Identifying trend shifts in vegetation greenness in China from 1982 to 2015

Abstract

AbstractUnderstanding vegetation evolution is critical for exploring changes in terrestrial ecosystems and identifying future challenges. However, analyses that simultaneously examine trend shifts in vegetation greenness at the national, regional, biome, and pixel scales in China are still rare. Using long‐term (1982–2015) satellite data and the breaks for additive season and trend (BFAST) technique, we identified breakpoints in normalized difference vegetation index (NDVI) in China. The results showed that the annual mean NDVI gradually increased. A total of 68.8% of the vegetated area exhibited upward trends in NDVI, most of which was distributed in Southeast China and the Loess Plateau. Changes in NDVI trends occurred in 78.7% of the total vegetated areas, while hotspots were concentrated in Northwest and North China. A rapid increase in breakpoints was detected after 1999, mainly concentrated in North and Northwest China, and corresponding to the times and areas with the highest ecological engineering efforts. Positive shifts in NDVI trends were more common and generally distributed on the eastern side of the Hu Huanyong line, while browning (negative) shifts were mainly distributed on the western side and were gradually expanding, indicating a possible tendency toward environmental degradation. Although unstable vegetation areas that underwent land cover type changes had higher frequencies of breakpoints, the proportion of stable vegetation experiencing NDVI trend shifts was higher after 2000, probably because human intervention buffered external disturbances in unstable areas. Identifying hotspot areas of shifts in vegetation greenness can help setting priorities when taking measures for ecosystem conservation, thus provide scientific reference for sustainable land development.