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. Examples include parks, reserves and wildlife sanctuaries. The term protected area includes Marine Protected Areas, which refers to protected areas whose boundaries include some area of ocean. There are over 147,000 protected areas in the world  with more added daily, representing a total area of , or over 13 percent of the world's land surface area, greater than the entire land mass of Africa. By contrast, as of 2 February 2009, only 0.8 of one percent of the world's oceans are included in the world's ~5000 Marine Protected Areas.
One definition, but not the only definition of "protected area", is provided by the International Union for Conservation of Nature (IUCN). A protected area, when using the IUCN definition, is:
"A clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values."—quote
Through its World Commission on Protected Areas (WCPA), IUCN have developed seven Protected Area Management Categories that define protected areas according to their management objectives and are internationally recognised by various national governments and the United Nations. The categories provide international standards for comparing the protected areas in different countries and encourage the planning of protected areas under management aims. The categories are: Ia Strict Nature Reserve; Ib Wilderness Area; II National Park; III Natural Monument of Feature; IV Habitat/Species Management Area; V Protected Landscape/ Seascape and; VI Protected area with sustainable use of natural resources.
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 at the Earth Summit (1992), and the Johannesburg Declaration 2002.
Some countries, such as China, Madagascar, Namibia and Venezuela, place a protection category over lands, but provide little enforcement, such that the areas are not substantively protected from development or misuse.
Protected areas often involve the exclusion of resources users from the protected area. As such, they have been criticized for the displacement of local population. Much of the new protected areas are in developing countries which makes the local population vulnerable.