In 1972, the United Nations Educational, Scientific and Cultural Organization (UNESCO) adopted the Convention Concerning the Protection of the World Cultural and Natural Heritage. The purpose of the Convention is to "encourage the identification, protection and preservation of cultural and natural heritage around the world considered to be of outstanding value to humanity." The Convention provides a mechanism by which member states can nominate important sites that are then evaluated by the World Heritage Committee. As of 2006, the World Heritage List includes 851 properties forming part of the cultural and natural heritage which the World Heritage Committee considers as having outstanding universal value. These include 660 cultural, 166 natural and 25 mixed properties in 141 nations. As of October 2006, 184 States Parties have ratified the World Heritage Convention.
Two of the four criteria by which Natural World Heritage Sites can be nominated relate respectively to ecological and biological processes, and to the in-situ conservation of biological diversity. Accordingly, the United Nations Environment Programme (UNEP) and the IUCN teamed with UNESCO to produce a separate sub-listing of all sites inscribed on the World Heritage List for natural or mixed natural and cultural reasons.
This Collection contains the descriptions of these sites, which are compiled and maintained by UNEP-WCMC on behalf of UNESCO.