The Evolution Of Urban Landscape Pattern And Its Impact On Ecological Security In Shanghai

In the process of rapid urbanization dramatic land use and land cover change, which made irrational use of land resources, results in kinds of ecological and environmental problems such as air pollution, urban heat island, water deterioration, land subsidence, and decrease of biological diversity. This affects directly the state of regional ecological security and sustainable development, therefore, the research of urban land use/cover change and its impact on ecological security is imminent ahead. As the most densely populated and rapidly developed city in China, Shanghai area's land use and landscape pattern are changing tremendously since reform and opening to outside especially after PuDong developing, so a case study was conducted at the scale of Shanghai regional area. Starting from urban land use/cover change, the thesis analyzed landscape pattern evolution and its impact on air, thermal and water environment by using remote sensing and geographic information system techniques, as well as statistics analysis methods. Then the states of ecological security in recent years were evaluated, and accordingly regional ecological security pattern of Shanghai was constructed by means of idea from landscape ecology.First, urban land use and land cover patterns for April 11, 1997 and July 19, 2004 were mapped by the use of Landsat 5 Thematic Mapper images. In the analysis of these maps, tremendous land use change was found from the aspect of urban morphology, which was more complicated and expanding outward along major transportation lines. This made whole regional network system more complete. Several landscape indices were employed to quantitatively analyze land use change and landscape pattern. Results showed that on the level of landscape the built-up area increased greatly, and the vegetation area kept nearly unchangeable, while the water area declined slowly. On the level of landscape class, the number of patches and patch density got obvious increase in built-up,vegetation and water, which means more fragmented in the urban landscape. The decrease of contagion index implied that the landscape patches were at small scale and in the state of being divided. There was obvious increase in landscape shape index, suggesting the tendency of irregular and complicate shape in landscape patches.Based on the analysis of urban land use and pattern change in Shanghai, the thesis discussed the interaction and potential relationship between urban landscape evolvement and eco-environmental effects in the following ways. First of all, the air environment's response to the urban landscape pattern change was analyzed. According to the comparison between different periods spatial distribution pattern of several atmospheric pollutants, it was observed that the annual concentration of NO₂ and SO₂ showed an upward tendency but a downward one in PM₁₀ and atmospheric dust. The correlation of disease death rate of urban inhabitants with atmospheric pollutants was analyzed. Significant positive relationship was found between NO₂ and diseases of circulatory system and urinary system, and relatively significant positive relationship between SO₂ and diseases of nervous system, as well as TSP and diseases of circulatory system, but negative relationship between SO₂ and parasitic & contagious disease. Then urban development index (UDI) was created to analyze its relationship with urban climatic index. It were seen that urban climatic indices correlated significantly with UDI and gradually ascend first before descend with the advance of urbanization process. The correlation analysis of UDI with disease death rate of urban inhabitant showed that urbanization significantly affects death rate of diseases, such as disease of respiratory system,tumor,psychosis,parasitic & contagious disease,endocrine autoimmune disease and diseases of nervous system.Secondly, the thermal environment effect of urban landscape pattern was analyzed. After calculating land surface temperature (LST), the spatial distribution pattern maps of urban heat island in two periods of 1997 and 2004 were obtained. According to analysis of these spatial distribution patterns, it was observed that urban heat island of 2004 at Shanghai regional level still concentrated on urban central area and showed a continuous expansion trend, more urban heat island centers appeared, and the difference between central area and suburban was shrinking. Then the spatial characteristics of the LST distribution were further exploited by using spatial autocorrelation and geo-statistics methods. Results showed that the significance of spatial autocorrelation in 2004 was better than that in 1997 and the autocorrelation scale of urban heat island patches increased. Spatial correlation of LST distribution belonged to moderate class, that is, some random factors has performed an important function to the spatial heterogeneity of UHI pattern except for structural factors. The results implied that some processes should not be allowed to be ignored in smaller scales. In this analysis the scale was on the 1km level. In order to understanding relationship between land use/cover types and surface temperature quantitatively and clearly, several land cover type indices were founded. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were found negative correlation with temperature, while the Normalized Difference Built-up Index (NDBI) and Normalized Difference Bareness Index (NDBaI) showed positive correlation with temperature.Thirdly, the impact of urban landscape pattern on water environment was analyzed. In six circular buffer areas with radius of 3000m around water quality stations along the main stream of Huangpu River, structure of land use were identified, and organic pollution index was founded to evaluate the water quality in several major stations. According to the correlation analysis of water quality change with surrounding land use structure, it was found that water quality correlated negatively with the proportion of the areas of forest and green space land. The tendency of water quality change of major rivers and lakes in Shanghai showed that Dianshan Lake was getting worse, Huangpu River improved slowly, and Suzhou River demonstrated a significant improvement but fall again in recent years.Finally, the level of regional ecological security of Shanghai was evaluated. Two factors including resource-supporting system factor and industrial environment factor were screened by using factor analysis method. Regional ecological security degree index (ESDI) was set up to carry out comprehensive assessment during1997 and 2004．Results indicated that the ecological and environmental construction and relate investment have certainly improved the situation of ecological security of this region, especially in 2003 the index takes a favorable turn and in 2004 rises sharply. Based on the current natural conditions, the spatial distribution pattern of landscape was also created in light of requirement of ecological security, which consists of ecological sourcc,ecological corridor,ecological patch and ecological wedge, then measures of controlling and improving the security situation were also introduced.