Relationship Between The Urbanization Process And The Regional Ecological Responses In The Arid Inland Basins Of The Northwest China

In the arid regions of the northwest China, the ecological environment is vulnerable and its evolution has relatively distinctive regularity. In this kind of vulnerable regions, the increase in the impacting intensity of disturbing factors will lead to changing of the environmental landscape and the chain reactions of the change will entirely or partly alter the regional ecological environment. Urbanization is a civilized life type with the strongest intensity of modern human activities and the most advanced life-style. Its disturbance and impact on the arid oases and the mechanism and extent of the ecological responses to the disturbance and impact, in the northwest China, (will) have been a focus of study on regional sustainable development at present and in a future period.On the basis of reviewing on the studies, both home and abroad, of the interaction between urbanization and ecological environment, its mechanism, patterns, and characteristics, the thesis retraces the coupling relationship between human activities and ecological environment in the historical times, taking the city of Zhangye in the Heihe river basin in the northwest China as a case study. From a perspective of intersectant subjects, the thesis, using the related geographical theory and methodology as its mainline and the theories and technological methods of ecology, ecological economics, meteorology, economics, urbanology, and other correlated subjects as supplements, explores the mechanisms of the impacts of urbanization in the Heihe river basin, under the arid environment, on the regional ecological environment. It puts emphasis on the responses of the coupling socio-economic ecological systems to the pattern and process of urbanization in the Heihe river basin and reveals the internal mechanism of regional ecological environmental feedback to urbanization process in the arid regions. It also studies quantitively the coupling relationship between development of regional urbanization and the evolution of ecological environment.The main conclusions are as follows:The relationship between human activities and regional ecological environmental change in the historic times.It is believed that, during the last 3,000 years, the main drivers of the ecological environmental change were natural forces, the perturbation of climate being the most influencing factor, and human activities were only the auxiliary forces which changed the regional geomorphologic landscape and utilization pattern of water resource before the Qianlong-Jiaqing period of Qing Dynasty. After that, with sharp population growth and intensifying oasis development, human activities gradually became the dominant forces changing the regional ecological environment. In the historic times, city and town development correlated closely to the intensity and stages of the regional agricultural development and changed with the evolution of oasis structure with the climatic fluctuation.The features of ecological environmental change in the city of Zhangye during the last 38 years.1). Climate change. During the last 38 years, the main trend of climate change of Zhangye has been obviously increasing of temperature and the precipitation has varied little, with slightly increase in winter and spring. The gale and sandstorm weather has apparently decreased. That has confirmed, in some degree, the climate shift from warm-dry to warm-humid in northwest China, put forward by Prof. Shi Yafeng.2). Water resource environmental change. The contradiction between demand and supply of the regional water resources has become gradually prominent. Water resource allocation in the Heihe River basin has greatly influenced the regional water resource quantity. The utilized amount of the water resource has decreased, while the demand has kept rising, and water used for industry, ecology and daily life has remarkably increased. Now, with the construction of water-efficient society, the regional structure of water use has gradually changed. The distribution of water resource has tended to be rational and the utilization of water resource has gradually shifted to industrial sectors with high water efficiency.3) Land use and land cover change. The land cover change has generally featured a deteriorating trend. In the last 20 years, the forest and grassland area has declined continually. Farmland has increased slightly with spatially transferred upstream. The urban area has an augmented notably, spatially extending along the direction of the river and traffic lines and expanding upstream to the middle and upper reaches of the Heihe River. Except Sunan county, the water areas in other districts and counties have all decreased in different degrees. Unused land has been in a trend of increase as a whole.The features of urbanization development in Zhangye city are as follows:1). The urbanization is speeding up obviously while many limiting factors exist in the labor transfer.2). In urbanization development, urban spatial structure is affected remarkably by the spatial pattern of oasis distribution and features an "agglomerate-axial direction". Generally, the city and towns adapting to the oases; they are located are small-scaled, with highly comprehensive while lacking spatially perfect structural system and network connection.3). On the basis of analyzing the regional emergy production and urban emergy consumption using the theory of emergy flow, it is believed that Zhangye oases have a great potential of emergy flow to support the urbanization scale. The elastic accommodation space of urbanization in the oases has a capacity to accept further 600,000 rural populations into the city and towns.In the aspect of the relationship between urbanization development and regional ecological environment, urbanization has disturbed and impacted the regional ecological environment to some extent and the ecological environment has responded to the disturbance in dual directions. The details are as follows:1). Relationship between urbanization and regional climate change. To a certain extent, urbanization plays a role in the climate change of Zhangye city. There is some relevance, strong or weak, positive or negative, between regional urbanization and some climatic elements changes, which caused by the contingent integration of regional climate change with urbanization(the inevitable result of historical development), thus constituting a feature of spatial dialectical development, short- vs long-term, microcosmic vs macrocosmic, of the regional system. Namely, global warming, to a certain degree, is resulted from modern human activities, but it also fosters the prosperity of social-economics in the Heihe valley and quickens the urbanization development of Zhangye oases. The urbanization development, vice versa, fosters further change of regional climate with certain range after it reaches a certain point.2). Relationship between urbanization and regional water resource utilization. The influence of urbanization on utilization change of regional water resource is just small at present and can not lead the regional population and industrial structure to transfer with large scale; neither is it capable to change the current utilization pattern of regional water resource. Through mathematically modeling, it is thought that regional urbanization is only a promoting factor to improve the utilizing efficiency of water resource in the pattern change of regional water resource utilization and can not change essentially the water use pattern among regional industrial sectors. And, with further development of urbanization and social-economics, urbanization will become a main effecting factor to drive the regional utilization pattern of water resource toward water-efficiency.3). Relationship between urbanization and LUCC. On the basis of GIS spatial analysis and mathematical analysis of land statistic data and from perspectives of Zhangye's macrocosmic region and of meso-cosmic oasis economic regions, the thesis investigates the impacts of land use change on regional ecological environment in the process of urbanization of Zhangye city from 1986 to 2006. Gererally, urbanization has some effect on the decline of ecological environment of Zhangye's macrocosmic region and meso-cosmic oasis economic regions. However, in Zhangye's macrocosmic region, urbanization's effect is relatively small and its contribution to the deterioration of regional ecological environment just accounts for 1.34% of the whole deterioration of ecological environment. While in the oasis regions, which are closely related to human activities, urbanization plays a important driving effect on the deterioration of regional ecological environment and the contribution of the correlative land-use transformation caused by urbanization to the deterioration of ecological environment of oasis economic region reaches 48.79% of the whole deterioration.