The study looked at how people in Nanjing, China impact the environment using a method called ecological footprint. They calculated that in 2010, each person in Nanjing used 4.21 hectares of land to support their lifestyle, but the land available was only 0.33 hectares per person. This means there's not enough land to support everyone sustainably. The researchers figured out why there's not enough land and suggested ways to help Nanjing develop in a more sustainable way.