Climate change threatens to knock crop yields

By Gerard Wynn

LONDON (Reuters) - Rapid rises in temperatures worldwide may overwhelm farmers' efforts to keep up, say experts who want funds to breed new crops and freeze heat-resistant strains bred over past centuries.

A Stanford University study to be published on Friday estimates that African growing seasons for the continent's staple foods -- maize, millet and sorghum -- will be hotter in nine out of 10 years by 2050.

Farmers can adapt by shifting growing times or using new varieties but the pace of change will require extra help, the study in the journal Global Environmental Change concludes.

"For a majority of Africa's farmers, warming will rapidly take climate not only beyond the range of their personal experience but also beyond the experience of other farmers within their country," said the study, whose authors were from Stanford and the Global Crop Diversity Trust.

The United States, Britain and the European Union have all recently reviewed the impacts of climate change.

The White House published this week a report which forecast that heat, floods, drought and pests would harm food yields and concluded, for example, that cranberry production may no longer be possible by 2050 in its East Coast heartland.

Britain said on Thursday that 2 degrees celsius hotter summers were "inevitable" in southern England by the 2040s and cited a survey of farmers which found half already affected.

The EU's executive Commission pointed in April to research which showed a net positive effect for the next 30 years, for example from milder winters, but with increasingly negative effects. "The magnitude of climatic changes may exceed the adaptation capacity of many farmers," it said.