Spatiotemporal evolution characteristics and driving forces of vegetation cover variations in the Chengdu-Chongqing region of China under the background of rapid urbanization

Abstract

：The research on the spatiotemporal changes and driving factors of ecosystems in rapidly urbanizing regions has always been a topic of widespread concern. As the fourth pole of China's economic development, the research on the Chengdu-Chongqing region has reference significance for the urbanization process of developing countries such as India, Brazil, and South Africa.The normalized difference vegetation index (NDVI) has been widely applied in studies of plant and ecosystem changes. Based on MODIS NDVI data from 2001 to 2020 and meteorological data of the same period, this study reveal the evolution of NDVI in the Chengdu-Chongqing region from three aspects: the spatiotemporal variation characteristics of NDVI, the prediction of future trends in vegetation coverage, and the response of vegetation to climate change and human activities. During the period of plant growth, the mean NDVI achieved a value of 0.78, and the vegetation coverage rate is increasing year by year. According to the Hurst index, the future NDVI in Chengdu-Chongqing region will tend to decrease, and its trend is opposite to that of the past period of time. The Chengdu-Chongqing region vegetation positively affected by human activities are greater than those negatively affected, and in terms of vegetation degradation, the impact of human activities is greater than climate change.

Analysis of the multiple drivers of vegetation cover evolution in the Taihangshan-Yanshan region

“…The results show that the response of FVC to different variables in the study area is very different, in which GDP, the proportion of GDP in the secondary industry, elevation and slope show positive and negative effects interactively, but in most of the area show negative inhibitory effects, GDP can reflect the state of economic development of a region, and the greater the intensity of human activities, the stronger the destruction of the vegetation cover of the ground surface 57 ; The topographic factors show a spatial pattern of high in the north-east and low in the south-west, and in the south-central plains area there is little restriction by the topography, the terrain is gentle and suitable for human habitation, and there are frequent human activities, facing the possibility of a decrease in FVC, and the northeastern hilly area is actively carrying out ecological engineering construction projects, which play a certain role in the promotion of FVC 58 ; Population size, the proportion of urban population, the proportion of GDP in the primary and secondary industries, and night-time lighting data are all negatively inhibited, and the night-time lighting data are particularly significant, the spatial heterogeneity of the FVC is obvious, manifesting itself in a distribution pattern of low in the southwest and high in the northeast, night-time lighting is mostly from the city-wide man-made sources, and the differences in human night-time activities can, to a certain extent, reflect the inter-regional development situation. In the process of rapid urbanisation, human activities have led to a decline in vegetation cover, revealing in depth the strong driving force of human activities on vegetation degradation 59 , suggesting that human activities have a strong driving force on vegetation, attaching importance to its dominant role in vegetation restoration, strengthening the construction of an ecological civilisation, and actively implementing ecosystem protection and restoration projects to comprehensively promote the construction of a beautiful China.A total of 18 explanatory factors were selected for study in this paper, but there are still some factors (e.g., groundwater storage, solar radiation, wind speed, wind direction, etc.) that were not included, which makes the results incomplete.…”