Indicator Assessment

Soil organic carbon

Indicator Assessment

Prod-ID: IND-195-en

Also known as: LSI 005 , CLIM 027

Published 08 Sep 2008 Last modified 11 May 2021

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Topics: Climate change mitigation Soil

This page was archived on 25 Aug 2017 with reason: A new version has been published

Soil in the EU contains around 71 gigatonnes of organic carbon, nearly 10 % of the carbon accumulated in the atmosphere. An increase in temperature and a reduction in moisture tend to accelerate the decomposition of organic material, leading to a decline in soil organic carbon stocks in Europe and an increase in CO₂ emissions to the atmosphere. This could wipe out all the savings that other sectors of the economy are achieving to reduce anthropogenic greenhouse gas emissions.
Losses of soil organic carbon have already been observed in measurements in various European regions over the past 25 years.
The projected changes in the climate during the 21st century will change the contribution of soil to the CO₂ cycle in most areas of the EU. Adapted land-use and management practices could be implemented to counterbalance the climate-induced decline of carbon levels in soil.

Update planned for November 2012

Changes in soil organic carbon content across England and Wales between 1978 and 2003

Note: The map shows the difference in soil organic carbon content

Data source:

Bellamy, P. H.; Loveland, P. J.; Bradley, R. I.; Lark, R. M. and Kirk, G. J. D., 2005. Carbon losses from all soils across England and Wales 1978-2003. Nature 437: 245248.

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Projected changes in soil organic carbon for cropland 1990-2080

Note: Predicted changes in soil organic carbon for croplands 1990–2080. The image on the left shows changes due to climate change only while the map on the right shows changes as a result of variations in net primary production and the advent of new technologies related to crop management (e.g. machinery, pesticides, herbicides, agronomic knowledge of farmers) and breeding (development of higher yielding varieties through improved stress resistance and/or yield potential) that result in yield increases.

Data source:

Smith, P.; Smith, J.; Wattenbach, M.; Meyer, J.; Lindner, M.; Zaehle, S.; Hiederer, R.; Jones, R. J. A.; Montanarella, L.; Rounsevell, M.; Reginster, I. and Kankaanpää, S., 2006. Projected changes in mineral soil carbon of European forests, 1990-2100. Canadian Journal of Soil Science 86: 159169.

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Past trends

In the past, losses in organic carbon in the soil were driven mainly by conversion of land for the production of agricultural crops. A survey of Belgian croplands (210 000 soil samples taken between 1989 and 1999) indicates a mean annual loss in organic carbon of 76 gCm^-2 (Sleutel et al., 2003). A large-scale inventory in Austria estimated that croplands were losing 24 gCm^-2 annually (Dersch and Boehm, 1997). The general intensification of farming in the past is likely to have exceeded the effect of changes in the climate on soil organic carbon on agricultural land. Peat lands in Europe have been a significant sink for atmospheric CO₂ since the last glacial maximum. Currently they are estimated to hold about 42 Gt carbon, about 60 % of all carbon stocked in European soils, and are therefore a considerable component of the European carbon budget (Byrne et al., 2004). The annual loss of carbon due to drainage of peat lands is in the range of 0 to 47 gCm^-2 (Lappalainen, 1996).

Projections

The amount of organic carbon in the soil is determined mainly by the balance between net primary production (NPP) from vegetation and the rate of decomposition of the organic material. Without an increase in NPP, soil carbon for cropland may decrease by 9 to 12 t C ha^-1. When taking account of changes in NPP and technological advances, the amount of organic carbon on cropland could increase by 1-7 t C ha^-1 (Smith, et al., 2005). Figure 2 shows that climate change may cause loss (red) of soil organic carbon for most areas in Europe. This decline could be reversed (blue) if adaptation measures in the agricultural sector to enhance soil carbon were implemented. It should be noted that these modelled projected changes are very uncertain.

Supporting information

Indicator definition

Changes in soil organic carbon content across England and Wales between 1978 and 2003
Projected changes in soil organic carbon for cropland 1990-2080

Units

http://www.eea.europa.eu/publications/eea_report_2008_4/pp111-148CC2008_ch5-7to9_Terrestrial_ecosystems_soil_and_agriculture.pdf

Rationale

Justification for indicator selection

Organic carbon in the soil is a dynamic part of the carbon cycle, which includes the atmosphere, water and constituents of the above- and below-ground biosphere. The main source of organic carbon is organisms that synthesise their food from inorganic substances (autotrophic), such as photosynthesising plants. In this process atmospheric carbon is used to build organic materials and enters the soil layers through decomposition and the formation of humus.
Climatic conditions strongly influence both the trends and rates of accumulation and transformation of organic substances in the soil. Increases in temperature and aridity lead to a decrease in the amount of organic carbon in soils in affected areas. Lower levels of organic carbon in the soil are generally detrimental to soil fertility and water retention capacity and tend to increase soil compaction, which leads to increases in surface water runoff and erosion. Other effects of lower organic carbon levels are a depletion of biodiversity and an increased susceptibility to acid or alkaline conditions. The projected changes will accelerate the release of CO₂ from the soil, contributing to higher concentrations in the atmosphere (Janssens, 2004; Bellamy, 2005). The main measures to reduce the detrimental effect of higher temperatures combined with lower soil moisture on the amount of soil organic carbon are changes in land cover and adaptation of land-management practices (Liski et al., 2002; Janssens et al., 2004; Smith et al., 2005, 2006). Under given climatic conditions, grassland and forests tend to have higher stocks of organic carbon than arable land and are seen as net sinks for carbon (Vleeshouwers and Verhagen, 2002). Land-management practices aim at increasing net primary production and reducing losses of above-ground biomass from decomposition. Adaptive measures on agricultural land are changes in farming practices, such as a reduction in tilling or retaining crop residues after harvesting.

Scientific references

No rationale references available

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 aim is to increase the resilience to climate change of health, property and the productive functions of land, inter alia by improving the management of water resources and ecosystems. More knowledge is needed on climate impact and vulnerability but a considerable amount of information and research already exists which can be shared better through a proposed Clearing House Mechanism. The White Paper stresses the need to mainstream adaptation into existing and new EU policies. A number of Member States have already taken action and several have prepared national adaptation plans. The EU is also developing actions to enhance and finance adaptation in developing countries as part of a new post-2012 global climate agreement expected in Copenhagen (Dec. 2009). For more information see: http://ec.europa.eu/environment/climat/adaptation/index_en.htm

Targets

No targets have been specified

Methodology

Methodology for indicator calculation

http://www.eea.europa.eu/publications/eea_report_2008_4/pp111-148CC2008_ch5-7to9_Terrestrial_ecosystems_soil_and_agriculture.pdf

Methodology for gap filling

http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf

Data sets uncertainty

http://www.eea.europa.eu/publications/eea_report_2008_4/pp193-207CC2008_ch8_Data_gaps.pdf

Rationale uncertainty

No uncertainty has been specified

Data sources

National Soils Inventory (NSI)
provided by Cranfield University (National Soil Resources Institute)

Other info

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

Indicator codes

LSI 005
CLIM 027

EEA Contact Info info@eea.europa.eu

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Geographic coverage

Austria Belgium Czechia Denmark Finland France Germany Greece Ireland Italy Luxembourg Netherlands Norway Portugal Slovenia Spain Sweden Switzerland United Kingdom England (England, UK) Europe Wales (Wales, UK)