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Planting crop varieties that better reflect sunlight back out to space could reduce summertime temperatures by more than one degree Celsius in some parts of the world, researchers announced yesterday (15 January).

The reduction, they say, would at certain latitudes be equivalent to a seasonal offset of about 20 per cent of the regional warming expected by the end of this century due to the build-up of carbon dioxide.

Researchers from the United Kingdom say that such a plan could be achieved without disrupting food production, either in terms of yield or the types of crops grown.

Their paper, published in Current Biology, argues that by choosing between different varieties of the same crop species, it would be possible to increase solar reflectivity without changing the type of crop. Strains would be selected for their leaf "glossiness" or the arrangement of their leaves to provide a canopy.

"Biogeoengineering" would be less expensive and audacious than some projects that have been proposed and would require less global cooperation, said Andy Ridgwell, lead researcher of the project, from the School of Geographical Sciences at the University of Bristol.

Global agriculture already produces a cooling of climate because crop plants generally reflect more sunlight back out to space than the natural vegetation they have replaced — a property known as albedo.

Further regional cooling could be achieved through selective breeding of plants with even greater reflective properties or by genetically modifying crop plants to optimise their albedo.

"Our proposal cannot provide a full solution to climate change, but it can reduce the severity of agricultural and health impacts of heat waves as well as droughts in much of central North America and mid-latitude Eurasia," said Ridgwell.

But, he told SciDev.Net, "our initial research suggests relatively limited potential for climate mitigation outside of the mid latitude Northern Hemisphere".

He said that the density of arable land — suitable for growing crops — and the greater distances between major arable regions appeared to be important factors. Cloudiness in the summer months also appears to lessen the impact of crop plant reflectivity changes in India and China.

"Higher resolution analysis and, particularly, regional-scale modelling would help better identify the potential for biogeoengineering in these regions," he added.

But the potential for benefit for developing countries will grow as arable agriculture develops. 

Magdi Tawfik Abdelhamid, plant biotechnologist at Egypt's National Research Centre, welcomed the study. He called for an open access database for plant varieties with morphological traits that maximise solar reflectivity.

Link to abstract in Current Biology