Protected areas are locations which receive protection because of their environmental, cultural or similar value. A large number of kinds of protected area exist which vary by level of protection and by the enabling laws of each country or rules of international organization.

A protected area as defined by the World Conservation Union (IUCN) is An area of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources, and managed through legal or other effective means.

The IUCN specifies six categories of protected areas:

• I. Strict nature reserve/wilderness area: protected area managed mainly for science or wilderness protection
• II. National park: protected area managed mainly for ecosystem protection and recreation
• III. Natural Monument: protected area managed mainly for conservation of specific natural features
• IV. Habitat/Species Management Area: protected area managed mainly for conservation through management intervention
• V. Protected Landscape/Seascape: protected area managed mainly for landscape/seascape protection and recreation.
• VI. Managed Resource Protected Area: protected area managed mainly for the sustainable use of natural ecosystems.

International commitments to the development of networks of protected areas date from 1972, when the Stockholm Declaration from the United Nations Conference on the Human Environment endorsed the protection of representative examples of all major ecosystem types as a fundamental requirement of national conservation programs. Since then, the protection of representative ecosystems has become a core principle of conservation biology, supported by key United Nations resolutions - including the World Charter for Nature 1982, the Rio Declaration 1992, and the Johannesburg Declaration 2002.

Globally, national programs for the protection of representative ecosystems have progressed with respect to terrestrial environments, with less progress in marine and freshwater biomes.