Spatiotemporal Analysis of Vegetation Changes Along the Belt and Road Initiative Region From 1982 to 2015

As a key ecological zone of terrestrial ecosystem, the Belt and Road Initiative (BRI) region has experienced a significant change of vegetation coverage in recent years. Using the GIMMS NDVI3g, this study investigated the patterns of spatiotemporal variation of vegetation coverage in the BRI region during the period 1982-2015. The Theil-Sen Median trend analysis and Mann-Kendall method were used to analyze the data, followed by the calculation of Hurst index in order to analyze future trends of vegetation coverage. In addition, possible environmental factors affecting this variation were identified by using the partial correlation analysis and residual analysis methods. The results of the study showed that (1) the normalized difference vegetation index (NDVI) of the study area revealed a slow decrease during 1982-2015, with the linear tendency being -0.1%/10a. During this period, a stable increase was detected before 1997 (linear tendency 1.4%/10a), followed by a sharp decline after 1997 (linear tendency -1.8%/10a). (2) In spatial, the areas with increased vegetation NDVI are mainly distributed in Europe, India and China, whereas the regions with decreased vegetation NDVI are mainly distributed in northern Russia, Central Asia, Southeast Asia, the Malay Islands, and northeast China, of which, the magnitude of decrease in the north of Russia is particularly remarkable. This phenomenon indicates that vegetation activities in high latitude regions declined, such as coniferous forest of subfrigid zone and tundra vegetation. (3) The same characteristic of vegetation coverage change were stronger than the reverse characteristics. A total of 89.2% of the study area's vegetation will change in the same way as in the past, with a continuously increasing area accounting for 34.0% and a continuously decreasing area accounting for 21.6%. (4) Although climate change may play a key role in vegetation growth trends on a long-term scale, human activities are also an important factor driving vegetation change in the BRI area, especially for areas with increased vegetation coverage such as China, India, and Europe.