The Qinghai-Tibet (QTP) plateau is featured with predominant grasslands and dotted cities. The dominant land cover types include alpine meadow, steppe, forest, and desert steppe. The household registered population in Tibet and Qinghai is 2.67×106 and 5.39×106 in 2015, respectively. The gross domestic production (GDP) of these two provinces was ranked the last two among the 34 provincial units in China. Regardless of their relative low economic and population growth, the QTP witnessed the rapid urbanization in the last two decades due partially to governmental investments. The secondary and tertiary industries (GDP2-3) and urban population (POPurban) have steadily increased since 2000. An apparent challenge amid this unprecedented urbanization is to maintain the sustainability of social-environmental systems (SES) in the rural-urban fringe. Our study objective therefore is to explore the spatiotemporal changes of SES in the rural-urban fringes of medium-large cities on the plateau. Fifteen prefecture-level cities with populations of >20000 exist and are examined for the interdependent changes of GDP2-3, POPurban, and net primary production (NPP) of ecosystems since 2000. Data from remote sensing products, statistical yearbooks and land cover are used to quantify the changes from urban centers to their rural landscapes within 30-50 km.
Results/Conclusions
Annual GDP2-3 and the POPurban increased significantly for all cities, with GDP2-3 jumped by more than 10 fold from 2000 to 2015. The highest GDP2-3 growth rate was found for Ngari where a 22 fold increase from $0.23×108 in 2000 to $5.10×108 in 2015 was detected albeit its urban population remained the lowest at 28,900. The highest POPurban was in Xining (1.55 million in 2015). The increase in POPurban was mainly from migration of rural population rather than immigration from other regions. The harsh, climatic extremes in alpine hypoxia made it difficult to inhabit for people -- another reason for immigration to cities. The increase in POPurban was also coupled with economic booming that reduced dependence of rural communities on natural resources. In addition, the government policy also favored migration to cities. These changes in population resulted in reduced grazing pressure on grasslands. We analyzed the change in NPP within 30-50 km peripheral areas of the 15 cities during 2000-2015 to quantify the consequences on vegetation due to urbanization. We found three very different types of NPP gradients along the rural-urban fringe. The NPP gradients in Tibet show significant higher variation than those in Qinghai.