Soil is the earth’s living skin and provides us with essential services for life in our planet: production of food; infiltration and cleansing of water and protection against flooding; habitat for plants; areas for recreation and mental health; micro climate regulation, etc. It is such a crucial resource that it can’t be ignored. However, particularly in urban areas, soil is being sealed off with increasing housing and infrastructure.
Soil sealing is the covering of the soil surface with materials like concrete and stone, as a result of new buildings, roads, parking places but also other public and private space. Depending on its degree, soil sealing reduces or most likely completely prevents natural soil functions and ecosystem services on the area concerned.
A diverse situation
EEA produced recently a high resolution soil sealing layer for the whole of Europe for the year 2006 based on the same satellite pictures as used for CORINE land cover data. An analysis of soil sealing in European cities shows that they perform very differently. Furthermore, comparing their mean levels of soil sealing per built up area can differ much from comparing the values per inhabitant; it can even be reverse (figure 1).
Considering that the mean temperature in Europe rises and the number of heat waves is expected to increase, a high soil sealing will further exacerbate the already existent heat island effect of cities increasing their vulnerability against heat wave impacts. Map 5 shows the mean soil sealing of European cities underlaid by the projected increase in the number of tropical nights (Tmin>20C). Cities with high levels of soil sealing in areas with a higher projected increase of the number of tropical nights are more vulnerable to climate change and need appropriate adaptation measures like boosting urban green also on walls and roof areas, white walls, building isolation, shadow blinds etc.
Map 5: degree of mean soil sealing in Europe’s cities (UMZ) in 2006 and modelled change in number of tropical nights (Tmin>20C) during summer between 1961-1990 and 2010-2040 indicating higher risks for heat waves
Another climate related effects is the reduction of the water infiltration potential of the soil, which increases the run-off of water and the risk of river flood. In the event of heavy rain falls, in cities with a high soil sealing, also the capacity of the sewage system might no longer be able to cope with the high run-off of water and cause surface flooding. Indeed, much of the flooding in England in the summer of 2007 was due to surface water (The Pitt Review, 2008).