Classifying threatened species of India using IUCN criteria

Abstract

Assigning threat status to a species is essential for prioritization of species under any conservation programme, and therefore, a pre-requisite for species conservation. In India, due to inadequate data, threat status has not been assigned to several plant species, although their population sizes are quite small and they are considered important from conservation point of view. Besides, there is a need for reassessment of threat status assigned by various agencies using updated data on population size, number of mature individuals, area of occupancy, and geographic extent of occurrence. This is crucial as the natural habitats as well as populations of such species are being affected by anthropogenic activities, exotic species invasion, and climate change. In the present study, we assessed the threat status of 59 selected plant species following the IUCN criteria (ver. 3.1). The species were selected after consultation with various experts throughout the country. Field surveys were carried out in various ecoregions of India to locate the species. Population size and number of mature individuals were enumerated following quadrat/plot-based sampling. The exogenous and endogenous factors leading to decline in population and rarity were identified based on field observations as well as laboratorybased seed viability and germination tests. Based on these studies, 20 species were classified under critically endangered category, 21 under endangered, 11 under vulnerable, five under near threatened, and one species each under data deficient and least concern category. Threat assessment for 41 species was done based on number of locations and geographical range of occurrence, while for 18 species it was done based on restricted population and number of mature individuals. Over-exploitation and habitat degradation or loss were the dominant exogenous factors leading to decline in natural populations of the selected species. The major endogenous factors that lead to population decline and species rarity were low seed viability and germination, long dormancy period, less seedling recruitment, low population size, habitat specificity and narrow niche leading to restricted distribution.