The surprising link between land use and rainfall

A tree in regional South Australia. SCIENCE AND TECHNOLOGY

While Adelaide was spared a scorching summer this year, the city did experience one of its driest periods in recent decades. Rainfall – or lack thereof – once again became the focus of conversation.

UniSA’s Professor of Environmental Mathematics, John Boland joined the conversation last month, delivering a public lecture about the nexus between rainfall, land use and people’s perceptions of landscape.

While significant attention has been paid to the effects of climate on landscape, Prof Boland says he is investigating the effects of land use change on climate – particularly rainfall, and how people’s perceptions of their landscape might play a role in that connection.

“Many studies detail the harmful effects of vegetation clearance on rainfall totals and while originally it was thought that this decline was due to climate change alone, there is now evidence that some of the reduction in rainfall is from land use change,” Prof Boland says.

“This introduces an important question – if land use change in the form of vegetation clearance reduces rainfall, can the opposite also be true?

“Initial research I have undertaken in South Australia indicates that increased vegetation, if placed advantageously, may well enhance rainfall.”

Based at the School of Information Technology and Mathematical Sciences, Prof Boland conducted a statistical analysis of the Monarto plateau region in South Australia, which experienced extensive revegetation in the 1970s.

He concluded that while there is insufficient statistical evidence to prove the revegetation increased rainfall, there is enough evidence to infer a link between the revegetation program and rainfall, a link which warrants further exploration.

“It’s not conclusive but there is evidence that rainfall around the Monarto plateau was maintained, and even increased, soon after the revegetation of the area,” he says.

“This could have a significant impact on how we look at revegetation projects. Through targeted projects, we may be able to keep rainfall in an area stable or possibly enhance it.

“We can also grow ecosystems, rather than monocultures, and in the process this could lead to saving endangered plant species as well as providing habitat for fauna.

“If we are able to increase rainfall through targeted revegetation projects we can make the whole ecosystem more robust in terms of coping with the pressures of present heat in South Australia and the prospect of increasing frequency of heat waves under climate change.”

Prof Boland has been working with Kaurna Elder Dr Lewis O’Brien on an Australian Research Council Discovery Indigenous Development Grant, which is identifying specific locations in Australia where revegetation projects might be able to enhance rainfall.

As part of the project, the researchers are also looking at how people’s perceptions of their landscape can impact on how they choose to use it.

“Historically, people have always had a relationships with their natural environment and this in turn has affected the way people interact with it,” Prof Boland says.

“In Europe, there is a lot of mythology about Europeans who feared the forest – in Grimm’s Fairy Tales and in references to werewolves for example. I suspect the English settlers in Australia probably shared that fear and, like they had done in England, they embarked on wholesale clearance of vegetation.

“They wanted to change their landscape based on their cultural perceptions of it and in the case of Australia, they wanted to introduce farming techniques that they knew worked at home – disregarding the fact that the landscape and climate in Australia is very different to what they were used to.

“I believe that if we can place more importance on listening to the land and understanding our natural landscapes – free from constructed perceptions of landscape tied up with culture – we will be better equipped to adapt and thrive in our natural environments.”