We should conserve biodiversity for the following reasons: (1) narrowly utilitarian reasons - humans derive direct economic benefits, such as food, firewood, fibre, medicines and industrial products, from biodiversity; (2) broadly utilitarian reasons - biodiversity provides important ecosystem services, such as the production of oxygen, pollination, and climate regulation; and (3) ethical (moral) reasons - every species has an intrinsic value and a right to exist, and we have a moral duty to protect them and pass on the biological wealth to future generations.

The four major causes of biodiversity loss, together called the Evil Quartet, are: (1) habitat loss and fragmentation - the most important cause, in which natural habitats such as forests are destroyed or broken up (for example, deforestation of tropical rainforests); (2) over-exploitation - excessive hunting, fishing and harvesting of species for human use; (3) alien (invasive) species invasions - the introduction of foreign species that harm the native species; and (4) co-extinctions - when a species becomes extinct, other species associated with it (such as its parasites or partners) also become extinct.

Biodiversity hotspots are regions with a very high level of species richness and a high degree of endemism (species found nowhere else), which are also under serious threat of habitat loss and destruction. They are given special priority for conservation. Three biodiversity hotspots extend into India: (1) the Western Ghats and Sri Lanka, (2) the Himalaya, and (3) the Indo-Burma region. Protecting such hotspots can greatly reduce the ongoing loss of species.

An endangered species is a species that is in serious danger of becoming extinct in the near future if the factors threatening it continue (for example, the tiger and the Great Indian Bustard). An endemic species is a species that is naturally found only in a particular geographical area or region and nowhere else (for example, the lion-tailed macaque of the Western Ghats). The IUCN (International Union for Conservation of Nature) Red List (Red Data Book) is a document that keeps a record of all endangered and threatened species of plants and animals.

Sacred groves are patches of forest or natural vegetation that are traditionally protected by local communities because of their religious and cultural beliefs, as they are dedicated to a deity or considered holy. In India they are found in regions such as the Khasi and Jaintia Hills of Meghalaya, the Western Ghats of Karnataka and Maharashtra, and the Aravalli Hills. Because cutting even a single tree is often forbidden, these groves are undisturbed and serve as important refuges for many rare, endemic and threatened species of plants and animals, thus helping in in-situ conservation of biodiversity.

Extinction is the complete disappearance of a species from the earth, so that no living individual of that species remains anywhere. It may occur naturally over a long time, but human activities (such as habitat destruction, over-exploitation and pollution) have greatly increased the rate of extinction. The Red Data Book (maintained by the IUCN) is an official document that contains a record of all the species that are endangered, vulnerable, rare or recently extinct, so that special conservation efforts can be directed towards protecting them.