Ecological Risks Arising from the Impact of Large-scale Afforestation on the Regional Water Supply Balance in Southwest China

Ecological degradation impedes sustainable development in Southwest China, and artificial afforestation has been a key strategy of the Government of China to effectively curb it. However, the water consumed by large-scale afforestation has a huge impact on water supply in Southwest China, which also arise a new challenge causing severe drought here recently. In order to determine the impact of artificial afforestation on the region, this study conducts spatiotemporal, abrupt change, and correlation and regression analyses. Results show that although water resources fluctuate, they exhibit a general declining trend. Especially after 2000, water resources showed a significant downward trend. In terms of spatial tendency, there has been an obvious decrease in water resources in the Sichuan Basin, the mountainous region of eastern Chongqing, and the Yunnan–Guizhou Plateau. Due to extensive afforestation and vegetation cover growth, there has been an increase in most trends of forest-shrub ecosystems, resulting in substantially enhanced evapotranspiration effects. The uptake of water by afforestation in Southwest China could reach 40.42 billion m3, which is equivalent to 10.69% of its annul available water supply (1980–2015). Generally, afforestation disrupts the water balance of the region. This study recommends substituting afforestation for natural restoration or, at the very least, selecting vegetation that requires less water for the restoration of the ecological environment of Southwest China, which provide scientific method for regional sustainable development.