Rubber Plantations Expand in Mountainous Southeast Asia: What Are the Consequences for the Environment?

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, ginger, cardamom, or opium poppies (Mertz et al. 2009). Fruit trees or other useful tree species may be planted on fallow plots, or the fallows may be left entirely to natural regrowth. These practices produce a unique landscape mosaic combining small agricultural plots with secondary forests. Although studies in the region have been limited, researchers largely agree that these traditional land-use systems are environmentally sustainable, protecting the region's rich biodiversity and soil and water resources (Ziegler et al. 2011). Over the past decades, traditional forms of land use in many of these areas have evolved into more intensive agricultural systems. Plots tend to remain under cultivation longer, with less time allowed for the regrowth of secondary forests. In many instances, shifting cultivation has been replaced by permanent cropping, and in particular by rubber plantations.One factor driving the transition toward more intensive agriculture has been population growth, including substantial migration from the lowlands. Another factor has been the expansion of road networks and markets, making it easier for farmers to purchase agricultural inputs and to sell their crops.Government-sponsored crop-substitution programs have also driven a shift toward rubber. Several countries, including the United States and China, have made substantial investments in programs designed to eliminate the cultivation of opium poppies in the region. The ability to store and transport rubber easily as well as the overall return on investment make rubber far superior to any other cash crop as a replacement for opium.National governments have accelerated land-use changes by introducing explicit policies to replace traditional shifting-cultivation systems with other forms of land use, including the permanent cultivation of annual crops, rubber and other tree-crop plantations, and greenhouse-based horticulture. Policies have included the outright banning of shifting cultivation, the creation of forest-protection areas that exclude population groups that have lived in the forests for hundreds of years, and the movement of people into more crowded settlements along the main roads and in the lowlands.Attracted by the opportunity to convert traditional farming areas into high-value commercial operations, outside entrepreneurs, corporations, and governments have sought to gain control of land in the region through schemes ranging from joint ventures with local farmers to outright dispossession. Some farmers have enhanced their income by switching to the intensive production of cash crops. Others have been forced into contracts with unfavorable terms or have lost their land entirely.While more intense agricultural production may pose a threat to fragile local environments, it is not possible to turn back the clock. Rubber plantations, in particular, have proven highly profitable. Given financial realities, neither local farmers nor outside entrepreneurs are likely to return to less profitable forms of agriculture, even if the earlier forms are potentially more environmentally friendly. …