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European Commission > Joint Research Centre > Institute for Environment and Sustainability > Land Resource Management Unit

Soil Themes > Soil Biodiversity

DECLINE IN SOIL BIODIVERSITY is the reduction of forms of life living in soils, both in terms of quantity and in variety.

Soil biodiversity is a term used to describe the variety of life below-ground. The concept is conventionally used in a genetic sense and denotes the number of distinct species (richness) and their proportional abundance (evenness) present in a system, but may be extended to encompass phenotypic (expressed), functional, structural or trophic diversity. The total biomass below-ground generally equals or exceeds that above-ground, whilst the biodiversity in the soil always exceeds that on the associated surface by orders of magnitude, particularly at the microbial scale. A handful of grassland soil will typically support tens of thousands of genetically distinct prokaryotes (bacteria, archaea) and hundreds of eukaryotic species across many taxonomic groups. The soil biota plays many fundamental roles in delivering key ecosystem goods and services, and is both directly and indirectly responsible for carrying out many important functions.
Ecosystems goods provided by soil biota:
  • food production
  • fibre production
  • provision of secondary compounds (e.g. pharmaceuticals / agrochemicals)
Ecosystems services provided by soil biota :
  • driving nutrient cycling and regulation of water flow and storage
  • regulation of soil and sediment movement and regulation of other biota (including pests and diseases)
  • detoxification of xenobiotics and pollutants and regulation of atmospheric composition

The value of soil biodiversity

Soil biodiversity carries a range of values that depend on the perspective from which they are being considered. These include:

  • Functional value, relating to the natural services that the soil biota provides, the associated preservation of ecosystem structure and integrity, and ultimately the functioning of the planetary system via connections with the atmosphere and hydrosphere.
  • Utilitarian (“direct use”) value, which covers the commercial and subsistence benefits of soil organisms to humankind.
  • Intrinsic (“non-use”) value, which comprises social, aesthetic, cultural and ethical benefits
  • Bequest (“serependic”) value, relating to future but as yet unknown value of biodiversity to future planetary function or generations of humankind.
The ecological value of soil biodiversity is increasingly appreciated as we understand more about its origins and consequences. The monetary value of ecosystem goods and services provided by soils and their associated terrestrial systems, an entirely human construct which assists putting their significance into an economic context, was estimated in 1997 to be thirteen trillion US dollars ($13 x 1012). The soil biota underwrites much of this value.

In the image , you can view an approximate number and diversity of organisms typically found in a handful of temperate grassland soil (KR & JJIM).

Threats to soil biodiversity

A healthy soil biota needs an appropriate habitat. In soil, this is essentially the space denoted by the complex architecture of the pore network, and the associated supply and dynamics of gases, water, solutes and substrates that this framework supports. Hence threats to soil such as erosion, contamination, salinisation and sealing all serve to threaten soil biodiversity by compromising or destroying the habitat of the soil biota. Management practices that reduce the deposition or persistence of organic matter in soils, or bypass biologically-mediated nutrient cycling also tend to reduce the size and complexity of soil communities. It is however notable that even polluted or severely disturbed soils still support relatively high levels of microbial diversity at least. Specific groups may be more susceptible to certain pollutants or stresses than others, for example nitrogenfixing bacteria that are symbiotic to legumes are particularly sensitive to copper; colonial ants tend not to prevail in frequently-tilled soils due to the repeated disruption of their nests; soil mites are a generally very robust group.

Consequences of soil biodiversity

The relationships between biodiversity and function are complex and somewhat poorly understood, even in aboveground situations. The exceptional complexity of belowground communities further confounds our understanding of soil systems. Three important mechanisms underlying relationships between biodiversity and function are:
  • Repertoire: for a biologically-mediated process to occur, organisms that carry out that process must be present; Interactions: most soil organisms have the capacity to directly or indirectly influence other organisms, either positively or negatively;
  • Redundancy: the more organisms there are that can carry out a function in a particular soil, the more likely it is that if some are incapacitated or removed the process will remain unaffected; those that remain fill the gap.
There is evidence that soil biotic communities are coupled to their associated vegetation, such that there is a mutual dependence between above-ground and below-ground communities, and hence that compromised soil communities may curtail particular plant assemblages from forming.

In the image, you may view Simplified soil food web. Energy and nutrient elements are transferred from one trophic level to another. Note that there is also a continual movement of material from all trophic levels back to the detritus/organic matter pool and the base of the series (Tugel, A.J. & A.M. Lewandowski, eds., Soil Biology Primer.

Consequences of decline in soil biodiversity

richness per se is of little consequence; rather it is the functional repertoire of the soil biota that is critical. For processes such as decomposition, there is evidence that there is a high degree of redundancy at a microbial level. Other processes, such as nitrification (the oxidation of ammonium), are carried out by a narrower range of bacteria and there is less redundancy in this group, whereas for highly specific symbiotic associations, such as those between orchids and certain mycorrhizal fungi, there is total dependence and hence zero redundancy. A depletion of biodiversity will therefore have differing consequences in relation to different processes.

In some circumstances it has been demonstrated that there are threshold levels of soil diversity below which processes are impaired, although these are usually related to narrow processes and are manifest under experimentally constructed systems of exceptionally low levels of diversity, as opposed to natural systems. From the intrinsic and bequest perspective, any loss of biodiversity is undesirable. Given our limited state of understanding of the consequences of soil biodiversity, it is common sense that a strong precautionary principle needs to be applied.

On-line Publications

Working Goup

The JRC has created in middle 2008 a Biodiversity expert group to provide it with advice and assistance regarding its scientific and technical activities in support to EU soil policy making and research. Find more information about:

Many initiatives dedicated to soil biodiversity are taking place in Member States, but they are not coordinated at European scale. A first initiative coming from Joint Research Centre, SOIL Action is to invite experts to participate in the implementation of a Soil Biodiversity Inventory in Europe (Evaluate ongoing soil biodiversity monitoring activities in the Member States in various scales). In case of interest, we would be pleased to be informed about on-going activities (Databases, Data Collection, Reports, Maps, etc) that National, Regional or Local Institutes perform in relation to Soil Biodiversity. Contact Point: Ciro Gardi, Tel: +39 0332 785015, Fax: +39-0332-786394

Events

1st Experts Meeting (Ispra, 19-20 June 2008)
The Joint Research Centre (JRC) of the European Commission organised an experts meeting (Ispra, 19-20 June 2008) in support of its contribution to the Soil Biodiversity component of the EU’s Soil Thematic Strategy and the Proposal for a Soil Framework Directive.
Find the presentations of the meeting.

What lives below? The soil is alive!
A public awareness event organised by the European Commission on the occasion of World Biodiversity Day (22nd May 2008) at the Ninth Meeting of the Parties to the Convention on Biological Diversity (CBD)
Forenzelt "Campus", Plaza der Vielfalt (in front of Maritim Hotel), Bonn, Germany. Find more information.......

Contact Points

Roberto Cenci,
Tel: +39 0332 789771, Fax: +39-0332-786394, E-Mail: roberto.cenci@jrc.ec.europa.eu

Ciro Gardi,
Tel: +39 0332 785015, Fax: +39-0332-786394, E-Mail: ciro.gardi@jrc.ec.europa.eu

Simon Jeffery,
Tel: +39 0332 783682, Fax: +39-0332-786394, E-Mail: simon.jeffery@jrc.ec.europa.eu

Links

Soil biodiversity: functions, threats and tools for policy makers
Did you know that every year soil organisms process an amount of organic matter equivalent in weight to 25 cars on a surface area as big as a soccer field? Or that one hectare of soil can contain the equivalent in weight of two cows of bacteria? Or that some fungi are extremely big and can reach a length of several hundred metres?

If you are interested in all that, plus the relationship between worms and erosion, microbes and clean water, or why soil organisms are important for antibiotic production, you will find a wealth of information in the report Soil biodiversity: functions, threats and tools for policy makers now available at http://ec.europa.eu/environment/soil/biodiversity.htm. A press release issued on this occasion is attached below. The report has been prepared by a consortium formed by BIO Intelligence Service, IRD (Institut de recherche pour le développement) and NIOO-KNAW (Netherlands Institute of Ecology) on behalf of the Environment Directorate-General of the European Commission.

One of the authors of the report (professor Van der Putten) had intervened at Green Week in the session 'The soil life we walk on: does it matter?' to held in Brussels on Wednesday 2 June 2010.



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