The term "sealed area" is used when land is covered with practically impermeable materials. This primarily concerns buildings, roads, energy supply facilities (e.g. dams) and landfills. Sealing is the most drastic change that can be made to an area of land through human intervention in the landscape.
It means that the soil loses practically all its natural ecological functions, e.g. absorption of rainfall, production of biomass, binding of CO2 as storage and filter medium. The altered intensity of light reflection, which greatly depends on the properties of the surface, can also give rise to changes in the microclimate.
Sealing also changes the character of the landscape, turning a formerly open and natural area into an engineered one characterised by building structures and roads. This can adversely affect the attractiveness of Switzerland as a holiday destination and a region for recreation and outdoor activities.
It is in principle possible to restore a sealed area of land by removing the material and structures, but this process normally damages the basic ecological functions of the soil to such an extent that restoring the land to its original state is not possible over the medium term.
The area of sealed land in Switzerland increased by almost 13% in the period from 1985 to 1997. The total area of sealed land in 1997 amounted to 1,269 square kilometres, which is almost 3% of the country's entire surface.
If we take a closer look at the 5 main regions, we can see that the degree of land sealing differs considerably from region to region. The lowest proportion of sealed land is in the Central Alps. The degree of sealing in the Southern and Northern Alps is twice as high as in the Central Alps. In all three sections of the Alps, land sealing is taking place to an alarming extent in small regions in which people live and work. In the Jura region the development rate is three times that of the Central Alps. By far the highest rate of land sealing is in the Central Plateau (Mittelland), where it is six times higher than that of the Central Alps.
The growing population is the most important factor in the constant increase in land sealing, but the fact that people are becoming ever more mobile and demanding ever more residential space intensifies the problem.
Even in protected areas such as landscapes and natural monuments of national importance, in mire landscapes and nature reserves and parks, sealing has progressed at a similar rate (between 10 and 14%) as in the rest of the country.
The collection of data for this indicator is based on the land use statistics for Switzerland. Of the 72 different types of land cover classified in the land use statistics, 17 constitute sealed areas. This type of land cover encompasses buildings (8 categories), special urban areas such as landfills, sewage treatment plants and energy supply facilities (4 categories), and transportation areas, e.g. roads and airfields (5 categories). The surveying interval for zone statistics is 12 years, which means that short-term changes in sealed areas are not ascertainable. The statistics are based on random sampling. Surveys and evaluations for the 1985 land use statistics were carried out between 1979 and 1985, while those for the 1997 statistics were carried out between 1992 and 1997. The third survey using aerial photographs was initiated in 2004, and the results for the whole of Switzerland will be available in 2013.