Magnitude of biodiversity

Biodiversity is usually quantified as the number of species present in a region at a given time, and the current estimate for the whole planet is around 8-9 million species — though the true figure remains genuinely unknown, a gap the chapter calls the 'taxonomic impediment'. So far only about 1.5 million species of micro-organisms, animals and plants have actually been described, with roughly 10-15 thousand new species identified and published every year, three-quarters of them invertebrates; the number of species that remain entirely undescribed is undoubtedly far larger still. India punches well above its geographic weight in this global picture: with only about 2.4% of the world's total land surface, it represents two of the world's major biogeographic realms (the Palearctic and the Indo-Malayan) and three biomes (tropical humid forests, tropical dry/deciduous forests, and warm deserts/semi-deserts), and hosts over 8% of the world's animal species — around 92,000 known species. As the world's seventh-largest country by area, India spans hills, valleys, plateaus, sea shores, mangroves, estuaries, glaciers, grasslands and river basins, giving it a correspondingly wide range of climate, rainfall, temperature and soil conditions; it is one of only 17 recognised mega-biodiversity countries worldwide and has ten distinct biogeographic zones, each with its own characteristic habitat and biota (detailed in the next section). As the World Wil …