Abstract:

Urbanization is arguably the most dramatic form of land transformation that profoundly influences natural environment, biological diversity and human life. Understanding the causes, processes, and consequences of land use and land cover change is essential in ecology as well as in landscape and urban planning, and urbanization represents the extreme form of land transformation. Quantifying landscape pattern and its change is essential for the monitoring and assessment of the ecological consequences of urbanization. As the largest city in the country, metropolitan Shanghai is now the fastest growing area among all major Chinese cities that have more than 13 million residents. Using the 1994 GIS_based land use data set and combining gradient analysis with landscape metrics, we attempted to quantify the spatial pattern of urbanization in the Shanghai metropolitan area. Seventeen landscape metrics were computed along a 64 km long and 6 km wide west_east transect and another 66 km long and 6 km wide south_north transect, crossing at the urban center, with a moving window. The research was designed to address two questions: 1) do different land use types have their own unique spatial signatures (e.g., the shape of the change curve along an urban_rural transect)? 2) can urbanization gradients be detected using landscape pattern analysis? The results of transect analysis with landscape_level metrics showed that the spatial pattern of urbanization could be reliably quantified using landscape metrics with a gradient analysis approach, and the location of the urbanization center could be identified precisely and consistently with multiple indices of the 17 landscape metrics used in this study. Urbanization in the metropolitan Shanghai region has resulted in dramatic increases in patch density, edge density, and patch and landscape shape complexity, and sharp decreases in the largest and mean patch size, agriculture land use type, and landscape connectivity. The general pattern of urbanization was that the increasingly urbanized landscape became compositionally more diverse, geometrically more complex, and ecologically more fragmented. Although some of these changes were discernable visually from the land use maps, landscape metrics provided a useful way of quantifying these changes so that they could be further used to relate ecological patterns and processes in this urban landscape. In addition, our results supported a series of hypotheses on landscape structural responses along a human modification gradient: that, with increasing urbanization, patch density increases while patch size and landscape connectivity decrease. However, our results on patch shape seemed to disagree with the hypothesis that patch shape becomes more regular as human modification to landscapes intensifies. Our interpretation is that, when the degree of urbanization is high, not only the density, but also the shape complexity, of patches will increase. Future studies are needed to further confirm these findings.