Lindsay Renwick, the mayor of Deniliquin, a country town in New South Wales, misses the constant whir of the rice mill whose giant fans dried the rice. The Deniliquin mill, the largest rice mill in the Southern Hemisphere, once processed enough grain to meet the needs of 20 million people globally. But six years of drought have had a destructive effect, reducing Australia’s rice crop by 98 percent and leading to the mothballing of the mill last December.

Drought affects every agriculture industry based in Australia, not just rice – from sheep farming, the country’s other backbone, to the cultivation of grapes for wine, the fastest-growing crop there, with that expansion often coming at the expense of rice. The drought’s effect on rice has produced the greatest impact on the rest of the world, so far. It is one factor contributing to skyrocketing prices, and many scientists believe it is among the earliest signs that a warming planet is starting to affect food production.

Researchers are looking for solutions to global rice shortages – for example, rice that blooms earlier in the day, when it is cooler, to fight against global warming. Rice plants that happen to bloom on hot days are less likely to produce grains of rice, a difficulty that is already starting to emerge in inland areas of China and other Asian countries as temperatures begin to climb. “There will be problems very soon unless we have new varieties of rice in place,” said Reiner Wassmann, climate change director at the International Rice Research Institute (IRRI). The recent reports on climate change carried a warning that could make the news even worse: that existing models for the effects of climate change on agriculture did not yet include newer findings that global warming could reduce rainfall and make it more variable.

Meanwhile, changes like the use of water to grow wine grapes instead of rice carry their own costs, as the developing world is discovering. "Rice is an essential food," sail Graeme Haley, the general manager of the town of Deniliquin. "Wine is not."

Yet the effects of climate change are not uniformly bad for rice. Rising concentrations (浓度) of carbon dioxide, the main greenhouse gas, can actually help rice – although the effect reduces or disappears if the plants face unnecessary heat, inadequate water, severe pollution or other stresses. Still, the flexibility of farmers here has persuaded some climate experts that, particularly in developed countries, the effects of climate change may be relieved, if not completely avoided. “I’m not as negative as most people,” said Will Steffen, director of the Fenner School of Environment and Society at Australian National University. “Farmers are learning how to do things differently.”