Terrestrial Ecosystem and Types of Forest in India

A terrestrial ecosystem is a land-based ecosystem in which the community of plants, animals and micro-organisms interacts with a physical environment whose defining constraint is the scarcity and unreliability of water. Forests, grasslands, deserts and tundra are the four terrestrial ecosystems recognised at the global scale, and every one of them occurs in India — from the wet evergreen forests of the Western Ghats to the cold desert of Ladakh.

This page is the base reference for the topic. It builds the concept from first principles (structure, energy flow, productivity, limiting factors), then applies it to India’s terrestrial ecosystems with the latest official data — India State of Forest Report (ISFR) 2023, the Champion & Seth forest classification, the ICAR grassland types, and the ISRO desertification atlas — and closes with verified UPSC previous year questions.

What Is a Terrestrial Ecosystem?

An ecosystem is any unit in which living organisms and the non-living environment interact through energy flow and nutrient cycling. When that unit sits on land, it is a terrestrial ecosystem. The land setting changes almost every physical variable that ecology depends on, and those changes explain nearly all the structural differences you see between a forest and a coral reef. (For the parent concepts, see What is Ecology and Environment.)

The Four Physical Conditions That Define Life on Land

1. Water is the master limiting factor. Aquatic organisms live inside their solvent; terrestrial organisms must acquire, transport and conserve it. Water availability is therefore the single strongest predictor of which terrestrial ecosystem develops at a place.
   • Every major land adaptation — cuticles, stomata, deep tap roots, succulence, leaf-shedding, concentrated urine, nocturnality — is fundamentally a water-economy adaptation.
2. Temperature fluctuates far more. Land surfaces experience much larger diurnal and seasonal temperature swings than water bodies in the same climate.
   • Water has a high specific heat, a high latent heat of vaporisation and a high latent heat of fusion compared with air. These buffer aquatic systems against thermal change; the atmosphere provides no such buffer.
   • Consequence: terrestrial organisms need thermoregulatory traits — fur, feathers, hibernation, aestivation, migration, deciduousness.
3. Light is more available. The atmosphere is far more transparent than water, which absorbs and scatters light rapidly with depth.
   • Photosynthesis on land is therefore not depth-limited, which allows tall, multi-layered vegetation and a large standing crop of biomass.
4. Gases are freely available. Carbon dioxide, oxygen and nitrogen diffuse roughly 10,000 times faster in air than in water.
   • CO₂ — substrate for photosynthesis; O₂ — substrate for aerobic respiration; N₂ — substrate for biological nitrogen fixation.
   • This is why land ecosystems rarely face the oxygen-depletion crises (hypoxia, dead zones) that structure aquatic systems.

The Two-Tier Environment: Subterranean and Atmospheric

A terrestrial environment is vertically segmented into two functionally different halves, and every land plant must operate in both simultaneously. This is the structural signature of terrestrial life.

Segment	What the organism obtains here	Key adaptation
Subterranean portion (soil)	Almost all water and mineral ions; anchorage; a reservoir of decomposers	Root systems, root hairs, mycorrhizal associations, nitrogen-fixing nodules
Atmospheric portion (above ground)	Gases (CO2, O2) and light energy, which is converted into the chemical energy of carbon–carbon bonds	Stems, leaves, stomata, canopy architecture, supporting tissue (lignin)

Terrestrial vs Aquatic Ecosystem: The Comparison That Gets Tested

Parameter	Terrestrial ecosystem	Aquatic ecosystem
Limiting factor	Water (moisture availability)	Light, dissolved oxygen and nutrients
Temperature variation	Large, diurnal and seasonal	Small and buffered
Light penetration	High; atmosphere is transparent	Low; restricted to the photic zone
Gas availability	High; rapid diffusion in air	Low; O2 solubility falls as temperature rises
Dominant producers	Large, long-lived vascular plants (trees, grasses)	Microscopic, short-lived phytoplankton (in open water)
Pyramid of biomass	Upright — a huge standing crop of producers	Inverted in open water — small producer biomass, high turnover
Dominant food chain	Detritus food chain (DFC) carries the bulk of energy	Grazing food chain (GFC) dominates in open water
Nutrient storage	Mostly locked in biomass and soil	Mostly dissolved in the water column and sediment
Support	Skeletal / lignified tissue needed against gravity	Buoyancy provides support

Structure of a Terrestrial Ecosystem

• Abiotic components: climate (temperature, precipitation, light, wind), edaphic factors (soil texture, depth, pH, nutrients), topography (altitude, slope, aspect) and inorganic/organic substances (C, N, P, water, humus).
• Biotic components:
  • Producers — rooted vascular plants that fix solar energy.
  • Consumers — herbivores (primary), carnivores (secondary, tertiary) and omnivores.
  • Decomposers — fungi, bacteria and soil fauna that mineralise dead organic matter. On land, decomposition is slower and more temperature-sensitive than in water, which is why cold ecosystems accumulate peat and permafrost carbon.
• Vertical stratification: a mature forest shows an emergent layer, canopy, understorey, shrub layer, herb layer and forest floor, plus a root zone. Each stratum has its own microclimate and its own fauna — this is why a rainforest can pack so many species into a small area.
• Horizontal zonation: ecotones and gradients — forest grading into savanna, savanna into thorn scrub, scrub into desert — track declining rainfall.

Function: Energy Flow, Productivity and Nutrient Cycling

• Energy flow is one-way. Solar energy is fixed by producers and passes through trophic levels, degrading to heat at each transfer (roughly a 10% transfer efficiency, Lindeman’s ten per cent law).
• The detritus food chain dominates. In most terrestrial ecosystems, far less than half of net primary production is eaten alive. Grasses, leaves and wood mostly die and enter the soil, where detritivores and decomposers process them. The DFC is therefore the major conduit of energy flow on land.
• Nutrient cycles are largely closed and soil-mediated. Carbon, nitrogen, phosphorus and water cycle between vegetation, litter, soil organic matter and the atmosphere. Removing the vegetation breaks the cycle and the nutrients are lost by leaching and erosion — the mechanism behind post-deforestation soil exhaustion.

Net Primary Productivity of the Major Terrestrial Ecosystems

Terrestrial ecosystem	Approximate NPP (g dry matter/m²/year)	Note
Tropical rainforest	2,000 – 3,000	Highest of all terrestrial ecosystems; warm, wet, aseasonal
Temperate deciduous forest	1,000 – 1,500	Productive but seasonally shut down in winter
Boreal forest (taiga)	600 – 900	Short growing season; huge area, so large total contribution
Savanna / tropical grassland	500 – 1,500	Rainfall-limited and fire-maintained
Temperate grassland	300 – 800	Most production is below ground, in roots
Tundra	100 – 400	Temperature- and season-limited; among the lowest
Desert and semi-desert scrub	10 – 250	Least productive terrestrial ecosystem; water-limited

What Decides Which Terrestrial Ecosystem Forms?

Two climatic variables — mean annual temperature and mean annual precipitation, together with their seasonality — explain the global distribution of terrestrial ecosystems. This is the logic behind Whittaker’s biome diagram and behind the Köppen climate classification.

• Rotation of the Earth around the Sun and the tilt of the Earth on its axis together fix the latitudinal distribution of solar energy, hence temperature belts and seasons.
• Annual variation in precipitation then splits each temperature belt into wet and dry formations — rainforest versus savanna versus desert within the same tropical belt.
• Altitude reproduces latitude: climbing a mountain passes through the same sequence of formations as travelling poleward, which is why alpine tundra exists at the equator on high peaks.
• Locally, edaphic and biotic factors (soil, fire, grazing) can hold vegetation below its climatic climax — a fire-climax savanna or a grazing disclimax grassland.

The Four Terrestrial Ecosystems

Terrestrial ecosystems are conventionally grouped into four types — forest, grassland, desert and tundra. The sequence is not arbitrary: it is a declining moisture gradient in the tropics and mid-latitudes (forest → grassland → desert) crossed by a declining temperature gradient towards the poles and towards high altitude (forest → tundra). For the full global treatment, see Biomes of the World.

Ecosystem	Controlling condition	Dominant life form	Approx. share of land surface
Forest	Rainfall sufficient and reliable enough to support trees	Trees with a closed or near-closed canopy	About 31% of land area
Grassland	Rainfall too low or too seasonal for trees, too high for desert	Perennial grasses, scattered drought-resistant trees	About 20% of land area
Desert	Severe water deficit; high evaporation, high wind velocity	Xerophytic shrubs, succulents, ephemerals	About one-seventh (roughly 14%) of land area
Tundra	Extreme cold; short growing season; permafrost (arctic tundra)	Mosses, lichens, sedges, dwarf shrubs	About 10% of land area

1. Forest Ecosystem

Forests are large areas supporting a rich growth of trees, with a closed or nearly closed canopy, multiple vertical strata and a deep litter layer. They hold the greatest biomass, the greatest biodiversity and the greatest terrestrial carbon stock of any land ecosystem. By climate and dominant trees they fall into three global classes.

a) Tropical Rainforest (Tropical Wet Evergreen)

• Distribution: high-rainfall belts on either side of the Equator — the Amazon basin, the Congo basin, South-East Asia, and in India the windward Western Ghats, the north-eastern hills and the Andaman & Nicobar Islands.
• Climate: continuously high temperature and humidity with above 200 cm of annual rainfall and no true dry season. Soils are lateritic and, despite rich surface humus, nutrient-poor at depth because rapid decomposition and heavy leaching move nutrients quickly into biomass.
• Flora: extraordinary species richness — Brazilian rainforest can carry more than 300 tree species in 200 sq km. Trees reach 50–60 m, with buttressed trunks and drip-tip leaves.
  • Abundant epiphytes (orchids, ferns, bromeliads), lianas (woody climbers) and stranglers — life forms that exist only where light is the contested resource.
• Fauna: dominated by arboreal species — monkeys, flying squirrels, tree frogs, hornbills — alongside a huge forest-floor invertebrate fauna of snails, centipedes, millipedes, ants and termites.
• Key functional trait: nutrients are held in the living biomass, not in the soil. Clearing a rainforest exports the nutrient capital in one step, which is why cleared land loses fertility within two to three cropping cycles.

b) Temperate Deciduous Forest

• Distribution: north-west, central and eastern Europe, eastern North America, north China, Korea, Japan, far-eastern Russia and parts of Australia. Trees shed their leaves in autumn and refoliate in spring.
• Climate: moderate, with a temperature range of roughly 10–20°C, a winter about six months long, and annual rainfall of 75–150 cm. Soils are brown forest soils, rich in nutrients because cool temperatures slow decomposition and allow humus to accumulate.
• Flora: oak, beech, maple, chestnut, birch, heath and pine, with a clear understorey of saplings, shrubs and tall herbs.
• Fauna: deer, bison and rodents are the prominent grazers; rodents are ecologically pivotal as seed and fruit consumers and as seed dispersers.
  • Omnivores include black bear, raccoon, wild cat, wolf, fox and skunk.
  • Hibernation (winter sleep) is the signature adaptation. Invertebrate fauna includes green flies, aphids, moths and butterflies.
• Deciduousness is a water adaptation, not only a cold adaptation: frozen soil water is physiologically unavailable, so shedding leaves prevents fatal winter transpiration.

c) Boreal or Northern Coniferous Forest (Taiga)

• Distribution: a continuous belt across North America and northern Eurasia, immediately below the arctic tundra. There is no counterpart in the southern hemisphere because there is almost no land at the corresponding latitudes — a favourite examiner detail.
• Climate: cold, with long harsh winters and a mean annual temperature below 0°C. Soils are podzols — acidic and nutrient-poor, because conifer needles decompose slowly into acidic litter.
• Flora: evergreen, drought-resistant, woody conifers (gymnosperms) — spruce, fir and pine — bearing naked seeds in cones. Conical crowns shed snow; needle leaves with thick cuticle and sunken stomata resist physiological drought.
• Fauna: red squirrel, deer, mule, moose and goat; carnivores include timber wolf, lynx and bear. Birds include crossbill, thrush, warbler, flycatcher, robin and sparrow — the crossbill’s bill is a textbook adaptation for extracting conifer seeds.
• Global significance: the taiga is the largest terrestrial biome by area and, with its cold waterlogged soils, one of the planet’s largest carbon stores.

Why Forests Matter: Ecological and Economic Functions

• Provisioning: fuelwood, timber, pulp, bamboo, fodder, and minor forest produce — essential oils, medicinal plants, resins, turpentine, lac, tendu and honey. Forests are a renewable resource if harvest stays within increment.
• Regulating: climate regulation and carbon sequestration; watershed protection and groundwater recharge; flood moderation; soil binding against erosion; local cooling through evapotranspiration.
• Supporting: habitat and food for wildlife, protection against climatic extremes, and a reservoir of genetic diversity underpinning crop and medicinal improvement.
• Cultural: forests met the food, clothing and shelter needs of early humans, and remain a source of aesthetic, spiritual and cultural value — sacred groves are the oldest form of community conservation in India.

2. Grassland Ecosystem

Grasslands are areas dominated by grasses, occupying about 20% of the earth’s land surface. They occur in both tropical and temperate regions where rainfall is insufficient or too seasonal to support a closed tree canopy but too high for desert. Well-defined hot-and-dry and warm-and-rainy seasons are typical.

Tropical Grasslands (Savanna)

• Distribution: eastern Africa, South America, northern Australia and India.
• Structure: a complex ecosystem of tall grasses with scattered medium-sized, drought-resistant thorny trees — a “parkland” landscape.
• Maintenance: savannas are held open by fire and grazing as much as by rainfall. Many savanna grasses and trees are fire-adapted (thick bark, underground storage organs, rapid resprouting).
• Fauna: large migratory grazing herds (zebra, antelope, wildebeest, ass, badger, fox) supporting large predators, plus abundant rodents, reptiles and insects — termites are keystone decomposers.

Temperate Grasslands

• Structure: shorter, denser sward with almost no trees; the bulk of production is below ground in root systems.
• Soils: the world’s most fertile soils — chernozems and prairie soils — formed from the humus of dense fibrous roots. This is why temperate grasslands became the world’s grain belts and why so little natural grassland survives.

Regional Names of Grasslands

Name	Region / country	Type
Prairies	North America	Temperate
Pampas	Argentina and Uruguay (South America)	Temperate
Steppes	Europe and Northern Asia	Temperate
Veld	South Africa	Temperate
Downs	Australia	Temperate
Canterbury	New Zealand	Temperate
Pustaz	Hungary	Temperate
Savanna	Africa and northern Australia	Tropical
Llanos	Venezuela (Orinoco basin)	Tropical
Campos	Brazil (Brazilian Highlands)	Tropical
Selvas	South America	Not a grassland — equatorial rainforest (a common distractor)
Taiga	Europe and Asia	Not a grassland — boreal coniferous forest (a common distractor)

Importance of Grasslands

• Forage and livelihoods: grasslands convert vegetation humans cannot eat into milk, meat, wool and leather through grazing animals — the basis of pastoral economies.
• Soil formation and protection: dead root residues generate humus and the fibrous root system builds soil structure directly; the surface cover shields soil and adjacent croplands from water and wind erosion and from deflation.
• Biodiversity: grasslands are the natural habitat of specialised grassland species — in India the Great Indian Bustard, lesser florican, blackbuck, Indian wolf and caracal depend on them entirely.
• Medicinal and genetic resources: a large share of traditionally collected herbs and the wild relatives of cereal crops are grassland species.
• Carbon: grasslands store most of their carbon below ground, making them a more fire-secure and drought-secure carbon store than forests in dry regions.
• Amenity and energy: lawns, parks, sports grounds and golf courses; and, as managed “energy grass” biomass, a renewable energy source.

Impact of Overgrazing on Grasslands

• Heavy grazing pressure deteriorates sward quality rapidly, reduces the mulch cover of the soil, dries the microclimate, and allows invasion by xerophytic and unpalatable plants.
• Loss of the humus cover exposes the mineral soil surface; trampling when wet puddles the surface layer, which reduces infiltration and accelerates runoff — producing drought in a landscape that still receives rain.
• These changes reduce energy flow and disrupt the stratification and periodicity of primary production, breaking down the biogeochemical cycles of water, carbon and nitrogen.
• Water and wind erosion then complete the degradation of the dry grassland microclimate.
• Intensive grazing expands areas of bare soil, creating habitat for burrowing animals — mice, jackrabbits, gophers, prairie dogs, locusts — which can render large areas of forage land sterile.

3. Desert Ecosystem

Deserts are regions of severe water shortage, high evaporation and high wind velocity, with extremes of temperature between day and night. They occupy about one-seventh of the earth’s surface. Aridity, not heat, is the defining condition — which is why cold deserts such as Ladakh and the Gobi are true deserts. For the landform side of the topic see Desert Landforms.

• Flora: cacti, Acacia, Euphorbia, prickly pear, Prosopis and ephemeral herbs that complete their life cycle in a single wet spell.
• Fauna: shrew, fox, wood rat, rabbit, camel and goat among mammals; plus reptiles, burrowing rodents and insects. Vertebrate diversity is low but adaptation is extreme.

Adaptations of Desert Plants (Xerophytes)

• Mostly shrubs rather than trees — low stature reduces exposure and transpiring surface.
• Leaves absent or reduced in size, often to spines, cutting transpiration and deterring herbivores.
• Succulent, water-storing leaves and stems; in many species the stem itself contains chlorophyll and takes over photosynthesis.
• Thick cuticle, sunken stomata, and stomata that open at night (CAM photosynthesis) to fix CO₂ when evaporative demand is lowest.
• Well-developed root systems — either shallow roots spread over a very large area to catch light rain, or deep tap roots reaching the water table.

Adaptations of Desert Animals

• Many are fast runners, covering long distances between water and forage.
• Nocturnal habit — activity is shifted to the night to avoid daytime heat.
• Water is conserved by excreting highly concentrated urine and dry faeces.
• Animals and birds often have long legs that keep the body away from the hot ground, where near-surface air temperature is highest.
• Lizards are largely insectivorous and can live without drinking water for several days, meeting their needs from prey.
• Herbivores obtain sufficient water from the seeds they eat, supplemented by metabolic water from respiration — the kangaroo rat is the classic example.
• Aestivation and burrowing carry many species through the hottest, driest period.

4. Tundra Ecosystem

The word tundra means “barren land”. Tundra occurs where environmental conditions are so severe that trees cannot grow — beyond the tree line in latitude or in altitude. There are two types: arctic and alpine.

Feature	Arctic tundra	Alpine tundra
Location	A continuous belt below the polar ice cap and above the tree line in the northern hemisphere — northern fringe of Canada, Alaska, European Russia, Siberia and the Arctic Ocean islands	High mountains above the tree line, at all latitudes, including the tropics
Southern hemisphere	Almost absent — Antarctic tundra is very small because most of the corresponding area is ocean or ice cap	Present on high mountains in both hemispheres (Andes, East African peaks, Himalaya)
Permafrost	Present — a permanently frozen subsoil that impedes drainage and creates waterlogged summer soils	Usually absent; drainage is good
Temperature regime	Strong seasonal variation; continuous daylight in summer, polar night in winter	Strong diurnal (day–night) variation, because mountains occur at all latitudes
Growing season	Very short (about 50–60 days)	Short, but longer at lower latitudes

Flora and Fauna of the Tundra

• Typical vegetation of the arctic tundra: cotton grass, sedges, dwarf heath, willows, birches and lichens — no trees, shallow rooting, cushion and mat growth forms.
• Animals: reindeer, musk ox, arctic hare, caribou, lemming, arctic fox and squirrel; snowy owl and ptarmigan among birds.
• Longevity as an adaptation: many tundra plants are extremely long-lived — the arctic willow (Salix arctica) can live 150 to 300 years, growing only millimetres a year.
• Plant adaptations: protection from chill by a thick cuticle and epidermal hair; dark pigmentation to absorb heat; growth close to the ground to escape wind.
• Animal adaptations:
  • Large body size with small tails and ears to minimise the surface-area-to-volume ratio and reduce heat loss — Bergmann’s and Allen’s rules in practice.
  • Bodies covered with fur for insulation; thick subcutaneous fat.
  • Insects have very short life cycles, completed entirely within the brief favourable period of the year.
• Fragility: low productivity, slow decomposition and slow growth mean recovery from disturbance takes decades to centuries — tundra is the least resilient terrestrial ecosystem.

Terrestrial Ecosystems of India

India contains every terrestrial ecosystem type described above — wet evergreen forest, deciduous forest, thorn scrub, savanna and floodplain grassland, hot desert, cold desert, temperate forest, sub-alpine forest and alpine tundra — compressed into a single subcontinent by the interaction of the monsoon, latitude and the Himalayan altitudinal gradient. That compression is why India holds four of the world’s biodiversity hotspots on about 2.4% of the global land area.

India’s Forest Cover: The ISFR 2023 Baseline

The Forest Survey of India (FSI), Dehradun, publishes the India State of Forest Report (ISFR) every two years using satellite data. ISFR 2023, released in December 2024, is the current edition and the figures below are the ones to quote.

Forest Cover by Canopy Density

FSI maps any patch of one hectare or more with a tree canopy density of 10% or above as “forest cover”, and then splits it by density.

Density class	Canopy density	Approx. share of India’s geographical area
Very Dense Forest (VDF)	70% and above	About 3.04%
Moderately Dense Forest (MDF)	40% to less than 70%	About 9.33%
Open Forest (OF)	10% to less than 40%	About 9.34%
Scrub	Below 10%	Counted separately — not part of forest cover

State Rankings

Ranking basis	1st	2nd	3rd
Largest forest cover by area	Madhya Pradesh (77,073 sq km)	Arunachal Pradesh (65,882 sq km)	Chhattisgarh (55,812 sq km)
Highest forest cover as % of area	Lakshadweep (91.33%)	Mizoram (85.34%)	Andaman & Nicobar Islands (81.62%)
Maximum increase since 2021	Chhattisgarh (+684 sq km)	Uttar Pradesh and Odisha (+559 sq km each)	Rajasthan (+394 sq km)

Forest Types of India: The Champion & Seth Classification

H. G. Champion and S. K. Seth (1968), in A Revised Survey of the Forest Types of India, classified Indian forests into five major groups and sixteen type groups, using temperature and moisture as the primary criteria and altitude as the secondary one. It remains the official classification used by FSI and the state forest departments. A fuller treatment sits on Natural Vegetation of India and Types of Forests in India.

Major group	Type groups	Broad condition
I. Moist Tropical	1. Tropical Wet Evergreen 2. Tropical Semi-Evergreen 3. Tropical Moist Deciduous 4. Littoral and Swamp	High rainfall, high temperature
II. Dry Tropical	5. Tropical Dry Deciduous 6. Tropical Thorn 7. Tropical Dry Evergreen	Low to moderate rainfall, high temperature
III. Montane Sub-Tropical	8. Sub-tropical Broad-leaved Hill 9. Sub-tropical Pine 10. Sub-tropical Dry Evergreen	Hills, roughly 1,000–1,800 m
IV. Montane Temperate	11. Montane Wet Temperate 12. Himalayan Moist Temperate 13. Himalayan Dry Temperate	Roughly 1,500–3,300 m
V. Sub-Alpine and Alpine	14. Sub-Alpine 15. Moist Alpine Scrub 16. Dry Alpine Scrub	Above about 3,000 m, up to the snow line

The Type Groups in Detail

Forest type	Rainfall / condition	Where in India	Indicative species
Tropical Wet Evergreen	Above 200 cm; no marked dry season; canopy 30–45 m in four to five strata	Windward Western Ghats, north-east India, Andaman & Nicobar	Rosewood, mahogany, ebony, aini, telsur
Tropical Semi-Evergreen (about 13.8% of forest area)	150–250 cm; canopy 24–36 m; a transition between evergreen and deciduous	Western Ghats, Odisha coast, upper Assam, Andamans	Laurel, white cedar, Elaeocarpus, hollock, kail
Tropical Moist Deciduous (about 19.7% of forest area)	100–200 cm with a three to four month dry season; the “monsoon forest”	Foothills of the Himalaya, eastern slopes of the Western Ghats, Chhattisgarh, Odisha, Jharkhand, Bihar, West Bengal, north-east	Sal, teak, sandalwood, shisham, mahua, semul, haldu
Littoral and Swamp	Coastal, deltaic and waterlogged habitats; saline or freshwater	Sundarbans, Mahanadi, Godavari, Krishna and Cauvery deltas, Gulf of Kachchh, Andamans	Rhizophora, Avicennia, sundari, Bruguiera, screw pine, casuarina
Tropical Dry Deciduous (about 38% — the largest)	80–120 cm; trees generally under 25 m	A broad belt from the Himalayan foothills to Kanyakumari; peninsular interior	Dry teak in the south, dry sal in the north; axlewood, tendu, palas, amla, bel
Tropical Thorn	20–80 cm; semi-arid; open scrub 6–9 m tall	South-west Punjab, Haryana, Rajasthan, Gujarat, interior Deccan, Madhya Pradesh	Prosopis (khejri), acacias (babul, kikar), ber, wild date palm, euphorbias, cacti
Tropical Dry Evergreen	About 100 cm, largely from the north-east monsoon; hard-leaved evergreens 9–12 m	Coromandel coast of Tamil Nadu and Andhra Pradesh, parts of Karnataka	Jamun, tamarind, neem, Manilkara, toddy palm
Sub-tropical Broad-leaved Hill	1,000–2,000 mm at about 1,000–1,700 m	Eastern Himalaya, Khasi and Jaintia hills, Nilgiri and Palni hills	Oak, chestnut, ash, beech, laurel, birch
Sub-tropical Pine	Roughly 1,000–1,800 m in the central and western Himalaya	Jammu region, Himachal Pradesh, Uttarakhand, Arunachal Pradesh, Khasi hills	Chir pine (Pinus roxburghii)
Sub-tropical Dry Evergreen	About 50–100 cm, mostly winter rain; hot dry summer	Shiwalik foothills and the Bhabar tract, Jammu region	Olea cuspidata (wild olive), Acacia modesta, pistachio
Montane Wet Temperate	Above 1,500 m in the south and 1,800–3,000 m in the eastern Himalaya, with over 2,000 mm rainfall	Shola forests of the Nilgiris, Anamalais and Palnis; Sikkim, Arunachal, Manipur	Deodar, chilauni, Indian chestnut, birch, plum, cinnamon, rhododendron
Himalayan Moist Temperate	Roughly 1,500–3,300 m, 150–250 cm rainfall	Kashmir, Himachal Pradesh, Uttarakhand, Darjeeling, Sikkim	Oak, deodar, blue pine, spruce, silver fir, maple, walnut
Himalayan Dry Temperate	1,700–3,000 m, under 100 cm, largely as winter snow; inner dry ranges	Ladakh, Lahaul, Kinnaur, Chamba, inner Sikkim	Deodar, chilgoza pine, oak, juniper, ash, maple
Sub-Alpine	About 3,000 m to the tree line, across the Himalaya	Kashmir to Arunachal Pradesh	Silver fir, birch (Betula utilis, the largest deciduous element), rhododendron, juniper
Moist Alpine Scrub	Above the tree line to about 5,500 m; heavy snow, thick moss and humus layer	Higher Himalaya throughout	Almost entirely rhododendron species with some birch, black juniper
Dry Alpine Scrub	Xerophytic formation with under about 370 mm of precipitation	Trans-Himalayan Ladakh, Spiti, upper Kinnaur	Juniperus wallichiana, dwarf shrubs, honeysuckle, artemisia, alpine herbs

Mangroves and Littoral Swamp Forests

• Mangroves are the littoral and swamp type group of the moist tropical forests — salt-tolerant forests of the intertidal zone, structurally terrestrial but functionally a bridge between land and sea.
• India’s mangrove cover is 4,992 sq km (ISFR 2023). The Sundarbans is the largest single block of mangrove in the world; other major sites are Bhitarkanika, the Godavari–Krishna delta, Pichavaram, the Gulf of Kachchh and the Andamans. See Mangrove Sites in India.
• Adaptations:
  • Pneumatophores (breathing roots) to obtain oxygen from waterlogged, anoxic mud.
  • Stilt and prop roots for anchorage in soft substrate and against tidal scour.
  • Vivipary — seeds germinate while still attached to the parent plant, so the propagule can root quickly when it falls.
  • Salt exclusion at the root and salt excretion through leaf glands; thick succulent leaves.
• Functions: a physical buffer against cyclones, storm surge and tsunami; nurseries for fish and prawn; extremely high “blue carbon” sequestration per hectare; and coastline stabilisation against erosion.
• Pressures: aquaculture and salt-pan conversion, coastal construction, upstream damming that cuts freshwater and silt supply, pollution and sea-level rise.

Grasslands of India

India’s grasslands are ecologically distinct from its forests but are almost entirely absent from the legal category of “forest”. Most are recorded as “wasteland”, “revenue land” or “culturable waste”, which is the single biggest reason for their neglect. The global picture is on Grasslands of the World.

The Five Grass-Cover Types (Dabadghao and Shankarnarayan, ICAR)

Grass-cover type	Distribution	Dominant species
1. Sehima–Dichanthium	Semi-arid Deccan Plateau, central Indian highlands, Chota Nagpur plateau	Sehima nervosum, Dichanthium annulatum
2. Dichanthium–Cenchrus–Lasiurus	Arid and semi-arid north-west India — Thar desert, Rajasthan, Gujarat, Punjab, Haryana, western Uttar Pradesh	Lasiurus scindicus (sewan), Cenchrus ciliaris (anjan), Dichanthium
3. Phragmites–Saccharum–Imperata	Indus–Ganga–Brahmaputra floodplains and the Terai–Duar belt	Phragmites karka, Saccharum spontaneum (wild sugarcane), Imperata cylindrica
4. Themeda–Arundinella	Outer Himalaya — Jammu & Kashmir, Himachal Pradesh, Uttarakhand and the north-eastern hills	Themeda anathera, Arundinella nepalensis
5. Temperate–Alpine	Above about 3,000 m in the inner Himalayan ranges	Poa, Festuca, Agrostis, alpine sedges and herbs

Named Grassland Ecosystems of India

Grassland	Where	Why it matters
Banni grasslands	Kachchh, Gujarat	One of Asia’s largest contiguous tropical grasslands, over 2,500 sq km; home of the Maldhari pastoralists and the Banni buffalo; heavily invaded by Prosopis juliflora
Terai–Duar savanna and grasslands	Uttar Pradesh, Bihar, West Bengal, Assam foothills	Monsoon-fed floodplain grassland with elephant grass 4–6 m tall; prime habitat for the one-horned rhinoceros, swamp deer and hog deer (Kaziranga, Dudhwa, Manas)
Shola grasslands	Western Ghats above about 1,500 m — Nilgiris, Anamalais, Palnis	A natural mosaic of stunted evergreen shola forest in valleys and grassland on slopes; frost- and fire-maintained; habitat of the Nilgiri tahr; threatened by wattle, eucalyptus and pine plantations
Bugyals and margs	Uttarakhand and Jammu & Kashmir, 3,300–4,000 m	Alpine meadows used by transhumant pastoralists; the Valley of Flowers is the best-known
Semi-arid Deccan and Saurashtra grasslands	Maharashtra, Karnataka, Andhra Pradesh, Rajasthan, Gujarat	Last refuge of the Great Indian Bustard, lesser florican, blackbuck, Indian wolf and caracal — the most threatened grassland fauna in the country
Phumdis of Loktak	Manipur	Floating mats of vegetation forming Keibul Lamjao, the world’s only floating national park, and the sole habitat of the sangai deer

Deserts of India

The Thar — India’s Hot Desert

• Location: western Rajasthan and the Rann of Kachchh in Gujarat, east of the Indus plain and west of the Aravallis.
• Why it is arid: the Aravalli range lies parallel to the Arabian Sea branch of the south-west monsoon and so fails to obstruct it, while the Bay of Bengal branch is exhausted before it arrives. Descending air and a dry continental setting complete the picture.
• Landforms and processes: shifting sand dunes (barchans, seif), sand sheets, playas (rann), inselbergs; wind erosion and deflation dominate.
• Flora: Prosopis cineraria (khejri, the state tree), Calligonum, Capparis, Zizyphus, sewan and anjan grasses.
• Fauna: chinkara, blackbuck, Indian wild ass (Little Rann), desert fox, desert cat, spiny-tailed lizard and the Great Indian Bustard.
• Note: the Thar is the most densely populated desert in the world, so its ecology is inseparable from pastoralism, canal irrigation and, increasingly, solar infrastructure.

Ladakh — India’s Cold Desert

• Location: the trans-Himalayan region — Ladakh, Lahaul–Spiti, upper Kinnaur and parts of the Nubra and Changthang plateaus.
• Why it is arid: it lies in the rain shadow of the Greater Himalaya. Precipitation is under about 100 mm a year, mostly as snow.
• Vegetation: dry alpine scrub — Juniperus, Artemisia, sea buckthorn, dwarf willow along streams; the Changthang plateau carries sparse alpine steppe.
• Fauna: snow leopard, Tibetan wild ass (kiang), Tibetan antelope (chiru), blue sheep, Himalayan marmot, and the black-necked crane at Tso Moriri and Hanle.
• Human ecology: Changpa pastoralists and the pashmina goat; irrigation depends on glacial melt, which makes the region acutely climate-sensitive.

Desertification and Land Degradation in India

Desertification is the diminution or destruction of the biological potential of the land, ultimately producing desert-like conditions. Under the UNCCD it refers to land degradation in arid, semi-arid and dry sub-humid areas resulting from climatic variation and human activities. It is a process, not a place — which is why it can occur far from any existing desert.

Human Causes of Desertification

• Overgrazing and over-exploitation of grazing land, together with indiscriminate cutting of trees, leading to drought conditions, soil erosion, loss of fertility and stunted plant growth.
• Excessive mining in arid and semi-arid regions for minerals, coal or limestone, stripping the green cover and destroying the conditions in which vegetation can re-establish.
• Uneconomic land use — cultivation pushed onto marginal land, which then degrades and damages adjacent fertile land through erosion.
• Over-exploitation of water resources, causing water-table decline, seepage and salinisation and waterlogging — the classic canal-command failure in Punjab, Haryana and parts of Rajasthan.

India’s Commitments

• India ratified the UNCCD in 1996 and hosted COP-14 in New Delhi in 2019.
• Commitment to restore 26 million hectares of degraded land by 2030 and to achieve Land Degradation Neutrality (SDG target 15.3).
• Instruments include the Desert Development Programme, the National Action Programme to Combat Desertification, the Green India Mission, the Bonn Challenge pledge of 26 mha, and the Aravalli Green Wall Project.

India’s Alpine Zone: The Tundra Analogue

• Above the tree line, roughly 3,500–4,500 m and higher, the Himalaya carries alpine tundra — moist alpine scrub on the wetter southern slopes and dry alpine scrub in the trans-Himalayan rain shadow.
• Vegetation is rhododendron, juniper, dwarf willow, birch at the margin, and a brief but spectacular summer herb flora — the Valley of Flowers being the classic example.
• Fauna includes the snow leopard, Himalayan ibex, bharal, Himalayan tahr, musk deer, marmot and snow partridge.
• Climate signal: the Himalayan tree line and snow line are shifting upward, alpine meadows are being invaded by shrubs, and glacial retreat is altering the timing of meltwater — the terrestrial ecosystems most exposed to warming in India.
• Because recovery is measured in decades, alpine pastures degraded by over-grazing, unregulated tourism and road building do not recover within a planning cycle.

Pressures on Terrestrial Ecosystems

Deforestation

Deforestation is the removal or damage of vegetation in a forest to the extent that it no longer supports its natural flora and fauna. Understood broadly it includes repeated lopping, felling, removal of forest litter, browsing, grazing and trampling of seedlings. In its strict land-use sense it means permanent conversion of forest to non-forest use — cropland, pasture, settlement or desert. The full treatment is on Deforestation: Causes, Consequences and Conservation Measures.

Principal Causes

Cause	Mechanism and Indian detail
Expanding agriculture	The largest single driver. As demand for agricultural produce rises, forest, grassland, marsh and even submerged land are reclaimed. Forest soil cannot sustain cropping for long once the nutrient capital in the biomass is removed, so the land is abandoned to erosion and degradation — more ecological loss than agricultural gain.
Shifting cultivation (jhum)	A roughly 12,000-year-old slash-and-burn practice marking the transition from food collection to food production. About 5 lakh hectares of forest are cleared annually for it. Sustainable at long fallow cycles; destructive once cycles shorten to two or three years. Practised in Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura and the Andaman & Nicobar Islands.
Demand for firewood	Roughly 44% of global wood production is burnt as fuel; developed countries use only about 16% of their share this way. India consumes about 135–170 million tonnes of firewood a year, and 10–15 hectares of forest cover are stripped to meet minimum fuel needs of the urban and rural poor.
Industrial and commercial wood	Crates, packing cases, furniture, matchboxes, paper and pulp, plywood. About 1.24 lakh hectares of forest have been cut for industrial uses. The paper industry takes about 2% of annual wood consumption and meets about 51% of its requirement from bamboo — depleting bamboo stock across peninsular India. The apple industry in the Himalaya destroyed fir stands for packing boxes.
Urbanisation and development projects	Roads, railways, dams, townships, transmission lines, thermal power stations and mining for coal, metallic ores and minerals. Linear infrastructure also fragments habitat, which damages ecosystems out of all proportion to the area lost.
Forest fires	Hundreds of thousands of trees are lost annually. Warmer summers and milder winters lengthen the fire season; most Indian forest fires are anthropogenic in ignition even where climate is the enabling condition.

Principal Effects

• Climatic imbalance: trees release water vapour and provide shade that keeps soil moist. Removing them raises local temperature, lowers humidity, disturbs local rainfall and forces species out of habitats they are adapted to.
• Enhanced global warming: forests absorb CO₂; their loss both stops that uptake and releases the stored carbon, raising the greenhouse gas burden twice over.
• Soil erosion and loss of fertility: exposed soil dries, loses structure and is stripped by rain and wind. See Soil Erosion and Land Degradation.
• Floods and droughts: roots absorb and store rainfall and slow runoff. Without them, water arrives in the channel fast — floods downstream in the wet season, reduced base flow and drought in the dry season. Rapid tropical deforestation is a key driver of the annual rise in flood disasters.
• Wildlife loss and extinction: habitat loss displaces species; many cannot establish elsewhere and are pushed to extinction. Fragmentation isolates populations and erodes genetic diversity.

Strategies to Reduce Deforestation

• Address the demand side: slow population growth, raise per-capita incomes, and promote substitutes for fuelwood and timber (LPG, biogas, engineered wood).
• REDD and REDD+ — reducing emissions from deforestation and forest degradation, with payments for conservation, sustainable management and enhancement of carbon stocks.
• Increase the area and management standard of protected areas and of forest permanently reserved for timber production; expand forest plantations and social forestry and agroforestry on non-forest land.
• Raise the perceived and actual value of standing forest through payment for ecosystem services, non-timber forest produce value chains and certification.
• Participatory forest management and secure rights — Joint Forest Management and the Forest Rights Act, 2006; community forest resource rights are among the most effective anti-degradation instruments.
• Strengthen institutions, policy, legislation and regulation, with real enforcement and compliance; and invest in research, education, extension, monitoring and the information base.

Other Systemic Pressures

• Fragmentation and edge effects — small forest patches lose interior species even when total area looks adequate; wildlife corridors are the counter-measure.
• Invasive alien species — Lantana camara in deciduous forest, Prosopis juliflora in Banni and the Thar, wattle and eucalyptus in the sholas, Parthenium in grasslands and Mikania in the north-east.
• Grazing and fodder pressure on open forest and every grassland type.
• Climate change — poleward and upward range shifts, treeline advance, longer fire seasons, mismatch between flowering and pollinator activity, and drought-induced tree mortality. See Biogeography of Climate Change.
• Linear infrastructure and mining, and the diversion of forest land for non-forest use under the forest clearance regime.

Governance of Terrestrial Ecosystems in India

Instrument	Year	What it does
Indian Forest Act	1927	Consolidates forest law; creates Reserved, Protected and Village forests and regulates forest produce and transit
Wildlife (Protection) Act	1972	Creates national parks, wildlife sanctuaries, conservation and community reserves; schedules species for protection
Forest (Conservation) Act	1980	Requires prior central approval to use forest land for non-forest purposes — the single most important brake on forest diversion
National Forest Policy	1988	Sets the target of 33% of geographical area under forest and tree cover (and 66% in the hills); shifts the objective from revenue to ecological stability and local needs
Forest Rights Act	2006	Recognises individual and community forest resource rights of forest dwellers and gives the gram sabha a role in conservation and in consent for diversion
CAF Act (CAMPA)	2016	Governs the compensatory afforestation fund and net present value collected against diverted forest land
Van (Sanrakshan Evam Samvardhan) Adhiniyam — the Forest (Conservation) Amendment Act	2023	Renames and amends the 1980 Act; narrows the categories of land to which it applies and exempts certain strategic, security and infrastructure projects. The Supreme Court in 2024 directed that the broad “dictionary meaning” of forest laid down in T. N. Godavarman (1996) continues to govern what counts as forest land
Green Credit Rules	2023	Creates tradable green credits for plantation and other environmental activities — criticised for the risk of afforesting natural grasslands and open ecosystems

Targets to Remember

• National Forest Policy, 1988: 33% of geographical area under forest and tree cover. Current status is 25.17% — the gap has narrowed very slowly.
• Bonn Challenge: restore 26 million hectares of degraded land by 2030 (raised from an original 13 mha pledge).
• Nationally Determined Contribution: create an additional carbon sink of 2.5 to 3 billion tonnes of CO₂ equivalent through additional forest and tree cover by 2030.
• UNCCD / SDG 15.3: Land Degradation Neutrality and restoration of 26 mha of degraded land by 2030.
• Institutional anchors: Biosphere Reserves, National Parks, Tiger Reserves and biodiversity hotspots.

UPSC Exam Focus

Previous Year Questions — Prelims

1. UPSC CSE Prelims 2010

In India, which type of forest among the following occupies the largest area?

• (a) Montane Wet Temperate Forest
• (b) Sub-tropical Dry Evergreen Forest
• (c) Tropical Moist Deciduous Forest
• (d) Tropical Wet Evergreen Forest

Answer: (c) Tropical Moist Deciduous Forest. Tropical Dry Deciduous forest covers the largest area in India overall, but it is not among the options; of those listed, moist deciduous (the monsoon forest) is the most extensive.

2. UPSC CSE Prelims 2015

Which one of the following regions of India has a combination of mangrove forest, evergreen forest and deciduous forest?

• (a) North Coastal Andhra Pradesh
• (b) South-West Bengal
• (c) Southern Saurashtra
• (d) Andaman and Nicobar Islands

Answer: (d) Andaman and Nicobar Islands. The islands carry tropical wet evergreen and semi-evergreen forest in the interior, moist deciduous forest on drier aspects, and extensive littoral mangrove along the creeks — three formations in one small territory.

3. UPSC CSE Prelims 2014

If you travel through the Himalayas, you are likely to see which of the following plants naturally growing there?

• 1. Oak
• 2. Rhododendron
• 3. Sandalwood

Select the correct answer using the code given below: (a) 1 and 2 only  (b) 3 only  (c) 1 and 3 only  (d) 1, 2 and 3

Answer: (a) 1 and 2 only. Oak is characteristic of Himalayan moist temperate forest and rhododendron of the sub-alpine and moist alpine scrub. Sandalwood is a tropical dry deciduous species of the peninsular Deccan, not a Himalayan one.

4. UPSC CSE Prelims 2012

Which of the following can be threats to the biodiversity of a geographical area?

• 1. Global warming
• 2. Fragmentation of habitat
• 3. Invasion of alien species
• 4. Promotion of vegetarianism

Select the correct answer using the codes given below: (a) 1, 2 and 3 only  (b) 2 and 3 only  (c) 1 and 4 only  (d) 1, 2, 3 and 4

Answer: (a) 1, 2 and 3 only. Promotion of vegetarianism reduces pressure on land and is not a threat to biodiversity.

Previous Year Questions — Mains

• [GS-1, 2023] Identify and discuss the factors responsible for diversity of natural vegetation in India. Assess the significance of wildlife sanctuaries in rain forest regions of India.
• [GS-3, 2020] Examine the status of forest resources of India and its resultant impact on climate change.
• [GS-1, 2020] The process of desertification does not have climate boundaries. Justify with examples.
• [GS-1, 2019] Discuss the causes of depletion of mangroves and explain their importance in maintaining coastal ecology.

More at Environment Questions in UPSC Prelims and Environment and Ecology Questions in UPSC Mains.

Practice Questions

Practice MCQ 1

Consider the following:

• 1. Rotation of planet Earth around the Sun
• 2. Tilt of Earth on its axis
• 3. Annual variation in precipitation

Which of the above account for the formation of major biomes such as deserts, rainforests and tundra? (a) 1 and 2 only  (b) 2 and 3 only  (c) 1 and 3 only  (d) 1, 2 and 3

Answer: (d). The revolution of the Earth around the Sun and the tilt of its axis together determine the intensity and duration of insolation and hence the seasons; combined with the annual variation in precipitation, they account for the formation of the major biomes.

Practice MCQ 2

With reference to terrestrial ecosystems, consider the following statements:

• 1. The detritus food chain is the major conduit of energy flow in most terrestrial ecosystems.
• 2. The pyramid of biomass in a terrestrial ecosystem is generally inverted.
• 3. Water is the principal limiting factor distinguishing terrestrial from aquatic ecosystems.

Which of the statements given above are correct? (a) 1 and 2 only  (b) 1 and 3 only  (c) 2 and 3 only  (d) 1, 2 and 3

Answer: (b) 1 and 3 only. The terrestrial pyramid of biomass is upright, because a large standing crop of long-lived producers supports a much smaller consumer biomass. Inverted biomass pyramids are characteristic of open-water aquatic ecosystems.

Practice MCQ 3

Which of the following pairs is/are correctly matched?

• 1. Sehima–Dichanthium — semi-arid Deccan plateau
• 2. Phragmites–Saccharum–Imperata — Terai and the Gangetic floodplain
• 3. Themeda–Arundinella — Thar desert

(a) 1 only  (b) 1 and 2 only  (c) 2 and 3 only  (d) 1, 2 and 3

Answer: (b) 1 and 2 only. Themeda–Arundinella is the grassland type of the outer Himalaya and the north-eastern hills. The Thar carries the Dichanthium–Cenchrus–Lasiurus type.

Answer-Writing Angles for Mains

• Data first, always. Open a forest answer with ISFR 2023: 21.76% forest cover, 25.17% forest and tree cover, against the 33% National Forest Policy target.
• Use the forest cover versus recorded forest area distinction to add analytical value — it is the difference between a descriptive answer and an evaluative one.
• Bring in open natural ecosystems. The “wasteland” misclassification of grasslands and the risk of afforesting them is a high-value, under-used point.
• Draw a map or a simple sketch — a rainfall gradient from the Western Ghats to the Thar showing evergreen → moist deciduous → dry deciduous → thorn earns marks quickly.
• Close with governance and targets — Bonn Challenge 26 mha, NDC 2.5–3 billion tonnes CO₂e, Land Degradation Neutrality — rather than a generic conclusion.

Frequently Asked Questions

Conclusion

Terrestrial ecosystems are organised by two variables — how much water is available and how cold it gets — and everything else follows: the height of the vegetation, the number of strata, the productivity, the adaptations of the fauna and the rate at which the system recovers from damage. India compresses the entire global range of these systems into one subcontinent, which is both its ecological distinction and the reason its conservation problem is unusually complex. For the exam, hold three things: the fourfold classification with its diagnostic features, the Champion and Seth framework with the ISFR 2023 numbers, and the distinction between forest cover and recorded forest area, which is where most high-value analysis in this topic begins.

Continue with Biomes of the World, Natural Vegetation of India, Forest Resources in India and Ecosystem Management and Conservation.