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Indicator Specification
Data and indicators on the extent of, and change in, soil sealing or imperviousness (used synonymously) are important for a number of highly policy relevant issues. Imperviousness is defined as the covering of the soil surface with impervious materials as a result of urban development and infrastructure construction (buildings, constructions and layers of completely or partly impermeable artificial material, e.g. asphalt, metal, glass, plastic or concrete).
Changes in imperviousness can document land use intensification or land-cover/land-use change due to urban or industrial development and related increases in traffic infrastructure. All these changes have potentially significant implications for biodiversity, soil functions, hydrological properties, provision of ecosystem services and nature conservation. In particular, exchanges of energy, water and gases are restricted, and pressure on adjacent, non-sealed areas is increased. Until recently, the only European dataset available to indirectly document changes in imperviousness was Corine Land Cover (CLC). However, the associated ‘land take’ indicator covers a lot of surface that is not actually sealed. The imperviousness indicator supplements this ‘land take’ indicator, by providing information with a higher spatial resolution, based on a more direct measurement of imperviousness, and with a shorter update cycle.
Available dataset/indicator |
Spatial resolution/minimum mapping unit (MMU) |
Reference year/update cycle |
Main characteristics |
Suggested use case |
CLC status layer, classes 1** (Artificial surfaces) |
25 ha MMU |
1990, 2000, 2006, 2012 (currently six year update cycle) |
Vector and Raster versions. Long time series, 11 level 3 sub classes for artificial surfaces are distinguished |
Detailed, pan-European overview on land cover/land use, not limited to issues of land take and soil sealing. Not to be used for change mapping. |
CLC change products |
5 ha MMU |
1990-2000, 2000-2006, 2006-2012 |
Vector product. Best available detailed change information on pan-European land use and land cover. |
Analysis of change between CLC reference years. Analysis of land cover flows (not limited to artificial surfaces) |
Land take indicator |
5 ha MMU (from CLC change product) |
2000-2006, 2006-2012 |
Published indicator (not spatial dataset), based on aggregation of certain types of land cover flows in 1 km grid cells (LEAC CUBE) Captures the change in the amount of agriculture, forest and other semi-natural and natural land taken by urban and other artificial land development (in ha or km2). Results are presented as average annual change, percentage of total area of the country and percentage of the various land cover types taken up by urban development. |
Statistical and spatial analysis of land take, including extent, spatial pattern and dynamics (which land use/cover changed into which artificial land use class). Use as a proxy for sealing is not appropriate. |
Imperviousness indicator |
20 m spatial resolution (grid) |
2006-2009 2009-2012 (currently three year update cycle) |
Published indicator, based on the Copernicus high resolution layer (HRL) imperviousness (IMD). Yearly average change in IMD in percentage imperviousness, relative to the size of the reference unit. |
Spatially very detailed extent and pattern of soil sealing/ imperviousness. Limitation: no information on types of land cover/land use (besides percentage sealing change). Best analysed together with land take indicator and existing absolute sealing levels. |
The imperviousness indicator is defined as the yearly average imperviousness change between two reference years, as measured by imperviousness change products. The change is aggregated for a certain reference unit, and expressed and relative to the size of said unit (as a percentage). The imperviousness change value for a 100 m raster cell is based on 100 m imperviousness change products, corresponding to the difference in imperviousness status values (e.g. IMD2009-IMD2006). The default reference unit is the country, but the indicator can be aggregated based on different spatial units. For example, for a certain country, an imperviousness indicator value of 0.2 %, means that an additional 0.2 % of this country's area has been sealed annually during the period between the two reference years in question. If above a certain rate of increase (threshold values), this value can be used as a warning sign. The aggregation of imperviousness values to reference units is performed using the LEAC CUBE method.
The unit used for this indicator is the yearly average percentage change in imperviousness relative to the size of the reference unit. This was initially based on the total difference over the three reference years (2006-2009) divided by three, but it will be possible to calculate the indicator for different periods at a later stage (e.g. 2006-2012). It is important to note that the yearly average value is based specifically on the period 2006-2009.
The main policy objective of this indicator is to measure the extent and dynamics (change) of soil sealing, resulting from the development of urban and other artificial land uses.
At the United Nations Conference on Sustainable Development, held in Rio in 2012 (Rio+20), world leaders identified land and soil degradation as a global problem and committed to "strive to achieve a land degradation neutral world in the context of sustainable development”. At EU level, the 7th Environment Action Programme (7th EAP) includes a strong focus on unsustainable use of land and soil, including explicitly the issue of soil sealing. In this context the 7th EAP refers to a Commission Staff Working Document with the title "Guidelines on best practice to limit, mitigate or compensate soil sealing" (SWD/2012/0101).
In addition, land take is explicitly mentioned in chapter 23 of the 7th EAP, stating that "Every year more than 1 000 km² of land are taken for housing, industry, transport or recreational purposes. Such long-term changes are difficult or costly to reverse, and nearly always involve trade-offs between various social,economic and environmental needs. Environmental considerations including water protection and biodiversity conservation should be integrated into planning decisions relating to land use so that they are made more sustainable, with a view to making progress towards the objective of “no net land take”, by 2050."
In recognition of the importance of land in safeguarding natural resources, the Commission is considering a Communication on land as a resource.
Other important references can be found in 'A Sustainable Europe for a Better World: A European Union Strategy for Sustainable Development' (COM(2001)264) and the thematic documents related to it, such as the Commission Communication 'Towards a Thematic Strategy on the Urban Environment' (COM(2004)60), Cohesion Policy and Cities: the urban contribution to growth and jobs in the regions (COM(2006)385), Europe 2020 (COM(2010)2020), general provisions on the European Regional Development Fund, the European Social Fund and the Cohesion Fund Council Regulation (EC) No 1083/2006, as well as the concept of territorial cohesion.
Although, there are no quantitative targets for soil sealing/imperviousness at European level, different documents reflect the need for better planning to control urban growth and the extension of infrastructures. Policies relating explicitly to land-use issues, and especially physical and spatial planning, have, until now, generally been the responsibility of the authorities in Member States. The European Commission's Roadmap to a Resource Efficient Europe (COM(2011) 571) introduces, for the first time, a 'no net land take by 2050' initiative that would imply that all new urbanisation will either occur on brownfields or that any new land take will need to be compensated by reclaiming artificial land.
European policy, although it has no spatial planning responsibility, sets the framing conditions for planning. At European level, the 1999 European Spatial Development Perspective (ESDP), a non-binding framework that aims to coordinate various European regional policy impacts, already advocates the development of a sustainable, polycentric and balanced urban system with compact cities and a strengthening of the partnerships between urban and rural areas; parity of access to infrastructure and knowledge; and wise management of natural areas and cultural heritage. The 2008 Green Paper on territorial cohesion, and the 2007 EU Territorial Agenda and Action Plan by the Territorial Agenda of the EU and the Action programme for its implementation (COPTA, 2007) build further on the ESDP. Specific, relevant actions in the field of ‘Land’, in particular are Action 2.1d: ‘Urban sprawl’ and Action 2.2 ‘Territorial impact of EU policies’.
Demand for new urban areas may be partly satisfied by brownfield remediation. Its environmental advantages are clear: relieving pressure on rural areas and greenfield sites, reducing pollution costs, more efficient energy use and natural resource consumption, facilitating economic diversification and emerging habitat (housing) requirements. Europe has several examples of regional strategies for economic regeneration and brownfield development (The OECD Territorial Outlook 2001) and recycling of artificial surfaces in several countries reach 30 % or more compared to the total land take area (CORINE LC 2006 results). Stronger links between EU urban and soil policies could encourage this further (e.g. following up respective 6th EAP Thematic strategies).
No methodology references available.
No uncertainty has been specified
Work specified here requires to be completed within 1 year from now.
Work specified here will require more than 1 year (from now) to be completed.
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/imperviousness-change or scan the QR code.
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