Lindsay Renwick, the mayor of this dusty southern Australian town, remembers the constant whir of the rice mill. "It was our little heartbeat out there, ticketytick-tickety," he said, imitating the giant fans that dried the rice, "and now it has stopped." The Deniliquin mill, the largest rice mill in the Southern Hemisphere, once processed enough grain to meet the needs of 20 million people around the world. But six long years of drought have taken a toll, reducing Australia's rice crop by 98 per cent and leading to the mothballing of the mill last December. The collapse of Australia's rice production is one of several factors contributing to a doubling of rice prices in the last three months - increases that have led the world's largest exporters to restrict exports severely. Drought affects every agricul tural industry based here, not just rice - from sheepherding to the cultivation of wine grapes. 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. It is difficult to definitely link short-term changes in weather to long-term climate change, but the unusually severe drought is con sistent with what climatologists predict will be a problem. Drought has already spurred significant changes in Australia's agricultural heartland. Some farmers are abandoning rice, which requires large amounts of water, to plant less water-intensive crops like wheat or wine grapes. Scientists worry that the reallocation of scarce water resources - away from rice and toward more lucrative crops threatens poor countries that import rice as a dietary staple.