Observed evidence for a greening trend in the Chinese Loess Plateau: Grain-for-Green policy drivers and climate impacts

Background/Question/Methods Land degradation induced by soil erosion and anthropogenic activities in the Loess Plateau of China has been a major environmental concern for centuries. Vegetation restoration has been conducted since the 1950s to control soil erosion. However, despite great investments and tremendous efforts spent, vegetation remained poor and soil erosion was still severe until late 1990s. The Chinese government initiated the state-funded programme, Grain-for-Green, in 1999, to reduce soil erosion and improve the environment by converting farmlands to forests and grasslands, particularly in the fragile areas such as the Loess Plateau. However, it is not clear how effective this newly initiated project has been. In this study, we evaluated the integrated effects of current policy and climate on land cover change and water and soil loss in the area. This assessment is based on MODIS 250 m NDVI data, observed weather data and statistical data for the period 2000-2006.

Results/Conclusions Our result showed that NDVI increased in 63% of the study area of which more than 14% were statistically significant. A significant decrease occurred in 4.7% (p<0.05) of the area after the policy began to implement. Increases in NDVI concentrated in the northern Shaanxi province, as a result of extensive vegetation restoration. The large-scale vegetation recovery correlated with climate variables which alone only explain a relatively small part of the variance. Hence the major cause of the vegetation improvement was most likely associated with the new policy implementation. Since the Grain-for-Green project, average soil erosion rate of Wuqi country, for example, has decreased by 33% from 15280 t/yr^-1 km² in 1997 to 5865 t/yr^-1 km² in 2004. These results suggest that the policy has started to have measurable positive impacts on the restoration of degraded lands in this region.