RISING CO2 LEVEL TURNING WORLD'S DESERTS GREEN.

Melbourne: Elevated levels of atmospheric carbon dioxide are actually causing the deserts of the world to bloom with new green foliage, a new study claims.

Green foliage across the world's arid regions has increased over the past 30 years through a process called CO2 fertilisation, researchers said.

Satellite observations found that this CO2 fertilisation correlated with an 11 per cent increase in foliage cover from 1982-2010 across parts of the arid areas studied in Australia, North America, the Middle East and Africa, according to research scientist, Dr Randall Donohue from The Commonwealth Scientific and Industrial Research Organisation (CSIRO).

"While a CO2 effect on foliage response has long been speculated, until now it has been difficult to demonstrate," said Donohue.

"Our work was able to tease-out the CO2 fertilisation effect by using mathematical modelling together with satellite data adjusted to take out the observed effects of other influences such as precipitation, air temperature, the amount of light, and land-use changes," said Donohue.

The fertilisation effect occurs where elevated CO2 enables a leaf during photosynthesis, the process by which green plants convert sunlight into sugar, to extract more carbon from the air or lose less water to the air, or both.

If elevated CO2 causes the water use of individual leaves to drop, plants in arid environments will respond by increasing their total numbers of leaves.

These changes in leaf cover can be detected by satellite, particularly in deserts and savannas where the cover is less complete than in wet locations, according to Donohue.

"On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forestry and agriculture in such areas; however there will be secondary effects that are likely to influence water availability, the carbon cycle, fire regimes and biodiversity, for example," Donohue said.

"Ongoing research is required if we are to fully comprehend the potential extent and severity of such secondary effects," Donohue said.

The CSIRO study conducted in collaboration with the Australian National University (ANU), was published in the US Geophysical Research Letters journal.