What is Loss of Soil Biodiversity? 

Soil biodiversity is generally defined as the variability of living organisms in soil and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems¹. The threat - decline in Soil Biodiversity - has been described as a reduction of forms of life living in soils (both in terms of quantity and variety) and of related functions².

Soils are a globally important reservoir of biodiversity. They contain at least one quarter to one-third of all living organisms on the planet yet little is known about them, as only around 1% of soil microorganisms have been identified compared to 80% of plants3. At its simplest, the vast biodiversity of the soil can be divided into four major groups:

• Microbes and microfauna with body widths of less than 100 micrometres
• Mesofauna with body widths between 100 micrometres and 2 millimetres
• Macrofauna, which are larger than 2 millimetres than 2 millimetres

Where does it occur?

In general and geographical terms, the state of soil biodiversity has been well described in the European Atlas of Soil Biodiversity³. Soil biodiversity decline is usually related to some other deterioration in soil quality and at local levels, it is clear that biodiversity is in decline. For example, soil sealing (the permanent covering of soil with hard surfaces, such as roads and buildings) causes the death of the soil biota by cutting off water and carbon and nutrient inputs. In other cases, soil biodiversity decline can be linked with erosion, organic matter depletion, salinization, contamination and compaction.

What causes it?

Soil biodiversity is subject to considerable disturbances through any number of threats. The soil biota has its own unique capacity to resist events that cause disturbance or change and a certain capacity to recover from these perturbations. The capacity to recover from change is considered a key attribute of biodiversity. The figure below provides a simple schematic that describes the concept of Resistance and Resilience.

Land Management
Land management can have varying effects on belowground biodiversity. A primary driver of this is the close link between soil biodiversity and soil organic matter, although the relationship is not fully understood. As the source of energy underpinning food-webs, carbon losses from organic matter may lead to reduced biodiversity. Coupled with this, the general use of fertilizers, pesticides and herbicides as part of agricultural intensification are a significant cause of soil biodiversity loss. The agricultural techniques/management that lead to loss of soil biodiversity are monoculture cropping, removal of residues, soil erosion, soil compaction (both due to degradation of the soil structure) and repeated application of pesticides ⁴.

Climate
Climate change leading to flooding and subsequent lack of oxygen and compaction, loss of organic matter through enhanced oxidation, and prolonged periods of drought (in typically un-droughted landscapes) are the drivers of biodiversity loss in soil. Many of these factors link with, and may be compounded by, local and regional land management practices.

For Europe, the main pressures have been recognised for three levels of biodiversity:

• Ecosystem-level - the main pressures are thought to derive from land use change, overuse and exploitation, a change of climatic and hydrological regime and change of geochemical properties.
• Level of species of organism in the soil - the main pressures on biodiversity are thought to derive from a change in environmental conditions of geochemistry, competition with invasive species and ecotoxins.
• Genetic level - the main pressures are thought to derive from a change of environmental conditions, ecotoxins and “Genetic pollution” 3.

How can it be measured or assessed?

 The table below lists key and/or proxy indicators for loss of soil biodiversity identified by RECARE and ENVASSO projects. 

The table below lists key indicators of a decline in soil biodiversity, the purpose of the indicator and methods used for measuring or assessing a decline in soil biodiversity

How can it be prevented or remediated?

There are a number of different measures that can be taken to prevent the loss of soil biodiversity or remediate damage, but broadly it does not decline independent of other factors and is usually related to some other deterioration in soil quality.

Case Study Experiments

How does it interact with other soil threats?

The decline in soil biodiversity is usually related to other deteriorations in soil quality and can be linked with other threats like erosion, organic matter depletion, salinization, contamination and compaction. An expert group weighted the potential threat – for a selection of possible soil threats - to soil biodiversity³. This illustrates that soil biodiversity is highly influenced by the other threats.

How does it affect soil functions?

As the figure shows, the activities of the soil biota are essential to all of the soil functions. The primary services that soil biota undertake include (i) nutrient cycling; (ii) regulation of water flow and storage (iii) regulation of soil and sediment movement; (iv) biological regulation of other biota (including pests and diseases); (v) soil structural development and maintenance; (vi) the detoxification of xenobiotics and pollutants; and (vii) the regulation of atmospheric gases.

References

¹ UNEP (1992) Global Biodiversity Strategy. Washington, DC: WRI.
² Huber, S., Prokop, G., Arrouays, D., Banko, G., Bispo, A., Jones, R., Kibblewhite, M., Lexer, W.,Möller, A., Rickson, J., Shishkov, T., Stephens, M., Van den Akker, J., Varallyay, G., Verheijen, F., 2008. Indicators and Criteria report. ENVASSO Project (Contract 022713) coordinated by Cranfield University, UK, for Scientific Support to Policy, European Commission 6th Framework Research Programme.
³ Jeffery S, Gardi C, Jones A, Montanarella L, Marmo L, Miko L, Ritz K Peres G, Römbke, J & Van der Putten W. (2010). European Atlas of Soil Biodiversity. Publications Office of the European Union.
⁴ Wachira, PM, Kimenju JW, Okoth SA, Kiarie JW. 2014. Conservation and Sustainable Management of Soil Biodiversity for Agricultural Productivity . Sustainable Living with Environmental Risks. , Japan: Springer
⁵ Jones, R.J.A., Verheijen, F.G.A., Reuter, H.I., Jones, A.R., 2008. Environmental Assessment of Soil for Monitoring Volume V : Procedures & Protocols.
⁶ Van Straalen, N. M. 1998. Evaluation of bioindicator systems derived from soil arthropod communities. Applied Soil Ecology, 9(1), 429-437.
⁷ Degens, B. P., & Harris, J. A., 1997. Development of a physiological approach to measuring the catabolic diversity of soil microbial communities. Soil Biology and Biochemistry, 29(9), 1309-1320.
⁸ Campbell, C. D., Chapman, S. J., Cameron, C. M., Davidson, M. S., & Potts, J. M. 2003. A rapid microtiter plate method to measure carbon dioxide evolved from carbon substrate amendments so as to determine the physiological profiles of soil microbial communities by using whole soil. Applied and environmental microbiology, 69(6), 3593-3599.Ceccato, P., Flasse, S., Tarantola, S., Jacquemoud, S., Grégoire, J.-M., 2001. Detecting vegetation leaf water content using reflectance in the optical domain. Remote sensing of environment 77, 22–33.
⁹ Wall, D. Neilsen, U. Six, J. 2015. Soil biodiversity and human health. Nature 528, 69-76.

Useful links

• FAO UN - Soil biodiversity portal
• FAO UN - Agriculture and soil biodiversity
• FAO UN - What is soil biodiversity (1998)
• FAO UN - Soil biodiversity and sustainable agriculture (2002)

What is Soil Contamination?

Soil contamination is the occurrence of contaminants in soil above a certain level causing deterioration or loss of one or more soil functions.¹ It occurs in 2 forms:

• ‘Point pollution’, caused by a specific event or series of events to a particular place, such as a former factory site. This is relatively well mapped and understood.
• ‘Diffuse pollution’, this involves low levels of contaminants spread over very wide areas that become lodged in the soil as it acts as a sink. This is difficult to analyze and track. Examples of such contaminants would be heavy metals or herbicides or pesticides used in agriculture.

Soil pollutants can consist of various forms, such as organic and inorganic or particulate pollutants.²

Where does it occur?

Heavy metal content in European soils3

As the name suggests point pollution can be found in particular places, such as ex-industrial land, or areas subject to accidental spillage of contaminants. Diffuse pollution is much more widely spread but as the maps below illustrate there is great variation between nations and areas depending on the practices that give rise to this form of contamination.

There may be as many as 2.5 million potentially contaminated sites across Europe, which need to be investigated. Of these, approximately 14% (340,000 sites) are expected to be contaminated and likely to require remediation. Approximately one-third of these contaminated sites have already been identified and around 15% have been remediated.⁴

What causes it?

Human activities

The most important sources of contamination in soils are those connected with human activities. Examples of point pollution include metal mining and smelting, industrial production, waste disposal and diffuse pollution examples include industrial activities, car emissions, application of agrochemicals, manure containing veterinary drugs, etc.

Municipal and industrial wastes contribute most to soil contamination (37%), followed by the industrial/commercial sector (33%). Mineral oil and heavy metals are the main contaminants contributing around 60% to soil contamination. In terms of budget, the management of contaminated sites is estimated to cost around 6 billion Euros (€) annually.⁵

How can it be measured or assessed?

The table below shows the list of indicators for soil pollution.^{6, 7}

How can it be prevented or remediated?

Soil contamination can pose a direct threat to human well-being, with prevention being the focus of most policy measures.  The table below shows a Draft outline of a strategy for sustainable land management

Case Study Experiments

Guadiamar, Spain

Reduction in contamination through amendment additions and afforestation

Copşa Mică, Romania

Immobilization of heavy metals using soil amendments

How does it interact with other soil threats?

Soil contamination leads to decreased activity of soil biodiversity and therefore to a decline of aggregate stability and in decomposition processes. Strong correlation can also be seen between contamination and erosion. A decline in aggregate stability and organic matter caused by soil pollutants increases the erodibility and therefore the risk of wind and water erosion. Landslides, flooding, wind and water erosion may also lead to pollutants being transported off site as solutes or particles and in turn pollute the connected aquatic environment or soils downslope.

How does it affect soil functions?

• Biomass production - a contaminated soil loses the productivity and the capacity to support plants properly.
• Storing, filtering and transforming – these functions are all disrupted or prevented in contaminated soil. In particular, organic matter decomposition can be disrupted affecting the cycling of nutrients.
• Gene pool (biodiversity) - plants, micro-organisms and enzyme activity in the soil is disrupted and lessened in contaminated soil, leading to a decline in soil biodiversity.

Fact sheet

References

¹ JRC.2014. Soil themes: soil contamination. http://eusoils.jrc.ec.europa.eu/library/ themes/contamination/ (last accessed at 29.07.2014)

² Mirsal, I.A., 2008. Soil Pollution.Origin Monitoring & Remediation.2nd Edition. Springer-Verlag, Berlin

³ Lado, L. R., Hengl, T., & Reuter, H. I. 2008. Heavy metals in European soils: A geostatistical analysis of the FOREGS Geochemical database. Geoderma, 148(2), 189-199.

⁴ JRC. 2014. Progress in the management of Contaminated Sites in Europe. http://eusoils.jrc.ec.europa.eu/ESDB_Archive/eusoils_docs/other/EUR26376EN.pdf (last accesed at 25/02/2016).

⁵ Panagos P, Liedekerke MV, Yigini Y, Montanarella L. 2013. Contaminated sites in Europe: review of the current situation based on data collected through a European network. Journal of Environmental and Public Health. Article ID 158764.

⁶ Huber, S., Prokop, G., Arrouays, D., Banko, G., Bispo, A., Jones, R., Kibblewhite, M., Lexer, W., Möller, A., Rickson, J., Shishkov, T., Stephens, M., Van den Akker, J., Varallyay, G., Verheijen, F., 2008. Indicators and Criteria report. ENVASSO Project (Contract 022713) coordinated by Cranfield University, UK, for Scientific Support to Policy, European Commission 6th Framework Research Programme.

⁷ De la Rosa, D., Sobral, R., 2008, Soil quality and methods for its assessment, Land use and soil resources, Springer, pp. 167-200.

⁸ Shayler, H. et al , 2009 Sources and Impacts of Contaminants in Soils

Useful links

• FAO UN - Assessing soil contamination: A reference manual (2000)
• FAO UN - Soil contamination leaflet - World Soil Day (2016)
• Environment Agency - Land contamination: Technical guidance
• Everything Connects - Soil pollution
• Environmental Pollution Center - What is soil pollution

What is loss of organic matter in peat soils?

A decline of soil organic matter in peats soil across Europe is mainly due to mineralisation (biochemical decomposition). Drainage to reclaim peatlands results in subsidence and decomposition of the peat. Peatlands are one of the major stocks of carbon (C) in the world and the loss of organic matter in peat soils, turn them into a major source of CO₂ and N₂O.

Where does it occur?

It is estimated that the EU (27) had in 2008 about 229 000 km2 peat soils with a conservative estimated C stock of 18 700 Mton of C. CO₂ emission of drained peat soils of the EU (27) is estimated at 173 Mton CO₂ per year, which means that the European Union is, after Indonesia and before the Russian Federation, the world’s second largest peatland emission hotspot. 

Relative cover (%) of peat and peat-topped (0 – 30 cm) soils in the SMUs of the European Soil Database3

More than 50% of this peat area is in just a few northern European countries (Norway, Finland, Sweden, United Kingdom) and the remainder mainly in Ireland, the Netherlands, Germany, Poland and the Baltic states. Of this area, approximately 50% has already been drained, while most of the undrained areas are in Finland and Sweden. It is estimated that the decline of organic matter (OM) in drained agricultural peat soils due to mineralisation is about 10-20 tonnes OM per hectare per year.

What causes it?

Human activities
A major reason for the decline in organic matter in peat is reclamation and drainage of peat soils for forestry and agricultural land and feed and food production. Fen peat soils are particularly suited for agricultural use and practices, such asthe drainage, cultivation, liming and fertilizer use, has causesd rapid mineralisation of organic matter.

Climatic factors
It is predicted that climate change will have a major impact on peat soil degradation and increase CO₂ emissions, partly due to the increase of decomposition rate by the temperature rise, and mainly by the more often occurrence of long periods with extreme drought. Climatic conditions in natural peatland areas can gradually change from favourable for peat growth into peat degrading conditions.

How can it be measured or assessed?

 The table below lists key indicators, purpose of the indicator, methods and corresponding references for measuring peat stocks.

How can it be prevented or remediated?

Much of the decline in organic matter caused by peatland drainage can be reversed by raising water tables to the land surface, a process known as rewetting. This will exclude agricultural use and to a large extent also forestry. There is no universal strategy for rewetting a drained peatland, however, malpractices can result in a boost of GHG emissions and severe pollution of surface waters. Other major constraints are the costs and the lack of water now or in the future due to climate change. Specifically, rewetting of agricultural peat soils can be very costly and de facto impossible due to socio-economic and cultural, historic reasons. There can be various causes for the drained conditions, and the rewetting options vary widely depending on climate, water availability and topography. 

An alternative experimental measure is cropping and afforesting on wet and rewetted peatlands with crops adapted to the wet soil conditions, known as Paludiculture, which may maintain and add organic matter to peatlands.

Case Study Experiments

How does it interact with other soil threats?

Natural peat soils are hotspots of biodiversity. As the source of energy underpinning food-webs, a decline in OM may lead to reduced biodiversity. Natural peatlands and even not completely degraded peat lands store water and act as a sponge. They absorb and retain water during periods with a surplus of precipitation and slowly release water in times of water deficit. In this way, peat lands slow down peak discharge and reduce incidences of flooding and prevent water erosion. Degraded peat soils in arable agriculture or in overgrazed grassland are vulnerable to water and wind erosion. Water erosion is especially a problem in overgrazed blanket peats. Wind erosion is a serious problem on peat soils in arable agriculture.

How does it affect soil functions?

• Biomass production - Oxidation of peat soils results not only in emissions of CO₂, but also in mineralization of N, which makes the degradation of peat soils an important supply of nutrients and therefore can increases food and biomass production considerably. However, on-going oxidation and loss of peat results in time in the total loss of the peat layer. The level of biomass production then depends on the fertility and soil physical properties of the soil underneath the original peat layer, many of which are acid.
• Storage/filtering/transforming - Peat soils have a high storage, filtering, buffering and transformation capacity. Loss of peat results in loss of these capacities, especially the storage of C.
• Gene pool (biodiversity) Drainage of natural peat soils results in a significant change in biodiversity and more so in peatland meadows than peat soils in arable agriculture.
• Cultural heritage - Peat soils are by nature historical archives and can store artefacts of ancient cultures and human bodies. Drainage and oxidation of peat results in a total loss of this historical archive. On the other hand in e.g. the Netherlands the historic drained peat meadow landscape is also considered part of the cultural heritage.

References

¹ Montanarella, L., Jones, R.J.A. and Hiederer, R., 2006. The distribution of peat land in Europe. Mires and Peat, 1, 1-10. http://mires-and-peat.net/pages/volumes.php
² Couwenberg, J., J. Augustin, D. Michaelis and H. Joosten, 2008. Emission reductions from rewetting of peat lands - Towards a field guide for the assessment of greenhouse gas emissions from Central European peat lands. Duene /Greifswald University, Report RSPB, Bedfordshire, 28 pp
³ Hendriks, R.F.A., Wolleswinkel, R.J. and Van den Akker, J.J.H., 2008. Predicting greenhouse gas emission in peat soil depending on water management with the SWAP-ANIMO model. Proceedings 13th International Peat Congress, Tullamore, Ireland, International Peat Society.

Useful links

• FAO UN - The importance of soil organic matter: Key to drought-resistant soil and sustained food production (2005)
• European Communities - Organic matter decline (2009)
• University of Minnesota Extension  - Organic matter management
• US Department of agriculture: Soils and Men, Yearbook of Agriculture; Loss of Soil Organic Matter and Its Restoration By William A. Albrecht (1938)

RECARE Project - FLOODING IN NORWAY (English subtitles) 
 

What are Floods and Landslides?

Where do they occur?

The maps below show the combination of the potential damage and the risk of flooding and a general schematic summary of the flood changes observed in Europe.

Flood damage potential in the European Union. (Source: http://floods.jrc.ec.europa.eu)		Arrows in the schematic indicate the majority of flooding trends, including regions with weak and/or mixed change patterns. Areas with no/inconclusive studies due to insufficient data (e.g., Italy) and inconclusive change signals (e.g., Sweden) are not shown – Hall et al. (2014).

Landslides are dominantly considered as a local soil threat in mountainous regions and on slopes. Hazards posed by landslides are accidental and dynamic. Landslides are increasingly recognised as a severe problem, as evidenced by the numerous studies that try to assess the most susceptible areas all over Europe.⁶

 Landslide susceptibility map of Europe 6 7

What causes them?

The driving forces/pressures for flooding and landslides are of natural, social, economic, and ecological origins which interact in complex ways

Climate and climate change.
Climate and climate change controls precipitation and snowmelt (frequency, intensity and magnitude, seasonality, cyclonality and the respective changes), and are the most important external drivers for landslides and flooding.

Land use changes.
One of the main socio-economic drivers for flooding and landslides are changes in land use. Changes from grassland to arable farming systems, field drainage, changes in forest covers and soil sealing can all increase runoff and incidences of flooding. Decreases in vegetation/forest cover can increase landslide activity and soil loss and the abandonment of the lands in the terraced slopes in the Mediterranean environment of southern Europe has led to an increase in shallow landslide activity.

How can they be measured or assessed?

 The table below lists key indicators, purpose of the indicator and methods for measuring flooding and landslides.

How can it be prevented or remediated? 

Floods and landslides are distinctive soil threats, as the measures for prevention and remediation, can be very local but often involve coordination across national borders. The actors can range from householders taking out insurance and moving their possessions to upper floors of their homes through to transnational integration of river basin management.

Italics – landslides non-italic flooding

​​​​​​Case Study Experiments

Vansjø-Hobøl Catchment, Norway

Preventing floods and landslides

Myjava Catchment

Mitigating muddy floods and soil erosion

How do they interact with other soil threats?

Effects of flooding
Small and large-scale temporary flooding of soil can cause significant soil deterioration effects. Floods over slopes in the form of overland flow, sheet flow, return flow, groundwater ridging, etc. are obviously connected to soil erosion and landslides. The floodwater along with saturated conditions may destroy soil macropores and the soil organisms that create a soil’s structure. Under such conditions, the soil can be more susceptible to compaction, crusting, and high bulk-density problems. Floodwaters are likely to be contaminated, with for example sewage and as such may pose health risks to citizens exposed to pathogens in these waters and soil. There are many adverse effects of flooding on plant growth; all the developmental stages of flood-intolerant plants are affected, including; the inhibition of seed germination, vegetative and reproductive growth, and changes in plant anatomy. Floods may lead to a decline in soil biodiversity if anaerobic conditions prevail and flood-related waterlogging may potentially lead to local salinization.

Effects of landslides
The linking of landslides to soil erosion by water is evident as landslides can be seen as a primary source of erosion by increasing the sediment yield in the drainage basins where they occur. Landslides can also be seen as a secondary source of erosion, since the material that accumulates in the deposition area is looser than in the neighbouring areas. In human-modified environments, especially industrial sites and areas that have been intensively cultivated, if a landslide occurred, it would most probably lead to the increase of erosion potential and release and transport of contaminating substances. Short-lived landslide dams that form and fail within the duration of a rainfall-induced flood event in mountainous environments can generate flash floods or aggravate flooding in a basin.

How do they affect soil functions?

Biomass production - Floods will affect food production either through soil erosion and the leaching of nutrients (usually upstream), or by the inundation and siltation of agricultural land (usually downstream). In the case of landslides that affect cultivated or natural areas, food, biological and environmental functions are lost in a very short period. However, landslides can lead to a rejuvenation of soils favouring the development of new biological and ecological systems and the restoration of soil functions in a short time period (< 5 years).

Physical basis - Soil as a platform for man-made structures (such as buildings and highways) is affected by floods, but most often the impact is not attributed to the soil itself. The soil is, in these cases, usually covered by an infrastructure (road, foundations, and urban sealed surfaces). Foundations exposed to (repeated) flooding are not supported by subsoil from the  bottom or cannot reach their design bearing capacity due to the  lack of soil overburden. Erosion can lead to the loss of a significant  soil volume below foundation structures, thus producing deformations  and cracks in the superstructure. An uneven settlement or a collapse of the whole structure can occur. The effects of landslides are similar to those listed for floods, affecting the stability and functionality of the structure and sometimes completely destroying it. 

Useful links

References

¹ WMO: International glossary of hydrology, 2012. WMO-No. 385, World Meteorological Organization. ISBN 978-92-63-03385-8, 1-461.

² Jackson, B.M., Wheater, H.S., McIntyre, N.R., Chell, J., Francis, O.J., Frogbrook, Z., Marshall, M., Reynolds, B., Solloway, I., 2008. The impact of upland land management on flooding: insights from a multiscale experimental and modelling programme. Journal of Flood Risk Management, 1, 71–80.

³ Huber, S., Prokop. G., Arrouays. D., et al., 2008. Environmental assessment of soil for monitoring. Volume I indicators & criteria. EUR 23490 EN/1, Office for the Official Publications of the European Communities, Luxembourg, DOI 10.2788/93515, 339pp.

⁴ Hungr, O., Evans, S.G., Bovis, M., Hutchinson, J.N., 2001. Review of the classification of landslides of the flow type. Environmental and Engineering Geoscience, 7, 221.

⁵ Hall, J., Arheimer, B., Borga, M., Brázdil, R., Claps, P., Kiss, A., Kjeldsen, T.R., Kriaučiūnienė, J., Kundzewicz, Z.W., Lang, M., Llasat, M.C., Macdonald, N., McIntyre, N., Mediero, L., Merz, B., Merz, R., Molnar, P., Montanari, A., Neuhold, C., Parajka, J., Perdigão, R.A.P., Plavcová, L., Rogger, M., Salinas, J.L., Sauquet, E., Schär, C., Szolgay, J., Viglione, A., Blöschl, G., 2014, Understanding flood regime changes in Europe: a state-of-the-art assessment. Hydrol. Earth Syst. Sci., 18, 2735-2772.

⁶ Günther, A., Reichenbach, P., Malet, J. P., Van Den Eeckhaut, M., Hervás, J., Dashwood, C., Guzzetti, F., 2013. Tier-based approaches for landslide susceptibility assessment in Europe. Landslides, 10, 529-546.

⁷ Panagos, P., Van Liedekerke, M., Jones, A., Montanarella, L., 2012. European Soil Data Centre: Response to European policy support and public data requirements. Land Use Policy, 29, 329-338.

⁸ Fressard, M., Thiery, Y., Maquaire, O., 2014. Which data for quantitative landslide susceptibility mapping at operational scale? Case study of the Pays d’Auge plateau hillslopes (Normandy, France). Natural Hazards and Earth System Sciences, 14, 569-588.

⁹ Guzzetti, F., Reichenbach, P., Cardinali, M., Galli, M., Ardizzone, F., 2005. Probabilistic landslide hazard assessment at the basin scale. Geomorphology, 72, 272-299

¹⁰ Guame, e. et al 2009. A compilation of data on European flash floods. Journal of Hydrology. Vol 367, 1–2, 70-78
 

• FAO UN - FAO in emergencies: Landslides
• FAO UN - FAO in emergencies: Floods
• FAO UN - Forests and landslides (2011)