By Dr. R.K. Ranjan Singh
The living organisms are found almost everywhere on earth. Hot desert, extremely cold places, like north and south pole, high mountains, deep oceans, dark caves etc. are all inhabited by one or other kind of organisms. The types of organisms found on different places differ from one another. For example, plants, animals, insects etc. living in pond are different from those on land. Likewise plants, animals and even human beings found in different parts of the world differ in many ways. The planet earth is thus repository of innumerable varieties of living organisms ranging from very small microscope such as bacteria, which cannot be seen by naked eyes, to very large macroscopic like elephants, whales, giant banyan tree etc. The richness of variety of life forms is termed as biological diversity, popularly referred to as biodiversity.
Life has existed on Earth for over 3.5 billion years. Over 95% of the species that ever existed have gone extinct. So why should we be concerned about current extinction rates and conserving biodiversity?
Currently the planet is inhabited by several million species in about 100 different phyla (Dirzo & Raven 2003). About 1.8 million have been described by scientists (Hilton- Taylor 2008), but conservative estimates suggest that there are 5-15 million species alive today (May, 2000), since many groups of organisms remain poorly studied. Over 15,000 new species are described each year (Dirzo & Raven 2003), and new species are evolving during our lifetimes. However, modern extinction rates are high, at 100 to 1000 times greater than background extinction rates calculated over the eras. Although new species appear, existing species go extinct at a rate 1000 times that of species formation (Wilson 2003). Many biologists agree that we are in the midst of a mass extinction, a time when 75% or more of species are lost over a short geological time scale (Raup 1994). The last great mass extinction was 65 million years ago, at the end of the Cretaceous, when the dinosaurs went extinct. The International Union for the Conservation of Nature estimates that 22% of known mammals, 32% of amphibians, 14% of birds, and 32% of gymnosperms (all well-studied groups) are threatened with extinction (Hilton-Taylor 2008). Species that were abundant within the last 200 years have gone extinct. For example, passenger pigeons, which numbered three to five billion in the mid-1800s (Ellsworth & McComb 2003), are now extinct.
Why should we be concerned about this loss of biodiversity? The answer lies in the fact that, for the first time in Earth’s history, single species, HOMO SAPIENS, could cause a mass extinction, precipitating its own demise. The primary cause of today’s loss of biodiversity is habitat alteration caused by human activities. Let’s think about the meaning of biodiversity. Most people understand that biodiversity includes the great heterogeneous assemblage of living organisms. This aspect of biodiversity is also known as species diversity. Biodiversity includes two other components as well- genetic diversity and ecosystem diversity.
Biological resources are those products that we harvest from nature. These resources fall into several categories: food, medicine, fibres, wood products, and more.