Uses and Limitations of CLC data

The Corine Land Cover (CLC) dataset maps the landscape based on two main properties - its natural bio-geographical properties (e.g. peatlands and natural grasslands), or in terms of its anthropogenic uses (e.g. pastures, arable land, fruit plantations). The statistics derived from the spatial dataset give a 'snapshot in time' of the state of the Irish landscape and how it is changing from one mapping period to another. These changes can be naturally occuring but often are due to human activity where land is used for housing, grazing livestock, food production and transport.

CLC's spatial parcels represent elementary landscape systems that can be interpreted individually or 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 is mapped at a spatial scale of 25 hectares 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.

Providing a wider context

The CLC data series is a key background reference dataset across Europe. The landcover change statistics enable the study anf understanding of changes in Europe's environment over time. It enables the identification of potential conflicts between socio-economic landuse and ecological systems, biodiversity and natural landscape. On a more local scale, the dataset can show how man-made surfaces, agricultural lands and ecological commumities are chainging and interacting.


This satellite-based mapping approach (Remote Sensing) complements on-the-ground monitoring by showing the wider land use context for individual sites. 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. It also enables efficient mapping over large areas and inaccessible lands without the need for time consuming field surveys. 

Assisting analysis

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.

Limitations

It is widely recognised that the Corine dataset has some key limitations which is all the more pertinent in Ireland as it is our only national scale land cover dataset. Corine was designed as a pan-European dataset and not as a national data set. Its classification structure and spatial resolution has been designed to fit the wide range of environmental regions of Europe and not any one country. It has a relatively large minimum mapping unit of 25 hectares and, as part of its classification schema, contains landcover units that do not exist in Ireland (e.g. glaciers and rice fields).

It has a number of mixed classes that could be considered to be ambiguous and overlap in their description and content (e.g. "discontinuous urban fabric" or "land principally occupied by agriculture with significant areas of natural vegetation"). Whilst at the same time there are classes such as "Construction sites" and "Sports recreation facilities" that, in Ireland at least, are unnecessarily detailed and un-mappable at a resolution of 25 hectares.

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.

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 misinterpretation, users have access to numerous datasets: CLC1990-revised, CLC change 1990-2000, CLC2000, CLC2000-revised, CLC change 2000-2006 and CLC2006.

Using older datasets

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 should not be applied to earlier datasets.

 

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