ABSTRACT
Two-thirds of the rice-growing areas in the world are in Asian countries and hundreds of millions of people depend on rice as their staple food source. Paddy fields have been considered one of the likely and most important sources of atmospheric methane since the rapid increase in atmospheric methane was recognized in the early 1980s (Wassmann, Lantin, and Neue, 2003). Paddy field cover is an important variable for modeling regional biogeochemical cycles and climate (Dickinson, 1995). Agricultural water use by irrigation accounted for 70% of global freshwater withdrawals, and most of the Asian rice agriculture is irrigated, especially in eastern Asia, including Japan, Korea, and China (Huke and Huke, 1997). The improved understanding of paddy field distribution at large spatial scales has increased the interest in deriving crop yield, methane emission, and water use estimations.
