Biodiversity is the variety of life on Earth in all its forms and combinations. It includes the diversity of genes, species and ecosystems. The term "biodiversity" was popularised by the biologist E. O. Wilson. Biodiversity is the foundation of human survival because it provides food, medicine, timber, clean air and water, and ecosystem services that sustain life. However, biodiversity is being lost at an alarming rate due to human activities, making conservation an urgent global priority.
Biodiversity is generally considered at three levels: genetic diversity (variety of genes within species), species diversity (variety of species in an ecosystem) and ecosystem diversity (variety of habitats and ecosystems in a region). It is not uniformly distributed; the tropics harbour far more species than temperate or polar regions. This uneven distribution and the threats facing biodiversity are the central themes of this chapter, along with the strategies for its conservation.
Genetic diversity refers to the total genetic information contained in the genes of all the individuals of plants, animals and microorganisms inhabiting a particular area. It is the variety of genes within a species. Genetic diversity allows species to adapt to changing environmental conditions and is essential for the survival and evolution of species. For example, different varieties of rice and wheat in India represent genetic diversity that is important for crop breeding.
Species diversity is the variety of species in a given ecosystem or region. It is measured in terms of species richness (the number of species) and species evenness (the relative abundance of species). India, for example, has about 8% of the world's known species despite having only 2.4% of the world's land area. The number of species on Earth is estimated to be between 5 and 50 million, of which only about 1.7 million have been described and named.
Ecosystem diversity refers to the variety of habitats, communities and ecological processes in a region. It includes terrestrial ecosystems such as forests, grasslands and deserts, and aquatic ecosystems such as rivers, lakes and oceans. India's diverse ecosystems range from alpine meadows in the Himalayas to tropical rainforests in the Western Ghats, deserts in Rajasthan and coral reefs in the Andaman and Nicobar Islands.
Biodiversity is important for ecological, economic and social reasons: - Ecological services: Biodiversity maintains the health of ecosystems through nutrient cycling, soil formation, pollination, water purification and climate regulation. - Economic value: It provides food, fibre, timber, medicines, fuel and raw materials. Many modern medicines are derived from plants, such as quinine from the cinchona tree and taxol from yew trees. - Social and cultural value: Biodiversity is part of the cultural and spiritual identity of communities; many communities depend directly on biodiversity for their livelihoods. - Biotic resources: Biodiversity provides the essential "biotic resources" without which human society cannot survive.
Biodiversity is not evenly distributed over the Earth: 1. Latitudinal gradient: Species diversity increases from the poles towards the equator. Tropical regions are richer in species than temperate or polar regions because of favourable climate and high productivity over long periods. 2. Species area relationships: Larger areas tend to have more species, as shown by the species-area relationship. 3. Tropical hotspots: The tropics contain the maximum biodiversity, including tropical rainforests, coral reefs and large tropical wetlands.
The most important cause of biodiversity loss is habitat loss and fragmentation, caused by deforestation, conversion of land to agriculture and urbanisation. When habitats are destroyed or broken into fragments, species lose their living space and decline.
Over-exploitation refers to the excessive use of species faster than they can regenerate. Over-hunting, over-fishing and illegal wildlife trade have pushed many species towards extinction. Examples include the depletion of fish stocks and the hunting of tigers, rhinos and elephants.
Pollution of air, water and soil damages habitats and poisons species. Chemical fertilisers and pesticides, oil spills and industrial waste harm biodiversity.
When non-native species are introduced into new areas, they may compete with, prey on or displace native species. For example, water hyacinth (an exotic weed) has spread over many Indian water bodies, and the introduction of Nile perch in Lake Victoria led to the extinction of several native fish species.
Climate change alters temperature and rainfall patterns, shifts habitats and threatens species that cannot adapt or migrate. Coral reefs are especially vulnerable to warming (coral bleaching).
Conservation is the management of the human use of the biosphere so that it may yield the greatest sustainable benefit to present generations while maintaining its potential to meet the needs of future generations. Conservation is of two types:
In-situ conservation involves the protection and management of species in their natural habitats. This is done through: - National parks: Large areas set aside for the protection of ecosystems and wildlife, where no human interference is allowed. Examples: Kaziranga National Park (one-horned rhinoceros), Corbett National Park (tiger). - Wildlife sanctuaries: Areas where animals are protected but some human activities may be permitted. - Biosphere reserves: Large areas designated to conserve biodiversity along with sustainable development, with buffer and transition zones. India has 18 biosphere reserves. - Sacred groves: Forest patches protected by local communities for religious and cultural reasons.
Ex-situ conservation involves the conservation of species outside their natural habitats. It includes: - Zoological parks (zoos): Captive breeding of animals. - Botanical gardens: Cultivation of plant species. - Seed banks: Storage of seeds of wild and cultivated plants for future use. - Gene banks: Preservation of genetic material.
International conventions such as the Convention on Biological Diversity (CBD, 1992) aim to conserve biodiversity and ensure the sustainable use of its components. India's National Biodiversity Action Plan and the Wildlife (Protection) Act, 1972 provide the legal framework for conservation. India has several tiger reserves under Project Tiger (launched in 1973) and elephant reserves under Project Elephant. The Red Data Book lists endangered species to guide conservation efforts.
| Level | Definition | Example |
|---|---|---|
| Genetic diversity | Variety of genes within a species | Different varieties of rice |
| Species diversity | Variety of species in an ecosystem | Species richness of Western Ghats |
| Ecosystem diversity | Variety of habitats and ecosystems | Forests, grasslands, coral reefs |
| Threat | Description | Example |
|---|---|---|
| Habitat loss | Destruction of natural habitats | Deforestation of rainforests |
| Over-exploitation | Excessive use of species | Over-fishing, hunting of tigers |
| Pollution | Contamination of environment | Pesticides, oil spills |
| Exotic species | Introduction of alien species | Water hyacinth, Nile perch |
| Climate change | Altered temperature and rainfall | Coral bleaching |
| Approach | Method | Examples |
|---|---|---|
| In-situ | Protect in natural habitat | National parks, sanctuaries, biosphere reserves |
| Ex-situ | Protect outside natural habitat | Zoos, botanical gardens, seed banks |
Biodiversity, the variety of genes, species and ecosystems on Earth, is fundamental to life and human well-being. It provides ecological services, economic resources and cultural value, and it is concentrated in the tropics, which contain the richest habitats on the planet. However, biodiversity is under severe threat from habitat loss, over-exploitation, pollution, invasive species and climate change. Conservation through in-situ methods (national parks, sanctuaries, biosphere reserves) and ex-situ methods (zoos, seed banks) is essential to protect this heritage. International agreements like the Convention on Biological Diversity and national programmes such as Project Tiger reflect the growing recognition that conserving biodiversity is not a choice but a necessity for the sustainable future of the Earth.
Keywords: Biodiversity, genetic diversity, species diversity, ecosystem diversity, habitat loss, over-exploitation, in-situ, ex-situ, biosphere reserves, Project Tiger.