Degradation in urban areas

Abstract Over the few last decades, increasing population and expansion of urban areas has triggered faster land degradation. This manuscript reviews the most significant soil and water degradation processes in urban areas and their environmental impacts. Urban soils are partially sealed and subject to severe compaction, erosion and contamination from several sources (e.g. vehicular traffic and inappropriate waste disposal), which restrict their ability to provide ecosystem services. Water resources are also under great urban pressure, due to changes in flow processes, namely increasing runoff and flashiness linked to enhanced flood hazard, and decreasing water quality and degradation of aquatic ecosystems. Persistent pollutants such as heavy metals and polycyclic aromatic hydrocarbons have been found in urban environments. Long-term monitoring programs to quantify better the magnitude of degradation processes and their environmental impacts are still required. Runoff, erosion and pollutant sources as well as their transport within the landscape are highly variable, and the impact of distinct urban patterns on water, sediment and pollutant connectivity between the sources and water bodies remains a research challenge. Information regarding land degradation processes and their spatio-temporal dynamics within urban catchments will help to guide decision-makers and policy actors towards sustainable solutions to achieve urban sustainability and the good ecological status of aquatic ecosystems.