Soil organic carbon

Assessment versions

Published (reviewed and quality assured)

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

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.

Indicator definition

• Variations in topsoil organic carbon content across Europe

Units

• Carbon content [%]

Policy context and targets

Context description

Targets

No targets have been specified.

Related policy documents

• Climate-ADAPT: Mainstreaming adaptation in EU sector policies
  Overview of EU sector policies in which mainstreaming of adaptation to climate change is ongoing or explored
• Climate-ADAPT: National adaptation strategies
  Overview of activities of EEA member countries in preparing, developing and implementing adaptation strategies
• DG Climate Action: What is the EU doing about climate change?
  Activities of the EU regarding climate change (both mitigation and adaptation)
• White paper - Adapting to climate change: towards a European framework for action
  EU framework for adaptation to climate change, leading to a comprehensive EU adaptation strategy by 2013

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.

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• European Soil Database 2003

Data sources in latest figures

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