Imperviousness and imperviousness change in Europe

Indicator Assessment
Prod-ID: IND-368-en
Also known as: LSI 002
Created 13 Sep 2019 Published 25 Mar 2020 Last modified 25 Mar 2020
15 min read
For the reference year 2015 ,  85 861 km 2   of the total area covered by the  EEA-39 countries were mapped and categorised as 'sealed surface' in the Copernicus imperviousness product. This corresponds to 1.466 % of the total EEA-39 area. Between 2006 and 2015, soil sealing (imperviousness) in all EEA-39 countries increased  by a total of 3 859 km2 , an annual average increase of 429 km 2 . During this period, the average annual increase in soil sealing relative to country area varied from 0 % to 0.088 %. In 2015, the percentage of a countries' total area that was sealed also varied greatly, with values ranging from 16.17 % (Malta) to 0.07 % (Iceland). The highest sealing values, as a percentage of country area, occurred in small countries with high population densities, while the lowest sealing values can be found in large countries with low population densities. The average annual increase in sealing was 460 km 2 between 2006-2009, increasing to 492 km 2 for the 2009-2012 period and slowing to 334 km 2 for the 2012-2015 period. The slow-down in the sealing increase between the two reference  periods occurred in 31 out of 39 countries. The same trend is visible for sealing figures normalised by the size of the country (the % of the country newly sealed on average annually for the three periods). The most problematic situation occurs in countries where there is already a high percentage of sealing and where the annual rate of increase relative to country area is high. Even more problematic are situations where, for 2012-2015,  the rate of sealing increase is accelerating, in contrast to the general trend of a slowing rate of increase.  

Key messages

For the reference year 201585 861 km2 of the total area covered by the EEA-39 countries were mapped and categorised as 'sealed surface' in the Copernicus imperviousness product. This corresponds to 1.466 % of the total EEA-39 area.

Between 2006 and 2015, soil sealing (imperviousness) in all EEA-39 countries increased by a total of 3 859 km2, an annual average increase of 429 km2. During this period, the average annual increase in soil sealing relative to country area varied from 0 % to 0.088 %.

In 2015, the percentage of a countries' total area that was sealed also varied greatly, with values ranging from 16.17 % (Malta) to 0.07 % (Iceland). The highest sealing values, as a percentage of country area, occurred in small countries with high population densities, while the lowest sealing values can be found in large countries with low population densities.

The average annual increase in sealing was 460 km2 between 2006-2009, increasing to 492 km2 for the 2009-2012 period and slowing to 334 km2 for the 2012-2015 period. The slow-down in the sealing increase between the two reference periods occurred in 31 out of 39 countries. The same trend is visible for sealing figures normalised by the size of the country (the % of the country newly sealed on average annually for the three periods).

The most problematic situation occurs in countries where there is already a high percentage of sealing and where the annual rate of increase relative to country area is high. Even more problematic are situations where, for 2012-2015, the rate of sealing increase is accelerating, in contrast to the general trend of a slowing rate of increase.


 

What are the extent, degree, dynamics and spatial pattern of surface sealing (imperviousness) in Europe?

Percentage soil sealing by country

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Absolute increase in sealing for all three time periods by country in km2

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Imperviousness density in 2015

Note: The map shows the density of soil sealing in 2012, based on a 10 km2 reference grid. Green and light orange colors show areas with no or very limited sealing, while red and dark red colors show highly to fully sealed grid cells (mainly urban areas).

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Percentage annual change 2006-2015 relative to sealed area 2006

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Annual average increase in soil sealing for the three time periods, relative to country area

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Average annual change in soil sealing, 2006-2015

Note: The map shows the percentage of the average annual change in soil sealing for each of the rectangular 10 km x 10 km grid cells, over the 2006-2015 period

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Introduction

Both absolute levels of soil sealing (in km2) and relative sealing levels (in % sealed of the country) vary greatly from country to country. Relevant factors affecting the extent of sealing are (among many others):

  • Population size and distribution
  • Area size, climate and geography of the country
  • Traffic, and industrial infrastructure and heritage
  • Dominant land use and land use history
  • Dynamics of population distribution
  • Trends in per-capita housing space, related long-term changes in marriage age, number of children, number of household occupants and preference for housing type
  • Availability of sites for urban densification (land recycling)
  • Economic development 

In general, it is important to keep in mind that real sealing levels in most countries are above those captured in the imperviousness products. The imperviousness change and status products reliably capture the spatial pattern and magnitude of sealing, and the general trends in sealing change, but due to the pixel-size of the satellite imagery used (20 m), very small-scale sealed surfaces are sometimes not captured. In addition, the product deliberately does not 'burn in' any additional datasets (e.g. road network data), because it would reflect directly any errors and inconsistencies in update frequency and quality of the additional input data. This needs to be considered if the sealed area from the imperviousness data is compared to sealing statistics available in some countries, which are based on very precise and constantly updated cadastral data. For the 2018 update of the imperviousness data, the status layers will dramatically improve in spatial resolution from 20m (currently) to 10m pixel size. This is expected to increase the level of small-scale sealing that can be detected. The change products for the upcoming 2015-2018 products will separate 'changes' due to technical improvement (so called 'technical changes') from real changes in sealing, and will be available at 20 m spatial resolution. 

Below, four dimensions of sealing and sealing change are explored to provide a comprehensive picture of the status and trends:
  1.  Absolute sealing and sealing change trends in terms of area (km2). This provides an idea of the magnitude of the issue, but the values are not directly comparable since the countries are so different in size.
  2.  Information on the percentage of the countries (and Corine Land Cover classes) that are sealed. The figures are relative to the country area. Interpretation also strongly depends on size of the country.
  3.  Average annual percentage increase, relative to sealed area in 2006. These measures look at the rate of sealing increase, relative to our 2006 baseline, but not normalised by country area.
  4.  Percentage of average annual sealing increase, relative to country area. This looks at the rate of sealing increase relative to the country area (which percentage of the country is newly sealed on average every year for the period 2006-2015).
To explore the Imperviousness data time-series in more detail (going beyond the maps and graphs provided here), please go to the Imperiousness interactive data viewer

Absolute sealing and sealing change trends sealing between 2006 and 2015

 In 2015, 85 861 km2 were mapped and categorised as sealed surface in the Copernicus imperviousness product. This corresponds to 1.466 % of the total EEA-39 area.

Between 2006 and 2015, soil sealing (imperviousness) increased in all EEA-39 countries by a total of 3 859 km2, corresponding to an annual average increase of 429 km2. The countries with largest sealed area in absolute terms in 2015 were Germany, with 15 419 km2, followed by France, Italy, the United Kingdom, Spain, Turkey, Poland, the Netherlands, Romania and Portugal. These 10 countries make up 76 % of the total sealed area in the EEA-39 (while comprising only 58 % of the total area).

 

While in all countries the sealed area continues to increase for all 3-year periods (2006-2009, 2009-2012 and 2012-2015), for most countries the rate of average annual increase is highest in the period 2009-2012, slowing down for the period 2012-2015. The average annual increase was:

  • 460 km2 for 2006-2009;
  • 491 km2 for 2009-2012; and
  • 334 km2 for 2012-2015.

The increases and their change over the three time periods (km2) are illustrated in detail in figure 2. The trends in four broad categories are summarised below, however, the absolute and relative sealing values differ quite a lot and need to be considered further. For example while sealing increase shows an accelerating trend and high absolute values for Turkey, the percentage of the country sealed is still very low compared to most EEA-39 countries):

  • Continuing increase in the rate of sealing over all three periods: Cyprus, Turkey, Kosovo (under UNSCR  resolution 1244/99) and Serbia.
  • Continued decrease in the rate of sealing increase over all three periods: Montenegro, Luxembourg, Island, Ireland, Croatia, France, Spain, Greece, Slovenia, Portugal and Czechia
  • Increase in the middle period, followed by a decrease in the rate of increase in the latest period. This is the most common trend: Norway, Finland, North Macedonia, Albania, Slovakia, Germany, Denmark, Hungary, Belgium, Switzerland, Austria, Bulgaria, Serbia, United Kingdom, Netherlands, Romania, Italy, Poland, Lithania, Estonia and Malta
  • Slow-down for the middle-period (2009-2012) with higher or equal rates in increase earlier and later: Bosnia and Herzegovina, Latvia and Lithuania 

 

Percentage of country area (and Corine Land Cover classes) sealed 

While on average, 1.414 % of the total (valid[1]) area covered by the countries was sealed in 2006, this increased to 1.481 % in 2015. See Figure 1 for a comparison of country averages between 2006 and 2015, and Figure 3 for a map of sealing density in 2015, based on a 10 km grid. 

Three groups of countries could be identified: 
a) Countries with a very low sealed area as a percentage of total (valid) area (i.e. <1.0 %), e.g. Iceland (0.067 %), Norway (0.236 %), Latvia (0.382 %), Sweden (0.384 %) and 11 other countries. 
b) Countries with medium-high sealing percentages (relative to the valid country area) between 1.0 % and 3.0 %. There are 17 such countries.
c) A considerable number of countries with high sealing values between 3.0 % and 16.15 %. There are seven such countries, including Germany (4.264 %), Liechtenstein (4.505 %), Belgium (6.039 %), the Netherlands (7.354 %) and Malta (16.152 %).

See Figure 1 for the full list of countries and their % sealing in all four reference years (2006, 2009, 2012 and 2015).

A more detailed spatial pattern of existing sealing in 2015, based on 10 km grid cells, can be seen in Figure 3. The main urban areas that have grid cells with high sealing levels are shown in dark red, while green areas represent grid cells without any sealing detected in the 2015 imperviousness product.

Given that the imperviousness indicator does not capture land cover flows, it is not possible to monitor directly which land cover is mainly affected by an increase in sealing. The indicator can, however, be used together with Corine Land Cover (CLC) to establish in more detail which land cover strata are mainly affected by sealing increases.

On average, most of the sealing increases between 2006 and 2015 occurred in the Corine Land Cover classes listed below. Most of the changes occurred in just a few of the classes.

 

Corine Land Cover classes with the highest percentage of sealing:

The percentage of Corine Land Cover classes (for 2018) covered with impervious surfaces (for the 2015 reference year) ranges from close to 0 % for many of the natural classes (peat bogs, moors and heathland etc.) to 63 % for Class no. 111 (Continuous urban fabric). The classes with the highest percentage of sealing are:

  • 111 Continuous urban fabric (63 %)
  • 123 Port areas (51 %)
  • 121 Industrial or commercial units (42 %)
  • 112 Discontinuous urban fabric (26 %)
  • 122 Road and rail networks and associated land (25%)
  • 124 Airports (19 %)
  • 133 Construction sites (12 %)

Corine Land Cover classes with the largest average annual increase in imperviousness (in km2)

The largest yearly increase in sealing, for the 2012-2015 period happened in the Corine Land Cover class 112 (Discontinuous urban fabric), but also in some agricultural classes (211, Non-irrigated arable land, and 242, Complex cultivation patterns). This confirms that imperviousness is increased in part by consuming agricultural land. The five classes with the largest annual increases are:

  • 112 Discontinuous urban fabric (108 km2)
  • 121 Industrial and commercial units (82 km2)
  • 211 Non-irrigated arable land (33 km2)
  • 133 Construction sites (18 km2)
  • 242 Complex cultivation patterns (15 km2)

 

Annual percentage increase in sealing relative to sealed area in 2006

Sealing increased in all countries between 2006 and 2015. The average percentage annual increase for the period was 1.569 % across the EEA-39, with annual values ranging from 0.264 % for Malta, to 6.212 % for Iceland. See Figure 4 for yearly increases by country. However, it should be noted that in countries with little relative and absolute sealing (e.g. Norway), even relatively modest (absolute) increases create high rates of change.

Percentage of average annual increase in sealing area (2006-2015) relative to (valid) country area (imperviousness indicator)

The imperviousness indicator shows that, on average, the annual rate of increase amounted to 0.008 % of the total (valid) EEA-39 area for the 2006-2015 period. This means that on average, for that period, 0.008 % of the EEA-39 area was newly sealed every year. The overall trend for the whole EEA-39 showed an increase from an annual average increase of 0.009 % (2006-2009), to 0.011 % (2009-2012), followed by a decrease to 0.006 % for the latest period (2012-2015), similar to the trend in absolute figures. See Figure 5 for a graph with results by country, separate for all three periods, and Figure 6 for a map with the percentage annual increase in sealing area (for the whole period 2006-2015) relative to the 10 km grid cells used for the mapping.

The countries with the highest values for the latest period (2012-2015) are Cyprus, Kosovo, Poland,Turkey, Belgium and Germany, while the highest values for the period 2009-2012 were in the Netherlands, Malta, Luxembourg, Belgium, Cyprus and Switzerland.

In terms of the direction of trend there are again four main groups of countries, largely the same as those reported in the section on the changes in absolute sealing increase trends (but not exactly the same, as the figures here are normalised for country area).

  • Continuing increase in the percentage annual increase in sealing area relative to (valid) country area over all three periods: Cyprus, Turkey, Kosovo and Serbia;
  • Continued decrease in the percentage annual increase in sealing area relative to (valid) country area over all three periods: Montenegro, Luxembourg, Island, Ireland, Croatia, France, Spain, Greece, Slovenia, Portugal, Italy and Czechia;
  • Increase in the middle period, followed by a decrease in the percentage annual increase in sealing area relative to (valid) country area in the latest period. This is the most common trend: Norway, Finland, Macedonia, Albania, Slovakia, Germany, Denmark, Hungary, Belgium, Switzerland, Austria, Bulgaria, Serbia, United Kingdom, Netherlands, Romania, Poland, Lithuania and Malta;
  • Slow-down for the middle-period (2009-2012), with higher rates in the percentage annual increase in sealing area relative to (valid) country area earlier and later: Bosnia and Herzegovina, Latvia, Estonia and Lithuania. 


[1] When reporting relative sealing, we usually refer to the 'valid area' of the country. This refers to all pixels in that country that had valid sealing data in all four reference years (i.e. that did not have 'no data' at any time). Given that there are always changing areas of 'no data', e.g. due to clouds in all reference years, this allows the sealing trends to be mapped consistently and ensures comparability of the figures. The difference from the total area is small, with the valid area covering on average 99.01 % of the country area.

 


 

Indicator specification and metadata

Indicator definition

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 relative to the size of that unit (as a percentage). The imperviousness change value for a 100 m raster cell is based on 100 m imperviousness change products. 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 on average, 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 integrated spatial data platform at EEA.

Units

The unit used for this indicator is the yearly average percentage change in imperviousness relative to the size of the reference unit. It is important to note that the yearly average value is based specifically on the period reported, e.g. 2006-2009, 2009-2012 or 2012-2015, or for the whole time period for which data are available (2006-2015). 


Policy context and targets

Context description

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 the EU level, the Seventh Environment Action Programme (7th EAP) includes a strong focus on the 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.

Targets

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 the 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, as well as 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). On average, land recycling increased steadily between 1990 and 2012 on an annual basis, with considerable variation between countries, and within countries. Stronger links between EU urban and soil policies could encourage this further (e.g. following up respective 6th EAP Thematic strategies).

Related policy documents

Methodology

Methodology for indicator calculation

  • The 100 m imperviousness change product, produced as a deliverable in the 2009, 2012 and 2015 updates, is the basis for this indicator. 
  • Previous versions of this indicator were published separately for the 2006-2009 and 2009-2012 periods. However, improved production workflows and products, and challenges in comparing the results for the reference years, made it necessary to fully re-process the 2006-2009 and 2009-2012 change products as part of the production for the 2015 reference year. Therefore this update of the indicator uses the new and improved full time series of 2006-2009-2012-2015. Errors in previously published change products were corrected, and the new time series fully replaces any previously published versions.
  • Although imperviousness changes included in the 100 m change product could be summarised directly as certain reference units, the calculation of the indicator is performed by ingesting 100 m imperviousness change values into the EEA spatial data platform in order to create harmonised results with other spatial indicators using a similar methodology. The data cube approach used for the data platform enables the extraction of statistics based on a system of grid-cells with a 1 km side length (an area of 100 ha). 
  • Reference units, such as countries, NUTS3 regions etc. are already included in the cube as so called 'dimensions' and are used for the statistical aggregation of imperviousness changes corresponding to required reference units.
  • Yearly average imperviousness change values are calculated by dividing the average imperviousness change values by the number of years between two status years.

Methodology for gap filling

  • Known gaps were caused by image gaps (missing input Earth observation data) in both 2006 and 2009 data. For 2009 gaps, the available 2006 values were used for the 2009 status layer and gaps in 2012 image data were filled with imperviousness data from 2009. This means that in some areas (under image gaps), the real sealing change is not known for 2009 and 2012, and some under-estimation of the real sealing increase (for those areas) is likely (because data from previous reference years are used). This practice of gap-filling with previous reference year data was discontinued for the 2015 (and future) updates, but it was not possible to fully eliminate the effects from the 2009 and 2012 datasets. 

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

  • The methodology for deriving the indicator is simple and introduces very little uncertainty. However, it needs to be fully understood that the yearly averages are only valid for the 3-year reference period under consideration. Possible variation within the 3-year period (for individual years) is currently not captured.

Data sets uncertainty

  • This indicator is based directly on the mapping of soil sealing/imperviousness using Earth observation data of about 20 m spatial resolution (moving to 10 m from the 2018 reference year onwards). Real sealing will differ from the values derived in this way for various reasons:

    • The spatial resolution of the input imagery means that very small sealed surfaces will sometimes not be captured, e.g. small buildings and small paved roads, and other sealed surfaces with a very small footprint. This can lead to an underestimation of real sealing. It is expected that this issue will become less relevant as we move to 10 m spatial resolution products from the 2018 reference year onwards.
    • As with all Earth observation derived products, the data contain omission errors (sealed surfaces not detected) and commission errors (areas wrongly classified as sealed). The distribution of these errors depends on the quality of the input data, calibration during production and local differences in spectral contrast (which makes sealing in some locations 'easier' to detect than in other locations, depending on the context).
    • The 2015 production included a full re-processing of previous reference years and change products. Therefore the current 2015 product, and the latest versions of 2006-2009-2012 products fully replace the previous datasets. For the same reasons, this indicator update replaces all previous published imperiousness indicators. 
    • For imperviousness/soil sealing products, the term 'reference year' must currently be understood to comprise a maximum of 3 years (the year before the reference year, the actual reference year, and the year after the reference year for gap-filling). This means that the Earth observation data used to produce the '2009 reference year' are, in reality, a mix of 2008, 2009 and 2010 acquisitions. Due to radical improvements in image availability with the Sentinel Satellites, this situation already significantly improved for the 2015 reference year, and will further improve for the 2018 reference year (where the imagery is fully from the 2018 reference year).

Rationale uncertainty

No uncertainty has been specified

Data sources

Metadata

Topics:

information.png Tags:
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DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)

Dates

Frequency of updates

Updates are scheduled every 3 years

EEA Contact Info

Tobias Langanke
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