IN the mid-1980s, when concerns about global warming had not yet spread from the scientific community to the general public, environmental scientist Tom Lyons had a hunch that there was more to climate change in the South-West than greenhouse influences. "CSIRO released a map showing the marked decline in rainfall over WA's agricultural area," Prof Lyons says.

"But I had a look at all the meteorological data and I was intrigued to see that there had not been the same sort of decrease over the neighbouring native vegetation. I wanted to know, were there other things that might be impacting on the regional climate besides the global problem?"

Twenty years later his hunch is the subject of a $1 million international research project that is investigating the link between rainfall and land use.

Already his Murdoch University research team has discovered that, although the climate affects the state of the land, the reverse can be true, too.

Vital to the study is Western Australia's iconic rabbit-proof fence. Running from Esperance to Geraldton in a relatively straight line, it divides the Wheatbelt from untouched native bushland.

"There are very few places in the world where you can find the sorts of conditions that the rabbit-proof fence gives us," Prof Lyons says.

"It was built more than 100 years ago to keep rabbits out of the agricultural areas, so it divides those areas from native vegetation. Apart from land use, the soil and other conditions are the same on both sides. It acts like a natural lab, allowing us to compare what's happening on both sides."

In extensive tests, based at remote Lake King, south-east of Perth, Prof Lyons has found "significant differences" in cloud formation, and even the size of rain droplets, on either side of the fence.

Aerial and ground-level data, combined with satellite information, reveal a marked disparity in the turbulence and the amount of water being evaporated between the two sides.

 

Something in the air… BEWILDERED tourists and bleary-eyed clubbers have been startled to see groups of Murdoch University students taking samples of air in Perth's central business district. The students from the School of Environmental Science are part of a $300,000 project that is tracing the potential spread of gases released in the CBD. Led by Professor Tom Lyons, the research has serious implications for protecting Perth's population-dense centre in the event of a terrorist attack or accidental gas leak. "It is part of understanding what would happen if there was a spill or deliberate release of gas," Prof Lyons says. "If there is a toxic cloud, you would want to know where that stuff is going very quickly so FESA (the Fire and Emergency Services Authority) would know which areas to evacuate first." He says complex fluid dynamics models could take a week to come up with the answers. "The wind flows around those arcades off Hay Street Mall in very complicated and complex patterns. You can develop much simpler, faster models based on observation." Researchers have conducted 15 experimental releases of a harmless tracer gas and collected air samples from within a 2km radius of the release point. The experiments have taken place at different times of the day and night and under a range of weather conditions. "We get lots of questions from people wanting to know what we are doing, especially from tourists and drunks coming out of the nightclubs." Results of the research will be released later this year.

It appears that because native plants are darker, they absorb more heat and create more turbulence, which creates sufficient convection to lift the moisture high enough to form clouds.

"The native plants are darker and have their stomata closed so more energy goes in but they don't evaporate as much water," Prof Lyons says.

"The wheat and barley are lighter in colour, evaporate more moisture and they are nowhere near as tall so they create less turbulence.

"When we tell the farmers what we are doing, they've been anecdotally backing us up, telling us, yes it's the paddocks that back on to native vegetation that get the most rainfall."

Prof Lyons believes that bringing rain back to the Wheatbelt could involve planting native vegetation, and even black wheat, on the drought-stricken land. But, he says, the atmosphere doesn't respond to small changes in land use– replanting would have to cover areas of 20 square kilometres or more.

"The research has certainly started to attract a lot more attention. The Indian Ocean Climate Initiative started their investigations into WA climate change assuming land use was not going to be significant. Then they discovered that they couldn't find the answers they wanted in the Indian Ocean and that land use is actually a factor."

Prof Lyons is now using the latest satellite technology to take a detailed look at the type of clouds forming over the land.

"We have never claimed land use change is the whole story but it is a contributing factor," he says.

The research, which is partly funded by America's National Science Foundation, also involves scientists from Airborne Research Australia at Flinders University, the University of Alabama and the Institute for Meteorology and Climate Research in Germany.