EXTINCT, Extinct in wild, Critically Endangered, Endangered, Vulnerable, etc based on data collected across the world.IUCN has a Red List which provides a systematic list of plants and animals into various categories. Criteria for Critically Endangered:Reduction in POPULATION size:Reduction of population ≥ 90% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly REVERSIBLE AND understood AND ceased.Reduction of population ≥ 80% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible. Geographic range in the form of either B1 (extent of occurrence) OR B2 (area of occupancy):The extent of occurrence estimated to be less than 100 km2, and estimates indicating severely fragmented or known to exist at only a single location.Area of occupancy estimated to be less than 10 km2, and severely fragmented or known to exist at only a single location.Population size estimated to number fewer than 250 mature individuals and an estimated continuing DECLINE of at least 25% within three years or one generation, whichever is longer.Population size estimated to number fewer than 50 mature individuals.Quantitative analysis showing the probability of EXTINCTION in the wild is at least 50% within 10 years or three generations, whichever is the longer (up to a maximum of 100 years). IUCNIUCN is a membership Union uniquely composed of both government and civil society organizations.Created in 1948, it is the global authority on the status of the natural world and the measures needed to safeguard it.It is headquartered in Switzerland.The IUCN Red List of Threatened Species is the world's most comprehensive inventory of the global conservation status of plant and animal species.