Soil sealing in urban cities deprives the earth of its living skin
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.
Urban cities seal soil to create new buildings
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. The European Environment Agency (EEA) produced recently a high resolution soil sealing layer for the whole of Europe for the year 2006 based on satellite pictures. 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).
Why soil sealing matters – the example of the urban heat island effect
As mentioned above, soil sealing affects ecosystem services and
the quality of life in a city in many ways. One is the regulation
of temperature. 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.
Coping with soil sealing
From a European perspective, a low soil sealing per inhabitant
is definitely of favour as it reduces our overall ecological
footprint. Living in urban areas can provide such setting.
Nevertheless, a high compactness and thus soil sealing of cities
can also have negative impacts for the quality of life in them.
Therefore, cities will need a smart urban design by reducing all
soil sealing where not needed (parts of public places, parking
lots, brownfields etc.) and using all potentials to maximise
unsealed and green areas as well as further green elements like
street trees, green walls and roofs while maintaining their
compactness and urban density.