A study has identified the protected areas of the globe most critical to preventing extinctions of the world's mammals, birds and amphibians, scientists say. The study, the result of an international collaboration, calculates the "irreplaceability" of individual protected areas, based on data on 173,000 terrestrial protected areas and assessments of 21,500 species on the International Union for Conservation of Nature's Red List of Threatened Species. The analysis, comparing the contribution each protected area makes to the long-term survival of species, has identified 137 protected areas in 34 countries as exceptionally irreplaceable, an IUCN release said Thursday. The areas are home to populations of more than 600 bird, amphibian and mammal species, half of which are globally threatened, the study found. Many of these irreplaceable areas, such as Ecuador's famed Galapagos Islands, Peru's Manu National Park and India's Western Ghats are already designated as being of "Outstanding Universal Value" by the United Nations, half of the land covered by the protected areas does not have World Heritage recognition, the study said. "These exceptional places would all be strong candidates for World Heritage status," lead study author Soizic Le Saout said. "Such recognition would ensure effective protection of the unique biodiversity in these areas, given the rigorous standards required for World Heritage sites." "Protected areas can only fulfill their role in reducing biodiversity loss if they are effectively managed," said Simon Stuart, chair of the IUCN Species Survival Commission. "Given limited conservation budgets, that is not always the case, so governments should pay particular attention to the management effectiveness of highly irreplaceable protected areas."