Study: Climate change cuts crop harvests by 10%

Creative Commons: Chris Hartman, 2009.

Creative Commons: Chris Hartman, 2009.

Extreme heat events and droughts may already be taking their toll on global agriculture, cutting cereal yields by up to 10% on average, according to new research.

Published in the Nature journal, the study may be first comprehensive overview of how climate change affects aspects such as crop area, yields and production around the world since the 1960s.

Researchers from McGill University and the University of British Columbia analysed national production data for 16 cereals in 177 countries, all of which were included in an international database of extreme weather disasters.

Notably, the percentage of crop losses was found to be higher in developed nations than in developing countries.

In North America, Europe and Australasia, harvest levels dropped by an average of 19.9% because of drought − 8% to 11% more than in developing countries.

According to the researchers’ analysis of the effects of around 2800 weather disasters between 1964 and 2007, the impact from droughts has also increased since 1985.

The researchers reported:

Present climate projections suggest that extreme heat events will be increasingly common and severe in the future. Droughts are likely to become more frequent in some regions, although considerable uncertainty persists in the projections.

Senior author Professor Navin Ramankutty, professor in global food security and sustainability at the University of British Columbia said:

We have always known that extreme weather causes crop production losses. But until now we did not know exactly how much global production was lost to such extreme weather events, and how they varied by different regions of the world.

His co-author, Corey Lesk, a geographer at McGill University in Montreal said:

Across the breadbaskets of North America, for example, the crops and methods of farming are very uniform across huge areas, so if a drought hits in a way that is damaging to those crops, they will all suffer.

By contrast, in much of the developing world, the cropping systems are a patchwork of small fields with diverse crops. If a drought hits, some of those crops may be damaged, but others may survive.

One positive note emerged from the findings: the extreme weather events had no significant lasting impact on agricultural production in the years following the disasters.

Ramankutty said:

Our findings may help guide agricultural priorities and adaptation efforts, to better protect farming systems and the populations that depend on them.

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