Soil organic carbon (CLIM 027) - Assessment published Nov 2012

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Created : Nov 12, 2012 Published : Nov 20, 2012 Last modified : Nov 20, 2012 04:26 PM

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Sep 08, 2008 - Soil organic carbon (CLIM 027) - Assessment published Sep 2008

Generic metadata

Topics:

Climate change (Primary topic)

Tags:

climate change | land use | carbon | soil

DPSIR: Impact
Typology: Descriptive indicator (Type A – What is happening to the environment and to humans?)

Indicator codes

CLIM 027

Dynamic

Temporal coverage:

2003

Geographical coverage:

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Austria Belgium Bosnia and Herzegovina Bulgaria Croatia Cyprus Czech Republic Denmark Estonia Finland France Germany Greece Hungary Ireland Italy Latvia Lithuania Luxembourg Macedonia Malta Montenegro Netherlands Norway Poland Portugal Romania Serbia Slovakia Slovenia Spain Sweden Switzerland United Kingdom

Contents

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Indicator definition

Variations in topsoil organic carbon content across Europe

Units

Carbon content [%]

Key policy question: What is the trend in soil organic carbon in Europe?

Key messages

Soil carbon stocks in the EU-27 are around 75 billion tonnes of carbon; around 50 % of which is located in Ireland, Finland, Sweden and the United Kingdom (because of the large area of peatlands in these countries).
The largest emissions of CO₂ from soils are due to conversion (drainage) of organic soils, and amount to 20–40 tonnes of CO₂ per hectare per year. The most effective option to manage soil carbon in order to mitigate climate change is to preserve existing stocks in soils, and especially the large stocks in peat and other soils with a high content of organic carbon.
On average, soils in Europe are most likely to be accumulating carbon. Soils under grassland and forests are a carbon sink (estimated up to 80 million tonnes of carbon per year) whereas soils under arable land are a smaller carbon source (estimated from 10–40 million tonnes of carbon per year).
The effects of climate change on soil organic carbon and soil respiration are complex, and depend on distinct climatic and biotic drivers. However, they lack rigorous supporting datasets.

Climate change is expected to have an impact on soil carbon in the long term, but changes in the short term will more likely be driven by land management practices and land use change

Variations in topsoil organic carbon content across Europe

Note: The map shows the percentage of organic carbon content in the surface horizon of soils in Europe. The darker regions correspond to soils with high values of organic carbon. The darkest colours, especially in Estonia, Fennoscandinavia, Ireland and the United Kingdom, denote peatlands.

Data source:

European Soil Database 2003 provided by Joint Research Centre (JRC)

Corine Land Cover 2006 raster data provided by European Environment Agency (EEA)

Downloads and more info

Key assessment

Past trends

Around 45 % of the mineral soils in Europe have low or very low organic carbon content (0–2 %) and 45 % have a medium content (2–6 %) [i]. Figure 1 shows that low levels are particularly evident in southern Europe where 74 % of the land is covered by soils that have less than 2 % of organic carbon in the topsoil (0–30 cm) [ii]. However, areas of low organic carbon can be found almost everywhere, including in some parts of more northern countries such as Belgium, France, Germany, Norway and the United Kingdom. More than 50 % of EU soil organic carbon stocks are to be found in peatlands [iii].

In general, most soils across Europe are likely to be accumulating carbon. Except under drainage conditions, grassland soils accumulate carbon, although there is a high uncertainty as to the rate. Croplands generally act as a carbon source, although existing estimates are varied. Forest soils generally accumulate carbon (estimates range from 17 to 39 million tonnes per year [iv]).

However, estimates of European CO₂, CH₄ and N₂O fluxes between 2000 and 2005, using both top-down estimates based on atmospheric observations and bottom-up estimates derived from ground-based measurements, suggest that CH₄ emissions from livestock and N₂O emissions from arable agriculture are fully compensated by the CO₂ sink provided by forests and grasslands [v].

Projections

Soil organic carbon levels are determined mainly by the balance between net primary production (NPP) from vegetation and the rate of decomposition of the organic material. While climate change is expected to have an impact on soil carbon in the long term, changes in the short term will more likely be driven by land management practices and land-use change, which can mask the evidence of climate change impact on soil carbon stocks. The effects of climate change on soil are complex and lack rigorous supporting datasets.

[i] G. Louwagie, S. H. Gay, and A. Burrell, Final report on the project ‘Sustainable Agriculture and Soil Conservation (SoCo)’ JRC Scientific and Technical Reports (Luxembourg: European Commission, Joint Research Centre, 2009).

[ii] P. Zdruli, R.J.A. Jones, and L. Montanarella, Organic Matter in the Soils of Southern Europe European Soil Bureau Technical Report. (Luxembourg: Publications Office of the European Union, 2004).

[iii] R. Schils et al., Final report on review of existing information on the interrelations between soil and climate change (Climsoil). Final Report for the European Commission’s Directorate-General for the Environment (Brussels: European Commission, 2008).

[iv] Schils et al., Final report on review of existing information on the interrelations between soil and climate change (Climsoil). Final Report for the European Commission’s Directorate-General for the Environment.

[v] E.D. Schulze et al., „Importance of methane and nitrous oxide for Europe’s terrestrial greenhouse-gas balance“, Nature Geoscience 2 (2009): 842–850, doi:10.1038/ngeo686.

Data sources

European Soil Database 2003
provided by Joint Research Centre (JRC)

Justification for indicator selection

Biomass is generated by photosynthesis binding CO₂ from the atmosphere. If not harvested, this biomass becomes incorporated into the soil after the death of the plant and through root senescence. The dead plant material is decomposed with the help of micro-organisms and CO₂ is again released into the atmosphere. Part of the carbon is converted into stable (humic) soil organic matter. However, if soil is water-saturated due to poor drainage, the breakdown of carbon is slowed down and only highly specialised microorganisms are able to decompose carbon, releasing CO₂ and CH₄. Nevertheless, wet soils and peatlands act overall as important carbon reservoirs.

Low levels of organic carbon in the soil are generally detrimental to soil fertility, water retention capacity and resistance to soil compaction. Increases in surface water run-off can lead to erosion while lack of cohesion in the soil can increase the risk of erosion by wind. Other effects of lower organic carbon levels are a reduction in biodiversity and an increased susceptibility to acid or alkaline conditions.

Scientific references:

IPCC, 2007. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007; M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds); Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Policy context and targets

Context description

In April 2009 the European Commission presented a White Paper on the framework for adaptation policies and measures to reduce the European Union's vulnerability to the impacts of climate change. The White Paper stresses the need to improve the knowledge base and to mainstream adaptation into existing and new EU policies. The European Commission will be publishing an EU Adaptation Strategy in 2013. A number of Member States have already taken action, and several have prepared national adaptation plans.

The European Commission and the European Environment Agency have developed the European Climate Adaptation Platform (Climate-ADAPT, http://climate-adapt.eea.europa.eu/) to share knowledge on observed and projected climate change and its impacts on environmental and social systems and on human health; on relevant research; on EU, national and subnational adaptation strategies and plans; and on adaptation case studies.

Targets

No targets have been specified.

Methodology

Methodology for indicator calculation

Spatial data from the European Soil Database v2.0 (soil), Global Historical Climatology Network (http://www.ncdc.noaa.gov/oa/climate/ghcn-daily/) (climate), CORINE Land Cover 1990 and USGS Global Land Cover Characterization (http://edc2.usgs.gov/glcc/glcc.php) (land cover) is displayed.

Methodology for gap filling

Not applicable

Methodology references

Jones et al. 2010: Soil Atlas of the Northern Circumpolar Region Jones, A., Stolbovoy, V., Tarnocai, C., Broll, G., Spaargaren, O. and Montanarella, L. (2010) Soil Atlas of the Northern Circumpolar Region, 144. Publications Office of the European Union, Luxembourg.

Uncertainties

Methodology uncertainty

Not applicable

Data sets uncertainty

Quantitative information, from both observations and modelling, on the past trends and impacts of climate change on soil and the various related feedbacks, is very limited. For example, data have been collected in forest soil surveys (e.g. ICP Forests, BioSoil and FutMon projects), but issues with survey quality in different countries makes comparison between countries (and between surveys) difficult (Hiederer and Durrant, 2010). To date, assessments have relied mainly on local case studies that have analysed how soil reacts under changing climate in combination with evolving agricultural and forest practices. Thus, European-wide soil information to help policymakers identify appropriate adaptation measures is absent. There is an urgent need to establish harmonised monitoring networks to provide a better and more quantitative understanding of this system. Currently, EU-wide soil indicators are (partly) based on estimates and modelling studies, most of which have not yet been validated. Nevertheless, in absence of quantification, other evidences can indicate emerging risks. For example, shifting tree lines in mountainous regions as a consequence of climate change may indicate an extinction risk of local soil biota.

Finally, when documenting and modelling changes in soil indicators, it is not always feasible to track long-term changes (signal) given the significant short-term variations (noise) that may occur (e.g. seasonal variations of soil organic carbon due to land management). Therefore, detected changes cannot always be attributed to climate change effects, as climate is only one of the soil-forming factors. Human activity can be more determining, both in measured/modelled past trends (baseline), and if projections including all possible factors were to be made. The latter points towards the critical role of effective land use and management in mitigating and adapting to climate change.

Further information on uncertainties is provided in Section 1.7 of the EEA report on Climate change, impacts, and vulnerability in Europe 2012 (http://www.eea.europa.eu/publications/climate-impacts-and-vulnerability-2012/)

Rationale uncertainty

No uncertainty has been specified

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Geertrui Veerle Erika Louwagie

Ownership

EEA Management Plan

2012 2.0.1 (note: EEA internal system)

Dates

First draft created:

Nov 12, 2012 05:13 PM

Publish date:

Nov 20, 2012 04:25 PM

Last modified:

Nov 20, 2012 04:26 PM

Permalinks

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