According to new research reported in the Geophysical Research Letters, increased levels of carbon dioxide (CO2) over the past three decades have caused an 11 percent increase in green foliage over the globe’s arid regions through a process called CO2 fertilization.
Satellite data shows the per cent amount that foliage cover has changed around the world from 1982 to 2010 (Randall Donohue et al)
“In Australia, our native vegetation is superbly adapted to surviving in arid environments and it consequently uses water very efficiently. Australian vegetation seems quite sensitive to CO2 fertilization,” explained study lead author Dr Randall Donohue from the Commonwealth Scientific and Industrial Research Organization, Australia.
“This, along with the vast extents of arid landscapes, means Australia featured prominently in our results.”
“While a CO2 effect on foliage response has long been speculated, until now it has been difficult to demonstrate.”
“Our work was able to tease-out the CO2 fertilization effect by using mathematical modeling 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.”
The fertilization 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.
“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,” Dr Donohue said.
“Ongoing research is required if we are to fully comprehend the potential extent and severity of such secondary effects.”
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Bibliographic information: Randall Donohue et al. Impact of CO2 fertilization on maximum foliage cover across the globe’s warm, arid environments. Geophysical Research Letters, article published online June 19, 2013; doi: 10.1002/grl.50563
