Urban Areas

Urbanization and human activities create a wide variety of soils within urban environments, ranging from near natural (e.g., urban forest) to highly disturbed soils (e.g., soils in abandoned industrial areas), with great spatial and often vertical variability. Urban soils provide relevant ecosystem services, such as food production, water regulation and esthetical inspiration, but these vary depending on the intensity of landscape disturbance and degradation processes. Urban soils are highly affected by sealing, compaction (e.g. due to heavy machinery during construction activities, vehicles and human trampling) and erosion (mainly by water, particularly on bare soils, at construction sites and along road edges). Contamination from a variety of sources (e.g., inadequate waste disposal, stormwater runoff and atmospheric deposition), is often not only a major threat, but is usually very difficult to assess because of the great spatial variation of soil types, land use history, management activities and urban pattern. Heavy metals and polycyclic aromatic hydrocarbons have been widely identified in urban soils, but other chemicals also can cause contamination of urban soils (e.g., pharmaceuticals and pesticides). Biological degradation of urban soils, associated with changes in micro- and macroorganisms, affects biological activity and species richness, and can also constitute an important problem in urban areas. Depending on the degree of soil degradation, remediation (e.g., tilling and bioremediation) and restoration strategies (e.g., use of amendments, green infrastructures) might be required to enhance ecosystem functioning. Nature-based solutions are a useful approach to minimize land degradation and improve sustainable urban development.