# Spatio-Temporal Changes in Ecosystem Quality across the Belt and Road Region
## 1 Introduction  
The Belt and Road Initiative (BRI), which includes the \"Silk Road Economic Belt\" and the \"21 st Century Maritime Silk Road\", proposed by China in 2013, has become a great part of the practice of building a Human Destiny Community [1]. As one of the most influential international cooperation platforms, the BRI aims to promote the common development of regional trade and economy which assembles numerous developed and developing economies into an open and inclusive network of cooperation, providing unprecedentedopportunities for international enterprises to explore new markets in countries along the routes [2; 3]. Particularly, the implementation of the \"Vision and Action to Promote the Joint Construction of the Silk Road Economic Belt and the 21 st Century Maritime Silk Road (VAP)\" by China in March 2015 has promoted mutually beneficial cooperation and achieved great progress [4; 5]. However, for the unprecedented dimensions and the official major investment areas of the BRI, many scholars have shown concerns about its actual and potential negative influence on the ecological environment [6; 7; 8; 9; 10]. Therefore, ecological environment assessment over the Belt and Road (B&R) region has become crucial for sustainable development at both the regional and global scales. In fact, the B&R region has a complex and fragile ecosystem, which mainly includes arid, semi-arid and sub-humid regions. Moreover, its response to intensified global climate change and human activity is predicted to become more sensitive [6; 11]. Consequently, it is understandable that economic and social development may generate some inevitable influences on the ecological environment. Ecosystem quality is an important indicator for a sustainable ecological environment [12]. Therefore, objective and scientific ecosystem quality assessment is important for evaluating the impact of the BRI on the sustainable development of the B&R region and identifying the key areas for environmental protection, which would further maintain the health and stability of the ecological environment and promote regional sustainable development. Although the scientific conceptualization of ecosystem quality has not formed a common consensus in the current studies [13], researchers believe that a perfect ecosystem is healthy and can meet the sustainable development of human beings' needs, which is the important part of ecological environmental quality [14; 15; 16; 17]. Vegetation is the most important component of the Earth's ecosystem, which plays a key role in the circulation of energy, carbon and water, and its changes directly affect the climate, hydrology and soil of a region [18; 19]. Therefore, vegetation is an important indicator of regional ecosystem quality, which can reflect the overall ecological environment change characteristics of a region. For this study, the definition of ecosystem quality as defined by the Ministry of Ecology and Environment of China was adopted. Ecosystem quality refers to the quality of natural vegetation in an ecosystem that uses vegetation indicators to diagnose whether the ecosystem is healthy under environmental stress and human disturbance within a specific time and space [20]. Remote sensing technology can objectively and quantitatively evaluate spatiotemporal changes in ecosystem quality, which has become a focus of ecosystem quality assessment at the regional scale. Many studies have conducted numerous ecosystem quality assessments based on remote sensing data, which have mainly focused on the assessment of ecological environmental quality, ecosystem function and ecosystem health using different indicators by integrating different kinds of products over different regions. For example, [PERSON] et al. developed an eco-environmental quality index model using land use data, NDVI data from MODIS and statistical data to evaluate the ecological status of China and analyze its influencing factors during 2005-2010 [21]. [PERSON] et al.