Soil moisture

Assessment versions

Published (reviewed and quality assured)

• Soil moisture (CLIM 029) - Assessment published Nov 2012

Justification for indicator selection

The ability of soil to retain moisture is a significant aspect in the water cycle and is crucial for primary production. The amount of water held in soil is intrinsically linked to our climate and depends largely on texture, structure and the amount of soil organic matter. Variations in any of these variables will affect soil water retention characteristics and ultimately soil functions (e.g. groundwater recharge).

By absorbing many times its weight in water, soil organic matter in mineral soils can contribute to the mitigation of flooding following extreme rainfall events while storing water in the event of more frequent and severe droughts. At low soil carbon contents, an increase in carbon content leads to an increase in water retention in coarse soils and a decrease in fine-textured soils. At high carbon contents, an increase in carbon content results in an increase in water retention for all soil textures.

While water-holding capacity is an intrinsic soil property based on clay content, structure and organic matter levels, water content is highly dynamic and is the balance between rainfall and evapotranspiration. Changes in temperature and precipitation patterns and intensity will affect evapotranspiration, soil moisture and infiltration rates. Conversely, there is also observational evidence that soil moisture deficit exacerbates hot extremes in south-eastern Europe.

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

• Global surface soil moisture content based on remote sensing data

Units

• m³/m³

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

The satellite-borne sensor from the SMOS (Soil Moisture and Ocean Salinity) mission is used to make global observations of surface soil moisture. Launched in 2009, SMOS looks at microwave radiation emitted from Earth to calculate the amount of moisture held in the surface layer of soil, up to a depth of about 5 cm.

Methodology for gap filling

Not applicable

Methodology references

• Kerr et al. 2000: The Second of ESA's Opportunity Missions: The Soil Moisture and Ocean Salinity Mission – SMOS Kerr, Y., Font, J., Waldteufel, P., Berger, M., (2000). ESA Earth Observation Quarterly, 66, 18f. 

Data specifications

EEA data references

• No datasets have been specified here.

External data references

• Soil moisture and ocean salinity
• Daily Soil Moisture of Europe

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 . 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