Urbanization is tied to social, economic and environmental processes. There are six core aspects: air pollution, ecosystems, land use, biogeochemical cycles, water pollution, solid waste management, and the climate.

Urban ecosystems are generally highly disturbed systems, subject to rapid changes in soil and plant cover, as well as temperature and water availability. Buildings, roads, parking lots, and other constructions form a largely impenetrable covering of the soil that affects how water flows through the urban landscape and what can survive there.

Poor air and water quality, insufficient water availability, waste-disposal problems, and high energy consumption are exacerbated by the increasing population density and demands of urban environments. Strong city planning will be essential in managing these and other difficulties as the world's urban areas swell.