Does large-sized cities' urbanisation predominantly degrade environmental resources in China? Relationships between urbanisation and resources in the Changjiang Delta Region

Outward expansion of urban lands in the developing nations is often associated with a substantial loss of environmental resources such as forests, wetlands, freshwater and cash crop fields. Yet, determining how different aspects of urbanisation – such as city population size and spread pattern of built-up lands – contribute to the cumulative loss of resources remains controversial. In this study, data sets were constructed describing changes to land cover across 65,200 grid cells at 1 km2 spatial resolution for China's Changjiang Delta Region over the past 60 years. The results showed that the region lost 12.2% of total resource sites. The distribution of resource degradation showed a highly dispersed pattern and was not confined to a few intense areas associated with large cities. No empirical evidence was found that city population size alone accurately predicts the distribution of resource loss. Very large cities (N = 4) contributed 35% to the total loss, demonstrating impacts similar to those of much more scattered towns (N = 230). Urban expansion of large cities may lead to extensive resource loss; however, a set of non-linear mechanisms, such as the diminishing effects of per-unit area urban spread on resources and interactions between urban patterns and the size of urban spread, can also play a significant role in downsizing the negative effects of large cities on resource sites. Thus, effective urban policies should carefully weigh the cumulative urban spread mechanisms of both large and small cities responsible for spatially dispersed degradation of environmental resources.