Type of Indicator

Pressure. Uncontrolled urbanisation is a major driver of soil sealing, directly leading to the loss and degradation of agricultural land. Particularly in coastal plains, it accelerates the depletion of the ground water table due to uncontrolled exploitation causing also salinisation and pollution, and general alteration of the hydrological balance.

Objective

To assess the risk of desertification with particular reference to: i) loss and degradation of agricultural land with a high production potential, particularly in coastal plains; ii) depletion of the ground water table (uncontrolled exploitation); iii) salinisation and pollution of phreatic ground water and deep acquifers; iv) alteration of surface hydrology through soil sealing increasing run-off and the risk of flash floods and soil erosion.

Importance with respect to desertification

The analysis of the socio-economic context in which urban sprawl occurs is essential in order to define strategies to control and mitigate the process. In fact, so as to draw up and implement development and land use management plans it is necessary to permanently up-date mapping of urban sprawl. It will thus be possible to i) provide the physical basis for implementation of national urban planning legislation at the commune level (Communal Urban Plan), taking into consideration the development of urban centres and neighbouring agricultural and natural land; ii) provide the appropriate framework for defining the territorial units and their optimal use, integrating information on the bio-physical qualities of the environmental resources with those pertaining to historical land use; iii) develop standardised tools to provide mapped documentation of the processes of current urban expansion on the local, national and regional scales (e.g. Mediterranean Basin), to the greatest extent possible using remotely sensed satellite images.

International Conventions and agreements

The UNCCD emphasizes the fact that combating desertification must be tackled within the general framework of actions to promote sustainable development.

Within Agenda 21 urban sprawl is relevant to Chapter 12 - Management of fragile ecosystems: combating desertification and drought.

Secondary objectives of the indicator

Tackling the problems of urban sprawl is crucial to the implementation of strategies towards sustainable urban and regional development, reconciling sectoral rural and urban socio-economic policies, which is also a key requirement for combating desertification at national and regional levels.

Definitions and basic concepts

In the context of desertification the indicator was proposed within an interdisciplinary study undertaken in Sardinia in the framework of the MEDALUS project, since uncontrolled urban sprawl is one of the major causes of loss of environmental resources in the Mediterranean basin. Its approach is to compare and combine mapping methods based on field surveys and remote sensing image analysis for an efficient geo-referenced identification and quantification of the extent of dispersed built-up structures (discontinuous urban fabric) within semi-natural/agricultural areas.

Benchmarks Indication of the values/ranges of value

% or ha of soil sealed by built-up structures within agricultural and/or semi-natural land cover units. Changes (increase) of values over time.

Methods of measurement

The methodology calls for combination of: i) detailed reference ground surveys; ii) analysis of remote sensing data. Remotely sensed multitemporal images from satellites provide accurate and current information, over extensive areas, on possibly uncontrolled urban sprawl over semi-natural and agricultural areas. There are a number of well-documented techniques available to extract the information from different types of remote sensing data. Field surveys provide a means of calibrating and validating the procedure of quantifying urban sprawl based on the use of remote sensing data.

Limits of the indicator

The indicator can be applied at a range of spatial scales, from local municipalities to larger landscape units or regions, e.g. coastal plains around the Mediterranean Basin. The limits of the indicator are mainly linked to the time and manpower needed for collecting reference ground truth data over larger areas. New high resolution satellite data (e.g. IKONOS, Quick Bird), which allow direct identification of dispersed new built-up structures are still very expensive. Alternative techniques (e.g. spectral mixture modelling) to extract quantitatively information on diffuse urban sprawl from historical satellite data at moderate resolution (mainly Landsat-TM, 30x20 m2) are promising but need further validation to be included into semi-operational monitoring schemes which exist in a European context (e.g. 5 Mediterranean urban centres within the Moland project).

Linkages with other indicators

This indicator can usefully be combined with the common statistical and urbanisation indicators, for example the percentage of variation in the population of administrative units, or the variation in average density (inhabitants per ha) of population on fertile agricultural land and irrigated areas, to highlight the consumption of potential agricultural resources.

Data required to calculate the indicator

Multitemporal archives of satellite images and/or aerial photographs referring to the entire region and covering a sufficiently long period of time to enable comparison between different urban centres. Supporting information from maps of land cover/land use, soils, topography.

Data sources

Historical and recent land cover/land use and soil maps at the required scales (1:25000 to 1:100000) are available in most regions of the Mediterranean region.

Historical archives of air-photographs and satellite data provide a sufficient time sequence in many regions to analyse the development up to the last 50 years. In particular Landsat-TM archives covering approximately the last 20 years throughout the entire Mediterranean region allow a coherent approach and are now available at reasonable prices.

Availability of data from national and international sources

Many national and regional mapping agencies hold archives of Landsat images and air-photographs that could be used by national action plan initiatives and in the context of implementing activities in the RAP.

The Moland project of the JRC, in collaboration with the EEA, has analysed the development of 5 Mediterranean urban centres (Iraklion, GR; Istanbul, TR; Marseille, F; Nicosia, CY; Palermo IT) based on multi-temporal remote sensing data.

Main institutions responsible

Institute for Environment and Sustainability, DG JRC, European Commission, Ispra, Italy
University of Cagliari, Dept. of Soil Science.

Other contributing organizations

Bibliography

Sommer S., Loddo S., Puddu R., Indicators of soil consumption by urbanisation and industrial activities. Proceedings of the International Seminar held in Porto Torres, Italy 18-20 September 1998: pp 116-125

Other references

EEA Environmental issue report No 30. Towards an urban atlas: Assessment of spatial data on 25 European cities and urban areas. Prepared by: European Commission - Directorate General Joint Research Centre Institute for Environment and Sustainability - Land Management Unit, Ispra, Italy; IST, Technical University of Lisbon, Portugal; CNIG, National Centre for Geographical Information, Portugal

http://reports.eea.eu.int/environmental_issue_report_2002_30/en

Hill J. & Hostert P., 1995: Monitoring the growth of a Mediterranean metropolis based on the analysis of spectral mixtures - a case study on Athens (Greece). In: Progress in Environmental Remote Sensing Research and Applications. Ed. E. Parlow, Balkema, Rotterdam, pp. 21-21.

Contacts Name and address

EC, DG Joint Research Centre
Institute for Environment and Sustainability
Stefan Sommer <stefan.sommer@jrc.it>