Intensity and spatial pattern of urban land changes in the megacities of Southeast Asia

Knowledge about intensity and spatial pattern of urban land changes (ULCs), i.e., changes from non-built-up to built-up lands, is important to a wide range of issues, from understanding of human–environment interactions and provision of urban ecosystem services, to land use policy development for landscape and urban planning toward sustainable urbanization. In this context, this paper aims to provide better understanding of the geospatial dimensions of the urbanization and landscape changes in two megacities of Southeast Asia. Specifically, we examine and compare the intensities and spatial patterns of ULCs in Metro Manila, Philippines and Bangkok Metropolitan Region (Bangkok MR), Thailand, during the 1990–2000 and 2000–2010 periods, using remote sensing and Geographic Information System (GIS) tools and techniques. In the measurement of ULC intensity, an intensity scale is proposed to determine whether the rate of ULC during a particular time interval, i.e., 1990–2000 or 2000–2010, relative to the uniform intensity that is based on the whole time extent, i.e., 1990–2010, is very slow, slow, medium slow/fast, fast and very fast. To characterize the spatial patterns of ULCs, the concepts of the diffusion-coalescence urban growth theory were applied. The results revealed that for Metro Manila, its ULC was more intense during the 1990s (fast) than in the 2000s (slow). For Bangkok MR, it was more intense during the 2000s (medium fast) than during the 1990s (medium slow). The results also revealed that Metro Manila has been in the process of coalescence, while Bangkok MR is still largely in the process of diffusion and expansion. In this paper, we also discuss some of the possible factors influencing ULC intensity trends and spatial patterns, the advantages of the methods used for ULC analysis and some land use policy-related development plans for the two megacities.