BARCELONA, Jan 7 (Thomson Reuters Foundation) - Droughts and extreme heat have cut national cereal production by 9 to 10 percent on average around the world in the last half-century, and the impact has worsened since the mid-1980s, researchers said.
Cereal production losses averaged 13.7 percent in drought years from 1985, compared with 6.7 percent during earlier droughts, a new study published in the journal Nature found.
It examined the effects of some 2,800 weather disasters on 16 cereals in 177 countries from 1964 to 2007.
The trend could be due to any combination of rising drought severity - although whether droughts have got worse is still under debate - increasing vulnerability and exposure to drought, and greater reporting of drought events, the researchers said.
The study highlights the urgency for the global cereal production system to adapt to extremes in a changing climate, they added.
"Our findings may help guide agricultural priorities and adaptation efforts, to better protect farming systems and the populations that depend on them," said senior author Navin Ramankutty, professor of global food security and sustainability at the University of British Columbia.
The analysis did not identify any impact on crop production from floods and extreme cold in national data, they noted.
While the damage to cereal production from droughts and extreme heat was considerable, the effect was short-term, as agricultural output rebounded and continued to grow after the disasters, the study said.
Droughts - which can last for several years - appear to be more harmful, reducing cereal yield and causing complete crop failure in some areas, whereas extreme heat only affected yield, it added.
RICH COUNTRIES SUFFER
The study showed production took a bigger hit from extreme weather in technically advanced agricultural systems in North America, Europe and Australasia than in developing countries.
In wealthy nations, production dropped by nearly 20 percent due to droughts, double the global average.
In comparison, the average production deficit was around 12 percent in Asia and just over 9 percent in Africa, while extreme weather had no significant effect in Latin America and the Caribbean, the study said.
This could be explained by the differing approaches of large and small-scale farming, the authors 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," said Corey Lesk, a recent graduate of McGill University.
"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," Lesk added.
As farmers in wealthier countries rarely depend on harvests for food and can usually insure crops against bad weather, the best strategy for them may be to maximise yields rather than minimise the risk of weather-related crop damage, as subsistence farmers would seek to do, the researchers said.
(Reporting by Megan Rowling, editing by Tim Pearce. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit www.trust.org)