Asian Cities are Greening While Some North American Cities are Browning: Long-Term Greenspace Patterns in 16 Cities of the Pan-Pacific Region

Abstract

Pan-Pacific cities are home to nearly 55% of the world’s urban residents. As the fastest growing urban centers in the world, their growth comes with increasing demand for urban amenities such as greenspace. Yet, our understanding of greenspace trends within and among pan-Pacific cities is limited due to a lack of consistent long-term land cover data necessary for transnational comparisons. We tracked and compared greenspace patterns in 16 major pan-Pacific cities over 28 years. We asked: (1) How do long-term trends in greenspace heterogeneity differ among pan-Pacific cities? and (2) How do these patterns vary along urban–rural gradients? To characterize greenspace, we distinguished four vegetation density classes using normalized difference vegetation indices from annual Landsat composites spanning 1984–2012. First, we assessed long-term trends in greenspace spatial patterns. Second, we evaluated greenspace change along a gradient outward from city centers. We found that although GDP increased in all cities in recent decades, their greenspace patterns diverged into either greening or browning trends. In greening cities, expansion of dense vegetation, mostly in the outskirts of cities, resulted in greater greenspace connectivity. In contrast, browning cities lost dense vegetation in rural fringes, yet not in their urban centers. In Asian cities, dense vegetation increased in areal extent and connectivity over time as well as outward along the urban–rural gradient, in contrast to most North American cities. These differences in greenspace heterogeneity and connectivity over time and space imply that strategies and policies derived from North American cities may not be directly applicable to Asian cities.