Red Data Books, Natural Extinction, Pseudo extinction, Ammonoid, Graptolite, Brachipods, Gastropods, Bivalves, Homo Sapiens

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Biodiversity and its Conservation
Biodiversity and its Conservation Introduction
Current Levels of Biodiversity
Alpha (α) and Beta(β) Biodiversity
Extinction and Endangered Species
Reasons of Concern for Loss of Biodiversity
Ethical and Aesthetic Rewards
Economic Benefits
Essential Services Provided by Natural Ecosystems
Steps to Preserve Biodiversity
In Situ and Ex Situ Conservation Gene Banks
In Situ Conservation
Ex Situ Conservation
Ex Situ Conservation Efforts at International Level
Ex Situ Conservation Efforts by G-15 Countries
Ex Situ Conservation Efforts in USA

	Extinction and Endangered Species In many groups of plants and animals, there are groups of species, which are prone to extinction due to environmental changes so that a specific group is reduced to one or few threatened or endangered species (two grades - threatened vs endangered are recognized by conservationists). These threatened or endangered species have a high probability of extinction during the next few years or decades.
Red Data Books have been prepared (these books are periodically revised), which contain the lists of these endangered species of plants and animals. The extinction of these rare species may be natural or man made and both will be discussed separately. Natural extinction The species which are prone to extinction are characterized by small size of breeding population (thus promoting inbreeding) associated with high coefficient of variation. When the size of breeding population drops to a hundred or less, the likelihood of extinction is enhanced still further due to inbreeding depression. The overall extinction rate estimated from fossil data is one species per 107 species per year. This rate refers. to true extinction, which means extinction of a species and its descendents and differs from 'pseudo-extinction" , which is caused due to evolution of one species into another.
The longevity of a species defined as above (species and its descendents) varies from 1-2 million' years (e.g. mesozoic ammonoid and silurian graptolite) to as much as 10 million years (e.g. paleozoic and mesozoic invertebrates). It has also been shown that in general, planktonic arid sessile marine animals, including corals and brachiopods, have had higher extinction rates than mobile benthic animals, such as gastropods and bivalves. Human-caused Extinction Due to destruction of natural habitats by human interference, biodiversity is being lost at a fast rate, particularly in the tropical' regions (e.g. tropical rain forests and coral reefs), where not only biodiversity is high, but also the human interference is high due to population pressure. The rain forest cover has been reduced to 55% of the original area, due to human activities, and the rate of loss of these forests is increasing at an alarming rate.
For instance, the rate of loss of these forests was doubled during the period 1979-1989, and about 1.8% of the remaining forests are disappearing every year. This leads to an annual loss of 0.2 to 0.3 per cent of all species occurring in the forests at a particular time. In other words, if two million species are confined to the forests alone, 4000 species will be lost every year due to deforestation. Among these, if there are endemic species restricted to a particular area, the clearing of such an area may lead to immediate extinction of the species. Therefore, it is estimated that if the current rate of clearing the forests and other habitats continued, 25% or more of the total species on the Earth could be eliminated within 50 years. It is also estimated that almost 40% of net primary productivity (NPP, which makes food supply of all animals) on lands is now directly used or lost due to the activities of a single species- Homo sapiens. Further the human population is projected to become 10 billion in the next 50 years, and this is supposed to be accompanied with 5-10 fold increase in economic activity. If anything close to this level of increase in population and economic activity is witnessed in future, World's biodiversity is destined to be completely wiped out from the surface of the Earth. This demonstrates the crisis of the loss of biodiversity and also the need to conserve it.