Modis-Based Grassland Trends Within and Around the Kekexili Core Protection Zone of the Sanjiangyuan Nature Reserve

The Tibetan Plateau in the West of China has undergone significant changes over the last few decades as a consequence of far-reaching land-use changes and increasing effects of climate change. Numerous studies have described vegetation trends applying time-series of satellite data. However, the results of earlier studies are partly contradictory and the causal links between grassland dynamic patterns and potential drivers have not been fully understood. In this study we address this research gap by first conducting a time-series analysis based on MODIS NDVI data to derive grassland trends for the complete Tibetan Plateau. Then we apply a straightforward analysis comparing the initial grassland conditions at locations showing positive and negative vegetation trends in the surroundings of the Kekexili core protection area of the Sanjiangyuan National Nature Reserve where grassland degradations have been suspected due to recently increasing number of wildlife populations. The grasslands trends for the complete Tibetan plateau confirm results reported for earlier MODIS based studies, while the causal analysis showed that mostly formerly high-quality grasslands in the buffer zone of the protected areas are currently declining while positive trends can be mostly observed for areas that showed a sparse vegetation cover in 2000. This indirectly suggests a strong influence of land-use on grassland degradation as typically high-quality grasslands in the buffer zones are used for livestock keeping. These findings call for immediate management adaptations to stop currently ongoing grassland degradation in the buffer zones of the Kekexili nature reserve.