Food crisis is global warming's biggest threat, say UW, Stanford scientists

When searing temperatures blasted Western Europe in 2003, more than 50,000 people died and harvests of wheat, animal fodder and fruit fell by up to a third.

Imagine that heat being the norm over much of the world, and you'll have an idea what the future is likely to hold for agriculture — and humanity, says a new report from scientists at the University of Washington and Stanford University.

"I'm not worried about Greenland sliding into the sea. I'm not worried about sea levels going up," said UW atmospheric sciences professor David Battisti. "This is probably the most compelling reason why we need to deal with global warming."

By the end of this century, the odds are higher than 90 percent that average temperatures during the growing season will be higher than ever before in recorded history across a big swath of the planet, says the analysis published today in the journal Science. The hardest-hit areas will be the tropics and subtropics, which encompass about half the world's population and include Africa, the southern United States, and much of India, China and South America.

"We are headed for a completely out-of-bounds situation for growing food crops in the future," said report co-author Rosamond Naylor, director of Stanford's Program on Food Security and the Environment.

High temperatures cause crops like corn, wheat and rice to grow faster, but reduce plant fertility and grain production. With average growing-season temperatures expected to rise more than 6 degrees Fahrenheit, crop yields will fall 20 to 40 percent, the report estimates.

Even in the United States, where warmer temperatures are projected to initially increase some crop yields through the middle of this century, total harvests are projected to fall by 2100.

But worldwide, the impacts will fall most heavily on impoverished subsistence farmers, Battisti pointed out.

"You're talking about hundreds of millions of additional people looking for food because they won't be able to find it where they find it now," he said.

Michael Glantz, a political scientist who studies the social impacts of climate and climate change, said the study raises some good points, but the developing world faces so many immediate problems it's difficult to worry about what will happen in five decades or more.

"When I think about 2100 and climate-change impact on food security, I just glaze over," said Glantz, who directs the Consortium for Capacity Building at the University of Colorado, Boulder.

But Cary Fowler, director of the Rome-based Global Crop Diversity Trust, says the report is a wake-up call on the need to develop new heat-resistant crop strains.

"This research shows we're about to enter a whole new game," said Fowler, whose group receives funding from the Bill & Melinda Gates Foundation and operates the "doomsday" seed vault on the remote Norwegian island of Spitsbergen.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com