Relationships between urban expansion and socioenvironmental indicators across multiple scales of watersheds: a case study among watersheds running through China

Understanding the relationships between urban expansion and social/environmental features is fundamental to managing watershed and urban expansion. However, such relationships remain unclear, especially across multiple scales of watersheds. Here, we quantified the correlation between urban expansion measures and 255 socioenvironmental indicators across three scales of watersheds running through China (20, 103, and 349 watersheds) during 1992-2016 and analyzed their scaling relations. The results showed that the number of indicators showing a significant correlation with the area and speed of urban expansion increased from 132 and 153 to 234 and 237, respectively, from level 1 to level 3 watersheds. Among these indicators, urban expansion was significantly correlated with indicators of climate and anthropogenic impact. From a large scale (level 1 watershed) to a small scale (level 3 watershed), 104 and 84 socioenvironmental indicators shifted from uncorrelated to significantly correlated with urban expansion area and speed. The constraint line analysis further confirmed that some relationships were nonlinear, which suggested that the drivers and impacts of urban expansion have scaling effects. We argue that it is crucial to consider the scaling effects of urban expansion when we formulate urban or watershed management plans.