Original publication: March 2017
Authors: Wageningen University & Research: H.F.M. ten Berge, J.J. Schröder
Aarhus University: J.E. Olesen
University of Cordoba: J.-V. Giraldez Cervera
Short link to this post: http://bit.ly/2kCTK5o
Soils and soil services
Soil, as defined in the EU Thematic Strategy for Soil Protection (COM(2006) 231), is ‘the top layer of the earth’s crust, formed by mineral particles, organic matter, water, air and living organisms. It is the interface between earth, air and water and hosts most of the
biosphere’. Soil is differentiated into horizons of variable depth, which differ from the material below in morphology, physical make-up, chemical properties and composition, and biological characteristics. The most fertile portion of soil, generally the top 0-30 cm, is called ‘topsoil’. Soil fertility results from soil characteristics (e.g. texture), nutrient inputs and other management practices.
Soils are key to the delivery of a wide array of ecosystem services, including water and nutrient cycle regulation, food and fiber production, providing a physical basis for construction and habitat for various species. However, soils in the EU are exposed to numerous threats, which limit their ability to function and to deliver ecosystem services. These threats include erosion, floods and landslides, loss of soil organic matter, salinisation, contamination, compaction, sealing, and loss of soil biodiversity. Loss of soil functions and land degradation remain major concerns, and these will likely show continued deteriorating trends in the future (EEA, 2016).
The scale of soil degradation in the EU is significant with approximately 22% of European land affected by water and wind erosion. Around 45% of the mineral soils in Europe have low or very low organic carbon content, soil contamination is affecting up to three million sites, and an estimated 32-36% of European subsoils are having high or very high susceptibility to compaction. An increase in soil sealing results from construction and infrastructure. Drivers of soil degradation relate to increasing urbanisation, land abandonment, and intensification of agricultural production. Soil degradation reduces or eliminates soil functioning and their ability to support ecosystem services. It is therefore essential to maintain the services provided by soils by restoring soil functions. As such, soils should be sustainably managed, and degraded soils should be rehabilitated or restored.
For soils under agriculture, the five main ecosystem services include the provision of harvestable crops, clean freshwater and nutrients for plants and animals, conservation of suitable habitats for biodiversity, and maintenance of a benign climate. The corresponding soil functions are primary production, water regulation, nutrient cycling, habitat support and climate regulation. Relations between management and services are illustrated in the above figure.
Major threats to soils and soil services
Major soil threats at the whole-system level that call for policy action are:
- the degradation of peatland and similar organic soils by drainage under agriculture and forestry, mostly in Northern and North-Western Europe; and the potential encroachment of agriculture and forestry onto pristine peatlands as favoured by climate change in Northern Europe;
- the drastic alteration of traditional wood-pasture systems in various parts of the EU;
- the grabbing of productive agricultural land for non-agricultural use (sealing).
Any policies –new or existing – to address these threats merely need to aim at full conservation of the corresponding natural, semi-natural and agricultural status of these systems.
Both peatlands and extensive grassland and wood-pasture systems store large amounts of soil carbon. The protection of these soils and carbon stocks is vital in view of climate change mitigation, conservation of their rich biodiversity (in soil and aboveground), regulation of the water cycle, and (in the case of grasslands and wood-pastures) protection from water erosion. These systems need full protection at the whole-system level. Their loss cannot be reversed on the human time scale. In the case of wood-pastures, current legislation (EU level instruments and their local implementation) appears inadequate to offer protection to such cross-sectoral (agro-forestry) systems.
Growing global food demand in coming decades already calls for intensification of all suitable land in current use, and loss of productive land by sealing is therefore simply unaffordable. Such loss increases the need to further intensify production on remaining farmland, increasing pressure on extensive systems with high biodiversity, affecting soil services in both types of systems. Ironically, the best soils are often the first to disappear under urbanisation, as soils near original habitation have been historically better amended. As for the intention of ‘no-net land take’ by 2050 (COM 571/2011) –by the way, not legally binding – the projected time span seems too comfortably long, given the expected steep rise in global population and the associated increasing demands for food and biomass during this period. This is particularly worrying since other drivers such as climate change will likely deteriorate conditions for crop production in large parts of the EU and elsewhere.
Other major threats are:
- Soil erosion by water; and
- compaction of the subsoil by heavy machinery.
These, as opposed to the above threats, require policy measures that enforce the focussed adaptation of farming practices.
Water erosion occurs in many regions of the EU and the remedies must be chosen to match the local conditions. The formal delimitation of vulnerable zones, and the keeping of effective soil cover types, and/or tillage systems tailored to the local potential and needs of such zones should be considered, in our view, as necessary steps towards the enforcement of practices that reduce the loss of topsoil by erosion.
We regard subsoil compaction as a serious and wide-spread menace, and include it in our shortlist of major threats that call for policy action. Its main driver is the ongoing upscaling of farm mechanisation to increase labour productivity. This trend is likely to cause increasing damage to the subsoil and will threaten crop production under climate change. It would be a sensible precaution – comparable to speed limits on highways – to introduce a maximum permissible limit to the wheel load carrying capacity (WLCC; Schjønning et al., 2015) for traffic on all agricultural soils. This would trigger innovation towards lighter and smaller systems, autonomous transport systems for harvesting operations, and similar advances. (Because of its impact on farm economy –level playing field – such measure would need EU-level underpinning.)
Soil in the farm economy
Although the soil is the farmer’s most precious economic resource, there may be several reasons why farmers might not take specific actions to protect or improve their soil in their own commercial interest. These reasons include:
- Soils generally respond slowly to changes in management practices. Even given sufficient time, soil properties can only be improved within certain limits set by climate and parent material.
- Effects of soil improvements on crop yields remain often unnoticed. Inter-annual (weather-related) variation in attainable yield, timing of operations and the use of inputs, and crop genotype all have relatively strong effects on actual yield and quality of the produce, and can easily mask benefits from improved soil conditions, even in the long run. The low responsiveness of yield to management-induced soil improvements is, we believe, a major reason for farmers to avoid practices that may improve/protect one or more aspects of the soil, but bring disadvantages relative to current management.
- Benefits or problems may show only under extreme conditions (e.g., drought, waterlogging) or go unnoticed as long as critical thresholds are not crossed (disease suppressiveness).
- Farmers are unware of existing solutions to address the problem; or no ready-for- practice solutions really exist.
- Farmers can sometimes correct for soil-induced crop stresses, by using extra inputs (fertilisers; crop protection agents; irrigation) or alternative equipment (deep- plow; drainage) –thus largely externalising the cost of such ‘repair measures’ if their impacts (emissions; lowering groundwater table; loss of biodiversity) are mostly felt elsewhere.
- Threats are simply not present on the farm.
Public and European Union interests in soils
Various aspects justify the tackling of soil threats at the European Union rather than at the national level:
- Biophysical impacts of threats do not stop at member states’ borders.
- Economic impacts of threats, or consequences of the policy measures to counter them, are not limited to the member state either (‘spill-over’).
- The European Union level allows the spatial optimisation of interventions and the sharing of their costs.
- The cost efficiency of the necessary research and innovation efforts to make soil management more sustainable increases with the geographic extent of the application domain.
- Local democracy may hamper the implementation of unpopular measures, if these lack central underpinning at higher level.
Link to the full study: http://bit.ly/601-973
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