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Soil Themes > Soil Biodiversity


The Convention on Biological Diversity (CBD) defined the soil biodiversity as "the variation in soil life, from genes to communities, and the ecological complexes of which they are part, that is from soil micro-habitats to landscapes".

In other terms the soil biodiversity represents the variety of life belowground. 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 belowground generally equals or exceeds that aboveground, whilst the biodiversity in the soil always exceeds that on the associated surface by orders of magnitude, particularly at the microbial scale.

Some numbers describe well the soil biodiversity: a teaspoon of soil (about one gram) may typically contain one billion bacterial cells (corresponding to about ten thousand different bacterial genomes), up to one million individual fungi, about one million cells of protists, and several hundred of nematodes. Beside microorganisms and microfauna, soil harbours different species of meso and macro/megafauna represented by arthropods, earthworms and mammals.

The soil biota plays many fundamental roles in delivering key ecosystem goods and services. 

Ecosystems goods provided by soil biota are:

Ecosystems services provided by soil biota:

In the image, you may view a round up of soil dwellers.


Methods for studying SOIL BIODIVERSITY – The HOW

Soil organisms are extremely variegated in terms of morphology, quantity and lifestyle: we move from microorganisms invisible to the naked eye (e.g., bacteria and fungi) to invertebrates (e.g., earthworms) and vertebrates (e.g., mammals). Therefore, surveys on soil biodiversity require specific tools depending on which group of organism is studied.

Three ways are feasible for studying microbial diversity:

Investigations are more straightforward for animals and many invertebrates living in soils. Indeed, their taxonomic identification is relatively easier: what can be seen can be identified and counted. Due to their importance in soil quality assessment, standard guidelines are nowadays available for sampling of some soil invertebrates such as earthworms. Furthermore, it has been recently observed that molecular fingerprinting could be successfully applied to identify vertebrates and plants living below- and aboveground (A et al., 2011).

The identification of soil organisms is the first step to comprehend the role of soil biodiversity. Indeed, once you know the soil inhabitants you have to understand what they are doing, that means studying the function of soil biodiversity. Functional assays and analysis of genes expressed by the organisms, targeting soil RNA instead of DNA, help in replying this question.

Last step is the comprehension of large-scale effects coming from the interactions of different organisms in soil. That is the task of the ecology. Ecological experiments, such as set up of microcosms and in-field observations and measurements, allow to assess the soil function and impact as environmental service.

In the image, you can view an approximate number and diversity of organisms typically found in a handful of grassland soil (KR & JJIM). Because of their various features (quality and quantity), each group of organisms has its specific survey strategy.

soil biodiversity

Role of SOIL BIODIVERSITY in soil system – The WHERE

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.

In such a complex system, the relationships between biodiversity and function are intricate and somewhat poorly understood, even in aboveground situations. The exceptional complexity of belowground communities further confounds our understanding of soil systems. However, it is possible to define three important mechanisms underlying relationships between organisms and functions carried out in soil system:

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 a clear and 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 with less functional redundancy, whereas for highly specific symbiotic associations, such as orchid mycorrhizas (association between orchids and certain fungi), there is a total dependence and hence zero redundancy.

A depletion of biodiversity will therefore have differing consequences in relation to the functional repertoire: processes with high redundancy and weak interactions among organisms (e.g., decomposition) can be easily replaced, while the loss of a strong and specific link (e.g., one of the actors of orchid mycorrhizas) can alter the stability of the community. 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.

In the image, you may view a simplified soil food web. Interactions and links are present among all of different trophic levels with energy and nutrient elements transferred from one level to another. Note that the chain is cyclic with a continual movement of material from all trophic levels back to the detritus/organic matter pool and the base of the series (modified from Tugel, A.J. & A.M. Lewandowski, eds., Soil Biology Primer).

food web

Brief history of SOIL BIODIVERISITY and European Union – The WHEN

European Commission (EC) complies with the Convention on Biological Diversity (CBD) of United Nations, entered into force in 1993. The main aims of CBD are: 1) conservation of biological diversity; 2) sustainable use of biological diversity; 3) fair sharing of benefits coming from biological diversity.

At the European level the importance of preserving nature and biodiversity is well recognized and led to develop specific environmental policies over the years: from the EU's Bird Directive in 1979 to the Biodiversity Strategy in 1998.

In 2006 the soil theme becomes crucial for EU, with the adoption of the Soil Thematic Strategy in order to guarantee a high level of soil protection across the EU. In this frame the EC recognises the importance of soil biodiversity and undertakes to improve the knowledge of its function as environmental service. Indeed, in 2008 a soil biodiversity expert group is born in the Action SOIL of Joint Research Centre, aiming at providing and supporting the EC's decisions and policies on this topic.

The increasing relevance of soil themes, including biodiversity, at both global and European levels, is confirmed by recent international events as the Global Soil Week (November 18th-22nd, 2012 - and the World Soil Day 2012 (December 5th). Furthermore, the Global Soil Biodiversity Initiative ( involving different organizations, included the Joint Research Centre as key participant, has been launched in 2012.

Value and importance of studying SOIL BIODIVERSITY – The WHY

Ecosystem services were defined as the benefits supplied to people by the ecosystems. In this frame, soil biodiversity carries a range of values to humankind that depend on the perspective from which they are being considered. These include:

The overall ecological value of soil biota is increasingly appreciated, as we understand more about its origins and consequences. Soil biodiversity has also a monetary value in term of contribution to ecosystem services: estimates ranging from 1.5 to 13 trillion US Dollars (VdP, 2004).

Decline in soil biodiversity is the reduction of forms of life living in soils, both in terms of quantity and variety.

Soil biodiversity is more and more under pressure because of threats to soil, such as erosion, contamination, salinization and sealing. These events 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. It has been observed that specific groups may be more susceptible to certain pollutants or stresses than others (e.g., nitrogen-fixing bacteria that are symbiotic to legumes are particularly sensitive to copper). Additional studies on the negative effects of direct and indirect soil threats on specific organisms are required.

Any loss of biodiversity is surely undesirable. However, given our limited state of understanding of the consequences of soil biodiversity, further efforts will be necessary to know potential risks. At the moment, it is common sense that a strong precautionary principle needs to be applied before making any decision.

On-line publications

Working group

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


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

Ciro Gardi,
Tel: +39 0332 785015, Fax: +39-0332-786394, E-Mail:

Alberto Orgiazzi,
Tel: +39 0332 789671, fax +39-0332-786394


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 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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European Commission - Joint Research Centre
Institute for Environment and Sustainability
Marc Van Liedekerke(tel. +39-0332-785179)
Panos Panagos (tel. +39-0332-785574)