Influences of population pressure change on vegetation greenness in China's mountainous areas

Abstract

Mountainous areas in China account for two‐thirds of the total land area. Due to rapid urbanization, rural population emigration in China's mountainous areas is very significant. This raises the question to which degree such population emigration influences the vegetation greenness in these areas. In this study, 9,753 sample areas (each sample measured about 64 square kilometers) were randomly selected, and the influences of population emigration (population pressure change) on vegetation greenness during 2000–2010 were quantitatively expressed by the multivariate linear regression (MLR) model, using census data under the condition of controlling the natural elements such as climatic and landform factors. The results indicate that the vegetation index in the past 10 years has presented an increasing overall trend, albeit with local decrease in some regions. The combined area of the regions with improved vegetation accounted for 81.7% of the total mountainous areas in China. From 2000 to 2010, the rural population significantly decreased, with most significant decreases in the northern and central areas (17.2% and 16.8%, respectively). In China's mountainous areas and in most of the subregions, population emigration has significant impacts on vegetation change. In different subregions, population decrease differently influenced vegetation greenness, and the marginal effect of population decrease on vegetation change presented obvious differences from north to south. In the southwest, on the premise of controlling other factors, a population decrease by one unit could increase the slope of vegetation change by 16.4%; in contrast, in the southeastern, northern, northeastern, and central area, the proportion was about 15.5%, 10.6%, 9.7%, and 7.5%, respectively, for improving the trend of NDVI variation.

Response of net primary production to land use and climate changes in the middle‐reaches of the Heihe River Basin

“…Meanwhile, the temperature decreasing <1.2°C also promoted the NPP of hardy forest, grass, and crops (wheat, barley, and rapeseed) in high‐altitude mountains, due to the simultaneous precipitation increase. In addition, rural–urban migration has weakened the human activities (e.g., wood cutting and grazing) in mountain areas (Li et al, ; Li & Tan, ; Xiao, Hu, Tan, Li, & Li, ), which further increased the NPP in forested areas and grassland. However, warming‐induced water stress compromised photosynthesis (Zhao & Running, ), leading to a decline NPP in arid sparse grassland and desert areas.…”

“…According to the degree of human activity interference, previous research divided the six main land use types into four grades: Namely, the grading index of unused land was 1, that of forested areas, grassland, or water areas was 2, that of cropland was 3, and that of urban land was 4 (Li et al, ). In order to match the spatial resolution of NPP, we measured the land use intensity (LUI) at 1‐km spatial resolution.…”

“…However, most of the NPP produced by agro‐ecosystem was consumed by humans and had limited contribution to maintaining ecosystem sustainability (Erb, Krausmann, Lucht, & Haberl, ; Haberl et al, ; Imhoff et al, ). In contrast, returning or abandoning cropland to forest and grassland, forest transitions, and migration‐derived vegetation restoration has promoted ecosystem NPP (Li & Li, ; Li, Sun, Tan, & Li, ; Li, Li, Tan, & Wang, ; Song & Zhang, ; Wang et al, ).…”

Spatiotemporal variations of vegetation and its determinants in the National Key Ecological Function Area on Loess Plateau between 2000 and 2015

“…During the process of urbanization, a large number of rural labors in mountainous areas emigrated to urban areas, searching for more job opportunities and higher salaries, which bring about an impact on vegetation greenness (Li, Li, Tan, & Wang, 2017). During the process of urbanization, a large number of rural labors in mountainous areas emigrated to urban areas, searching for more job opportunities and higher salaries, which bring about an impact on vegetation greenness (Li, Li, Tan, & Wang, 2017).…”

“…Except for ecological protection policies, labor transfer also influences on vegetation change. During the process of urbanization, a large number of rural labors in mountainous areas emigrated to urban areas, searching for more job opportunities and higher salaries, which bring about an impact on vegetation greenness (Li, Li, Tan, & Wang, 2017). More people moved to urban areas, engaging in nonagricultural jobs, which reduced the pressure on local ecosystem, especially in places where people mainly depended on agriculture and animal husbandry for their livelihood.…”