Biodiversity & Conservation

Biodiversity and conservation is a consistently tested NEET topic, with questions focusing on the species-area relationship, biodiversity hotspot criteria, and conservation strategies. Precise numerical values and definitions matter here.

Three levels of biodiversity exist. Genetic diversity refers to variation in genes within a species — for example, the medicinal plant Rauwolfia vomitoria shows varying potency of reserpine across different Himalayan populations. Species diversity describes the variety of species in a region; globally, approximately 1.5 million species have been formally described, though estimates range from 5 to 50 million total. India harbours roughly 45,000 plant species and 100,000 animal species. Ecological diversity encompasses the variety of ecosystems within a region — India's ecological diversity spans deserts, tropical rainforests, mangroves, coral reefs, wetlands, and alpine meadows.

Biodiversity patterns reveal important gradients. The latitudinal gradient shows that species richness increases from poles toward the equator. Tropical regions harbour disproportionately more species due to longer evolutionary time (no glaciation disruption), greater solar energy driving higher productivity, and more opportunities for niche specialization. The species-area relationship, described by Alexander von Humboldt, follows the equation log S = log C + Z log A, where S is species richness, A is area, Z is the regression coefficient (slope), and C is the y-intercept. Within continents, Z typically ranges from 0.1 to 0.2. For islands, Z is significantly steeper at 0.6 to 1.2, meaning species richness drops sharply as island area decreases.

Biodiversity importance spans three domains. Direct/economic value includes food crops, timber, and medicinal plants (Cinchona yields quinine, Digitalis provides digitalis, Rauwolfia supplies reserpine). Indirect/ecological value encompasses ecosystem services — oxygen production, pollination, nutrient cycling, climate regulation, flood control, and soil formation — valued at approximately 33 trillion dollars annually (Robert Costanza's estimate). Ethical value recognizes every species' intrinsic right to existence, a principle termed biophilia by E.O. Wilson.

Causes of biodiversity loss follow the HIPPO framework. Habitat loss and fragmentation is the primary driver — tropical rainforests have been reduced from 14% to 6% of Earth's surface. Invasive alien species devastate native communities: the Nile perch introduction in Lake Victoria drove hundreds of endemic cichlid fish to extinction; Lantana camara, water hyacinth (Eichhornia crassipes), and Parthenium (Congress grass) are notorious invaders in India. Population growth and overexploitation caused the extinction of Steller's sea cow and the passenger pigeon. Pollution (pesticides, industrial effluents, plastics) and co-extinction (when a host species dies, dependent parasites and pollinators also perish) complete the picture.

The IUCN Red List categorizes species by extinction risk: Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD), and Not Evaluated (NE). Indian examples include the Asiatic lion and Bengal tiger (Endangered) and the one-horned rhinoceros and snow leopard (Vulnerable).

In-situ conservation protects species in their natural habitats. India has 18 biosphere reserves (Nilgiri, Sundarbans, Nanda Devi, among others), 106 national parks (Jim Corbett is the oldest; Kaziranga protects the one-horned rhino; Gir houses the Asiatic lion), and approximately 566 wildlife sanctuaries (limited human activity permitted, unlike national parks with strict protection). Sacred groves — forest patches protected by local communities on religious grounds, found in Meghalaya's Khasi and Jaintia Hills, Rajasthan's Aravalli Hills, and the Western Ghats — represent an in-situ strategy, not ex-situ. Globally, 36 biodiversity hotspots have been identified (originally 25 by Norman Myers). A region qualifies as a hotspot only if it meets both criteria: at least 1,500 endemic vascular plant species (0.5% of world total) AND at least 70% of original habitat lost. India contains four hotspots: Western Ghats and Sri Lanka, Himalayas, Indo-Burma, and Sundaland (including Nicobar Islands).

Ex-situ conservation protects species outside their natural habitats through zoological parks (captive breeding), botanical gardens (Indian Botanical Garden in Howrah — home to the Great Banyan Tree), seed banks (seeds stored at -196 degrees C in liquid nitrogen for cryopreservation), gene banks, and tissue culture/micropropagation of endangered species.

The Convention on Biological Diversity (CBD) was signed at the Earth Summit in Rio de Janeiro in 1992, with goals of conservation, sustainable use, and equitable benefit-sharing. India has over 75 Ramsar wetland sites (Chilika Lake, Wular Lake, Loktak Lake).

The key testable concept is the species-area relationship (log S = log C + Z log A) with Z = 0.1-0.2 for continents and Z = 0.6-1.2 for islands, and that India has exactly four biodiversity hotspots meeting both endemism and habitat loss criteria.