming and drying of eastern Australia.
He says native vegetation plays an important role in moderating climate because it is deep rooted, which leads to more moisture evaporating into the atmosphere over a longer period.
This is then recycled into the environment as rainfall.
Native vegetation also reflects less short-wave solar radiation into the atmosphere than crops, which keeps the surface temperature cooler and helps in cloud formation.
Looking to the future
McAlpine says the findings should help in the development of policies to deal with the effects of climate change.
"The first thing is we need to protect what vegetation remains," he says.
"We also need to carefully consider in regions such as Queensland where there is a lot of regrowth how we protect that so we are not leaving the landscape vulnerable.
"And we need initiatives in southern Australia to restore native vegetation."