Impact of large-scale tree planting in Yunnan Province, China, on the water supply balance in Southeast Asia.

Along with rapid economic development and population growth, anthropogenic disturbances to natural ecosystems increase the progressively worsening environmental problems in and around water resources, making the potential ecological risks more severe and unpredictable. In order to cope with the increasingly serious issues related to the ecological environment and poverty alleviation, the Government of Yunnan in Southwest China launched a large-scale afforestation campaign (plantation forestry) on the Yunnan-Guizhou Plateau, which is the main source of several major river systems in Southeast Asia. In this study, we use GIS to investigate the impacts of a large-scale afforestation on the water storage balance of Southeast Asia. Results show an expansion of the arid zone in the Yunnan-Guizhou Plateau in recent years, and runoff from rivers has decreased year after year. In contrast to natural forests, planted forests are a characteristic of more water shortages, less rainfall, and higher evapotranspiration rates. Moreover, planted forests may exacerbate conflicts between humans and nature over water resources. Additionally, with respect to downstream populations affected by the government's afforestation policy, China has bore the brunt of the resultant water scarcity predicament (approximately 52.29%), followed by Vietnam (26.39%), Laos (6.78%), Cambodia (6.16%), Thailand (4.42%), and Myanmar (3.96%). To alleviate this problem and the potential crises that may result from it, the Government of China should change its policy from its focus on afforestation to promoting natural vegetation conservation practices.