Field of Action Soils

freshly ploughed fieldClick to enlarge
The different impacts of climate change affect soil characteristics and functions.
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Impacts of Climate Change

Table of Contents

 

Precipitation

Climate projections predict changes in precipitation patterns. These modified precipitation conditions can have the effect that soils in winter and spring are moister in the future, while they are increasingly dry in summer and autumn.

If the amount of precipitation increases during winter months, soils will more often be extremely wet in the future. As a result, the stability of the soil structure may decrease, while the risk of compaction increases. As far as agricultural soils are concerned, this is especially relevant when they are driven on or processed. With the changed conditions, the structure of the soil and thus its features as a filter, habitat and location for food production change. This can mean that soils store fewer nutrients and therefore become less fruitful or that pollutants (e.g. from rain water) cannot be filtered as easily. The soil’s biodiversity can decrease and the nutrient balance can shift. This leads to a loss of natural soil functions.

If the number of frost days decreases simultaneously, the projected precipitation increase in winter causes extremely muddy soil surfaces. This leads to waterlogging and increased surface runoff, because the water cannot seep in sufficiently. This in turn can promote floodings.

Changes in precipitation amounts and distributions are expected to occur during summer, too. According to climate projections, more frequent and longer droughts will increasingly alternate with heavy precipitation. As droughts intensify evaporation, a faster drying and crusting of the topsoil is likely. Under these circumstances, the important filter effect of soil is impaired.

In addition, these conditions can cause two types of erosion: dry surface soils often involve deflation (wind erosion) when strong wind carries away sand and dry earth. In contrast, water erosion occurs if rainwater does not seep in fast enough, and instead drains off on the surface and carries away ground material. Both types lead to a loss of valuable soil material. Furthermore, they can cause local and regional flood events, waterlogging or floodings.

 

Temperature

If the atmosphere heats up, the soil temperature increases, too. Increased temperatures accelerate biological processes in soils: soil organisms and animals multiply, root growth accelerates and the organic soil matter decomposes more quickly. If organic matter is converted more quickly, there are more nutrients that stimulate plant growth, which also increases the water needs of plants. Provided the amount of water in the soil is sufficient, this process leads to higher crop yields. However, in case of a lack of water, plants suffer from drought damages and the crop yields decrease.

Nevertheless, the increased biological activity also means that the balance of the humus decomposition and the humus formation is varied. As a result of this process, the humus amount in the soil can decrease over time. During the decomposition of humus, the amount of organic carbon in the soil decreases and the greenhouse gas CO2 is released. Thus, soils are becoming increasingly important as a source of carbon dioxide.

When climate change leads to the degradation of organic substances, pollutants that are stored in the soil are mobilised. The previously bound substances can be outsourced by increased precipitation with the leachate and/or outgassed by higher temperatures at the surface.

If summers become warmer and drier and winters are milder, the evaporation rate increases. This can have the effect that less rainwater seeps into the soil and that the groundwater recharge decreases. If, organic substances in swamps are decomposed because of declining groundwater level, harmful greenhouse gases may be released.

 

Extreme weather events

Extreme weather events contribute to many of the previously described climate impacts affecting soils. Wind, storms and heavy rain increase the risk of erosion. They affect the soil structure and thus alter the soil functions.

Heavy precipitation in combination with frequent freezing and thawing cycles can promote water erosion especially in southern and south-western regions of Germany and favour mudslides, landslides and rockfalls. In the north and northeast, increasing wind speeds and more frequent droughts increase the risk of wind erosion.

If you are interested in obtaining information about possible adaptation measures in the field of action soils, please click here.

 

Sources

Adaptation to Climate Change

Technical measures

The aim of adaptation measures for soils is to preserve them as a resource. In addition, sustainable management and other fields of activity, such as agriculture or forestry, often protect soil functions.

In the context of soil protection, the main priorities are ecosystem and management measures. However, technical solutions can also help, for example against soil compaction. Vehicles and equipment that drive on exposed soils can be adjusted in a way that improves the distribution of the total mass and the specific surface pressure which again reduces the strain on the bearing capacity of the soils. In that regard, a possible measure is the use of wider tires with low tire pressure and large contact surfaces. In addition, the use of lighter machines with less load mass is also conducive to soil protection. If the number of times the vehicles drive across the respective soils is simultaneously reduced and timed in accordance with the respective soil conditions, soil damage is reduced significantly.

Ecosystem measures

Ecosystem measures focus on the sustainable protection of soils and aim at nature-orientated preservation. In this context, the agricultural use of soils plays a crucial role. Sustainable and good agricultural practices should be further developed and expanded with regard to possible climate impacts. Agriculture can also contribute to soil protection with a climate-sensitive selection of varieties and species and through appropriate crop sequences, sowing dates, fertilisation, tillage and ordering procedures. To reduce erosion and compaction risks, the measures should be implemented in a coordinated husbandry system. Soil-conserving husbandry should also include targeted erosion monitoring.

Apart from measures that can be taken within the agricultural sector, there are other strategies and procedures that contribute to soil protection and specifically to maintaining or restoring the CO2 storage function of soils. The overall objectives are a reduction of space requirements and the preservation of site-specific features of soils. Especially the preservation of humus contributes to soil fertility, soil stability and its water holding capacity.

The protection of soils and their functions also involves a protection against building. In case of destroyed areas, such as those that remain after surface mining, it is desirable to accomplish near-natural restoration (rehabilitation and recultivation). In addition, less grassland should be converted into agricultural land and swamps should be protected in general.

Legal, political and management measures

In order to protect soils it is important to better align soil protection policy with soil-related climate protection and adaptation measures. This includes taking the climate protection function of soils into account in laws as well as in planning and approval processes. There are numerous specific measures to strengthen the protection of soils. Here are some examples:

  • By including them in appropriate funding programmes and legislation, grassland areas can be protected and preserved permanently as CO2 storage facilities.
  • A reduced use of space in housing and transport development and de-sealing of land can help to ensure that rainwater has enough space to seep into soils and decrease the flood risk.
  • The de-sealing and recultivation of land contributes to an improved urban climate.
  • Land reserves in built-up areas can contribute to preserving the biomass production potential and the CO2 storage function of soils.
  • Areas with little or no vegetation can be converted into compensation areas for construction projects or into urban green spaces.
  • Land use planning should protect swamps and, if possible, regenerate drained swamps.

Since adaptation strategies need to be based on sound information, it is necessary to acquire more knowledge about the possibilities of climate change adaptation in the context of soils. In order to assess the impacts of climate change on soil functions, information on soil, land use and regional climate changes is needed. In this respect, climate change-related soil monitoring could be an important source of information. Against this background, existing measurement and collection programmes for soil data such as the nationwide erosion monitoring should be further developed.

If you are interested in obtaining information about concrete impacts of climate change in the field of action soils, please click here.

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