Interactions between climate change and human activities in dryland degradation in Beijing-Tianjin sand-storm source region, China

Grassland degradation in drylands results from the integrated impacts of climate change and human activities. It is necessary to discriminate between climate and human induced dryland degradation. We applied the method of residual trends(RESTREND) to Beijing-Tianjin sand-storm source region, using NOAA/AVHRR NDVI data from 1982 to 2006 and meteorological data within the same time period. Firstly, we quantitatively analyzed NDVI-rainfall relationship and temporal responses of vegetation to rainfall. Secondly, based on this relationship we maxima constructed a regression model using the first 13 years(1982-1994) of data for each pixel between annual maximal NDVI and precipitation. Thirdly, the difference or residuals between actual and predicted maximal NDVI were derived for the 1atter 12 years(1995-2006). The negative trends in the residuals are interpreted as human-induced degradation. Finally, we tested the effectiveness of RESTREND method in this region. The results showed that the whole study area experienced a human-induced restoration from 1995 to 2006 as the result of Ecological restoration program. The results are in accord with the status of Beijing-Tianjin sand-storm source region.