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The mountainous region of mainland Southeast Asia harbors a wealth of natural resources, including globally important forests, multiple plant and animal species, and the headwaters of major rivers. Defined as land above 300 meters elevation, the region covers about one-half of the combined land area of Cambodia, Laos, Myanmar, Thailand, Vietnam, and China’s Yunnan Province (Figure 1). Today, land use in the region is changing rapidly and on a wide scale, creating concerns about possible negative impacts on the local, and even the global, environment. For centuries, farmers in this region have practiced diverse systems of shifting cultivation, in which plots of land are cultivated temporarily and then allowed to revert to secondary forest during a fallow period. The staple crop is upland rice, but cultivated plots may include a range of secondary food and cash crops such as maize, cassava, banana, sugarcane …