India is known for its rich biological diversity .The country has already documented over 91,000 species of animals and 46,000 species of plants in its ten bio-geographic regions. Nearly 65,000 native plants are still used prominently in indigenous health care systems. The country is also recognised as one of the eight Vavilovian Centres of Origin and Diversity of Crop Plants. Here we have more than 300 wild ancestors and close relatives of cultivated plants still growing and evolving under natural conditions. At the same time we loose certain species or their number dwindles for various reasons. These are threatened plants.
Threatened plant species are any species which are vulnerable to extinction in the near future. International Union for Conservation of Nature (IUCN) is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories: vulnerable, endangered, and critically endangered, depending on the degree to which they are threatened.
Critically Endangered (Cr) is the highest risk category assigned by the IUCN for wild species. Critically endangered species means a species numbers have decreased, or will decrease by 80% within three generations. It is therefore considered to be facing an extremely high risk of extinction in the wild.
Endangered (EN) species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters. Also it could mean that due to deforestation there may be a lack of food and/or water. It is therefore considered to be facing a very high risk of extinction in the wild.
Vulnerable (VU) species is a species which has been categorised by the IUCN as likely to become endangered unless the circumstances threatening its survival and reproduction improve. It is therefore considered to be facing a high risk of extinction in the wild.
A species becomes extinct when the last existing member of that species dies. Extinction therefore becomes a certainty when there are no surviving individuals that are able to reproduce and create a new generation. A species may become functionally extinct when only a handful of individuals survive, which are unable to reproduce due to poor health, age, sparse distribution over a large range, a lack of individuals of both sexes (in sexually reproducing species), or other reasons.
An important aspect of extinction at the present time is human attempts to preserve critically endangered species, which is reflected by the creation of the conservation status “Extinct in the Wild” (EW). Species listed under this status by IUCN are not known to have any living specimens in the wild, and are maintained only in zoos or other artificial environments. Some of these species are functionally extinct; as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild.
Main reasons for extinction are either natural or manmade. Through evolution, new species arise through the process of speciation and species become extinct when they are no longer able to survive in changing conditions or against superior competition. A typical species becomes extinct within 10 million years of its first appearance although some species, called living fossils, survive virtually unchanged for hundreds of millions of years. Extinction, though, is usually a natural phenomenon; it is estimated that 99.9% of all species that have ever lived are now extinct.
Various anthropogenic activities causing extinction are manmade reasons. Only recently scientists have become alarmed at the high rates of recent extinctions due to various anthropogenic activities. Some of these anthropogenic activities include intentional or accidental introduction of invasive alien species, over exploitation and unscientific collection of Non-Timber Forest Produce (NTFPs) including medicinal plant, climate change, unsustainable tourism, habitat destruction, encroachment etc.
Extinct plants are enlisted in Red Data book of Botanical Survey of India. As per the Red Data book of Botanical Survey of India (BSI), 17 plants have been recorded as extinct. However, during recent exploration by BSI in some of the previously unexplored areas, numbers of such reported extinct species of plants have been rediscovered.
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