Endangered Species
How do we classify a species as endangered?
P.K. VARADARAJAN
Chennai
A species is considered endangered when it is at a very high risk of extinction in the wild. When a living organism is at or goes below a baseline number of existing specimens projected to be the less for normal breeding and continuation of that species, then it is ranked as Endangered Species. This critical status means that the species may become extinct.
The International Union for Conservation of Nature (IUCN) classifies a taxon under Endangered Species when the best available evidence indicates that it meets a rapid decline in population size of more than 50 per cent to 70 per cent over the last decade or three generations, whichever is the longer; an extent of occurrence of geographical range to be less than 5000 km2 or area of occupancy estimated to be less than 600 km2; population size estimated to number fewer than 2,500 mature individuals or an estimated continuing decline of at least 20 per cent within five years or two generations, whichever is longer or extreme fluctuations in number of mature individuals; population size estimated to number fewer than 250 mature individuals and quantitative analysis showing the probability of extinction in the wild is at least 20 per cent within 20 years or five generations, whichever is the longer. It is obvious from the criteria framed by IUCN that the decline in population size is the one used to classify a species to be endangered.
A complete list of all the critically endangered, endangered or vulnerable species is maintained by IUCN called the Red List. Many of the extinct species never made it to the endangered species list.
AZHWAR RAGHUNATH
Research Fellow, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu
