Chronicling urbanization and vegetation changes using annual gap free Landsat composites from 1984 to 2012

摘要

Cities impact nature often resulting in the ecological integrity of the environment being compromised or ignored. Effective and sustainable management of urban environments requires long-term, spatially explicit monitoring of urban expansion and vegetation dynamics. However, spatially consistent temporal information is difficult to access and utilize across different urban environments. Remote sensing based datasets such as Landsat imagery offers an exceptional source of data and an unique perspective for chronicling urban environmental changes due to its consistent and ubiquitous nature. In this paper, we examine changes in the urban environment and vegetation cover of three contrasting cities Manila (Philippines), Las Vegas (USA), and Vancouver (Canada) from 1984 to 2012 using a pixel-based image composite technique. The Enhanced Vegetation Index (EVI) was calculated using annual cloud-free Landsat composites to represent urban vegetation dynamics. Combined with a hexagon-based concentric ring model, the three urban environments demonstrate contrasting spatial and temporal vegetation patterns. We found a marked decrease in greenness in Manila likely caused by urban growth. Vancouver, however, showed only a minimal changes in EVI over the study period. Las Vegas in contrast experienced an overall vegetation increment. This research demonstrates the potential of using annual Landsat time series for assessing urbanization and urban vegetation dynamics, offering in-depth spatio-temporal information for sustainable urban planning, urban resources allocation, and policy drafting etc.