Changes predicted for the Simpson Desert's droughts and flooding rains

13 November 2012

In the face of climate change, central Australia is predicted to have more flooding rains followed by explosions in rodent populations. This forecast, based on over 100 years of historical data, was published this month by researchers in the School of Biological Sciences.

New research predicts climate change will lead to an increase in extreme rainfall in the desert (image courtesy of Aaron Greenville)
New research predicts climate change will lead to an increase in extreme rainfall in the desert (image courtesy of Aaron Greenville)

Extreme weather is a feature of Australian deserts - hot days and cold nights, long periods of dry followed by heavy rains. But even in a desert of extremes there are averages. In research just published in Ecology and Evolution, PhD candidate Aaron Greenville, used weather records from the past 100 years to investigate climate change. At the majority of weather station sites around the Simpson Desert he found a warming of the average minimum by almosttwo degrees Celsiusand a warming of the average maximum of over one degree Celsius.

However, the really interesting results came when Aaron looked at the extreme climatic events. "Most research has focused on how the climate will change or has changed based on average or median events," explained Aaron. "However, extreme climate events like long droughts, heat waves and more recently, hurricane Sandy, are important drivers for ecosystems, even though they are rare events."

By looking at trends in weather at the farthest edges of 'normal', Aaron and his co-authors and PhD supervisors Professor Chris Dickman and Associate Professor Glenda Wardle, were able to find patterns of change. "Australia is famous for being a land of extremes and this paper illustrates how extreme rainfall and temperature events have changed over the last century for central Australia." Aaron found that there has been an increase in these rare flooding rain events - not only are these events bigger but they are occurring more frequently.

As an ecologist, Aaron is also interested in what these extreme weather events might mean for the local wildlife. To investigate this he drew on over twenty years of small mammal trapping data from the Simpson Desert. The data showed that if the desert received a threshold rainfall of 418mm, the rodent population the following year would explode (or to use correct scientific language, the population would 'irrupt').

So what does it mean for the ecosystem if climate change yields more of these flooding rains? "Extreme rainfall events may drive more irruptions of native rodents," said Aaron, "but also provide conditions for feral predators to become established. In addition, introduced animals like house mice and rabbits may be able to establish in areas that they previously could not."

In a previous study by Aaron and his collaborators, published in the International Journal of Wildland Fire, they found that the risk of wildfires increased after two consecutive years of extreme rainfall. This prompted Aaron to suggest that climate change may lead to, "a change in wildfire frequency and intensity." An increase in wildfires will, of course, have additional consequences for the diversity of desert species.

To continue to monitor the climate of the Simpson Desert, theDesert Ecology Research Group, to which Aaron belongs, has installed thirteen automatic weather stations across its 8,000 square-kilometre study region. "Expanding the network of weather stations across Australia and into our more remote regions will greatly aid us in documenting climate change and also how various climate factors interact with species."