Corine Land Cover (CLC) is an analysis and mapping of landscape units on the basis of their physiognomy and their radiometric characteristics. CLC data gives a visible picture of both ecosystems (forests, lakes, pastures etc) and how land is used for human activities such as housing, food production, transport.
CLC mapping units are images of elementary landscape systems that can be interpreted, simultaneously, as land use systems and ecosystems. CLC is not a classification of pixels or a survey of hectares of a given homogenous type (as monitored by farm surveys or area sampling surveys).
CLC data reveals changes over time, and this information is assembled at a fairly detailed scale and in a consistent way all across Europe. This enables identification of trends at local, regional, national and European levels, helping policy makers to take appropriate action.
CLC is a key factor for understanding changes in Europe's environments and for identifying possible conflicts in land use and degradation of ecosystems This satellite-based mapping complements on-the-ground monitoring by showing the wider land use context for individual sites.
For instance, it allows specific land cover features such as a forest or a landfill site to be viewed in relation to their surrounding environment and their interactions with it.
Consistent geo-referenced information on land cover is key for "integrated" environmental assessments - looking at land, ecosystems and water courses together - that are most useful to policy makers.
CLC is an important background reference for analysing potential conflicts in the use of land and impacts of land use pressure on biodiversity. There is a growing need for spatial analysis in integrated environmental assessment by European Commission services such as DG-Regional policy, DG-Environment and DG-Agriculture as well as in the European Environment Agency and its European Topic Centres (ETCs).
The CLC 1990 (Ireland) database was the first complete land cover database for the country. Its data has been used widely by public bodies, researchers, scientists and private companies. Main applications include water management, air quality, land planning, waste management, telecommunications and agriculture/forestry.
The smallest mapped unit in CLC is 25 hectares, recognising landscape units as systems.
Changes in land cover often happen via so-called mixed classes ("discontinuous urban fabric" or "land principally occupied by agriculture with significant areas of natural vegetation") that can be considered as transition areas. These mixed classes facilitate the interpretation of the change process. CLC delivers information at the 1/100 000 scale. This is not sufficient for local applications such as urban planning, forest management or risk assessment, that require more detailed scales. For these, maps at the 1/50 000 to 1/10 000 may be needed. CLC, being a multi-thematic map, can be usefully overlaid with these maps in order to inform about the neighbourhood of these zones and changes in the environmental context. Due to the 25-hectare rule, CLC land units disappear or pop up when they come just below or just above this threshold. This is consistent with monitoring landscape systems.
Considering the mapping of changes in CLC2000 and CLC2006, the smallest mapped change is of five hectares. Therefore, it may happen (rarely in fact) that 5-24 hectare change influences the creation or deletion of a small zone. For avoiding any mis-interpretation, users have access to numerous datasets: CLC1990-revised, CLC change 1990-2000, CLC2000, CLC2000-revised, CLC change 2000-2006 and CLC2006.
CLC2000 and the more recent CLC2006 have been prepared and quality controlled very carefully by the European Environment Agency. CLC1990, an experimental programme, didn't meet the same standards but can be considered, after 10 years of an extensive use, as of a fairly good quality too.
During the CLC2000 process, the original CLC1990 dataset was revised, fixing possible errors and eliminating geometric discrepancies that could generate false change. However, problems remain at a European scale due to the dates of the first CLC, ranging from 1986 to 1994; for comparisons, the gap is mitigated by calculating annual averages (although some inconsistency will remain considering the median year).
During the CLC2006 process, the CLC2000 dataset was revised, fixing possible errors and eliminating geometric discrepancies that could generate false change. The revision of CLC2000 serves only the purposes of comparision with CLC2006 project. This is should not be applied to earlier datasets.
