Urbanization that hides in the dark - Spotting China's ghost neighborhoods from space

The excessive planning and construction of new cities and towns as well the massive expansion of planned settlement areas in China reveals a surprising phenomenon: extensive newly constructed areas that are characterized by severe under capacity. This phenomenon is described as ghost city and usually appears at the intra-urban scale. However, current data and methods are inappropriate to detect this phenomenon at this intra-urban scale for entire China. Besides, most studies neglect the usual immigration period of newly built areas. In this study, we suggest a new term, the ghost neighborhood, which refers to a new residential neighborhood that still runs at severe under capacity after a typical immigration period of five to six years. Based on this conceptual baseline, we identify ghost neighborhoods across China by developing a methodology to gradually exclude the non-ghost areas by predominantly relying on night-light emissions. The process is based on LJ1-01 night-light data, TanDEM-X data and Global Urban Footprint data, which feature evident advantages in spatial resolutions while being available for entire China. The main results are as follows: 1) we identify 1048 ghost neighborhoods across the urban landscapes of China with a total coverage area of 353.64 km(2); they are estimated to have the capacity to house 13.6 million people; 2) the identified ghost neighborhoods are particularly frequent and large in the dynamically urbanizing regions, such as the Pearl River Delta, the Yangtze River Delta and the entire Shandong province.