Arid Regions Green As CO2 Levels Rise

A new scientific paper reports on the greening of semi-arid regions since 1982, as a result of the “carbon fertilisation” effect.  Plants grow by photosynthesising atmospheric carbon dioxide and turning it into hydrocarbons to feed on.

Australian scientist Randall Donohue and his team predicted that rising atmospheric carbon dioxide levels, the result of increased fossil fuel burning worldwide, would increase the growth of plants in semi-arid areas.

Carbon fertilization effect

The amount of leaf cover, or foliage, is the clue to identifying the carbon fertilisation effect, according to Donohue, because,

“a leaf can extract more carbon from the air during photosynthesis, or lose less water to the air during photosynthesis, or both, due to elevated CO2.”

That is the CO2 fertilization effect.

Between 1982 and 2010, atmospheric carbon dioxide levels increased by 14%. The Donohue team’s mathematical model for carbon fertilisation predicted this rise would increase foliage in semi-arid areas by between 5-10%. They then tested this against actual data from 1982-2010 and found a strong correspondence between their model and what had happened in the real world, where data showed an 11 percent increase in foliage after adjusting the data for precipitation and other relevant variables.

In addition to greening dry regions, the CO2 fertilization effect could switch the types of vegetation that dominate in those regions. Donahue said,

“Trees are re-invading grass lands, and this could quite possibly be related to the CO2 effect. Long lived woody plants are deep rooted and are likely to benefit more than grasses from an increase in CO2.”

He added,

“The effect of higher carbon dioxide levels on plant function is an important process that needs greater consideration”

The paper CO2 fertilisation has increased maximum foliage cover across the globe’s warm, arid environments, by  Randall J. Donohue and Tim R. McVicar, Michael L. Roderick, Graham D. Farquhar, is published by the American Geophysical Union. People with access via university libraries etc can download it here .

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