The use of soil, a finite resource, is unsustainable. Settlement growth, the construction of transport infrastructures and erosion are all causing valuable soil to disappear. Pollutants that have been prohibited in Switzerland for decades are still present in its soil, while pollutants continue to be released by transport and agriculture in particular. These developments threaten the natural resource of soil, which is non-renewable within a human timeframe, and therefore have a negative impact on agricultural production, the regulation of water and material cycles, and biodiversity.
1. Housing, mobility, agriculture and forestry (drivers)
Economic and demographic growth, increasing mobility and a higher average living space per capita in recent decades have led to an increased demand for residential buildings and offices, roads and railway lines, shopping centres, industrial and commercial areas, and leisure and sports facilities.
Due to the continuous pressure to increase efficiency in forestry and agriculture, the machinery used is becoming increasingly powerful and generally heavier, increasing the risk of soil compaction and erosion.
The significance of soil’s ability to store carbon and water is growing because of climate change. At the same time, climate change affects the soil. While some gaps in our knowledge persist, the increased frequency of heavy precipitation increases, for example, the risk of erosion and pollutants being washed off the soil.
Soil is becoming increasingly scarce not only in Switzerland. About 40% of the planet’s ice-free land surface is currently being farmed. This percentage can be expected to rise even more as demand for food will likely more than double in South Saharan Africa and Southeast Asia by 2050 and increase by about a third in the rest of the world according to the FAO. At the same time, climate change can reduce harvests, and competition for land and specific land uses will continue to intensify.
2. Physical, chemical and biological pressures and land use (pressures)
Physical pressure from compaction and erosion presents major challenges. Soil compaction occurs for example when soil is handled or driven over by excessively heavy machines or vehicles. Compaction induces surface water runoff and thus soil erosion. The main cause of erosion in Switzerland are farming methods that are unsuited to the location.
Carbon is released in agricultural soil as organic matter (humus) decays, which contributes considerably to climate change and results in the soil no longer being available as a carbon sink.
Chemical pollution arises through the input of substances such as cadmium and uranium from fertilisers. Various measures, such as stricter air pollution rules, the ban on lead in petrol and the ban on the application of sewage sludge have helped to reduce the amount of industrial and commercial pollutants released into the soil in recent decades. However, inputs from the past remain in the soil. In addition, heavy metals are released into the soil locally through fertilisation. The high level of atmospheric nitrogen inputs in the soil remains problematic.
Biological impacts on the soil can arise through genetically modified, pathogenic or alien (for the most part inadvertently introduced) organisms. Throughout Switzerland, the pace of settlement growth and therefore land use has actually slowed since the turn of the millennium. Nevertheless, an area of soil roughly equivalent to eight football fields is built on every day. The first partial results of the current land-use statistical survey show that the settlement area—should the trend be confirmed nationally—may now be growing more slowly than the population for the first time ever. However, there are some spatial disparities: In urban agglomerations, settlement area use per capita stabilised between 1992/97 and 2004/09, which suggests that the densification process is underway. In rural areas, however, the settlement area per capita and job continued to increase until 2009.
Surfaces in residential areas are sealed or compacted as a result of construction activities. Soil sealing with air- and watertight materials such as tarmac or concrete is the severest modification of the soil by man. Soil sealing can only be reversed with great effort and at a very high cost.
3. State of soils (state)
The extent of soil damage caused by compaction and erosion depends on the soil type and management method. However, there has been no systematic survey to date. In agriculture, the problem of soil compaction is most severe in humid areas where arable and vegetable farming is practised, especially for crops like maize, sugar beets or potatoes, which are harvested late and often in bad weather. Nearly one-third of the area used for agricultural purposes in valley and hilly regions is classified as potentially at serious risk of erosion; hillsides, open arable land and areas with intensive vegetable cultivation are especially vulnerable.
Authorities have required a soil science consultant on large construction sites for several years now. Qualified experts are responsible for advising and assisting with soil protection measures, which generally ensures that soil protection goals are effectively achieved at large construction sites.
Completely uncontaminated soil no longer exists in Switzerland. Most contaminants are retained in the soil, where they can accumulate over decades. The following areas are often polluted:
- settlement areas (gardens and parks),
- land in the vicinity of certain types of industrial and transport facilities,
- land in special agricultural plantations (fruit production and viticulture).
Some types of chemical contamination are generally declining (e.g. lead and mercury), while others remain fairly constant (e.g. chromium and cadmium), and some pollutants have accumulated in recent years (e.g. zinc and copper in intensively farmed grasslands with livestock fattening operations). Due to a lack of surveys, the extent of pollution is largely unknown, with particular regard to organic pollutants, veterinary antibiotics, plant protection products and microplastics.
The critical value for nitrogen pollution from the air continues to be significantly exceeded in many habitats.
Biological pressures caused by genetically modified, pathogenic or non-native organisms are not an acute issue but need to be kept under surveillance.
The settlement area has steadily grown throughout Switzerland since the 1980s, increasing by 23.4%, or 584 square kilometres, between 1985 and 2009 (equivalent to the surface area of Lake Geneva). Settlements expanded especially in flat valleys, the catchment areas of cities and urban agglomerations and are thus putting pressure on particularly valuable and productive agricultural soils in Switzerland.
Over 62% of settlement areas are sealed (buildings and roads). Between the survey periods of 1979-1985 and 2004-2009, soil sealing in Switzerland increased significantly (by 29%). Approximately 4.7% of the national territory (1920 km2) was covered by buildings, roads and other infrastructure and, therefore, sealed. Throughout Switzerland, the pace of settlement growth has slowed since the turn of the millennium. The rate of soil sealing has also slowed but is far from reaching a sustainable level.
4. Impacts of soil pressures (impact)
Intact soil fulfils various ecological and economic functions. The term "soil functions" refers to the soil‘s ability to serve people and the environment. In accordance with the internationally accepted definitions, the following soil functions are distinguished:
- Habitat: the ability of soil to sustain life for organisms and to preserve the diversity of ecosystems, species and genes.
- Regulation: the ability of soil to regulate material and energy cycles, provide filtering, buffering and storage, and transform materials.
- Production: the soil’s ability to produce biomass, i.e. food and animal feed, and wood and fibre.
- Support structure: the soil’s role as a support structure for buildings.
- Raw materials: the soil’s ability to store raw materials, water and geothermal energy.
- Archive: the soil’s role as an archive for natural and cultural history.
Soil that has been removed by mechanical diggers or sealed over can no longer fulfil its natural functions in the ecosystem. When soil is sealed, it can no longer absorb rainfall, produce biomass or regulate climate change (mitigating the urban heat island).
Soil compaction damages soil structure and thus impairs biological processes in the soil. Because the capacity of the soil to store water is also reduced in this way, the risk of erosion and flooding increases. The compaction of the subsoil is usually irreversible.
Soil erosion results in the loss of valuable productive agricultural land. The arable soil that is washed away can impair infrastructures (e.g. roads and drainage systems). In addition, materials that are washed away pollute water bodies with nutrients. Importantly, plant protection products are washed off the soil.
Chemical soil contamination impairs soil fertility; its consequences can be divided into the following three categories:
- impairment of the mass balance (regulation function),
- defects in plant growth (production function),
- risks to the health of humans and animals through the consumption of contaminated harvested products, polluted groundwater and the direct intake of soil (e.g. by playing children).
Biological impacts caused by introduced, alien or genetically modified organisms can impair soil fertility and alter the natural networks of soil organisms through external influences, such as climate change or land use that is not suited to the location.
5. Soil protection measures and inward settlement development (Responses)
In order to ensure that soil is able to fulfil its life-sustaining functions in the future, a sustainable and integrated management approach that takes all soil functions into account and meets the various requirements for its protection and use is necessary. To address this challenge, the federal government adopted the Swiss Soil Strategy and a package of measures for the sustainable protection of soil as a resource at its meeting on 8 May 2020. The latter includes the sectoral plan for crop rotation areas (FFF), the Competence Centre for Soil (KOBO) and a concept for a nationwide collection of soil information.
To preserve and improve soil quality, the Confederation and the cantons are already implementing various measures, including the Ordinance relating to Impacts on the Soil (VBBo). Together with the construction, farming and forestry sectors, they have developed instruments and implemented preventive soil protection measures. For several years now, for instance, major construction sites have been required to call in a soil science consultant to prevent soil from being damaged and to preserve its fertility.
Federal authorities have set guide, trigger and clean-up values for some chemical pollutants, such as heavy metals, and for individual organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and dioxins.
For plant protection products, measurable goals and concrete measures have been set out in the federal Action Plan on Sustainable Use of Plant Protection Products.
In the interest of curbing soil loss, the Spatial Planning Act (SPA) requires the Confederation, cantons and communes to take a more economical approach to dealing with the resource of soil. This principle was given much greater emphasis in the first step of the partial revision of the SPA (in force since 2014). Settlement development should primarily occur in already existing building zones. The second step of the SPA revision currently underway focuses mainly on the issue of construction outside of building zones.
The federal government protects arable land through the Sectoral Plan for Crop Rotation Areas. As part of this plan, it requires the cantons to conserve their best arable soil in the long term.
Last modification 08.05.2020