Impact of rapid urban expansion on structure, function and connectivity of green space.

Abstract

Globally, rapid urban expansion has caused a significant decline in green spaces in urban areas. It affects the form and structural patterns of green space. As a result, green space area becomes reduced in size, spatial structure, connectivity and function in urban areas. These gaps extend beyond uncoordinated master planning, which lacks required information regarding the past, present and future structural changes in urban expansion and green space. However, the existing methods and adaptive tools designed to respond to such needs are uncertain. This research aims to understand the impact of rapid urban expansions on the structure, connectivity and function of green spaces and to develop models as diagnostic and decision support tools in three Southeast Asian cities which are all areas of rapid expansion: Kuala Lumpur, Malaysia; Jakarta, Indonesia; and Metro Manila, Philippines. This study has evaluated the changes in the spatial structures and patterns of green space in urban areas of the three cities over the last two decades. The performance of the integrated Land Change Modeler (LCM) and the Markov chain modelling were verified to simulate future urban expansion by 2030. To reveal the priority corridors on maps, a novel integrated model which combines circuit theory, connectivity analysis and the least-cost path modelling, was used based on the target species of the Eurasian tree sparrow (Passer montanus) and the Yellow-vented bulbul (Pycnonotus goiavier). Overall, this study found that the percentage of green spaces in all three cities had reduced in size as the function of rapid urban expansions over the 25-year period. Key findings clearly indicated that important differences exist in spatial distributions of green space in different cities. LCM-Markov chain models proved to be suitable for the simulation of future land use/land cover (LULC). There were also important differences in the predicted spatial structure for 2030 when compared to the planned development in each city; substantive differences in the size, density, distance, shape and spatial pattern. The increased fragmentation of the landscape will continue in 2030, more shape complexity will be observed and less connectivity between green space patches will be present. Evidence suggests that these spatial patterns are influenced by the rapid urban expansion and respective master planning policies of the municipalities in the cities. This study identified that, the emergence of potential corridors by integrating structure and functional connectivity of green space could increase the connectivity of green space for conservational significant areas. Therefore, the use of integrated remote sensing, Geographical Information Systems (GIS), landscape ecology analytics, simulation modelling and connectivity modelling tools provide significant insights into understanding the impact of rapid urban expansion on green space structure, identifies constraints and informs intervention for spatial planning and policies in cities, and contributes to the improvement of ecological networks in rapidly expanding cities.