Rising carbon dioxide: Greening some of the world's driest areas

Rising CO2 levels have been "greening" the globe's most arid areas in the past 30 years by "fertilizing" vast tracts of vegetation, Australian researchers say. Scientists at the Commonwealth Scientific and Industrial Research Organization say the fertilization effect occurs where elevated carbon dioxide levels enables a leaf to extract more carbon from the air during photosynthesis, the process by which green plants convert sunlight into sugar. It also leads to leaves losing less water to the air, they said, with the result that plants in arid environments respond by increasing their total numbers of leaves. Though seemingly a benefit, there are other considerations to be taken into account, CSIRO research scientist Randall Donohue said. "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." Using satellite observations, the researchers confirmed CO2 fertilization 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, a CSIRO release reported Monday. "In Australia, our native vegetation is superbly adapted to surviving in arid environments and it consequently uses water very efficiently," Donohue said. "Australian vegetation seems quite sensitive to CO2 fertilization."