WCMC has been compiling and analysing data on the world's protected areas for more than a decade. The WCMC Protected Areas Database holds data on over 40,000 sites around the world designated for nature conservation purposes, together with details of sites designated under international conventions and programmes, such as the Ramsar and World Heritage Conventions, and the UNESCO-MAB Biosphere Reserves Programme. The data are used to produce informational items such as the United Nations List of National Parks and Protected Areas.
Information about protected areas is obtained from official sources (those government agencies responsible for administering protected areas), and elsewhere, through a global network of contacts ranging in profession from policy-makers and administrators to land managers and scientists. The information in the databases includes such items as the site name, the IUCN management category, the size of the area and where possible the exact shape and location of the area in the spatial databases. For the current analysis all protected areas in management categories from I to VI were included (see annex).
The spatial database includes two types of locational information. In many cases there are polygons inserted for the site, where this information is known. Where this is not available a point has been inserted, representing the centre of the site. In order to carry out the overlay analysis the data had to be processed so that all sites were polygonised. Polygons were made for sites which only had point locations by using the area information in the textual databases and drawing a circular polygon of the relevant area around the point location of the site. In some places there was a significant amount of overlap of protected areas. This was mainly in instances where a site with stringent protection was located inside a site with a lesser degree of protection, or else where the circles drawn were not the exact locations of the sites, which in reality might not actually overlap because of their shape. To avoid massive over-representation of the amount of forest under protection due to the overlap factor, the protected areas layer was dissolved so that overlapping sites just dissolved into one polygon. This process may result in a slight under-representation of the amount of forest under protection, but the error would be much less than the overestimate that would have occurred had the dissolve not been carried out. More accurate results can only be obtained by building up and refining the spatial information on protected areas in the databases, which is an ongoing process.
The dissolved protected areas layer was then geographically divided for the analysis into Regions which corresponded exactly to the forest coverage divisions.
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