What biodiversity is

Biodiversity is the variety of life on earth, at every level of biological organisation. The term was popularised by the biologist Edward Wilson. It exists at three levels:

• Genetic diversity: variation within one species. The medicinal plant Rauwolfia vomitoria, growing in different parts of the Himalayas, varies in the potency and amount of the chemical reserpine it makes. India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.
• Species diversity: the variety of species in an area. The Western Ghats, for example, have more amphibian species than the Eastern Ghats.
• Ecological diversity: the variety of ecosystems. India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has far more than a country like Norway.

How many species are there? About 1.5 million have been described (IUCN, 2004). But many more await discovery, especially in the tropics and among insects and microbes. The ecologist Robert May estimates the global total at about 7 million. Prokaryotes are not even included in these estimates: they are hard to identify by ordinary methods, and many cannot be grown in the laboratory.

Of the recorded species:

• More than 70% are animals, and plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) are no more than 22%.
• Among animals, insects are by far the richest group: more than 70% of all animals.
• There are more species of fungi than of fishes, amphibians, reptiles and mammals put together.

India has only 2.4% of the world's land area, but its share of global species diversity is an impressive 8.1%. That makes it one of the 12 mega diversity countries of the world. About 45,000 plant species and twice as many animal species have been recorded, and many more are still undiscovered.