With the unsustainable way in which it treats its soil, Switzerland is missing opportunities to produce food, gain clean drinking water, use space for leisure activities, reduce greenhouse gases, conserve biodiversity and counter the growing stress of high temperatures. Inward urban development has slowed the urban sprawl to some degree, but soil sealing has picked up pace again over the past decade. Additionally, soils are still being compacted and contaminated with pollutants, and they are eroding.
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. With these growing demands, the demand for soil is expected to remain high.
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.
Climate change is also putting the soil under growing pressure as its services become even more important. More frequent heavy rainfall will increase the risk of erosion, and increasingly dry summers will make it all the more important for soils to be able to store water. Due to the increasing summer drought, the water storage capacity of soils is becoming greater and the climate-damaging release of CO2 from peat in drained peat soils is accelerating.
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, especially when wet. Compaction induces surface water runoff and thus soil erosion. At major construction sites, more care is now being taken of the soil because of the mandatory participation of soil protection experts. The main cause of erosion in Switzerland are, in particular, farming methods that are unsuited to the location.
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. The input of microplastics can also be observed across the board and is increasingly posing a problem.
Biological impacts on the soil can arise through genetically modified, pathogenic or locally invasive organisms, usually introduced through the displacement of soil material.
Overall, Switzerland's settlement areas grew by nearly a third between 1985 and 2018 (+776km2), although the rate of expansion has slowed down slightly in the last three decades. Residential areas saw particular growth, increasing by as much as 61% and therefore twice as fast as the population. Thus, land continues to be lost through overbuilding, largely at the expense of cultivated land. However, there are some spatial disparities.
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. Our soils have been thousands of years in the making. On average it takes a century to create a one-centimetre layer. Once destroyed, it cannot be restored within a human lifetime.
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. Around 20% of the area used for agricultural purposes in valley and hilly regions is classified as potentially at moderate to 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 can be 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.
Almost two thirds of settlement areas are sealed (buildings and roads). Thanks to inward urban development, the pace of settlement growth has slowed somewhat. Nonetheless, recent decades have seen a sharp rise in sealed surfaces, of 40% (594km2) between 1985 and 2018. While the increase slowed between 1997 and 2009, soil sealing picked up again during the most recent monitoring period from 2009 to 2018. Currently, 17.6km2 of soil are sealed in Switzerland per year, which is equivalent to almost seven football pitches per day.
The soil sequesters large quantities of carbon from the atmosphere in its humus. However, soil carbon levels are decreasing because of changes to land use and non-sustainable soil management. In the past 30 years, mineral agricultural soils have been neither sources nor sinks for CO2. While adapted management practices have succeeded in increasing the organic matter and carbon content of mineral soils, the loss of humus from drained peatlands is relevant. Although drained fenland accounts for less than 2% of agricultural land in Switzerland, it contributes some 10% of the farming sector's greenhouse gas emissions.
Settlement growth, an expanding infrastructure and intensive farming are concentrated on the Swiss Plateau and the floors of major Alpine valleys. This is naturally also where the greatest loss of soil by sealing and the greatest degradation of soil quality have been recorded. Since these locations are also where the best-quality crop-growing soils are to be found, the loss of soil surface area and quality is concentrated on these most fertile of soils.
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).
Compacted soil is less fertile than (non-compacted) intact soil. As it absorbs less rainfall, it carries a greater risk of landslides and flooding. Soil that has had its upper layer (topsoil) compacted takes years to recover. If its subsoil has also been compacted, the damage is virtually 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 burden water bodies with nutrients. Importantly, plant protection products are washed off the soil.
The consequences of chemical soil pollution endanger soil fertility. Plants absorb certain pollutants from the soil, which impairs the quality of food and feedstuffs. Pesticide residues also form in the soil. An in-depth study must still be done of the possible negative impacts that this might have on biological activity and soil organisms.
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 Council adopted the Swiss Soil Strategy at its meeting on 8 May 2020. This strategy calls for soil consumption to be reduced to net zero by 2050. This means that if soil functions are lost because of a new development, for example. they must be compensated for elsewhere by soil being deposited there. Other objectives include establishing a path towards sustainable soil use, minimal soil consumption, protections against harmful impacts, and the restoration of degraded soils. The Strategy must be implemented as part of spatial planning, agriculture, forestry, construction, the management of greenfield events, in settlement areas, in the handling of degraded soils, and at the international level.
Together with the Soil Strategy, the Confederation has also adopted a package of measures for the sustainable protection of soil as a resource. These include the crop rotation areas sectoral plan, the National Competence Centre for Soil (known by its German acronym KOBO) and a system for recording information about soils throughout Switzerland.
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.
The Terranimo simulation model is designed to avoid soil compaction as a result of agricultural practices. It enables farm managers to calculate the risk of soil compaction from the use of agricultural machinery.If farmers do not take action to prevent erosion damage in the future they risk having their direct subsidies cut. Completed in 2019, erosion risk maps for cropland and permanent pasture support farm managers and cantons with this task.
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 under way focuses mainly on the issue of construction outside of building zones.
Last modification 19.12.2022