Ecosystems
Ecosystems
An ecosystem is a functional unit of nature comprising living organisms (biotic community) and their non-living environment (abiotic factors) interacting as a system. India hosts diverse ecosystems — forests, grasslands, wetlands, deserts, marine, and freshwater — each with unique ecological characteristics.
Key Dates
A.G. Tansley coined the term "ecosystem" to describe the interaction of biotic and abiotic components
Lindeman proposed the 10% Law — only 10% of energy transfers to the next trophic level
Ramsar Convention on Wetlands — international treaty for conservation and wise use of wetlands
India became a signatory to the Ramsar Convention; Chilika Lake and Keoladeo NP were first two sites
Convention on Biological Diversity (CBD) adopted at Rio Earth Summit — India ratified in 1994
Biological Diversity Act enacted in India — established NBA, SBBs, and Biodiversity Management Committees
Wetlands (Conservation and Management) Rules — prohibited conversion and encroachment of wetlands
Kunming-Montreal Global Biodiversity Framework — 30x30 target (protect 30% of land and ocean by 2030)
India has 75 Ramsar wetland sites covering about 13.3 million hectares (as of 2023)
India has about 4,992 sq km of mangroves — 4th largest in the world; Sundarbans is the largest
India has 4 major coral reef areas — Gulf of Kutch, Gulf of Mannar, Andaman, Lakshadweep
India has 4 biodiversity hotspots — Western Ghats, Eastern Himalayas, Indo-Burma, Sundaland (Nicobar)
India has 18 Biosphere Reserves — 12 are in the UNESCO World Network (as of 2023)
Structure and Components of Ecosystems
Every ecosystem has two components: (1) Abiotic — non-living factors: sunlight (primary energy source for most ecosystems), temperature (determines species distribution and metabolic rates), water (most critical limiting factor in terrestrial ecosystems), soil (determines plant growth through minerals, pH, texture, and water-holding capacity), humidity, wind, nutrients (macro: N, P, K; micro: Fe, Mn, Zn), and pH. (2) Biotic — living organisms classified by function: Producers/Autotrophs (green plants, algae, cyanobacteria — convert solar energy to chemical energy via photosynthesis; form the base of all food chains; in aquatic ecosystems, phytoplankton are the primary producers), Consumers/Heterotrophs (Primary consumers — herbivores like deer, rabbit, grasshopper; Secondary consumers — small carnivores like fox, frog, spider; Tertiary consumers — top carnivores like lion, eagle, shark; Omnivores — bear, human, crow — eat both plants and animals), Decomposers/Saprotrophs (bacteria, fungi — break down dead organic matter, release nutrients back into soil, completing nutrient cycles; without decomposers, nutrients would remain locked in dead organisms). The interaction between biotic and abiotic components forms the functional ecosystem. Ecosystems can be natural (forest, ocean, desert, grassland, wetland) or artificial (crop field, aquarium, garden, urban ecosystem). They range from tiny (a rotting log, a puddle) to global (the biosphere — the sum of all ecosystems on Earth). Liebig's Law of the Minimum states that ecosystem productivity is limited by the factor in shortest supply, not by the total resources available.
Energy Flow and Food Chains
Energy flows unidirectionally through ecosystems: Sun to Producers to Consumers to Decomposers. Only about 1-2% of solar energy reaching the Earth is captured by photosynthesis (Gross Primary Productivity — GPP). After plants use some energy for respiration, the remainder is Net Primary Productivity (NPP = GPP - Respiration), which is available to consumers. Food Chain: a linear sequence of who eats whom — (1) Grazing food chain (GFC) — starts with green plants: grass to deer to tiger; contributes the major share of energy flow in terrestrial ecosystems; (2) Detritus food chain (DFC) — starts with dead organic matter: dead leaves to earthworm to bird; in a forest ecosystem, DFC may handle more energy than GFC because most plant material is not consumed alive but falls as litter. Food Web: interconnected food chains in an ecosystem forming a complex network; more realistic representation of energy flow; greater complexity of food webs generally indicates greater ecosystem stability. Ecological Pyramids: (1) Pyramid of Numbers — upright in grassland (many grass plants, fewer herbivores, fewest carnivores), inverted in tree ecosystem (one tree supports many herbivorous insects which support fewer predators); (2) Pyramid of Biomass — upright in terrestrial (producers have maximum standing biomass), inverted in open ocean/aquatic (phytoplankton biomass at any given time is less than zooplankton because phytoplankton reproduce extremely rapidly — high turnover rate); (3) Pyramid of Energy — always upright without exception; 10% Law (Lindeman, 1942): only about 10% of energy at one trophic level transfers to the next; rest is lost as heat through respiration. This fundamental constraint limits food chains to typically 4-5 trophic levels.
Biogeochemical Cycles
Nutrients cycle through ecosystems in biogeochemical cycles — moving between the atmosphere, lithosphere, hydrosphere, and biosphere: (1) Carbon Cycle — carbon moves between atmosphere (CO2 — currently 420+ ppm, up from 280 ppm pre-industrial), biosphere (photosynthesis fixes CO2 into organic matter; respiration releases it), lithosphere (fossil fuels — coal, oil, gas; limestone — CaCO3), and hydrosphere (dissolved CO2 and carbonates — oceans hold 50x more carbon than the atmosphere). Fossil fuel burning and deforestation have increased atmospheric CO2 by 50% since pre-industrial times, driving global warming. The ocean is a net carbon sink, absorbing about 25% of annual anthropogenic CO2 emissions. (2) Nitrogen Cycle — N2 constitutes 78% of the atmosphere but is unusable by most organisms; nitrogen fixation converts N2 to ammonia (NH3): biological fixation by Rhizobium bacteria in legume root nodules, free-living bacteria (Azotobacter, Clostridium), cyanobacteria (Anabaena, Nostoc), and lightning; nitrification (NH3 to NO2 to NO3 by Nitrosomonas and Nitrobacter); plants absorb NO3; denitrification returns N2 to the atmosphere (by Pseudomonas); excess nitrogen from synthetic fertilizers (Haber-Bosch process) causes eutrophication — nutrient enrichment leading to algal blooms and oxygen depletion (dead zones). (3) Phosphorus Cycle — sedimentary cycle (no significant gaseous phase); phosphorus from rock weathering enters soil, is absorbed by plants, passes through food chains, returns to soil/water via decomposition; essential for DNA, RNA, ATP, bones, and teeth; often a limiting nutrient in freshwater ecosystems; excess phosphorus from detergents and fertilizers causes eutrophication. (4) Water Cycle (Hydrological Cycle) — evaporation (from oceans, lakes, rivers), transpiration (from plants — together called evapotranspiration), condensation (cloud formation), precipitation (rain, snow), runoff, infiltration, and groundwater recharge. Human activities have disrupted all major biogeochemical cycles.
Terrestrial Ecosystems of India
India's diverse geography supports multiple terrestrial ecosystem types: (1) Forest Ecosystems — covering 21.71% of India (ISFR 2021); range from tropical evergreen (Western Ghats, NE India) to alpine scrub; tropical deciduous forests are the most widespread type; forests are the most biodiverse terrestrial ecosystems, hosting 70-80% of terrestrial species. (2) Grassland Ecosystems — found in semi-arid regions and high-altitude areas; the Banni Grasslands (Gujarat, Rann of Kutch) — India's largest grassland, supporting the Banni buffalo breed and the Indian wild ass; the high-altitude grasslands (bugyals) of Uttarakhand above 3,500 m used for seasonal grazing; the Shola grasslands of the Western Ghats — fire-maintained grasslands interspersed with stunted forests (sholas); Terai grasslands of UP and Uttarakhand; grasslands support species like the Great Indian Bustard (critically endangered — fewer than 150 remaining, mainly in Rajasthan and Gujarat), blackbuck, Indian wolf, and florican. (3) Desert Ecosystems — the Thar Desert (Great Indian Desert) of Rajasthan — about 200,000 sq km; receives less than 250 mm rainfall; xerophytic vegetation (babool, khejri, cactus); fauna: Indian wild ass (Little Rann of Kutch), Great Indian Bustard, desert fox, spiny-tailed lizard; the cold desert of Ladakh and Spiti Valley — high altitude arid ecosystem above 3,500 m; sparse vegetation; fauna: snow leopard, Tibetan wild ass (kiang), Tibetan wolf, Pallas's cat; the Deccan thorn scrub in rain-shadow areas. (4) Alpine Ecosystems — above the treeline in the Himalayas (above 3,500-4,000 m); alpine meadows, dwarf shrubs, and lichens; harsh conditions (extreme cold, wind, UV radiation, short growing season); unique species: snow leopard, Himalayan tahr, musk deer, Himalayan monal. India has 10 biogeographic zones (as classified by the Wildlife Institute of India), each with distinct ecosystems.
Aquatic Ecosystems — Freshwater and Marine
Aquatic ecosystems cover 71% of Earth's surface and are classified as: (1) Freshwater Ecosystems — include rivers (lotic — flowing water), lakes and ponds (lentic — still water), and wetlands. In India, the Ganga-Brahmaputra system, peninsular rivers, and thousands of natural and artificial lakes form a vast freshwater network. River ecosystems support the endangered Gangetic river dolphin (Platanista gangetica — India's National Aquatic Animal), gharial, and numerous fish species. Lake ecosystems: zonation includes littoral (shore zone with rooted plants), limnetic (open water with phytoplankton), profundal (deep, cold, dark zone), and benthic (bottom). India's freshwater ecosystems support about 1,500 species of freshwater fish. (2) Marine Ecosystems — India has an EEZ of about 2.02 million sq km and 7,500 km of coastline. Key marine ecosystems: coral reefs (4 major areas), mangroves (4,975 sq km), estuaries, lagoons, open ocean, deep sea, and continental shelf. Marine ecosystems support 15,000+ species in Indian waters, including 2,500+ fish species, 5 species of sea turtles, dugong, and numerous cetaceans (whales and dolphins). (3) Brackish Water Ecosystems — transitional between freshwater and marine; include estuaries, lagoons (Chilika, Pulicat), and backwaters (Kerala); highly productive due to nutrient input from both terrestrial and marine sources; support important fisheries; breeding grounds for many marine species. The concept of the ecological health of aquatic ecosystems is measured by indicators like Dissolved Oxygen (DO — healthy rivers have DO > 6 mg/L), Biochemical Oxygen Demand (BOD — high BOD indicates organic pollution), and species diversity indices.
Wetland Ecosystems and Ramsar Convention
Wetlands are transitional zones between terrestrial and aquatic ecosystems — areas where land is covered by water permanently or seasonally. Types: marshes (herbaceous vegetation), swamps (woody vegetation), bogs (acidic peat), fens (alkaline peat), mangroves, estuaries, floodplains, and rice paddies (artificial wetlands). India has about 7.57 lakh hectares of wetlands (4.63% of geographic area). The Ramsar Convention on Wetlands (1971, adopted in Ramsar, Iran) is the international treaty for wetland conservation and wise use. India became a signatory in 1982 with Chilika Lake and Keoladeo (Bharatpur) as first sites. India has 75 Ramsar sites (as of 2023) covering about 13.3 million hectares — second most after the UK. Tamil Nadu has the most Ramsar sites (16); followed by UP (10). Largest Ramsar sites by area: Sundarbans (West Bengal), Vembanad-Kol (Kerala). Wetland ecosystem services: (1) Water Purification — wetlands act as natural water treatment systems, filtering pollutants and sediments; (2) Flood Control — store excess water during floods, release slowly; the East Kolkata Wetlands treat 40% of Kolkata's sewage naturally; (3) Groundwater Recharge; (4) Carbon Sequestration — wetlands store about 20-30% of global soil carbon; (5) Biodiversity Habitats — support migratory birds, fish, amphibians, reptiles; (6) Fisheries — wetlands support about 20% of India's freshwater fish production; (7) Recreation and Tourism. Threats: drainage for agriculture, urbanization, pollution, invasive species (water hyacinth is the most significant invasive plant in Indian wetlands), and climate change. Wetlands (Conservation and Management) Rules 2017 under EPA 1986 prohibit conversion/destruction of wetlands and establish State Wetland Authorities. Notable wetlands: Chilika (Odisha — Irrawaddy dolphins, migratory birds), Loktak (Manipur — floating Phumdis, Keibul Lamjao NP, endangered Sangai deer), Wular (J&K — largest freshwater lake), Sambhar (Rajasthan — largest inland salt lake), Deepor Beel (Assam — Ramsar site).
Ecological Succession
Ecological Succession: The gradual, sequential replacement of one community by another in an area over time until a stable climax community is reached. It is a fundamental ecological process by which ecosystems recover from disturbance. Primary Succession: occurs on bare/lifeless substrate with no pre-existing soil (new volcanic island, retreating glacier, newly exposed rock); starts with pioneer species (lichens and mosses that can colonize bare rock, breaking it down into primitive soil); very slow (hundreds to thousands of years); stages: bare rock to lichens/mosses to herbs/grasses to shrubs to trees to climax forest; the process of soil formation (pedogenesis) is central to primary succession. Xerosere is succession on dry habitat; Hydrosere (or Hydrarch succession) is succession in aquatic habitat proceeding from open water through submerged vegetation, floating plants, marsh, meadow, to forest. Secondary Succession: occurs on previously vegetated area that was disturbed (abandoned farmland, forest fire area, logged forest); soil and seed bank already present; faster (decades to a century); the Bhopal lake cleanup after eutrophication or regrowth of Himalayan forests after a landslide are Indian examples. Climax Community: the final, stable stage of succession that is in equilibrium with the local climate; in most of India, the climax community is some form of forest (determined by rainfall and temperature). Disturbance-maintained ecosystems: some ecosystems require periodic disturbance to maintain their character — for example, savanna grasslands require fire; without fire, they would succeed to forest; the Shola grasslands of the Western Ghats are maintained by fire and frost; some fire ecologists argue that controlled burning is essential for ecosystem health.
Key Ecological Concepts for Exams
Key ecological concepts frequently tested in competitive exams: (1) Niche — the functional role of a species in an ecosystem (habitat + diet + behaviour + interactions); no two species can occupy exactly the same niche indefinitely (Gause's Competitive Exclusion Principle, 1934); resource partitioning allows similar species to coexist by dividing the niche. (2) Ecotone — transitional zone between two ecosystems (e.g., mangrove — between land and sea; grassland-forest boundary); has characteristics of both adjacent ecosystems; often richer in species (Edge Effect) because it contains species from both ecosystems plus ecotone-specific species. (3) Keystone Species — species whose impact on ecosystem is disproportionately large relative to its abundance (e.g., sea otters control sea urchins which would otherwise overgraze kelp forests; elephants maintain grassland-forest mosaics by knocking down trees; fig trees sustain numerous frugivores during lean seasons). (4) Flagship Species — charismatic species used for conservation campaigns (tiger, panda, elephant); their conservation indirectly protects entire ecosystems. (5) Umbrella Species — protecting their large habitat requirements protects many other species (tiger needs large contiguous forest — protecting tiger habitat protects all co-occurring species). (6) Indicator Species — species whose presence or absence indicates ecosystem health (lichens indicate clean air; mayfly nymphs indicate clean water; presence of vultures indicates healthy carrion cycle). (7) Endemic Species — species found nowhere else on Earth; India has high endemism especially in the Western Ghats and NE India. (8) Biological Magnification (Biomagnification) — concentration of persistent pollutants (DDT, mercury, heavy metals) increases at each trophic level; top predators have the highest concentrations; DDT caused eggshell thinning in raptors. (9) Eutrophication — nutrient enrichment of water bodies leading to excessive algal growth, oxygen depletion, and fish kills; caused by agricultural runoff and sewage.
Ecosystem Services and Valuation
Ecosystem services are the benefits that ecosystems provide to humanity, classified by the Millennium Ecosystem Assessment (2005) into four categories: (1) Provisioning Services — direct products: food (crops, fish, meat), freshwater, timber, fibre, medicinal resources, genetic resources; India's forests provide about Rs 1.5 lakh crore worth of provisioning services annually. (2) Regulating Services — regulation of natural processes: climate regulation (carbon sequestration by forests — India's forests sequester about 7% of India's annual CO2 emissions), flood control (wetlands store floodwater), water purification (wetlands filter pollutants), pollination (about 35% of global food production depends on animal pollinators — bees, butterflies, birds), pest control (natural predators regulate crop pests), disease regulation. (3) Cultural Services — non-material benefits: recreation and tourism (India's wildlife tourism generates about Rs 3,000 crore annually), aesthetic values, spiritual significance (sacred groves, sacred rivers), educational values. (4) Supporting Services — basic processes that underpin all other services: nutrient cycling, soil formation, primary production (photosynthesis), water cycling. Valuation methods: (a) Market-based (direct pricing of provisioning services), (b) Replacement Cost (cost of replacing a natural service with artificial means — e.g., water treatment plants to replace wetland purification), (c) Contingent Valuation (willingness to pay for ecosystem conservation), (d) Travel Cost (expenditure by visitors to natural areas). The Economics of Ecosystems and Biodiversity (TEEB) initiative estimated that the annual loss of natural capital due to land-use change costs $2-4.5 trillion globally. India's National Mission on Biodiversity and Human Well-being proposes integrating ecosystem service valuation into national accounting (Green GDP). The concept of Payment for Ecosystem Services (PES) is gaining traction — communities protecting forests, watersheds, or wetlands receive compensation for the services these ecosystems provide.
Biomes of the World and India's Position
A biome is a large-scale community of organisms defined by characteristic vegetation, climate, and soil type. The major terrestrial biomes are: (1) Tropical Rainforest — equatorial regions (0-10° latitude); high rainfall (>200 cm), warm year-round; highest biodiversity; in India: Western Ghats (Silent Valley, Agastyamalai), NE India (Meghalaya, Arunachal), Andaman & Nicobar. (2) Tropical Deciduous Forest — monsoon regions (10-30° latitude); seasonal rainfall; trees shed leaves in dry season; India's most widespread biome. (3) Tropical Grassland/Savanna — seasonal rainfall with long dry period; grasslands with scattered trees; Banni grassland (Gujarat), Terai grasslands. (4) Desert — extremely low rainfall (<25 cm); Thar Desert (hot), Ladakh (cold desert). (5) Mediterranean Scrub (Chaparral) — mild wet winters, hot dry summers; not found in India. (6) Temperate Grassland — continental interiors; Steppes (Eurasia), Prairies (N. America); not found in India except marginally. (7) Temperate Forest — deciduous (eastern continents); coniferous (higher latitudes/altitudes); in India: Himalayan temperate forests (oak, deodar, pine at 2,000-3,500 m). (8) Taiga/Boreal Forest — coniferous forest; not found in India. (9) Tundra — treeless, permafrost; Arctic and Antarctic; not found in mainland India (though the Himalayan alpine meadows above 4,000 m have tundra-like characteristics). (10) Aquatic Biomes — Marine and Freshwater. India, spanning 8°4'N to 37°6'N latitude with altitudes from sea level to 8,586 m (Kangchenjunga), hosts biome types ranging from tropical rainforest to alpine tundra within a single country — one of the most ecologically diverse nations on Earth. India holds about 8% of the world's known species with only 2.4% of the world's land area.
Productivity of Ecosystems
Ecosystem productivity measures the rate of biomass production. Key terms: (1) Gross Primary Productivity (GPP) — total rate of photosynthesis in an ecosystem (total carbon fixed); (2) Net Primary Productivity (NPP) — GPP minus plant respiration (R); NPP = GPP - R; NPP represents the energy available to consumers; (3) Net Ecosystem Productivity (NEP) — NPP minus heterotrophic respiration (consumer and decomposer respiration); positive NEP means the ecosystem is a carbon sink. Productivity varies across ecosystems: most productive terrestrial ecosystems — tropical rainforests (NPP: 2,200 g/m2/year), swamps and marshes (2,000 g/m2/year), tropical seasonal forests (1,600 g/m2/year); least productive — deserts (90 g/m2/year), tundra (140 g/m2/year). Most productive aquatic ecosystems — estuaries (1,500 g/m2/year), coral reefs (2,500 g/m2/year), algal beds; least productive — open ocean (125 g/m2/year) despite covering 65% of Earth's surface. The open ocean's low per-area productivity is offset by its vast size — it contributes about 40% of global photosynthesis. Factors limiting ecosystem productivity: light (especially at high latitudes and depths), water (in terrestrial ecosystems — the main factor in Indian deserts), temperature (in arctic/alpine regions), nutrients (nitrogen and phosphorus are commonly limiting; iron is limiting in parts of the open ocean). India's forest ecosystems have NPP estimated at about 1.5 billion tonnes of carbon per year. Agricultural ecosystems have been artificially boosted through irrigation, fertilizers, and high-yielding varieties (Green Revolution), but at the cost of biodiversity and long-term soil health.
Ecological Footprint and Carrying Capacity
Ecological Footprint: the area of productive land and water required to produce the resources consumed and absorb the waste generated by a population, using prevailing technology. It is measured in global hectares (gha). India's ecological footprint is about 1.2 gha per person (well below the global average of 2.75 gha), but the total national footprint exceeds India's biocapacity (available productive area), meaning India is in ecological overshoot — consuming more resources than its ecosystems can regenerate. The global ecological footprint is estimated at 1.7 Earths (meaning humanity uses 70% more resources than Earth can regenerate annually). Carrying Capacity: the maximum population that an ecosystem can sustain indefinitely without degradation. India's carrying capacity is a function of land productivity, water availability, energy resources, and waste absorption capacity. India faces carrying capacity constraints particularly in: (1) Water — per capita water availability has declined from 5,177 m3/year (1951) to about 1,486 m3/year (2021); projected to fall below 1,000 m3/year (water-scarce) by 2050 in several basins; (2) Arable Land — per capita arable land has declined from 0.34 hectares (1951) to 0.12 hectares (2021) due to population growth and urbanization; (3) Forest Resources — India's forest cover at 21.71% is below the 33% target. Sustainable Development requires living within the carrying capacity of ecosystems — this is the core principle behind the concept of sustainability, formalized by the Brundtland Commission (1987) as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs." India's Sustainable Development Goals (SDGs) National Indicator Framework tracks progress across 17 SDGs and 169 targets.
Invasive Alien Species in Indian Ecosystems
Invasive alien species (IAS) are non-native organisms that establish, spread, and cause ecological or economic harm in new environments. They are considered the second greatest threat to biodiversity after habitat loss. Major invasive species affecting Indian ecosystems: (1) Water Hyacinth (Eichhornia crassipes) — from South America; chokes water bodies, blocking sunlight and depleting oxygen; affects Loktak Lake, Dal Lake, and thousands of other water bodies; the "Terror of Bengal" due to its devastation of Bengali waterways. (2) Lantana camara — from Central America; a thorny shrub that has invaded about 40% of India's tiger habitat, replacing native understorey vegetation, reducing food availability for herbivores and consequently affecting tiger prey populations; extremely difficult to eradicate; some programmes now explore economic uses (furniture, biochar). (3) Prosopis juliflora (Vilayati babool/Mesquite) — from Central America; planted widely for afforestation in arid regions, now invasive in Rajasthan, Gujarat, and AP; out-competes native species; exploits deep groundwater. (4) Parthenium hysterophorus (Congress grass/Gajar ghas) — from tropical America; has invaded grasslands, wastelands, and agricultural fields across India; causes severe allergic reactions in humans (Parthenium dermatitis); reduces crop yields. (5) African catfish (Clarias gariepinus) — introduced for aquaculture; has escaped into Indian rivers and threatens native fish species through predation and competition; banned for aquaculture in several states. (6) Senna spectabilis — rapidly invading forests in the Western Ghats, particularly in Mudumalai and Wayanad; forms dense monocultures shading out native vegetation. India enacted the Prevention and Management of Invasive Alien Species guidelines under the National Biodiversity Authority, but enforcement is challenging given the scale of invasions.
Sacred Groves and Traditional Conservation
Sacred groves are patches of natural vegetation preserved by local communities on religious and cultural grounds. They represent one of the oldest forms of biodiversity conservation, predating formal protected areas by centuries. India has an estimated 100,000-150,000 sacred groves covering about 33,000 hectares, found across most states. Notable concentrations: (1) Meghalaya — "Law Kyntang" and "Law Lyngdoh" sacred forests (some covering hundreds of hectares); Mawphlang sacred grove is the most famous; maintained by the Khasi tribes. (2) Kerala — "Kavus" (sacred groves) — over 2,000 groves; harbour unique biodiversity including rare medicinal plants; associated with serpent worship (Sarpa Kavu). (3) Rajasthan — "Orans" — community-conserved sacred groves in the Thar Desert; the Bishnoi community of Rajasthan is famous for protecting trees and wildlife (the 1730 Khejarli massacre, where 363 Bishnois led by Amrita Devi sacrificed their lives to protect khejri trees, is considered India's first environmental movement). (4) Maharashtra — "Devrahati" or "Devrai"; (5) Karnataka — "Devarakadu" or "Devana kadu"; (6) Tamil Nadu — "Swami Solai" or "Kovilkadu"; (7) Chhattisgarh — "Sarna" (sacred groves of tribal communities); (8) Himachal Pradesh — "Devban" (god's forest). Ecological significance: sacred groves often preserve climax vegetation that has disappeared elsewhere due to deforestation; they serve as refugia for rare and endemic species; they maintain soil and water conservation in their vicinity; they preserve genetic diversity of wild relatives of crop plants. Threats: urbanization, younger generations losing traditional beliefs, and encroachment. The National Biodiversity Authority and some State Biodiversity Boards are working to document and protect sacred groves.
Relevant Exams
Ecosystems is a high-yield topic for UPSC Prelims (2-3 questions yearly). Questions on ecological pyramids, food chains/webs, Ramsar sites, and wetland conservation are very common. SSC/RRB exams test basic concepts like food chain, 10% law, and largest wetlands. Current affairs on new Ramsar site designations, invasive species, and ecosystem services appear every year. Biogeochemical cycles, succession, and ecological concepts (keystone, flagship, edge effect) are Mains favorites.