The series of publications produced by the International Union for the Conservation of Nature and Natural Resources (IUCN). They provide an inventory on the threat to rare plants and animal species. Information includes status, geographical distribution, population size, habitat and breeding rate. The books also contain the conservation measures, if any, that have been taken to protect the species. There are five categories of rarity status: endangered species; vulnerable organisms, which are those unlikely to adapt to major environmental effects; rare organisms, which are those at risk because there are few of them in the world, such as plants which only grow on mountain peaks or on islands; out of danger species, which were formerly in the above categories, but have had the threat removed because of conservation actions; and indeterminate species, which are the plants and animals probably at risk, although not enough is known about them to assess their status.