BharatNotes Why this chapter matters for UPSC: "Life on the Earth" was Chapter 15 of Fundamentals of Physical Geography until NCERT's rationalised edition (first printed December 2022) dropped it. The current book's Unit VI "Life on the Earth" now holds only Chapter 14, Biodiversity and Conservation, which still begins "You have studied about the ecosystem in the earlier chapter": this page is that earlier chapter, from the 2019-20 edition. Its ideas (ecosystems, food chains, biomes and the biogeochemical cycles) run through GS1 geography and GS3 environment questions on decomposition, carrying capacity, nutrient pollution and the carbon cycle.
Contemporary hook: The Global Carbon Budget 2025 puts the global mean atmospheric CO₂ concentration at 422.8 ppm for 2024 and projects 425.6 ppm for 2025, about 53% above the pre-industrial level of about 278 ppm. The carbon cycle this chapter describes is the system those numbers measure.
🧠 First Principles — Read This First
The biosphere is the part of the earth where life exists: the soil, the lower atmosphere, and the water of rivers, lakes and seas. It overlaps the other three realms. Plants take carbon dioxide from the air, water from the soil and minerals from weathered rock, so life depends on all of them.
An ecosystem is a group of living things together with their non-living surroundings, such as a pond, a forest patch or a grassland. Green plants capture sunlight and make food. Animals that eat plants get part of that energy, and animals that eat those animals get a smaller part. At each step energy is lost, so energy flows one way and must be supplied continuously by the sun.
Matter behaves differently. The carbon, nitrogen and water in a leaf are taken from the environment and returned to it when the leaf decays. The same atoms are used again and again. These loops are the biogeochemical cycles.
A biome is a very large plant and animal community, such as a forest, a desert or a grassland, whose boundaries are set mainly by climate. If you know the climate of a place, you can predict its natural vegetation.
PART 1 — Quick Reference
Table 1: Key terms (NCERT, 2019-20)
| Term | NCERT's meaning |
|---|---|
| Biosphere | All the living components of the earth: all plants and animals, including micro-organisms, and their interactions with the surrounding environment |
| Ecology | From Greek oikos ("house") + logy ("study of"); the scientific study of the interactions of organisms with their physical environment and with each other. First used by the German zoologist Ernst Haeckel, as oekologie, in 1869 |
| Ecological system | Interactions of a group of organisms with abiotic factors in a habitat, giving clearly defined energy flows and material cycles |
| Habitat | The totality of the physical and chemical factors that make up the general environment |
| Ecosystem | A system of biotic and abiotic components, all inter-related |
| Ecological adaptation | Plant and animal species adapting, through evolution, to the range of conditions in an ecosystem |
| Biome | A plant and animal community covering a large geographical area, its boundaries set mainly by climate |
| Food chain | The sequence of eating and being eaten, with the transfer of energy from one level to the next |
| Food web | Interlocked food chains, where each carnivore eats more than one kind of prey |
| Ecological balance | A state of dynamic equilibrium within a community of organisms, with the diversity of species relatively stable |
| Succession | A change in species distribution after a disturbance, as secondary species (grasses, bamboos, pines) overtake the native ones |
Table 2: Structure of an ecosystem (NCERT)
| Component | What it includes | NCERT's examples |
|---|---|---|
| Abiotic | Rainfall, temperature, sunlight, atmospheric humidity, soil conditions, inorganic substances | Carbon dioxide, water, nitrogen, calcium, phosphorus, potassium |
| Producers | Green plants, which make their own food by photosynthesis | Paddy |
| Primary consumers | Herbivores | Deer, goats, mice |
| Secondary consumers (carnivores) | Flesh-eaters | Snakes, tigers, lions |
| Top carnivores | Carnivores that eat other carnivores | Hawks, mongooses |
| Decomposers | Feed on dead organisms at every level and return nutrients to the soil | Bacteria and other micro-organisms (NCERT also lists scavengers such as vultures and crows; strictly these are consumers of dead matter, and the decomposers are bacteria and fungi) |
Table 3: World biomes (NCERT Table 15.1)
| Biome | Sub-type | Regions | Climate | Soil | Flora and fauna |
|---|---|---|---|---|---|
| Forest | Tropical: equatorial | 10° N–S | 20–25°C, rain evenly distributed | Acidic, poor in nutrients | Multi-layered canopy of tall, large trees; insects, bats, birds, mammals |
| Forest | Tropical: deciduous | 10°–25° N–S | 25–30°C; average annual rainfall 1,000 mm, seasonal | Rich in nutrients | Less dense; medium-height trees; many varieties co-exist |
| Forest | Temperate | Eastern North America, north-east Asia, western and central Europe | 20–30°C; rain evenly distributed, 750–1,500 mm; well-defined seasons with a distinct winter | Fertile, enriched with decaying litter | Moderately dense broad-leaved trees (oak, beech, maple); squirrels, rabbits, skunks, black bears, mountain lions |
| Forest | Boreal | Broad belt of Eurasia and North America (Siberia, Alaska, Canada, Scandinavia) | Short, moist, moderately warm summers; long, cold, dry winters; precipitation mostly snow, 400–1,000 mm | Acidic, poor in nutrients, thin | Evergreen conifers (pine, fir, spruce); woodpeckers, hawks, bears, wolves, deer, hares, bats |
| Desert | Hot and dry | Sahara, Kalahari, Marusthali, Rub-el-Khali | 20–45°C; rainfall under 50 mm | Rich in nutrients, little or no organic matter | Scanty vegetation; few large mammals; insects, reptiles, birds |
| Desert | Semi-arid | Margins of hot deserts | 21–38°C; rainfall under 50 mm | (as above) | (as above) |
| Desert | Coastal | Atacama | 15–35°C; rainfall under 50 mm | (as above) | (as above) |
| Desert | Cold | Tundra climatic regions | 2–25°C; rainfall under 50 mm | (as above) | Rabbits, rats, antelopes, ground squirrels |
| Grassland | Tropical savannah | Large areas of Africa, Australia, South America and India | Warm to hot; rainfall 500–1,250 mm | Porous, with a thin layer of humus | Grasses, no large trees or shrubs; giraffes, zebras, buffaloes, leopards, hyenas, elephants |
| Grassland | Temperate steppe | Parts of Eurasia and North America | Hot summers, cold winters; rainfall 500–900 mm | Thin, flocculated, rich in bases | Grasses, occasional trees (cottonwoods, oaks, willows); gazelles, zebras, rhinoceros, wild horses, lions |
| Aquatic | Freshwater | Lakes, streams, rivers, wetlands | Temperatures vary widely; cooler air, high humidity | Water, swamps, marshes | Algae and other aquatic plants; water-dwelling animals |
| Aquatic | Marine | Oceans, coral reefs, lagoons, estuaries | (as above) | Water, tidal swamps, marshes | Algal and marine plant communities; marine animals |
| Altitudinal | Slopes of high ranges: Himalaya, Andes, Rockies | Varies with the latitudinal zone | Regolith over slopes | Deciduous to tundra vegetation, changing with altitude |
Source: NCERT, Fundamentals of Physical Geography, ch 15 "Life on the Earth", Table 15.1 (2019-20 edition, pp. 126–127). NCERT's text names "forest, grassland, desert and tundra" as some major terrestrial biomes, and its table uses five classes: forest, desert, grassland, aquatic and altitudinal.
Table 4: The biogeochemical cycles (NCERT)
| Cycle | Type | What NCERT says |
|---|---|---|
| Water | Gaseous | Organisms, the atmosphere and the lithosphere keep water circulating in solid, liquid and gaseous form (the hydrological cycle, page 13 of these notes) |
| Carbon | Gaseous | Photosynthesis fixes CO₂ into carbohydrates (glucose, then sucrose, starch, cellulose); plants and herbivores release CO₂ in respiration; micro-organisms decompose dead matter and return carbon as CO₂. The biosphere holds "over half a million carbon compounds" |
| Oxygen | Gaseous | Oxygen is the main by-product of photosynthesis, is used in oxidising carbohydrates, combines with nitrogen to form nitrates and with minerals to form oxides (iron oxide, aluminium oxide) |
| Nitrogen | Gaseous | About 78% of the air; usable only after it is fixed; "ninety per cent of fixed nitrogen is biological" (soil micro-organisms with plant roots); also fixed by lightning and cosmic radiation, and by some marine animals; soil bacteria turn dead matter and wastes into nitrites, then nitrates; other bacteria return free nitrogen (denitrification) |
| Other minerals | Sedimentary | Phosphorus, sulphur, calcium, potassium come from the crust by weathering as salts dissolved in soil water and streams; some reach the sea, some return to land by sedimentation; organisms take them up and return them on death |
In the gaseous cycles the main reservoir of nutrients is the atmosphere and the ocean; in the sedimentary cycle it is the soil and the rocks of the crust.
Table 5: The global carbon cycle in numbers (Global Carbon Budget 2025)
| Flux or stock | Value | Year |
|---|---|---|
| Fossil CO₂ emissions | 10.3 ± 0.5 GtC per year | 2024 |
| Land-use change emissions (mainly deforestation) | 1.3 ± 0.7 GtC per year | 2024 |
| Total human CO₂ emissions | 11.6 ± 0.9 GtC per year (42.4 GtCO₂) | 2024 |
| Ocean sink | 3.4 ± 0.4 GtC per year | 2024 |
| Land sink | 1.9 ± 1.1 GtC per year | 2024 |
| Atmospheric growth | 7.9 ± 0.2 GtC per year (3.73 ppm a year) | 2024 |
| Budget imbalance | −1.7 GtC per year: the estimated sinks plus the atmospheric growth do not add up to the emissions | 2024 |
| Global mean atmospheric CO₂ | 422.8 ppm; projected 425.6 ppm for 2025 | 2024 / 2025 |
Source: Friedlingstein et al., "Global Carbon Budget 2025", Earth System Science Data 18, 3211–3288, published 13 May 2026. Derived arithmetic, not a published figure: the ocean took up about 29% of human emissions in 2024 (3.4 ÷ 11.6).
PART 2 — Concepts & Narrative
The biosphere and ecology
NCERT begins by noting that the book has covered the three other realms (lithosphere, atmosphere, hydrosphere) and now turns to the biosphere, which includes all the living components of the earth. Life is found almost everywhere: from the poles to the equator, from the bottom of the sea to several kilometres up in the air, from freezing waters to dry valleys, and in groundwater below the surface. Most organisms live on the lithosphere and in the hydrosphere and atmosphere; many move freely between realms. The biosphere interacts with land, water and soil and is shaped by temperature, rainfall, moisture and sunlight.
Ecology studies these interactions. The environment has abiotic and biotic components, and a healthy balance between them keeps the diversity of life going. The interactions of a group of organisms with abiotic factors in a habitat, producing clearly defined energy flows and material cycles on land, in water and in air, are ecological systems.
Habitat, ecosystem, biome. A habitat is the totality of physical and chemical factors that make up an organism's general environment. An ecosystem is the system of biotic and abiotic components, all inter-related, at any scale. A biome is a large plant and animal community whose boundaries are set mainly by climate (rainfall, temperature, humidity and soil). Ecosystems are of two major types, terrestrial and aquatic; terrestrial ecosystems are classified into biomes, aquatic ones into marine (oceans, estuaries, coral reefs) and freshwater (lakes, ponds, streams, marshes, bogs).
Structure and functions of ecosystems
The structure of an ecosystem is the description of its plant and animal species and its abiotic setting (Table 2). Producers are eaten by primary consumers, primary consumers by secondary consumers, and secondary by tertiary consumers. Decomposers feed on the dead at every level and turn them into nutrients and salts that keep the soil fertile.
NCERT's food chain: a plant-eating beetle feeds on a paddy stalk, a frog eats the beetle, a snake eats the frog and a hawk eats the snake. The transfer of energy from one level to the next is the flow of energy. Food chains are not isolated: a mouse eating grain may be eaten by several carnivores, which may be eaten by several top carnivores, so the chains interlock into a food web.
Grazing and detritus food chains, and why chains are short
In a grazing food chain the first level is plants (producers), the middle level herbivores and the last level carnivores. A detritus food chain is based on the decomposition of organic wastes and dead matter from the grazing chain. Energy is lost at every level through respiration, excretion and decomposition, so NCERT says a food chain has only three to five levels. NCERT's Class XII Biology book puts a number on the loss: by the "10 per cent law", only about 10 per cent of the energy at one trophic level passes to the next, which is why grazing chains stay short and top carnivores are few.
Biological magnification
A substance that organisms absorb but cannot break down or excrete, such as some pesticides, becomes more concentrated at each higher trophic level, so the top carnivore carries the highest load. NCERT's Class X Science (Chapter 13, "Our Environment") calls this biological magnification: because such chemicals are not degradable, they "get accumulated progressively at each trophic level".
Biomes
NCERT recognises five major biomes: forest, desert, grassland, aquatic and altitudinal (Table 3). Their order follows climate. Equatorial forests have rain in every month, deciduous forests a seasonal rainfall of about 1,000 mm, temperate forests a distinct winter, and boreal forests long, cold, dry winters with snow. Deserts get less than 50 mm of rain, whether hot (Sahara, Kalahari, the Marusthali of Rajasthan), semi-arid, coastal (Atacama) or cold (tundra regions). Grasslands are tropical savannahs with 500–1,250 mm of rain or temperate steppes with 500–900 mm and cold winters. On high mountains the altitudinal biome repeats the latitudinal sequence, from deciduous forest to tundra-like vegetation.
Taiga, tundra and permafrost
A common error is to say the taiga has no permafrost. In eastern Siberia, larch-dominated taiga grows on permafrost, and the two behave as a coupled system: the larch trees maintain the permafrost by controlling its seasonal thaw, and the permafrost supplies water to the trees (Zhang, Yasunari and Ohta, Environmental Research Letters 6, 024003, 2011). The difference between taiga and tundra is the presence of trees, not of frozen ground. High latitudes are warming fast: over 1979–2021 the Arctic warmed nearly four times faster than the globe (Rantanen et al., Communications Earth & Environment 3, 168, 2022). Permafrost soils store large amounts of organic carbon, and as they thaw, microbes release it as carbon dioxide and methane.
Biogeochemical cycles
The sun is the basic source of energy for life. Photosynthesis converts carbon dioxide into organic compounds and oxygen, but only a very small fraction of the solar energy reaching the surface, about 0.1 per cent, is fixed in photosynthesis; more than half of that is used in plant respiration, and the rest is stored or moved to other parts of the plant.
NCERT notes that for the last one billion years the atmosphere and hydrosphere have kept approximately the same balance of chemical components. That balance is maintained by the cyclic passage of elements through the tissues of plants and animals: organisms absorb the elements, and decomposition returns them to the air, water and soil. These cyclic movements, largely powered by solar energy, are the biogeochemical cycles ("bio" for living organisms, "geo" for the rocks, soil, air and water of the earth). Table 4 summarises the five that NCERT describes.
Nitrogen fixation. Air is about 78% nitrogen, but only a few organisms, certain soil bacteria and blue-green algae, can use it directly. It must first be fixed. NCERT: "Ninety per cent of fixed nitrogen is biological", mainly by soil micro-organisms with plant roots acting on nitrogen in the soil's pore spaces; lightning and cosmic radiation fix some in the atmosphere, and some marine animals fix it in the oceans. Green plants then assimilate it, herbivores eat the plants, bacteria turn dead matter and wastes into nitrites and other bacteria into nitrates, and denitrifying bacteria return free nitrogen to the air.
The carbon and nitrogen cycles today
Carbon. Burning fossil fuels and clearing forests add carbon to the air faster than the ocean and land sinks remove it. In 2024 humans emitted 11.6 GtC; the ocean took up 3.4 GtC, the land 1.9 GtC, and the atmosphere gained 7.9 GtC, with a budget imbalance of about 1.7 GtC that the authors could not account for (Table 5). The same report finds that climate change and deforestation have turned South-East Asian and large parts of South American tropical forests from CO₂ sinks into sources (Global Carbon Project key findings, 12 November 2025).
Nitrogen. Nitrogen and phosphorus washed off fields into rivers and the sea feed algal blooms; when the algae die and decompose, they use up the water's oxygen. The IPBES Global Assessment (2019) reported that fertilisers entering coastal ecosystems have produced more than 400 ocean "dead zones", totalling more than 245,000 km², an area larger than the United Kingdom. Nitrous oxide released from fertilised soils is also a greenhouse gas.
Ecological balance
Ecological balance is a state of dynamic equilibrium within a community of organisms, in which the diversity of living things stays relatively stable; gradual change comes only through natural succession. It is kept by competition and cooperation between species. In NCERT's example, grasslands support many herbivores (deer, zebras, buffaloes), while carnivores (tigers, lions), fewer in number, hunt them and keep their numbers in check. In forests, a disturbance such as clearing for shifting cultivation lets secondary species, grasses, bamboos or pines, overtake the native species and change the forest's structure: this is succession.
The balance can be upset by new species, natural hazards or human activity. NCERT says human pressure on resources has destroyed the originality of many ecosystems and brought on calamities such as floods, landslides, diseases and erratic weather, and that knowing the close links between plants, animals and their habitats is the base for protecting ecosystems.
India's biodiversity in the global picture
India includes parts of four of the world's 36 biodiversity hotspots: the Himalaya, the Western Ghats, Indo-Burma and Sundaland (MoEFCC, PIB, 9 October 2025). CEPF counts 36 hotspots, the latest, the North American Coastal Plain, recognised in 2016; it includes India's Nicobar Islands in Sundaland. India's fauna checklist, prepared by the Zoological Survey of India and released on 26 June 2024, lists 104,561 animal species (PIB, MoEFCC). Threats and the conservation response are covered in the next chapter, Biodiversity and Conservation.
Source for Part 2: NCERT, Fundamentals of Physical Geography, ch 15 "Life on the Earth", 2019-20 edition, pp. 123–129; NCERT Class XII Biology, ch 12 "Ecosystem" (10 per cent law).
PART 3 — UPSC Integration
Cross-paper relevance
- GS1 (Geography): the distribution of biomes and natural vegetation and why deserts and rainforests lie where they do.
- GS3 (Environment): decomposition and the carbon cycle, the carrying capacity of ecosystems, nutrient pollution and dead zones, carbon sinks and climate change, ecological balance and succession.
Frames that score.
- Ecosystem functioning: producers, consumers and decomposers; energy flow against nutrient cycling; why removing decomposers or top carnivores destabilises the system.
- Carbon cycle and climate: sources (fossil fuels, land-use change) against sinks (ocean, land); evidence that some sinks are weakening; the role of forests and soils.
- Nutrient pollution: fertiliser and sewage, eutrophication, loss of oxygen and dead zones, loss of fisheries; remedies such as balanced fertiliser use and wastewater treatment.
- Ecological balance: NCERT's predator–prey and succession examples, then human disturbance and its calamities, then conservation.
Exam Strategy
- Haeckel, 1869, first used the term ecology (oekologie).
- Food chain levels: three to five (NCERT); about 10 per cent of energy passes up each level (NCERT Class XII).
- Top carnivores in NCERT: hawks and mongooses.
- NCERT's five biomes: forest, desert, grassland, aquatic, altitudinal. Tropical grasslands are savannas; temperate ones steppes.
- Deserts: rainfall under 50 mm in all four sub-types; the Atacama is NCERT's coastal desert.
- Only 0.1 per cent of the solar energy reaching the surface is fixed in photosynthesis.
- Gaseous cycles have their reservoir in the air and ocean; the sedimentary cycle in soil and rocks.
- Ninety per cent of fixed nitrogen is biological; lightning and cosmic radiation fix the rest in the air.
- Denitrification returns nitrates to free nitrogen.
- Succession: grasses, bamboos or pines overtaking native forest after clearing.
- Taiga vs tundra: the difference is trees, not permafrost.
Practice Questions
Practice (UPSC-pattern, not past papers). Questions 1 to 4 are the old NCERT chapter's exercise MCQs.
Prelims:
Which one of the following is included in the biosphere?
(a) only plants
(b) all living and non-living organisms
(c) only animals
(d) all living organismsTropical grasslands are also known as:
(a) the prairies
(b) the savannas
(c) the steppes
(d) none of the aboveOxygen combines with iron found in the rocks to form:
(a) iron carbonate
(b) iron nitrites
(c) iron oxides
(d) iron sulphateDuring photosynthesis, carbon dioxide combines with water in the presence of sunlight to form:
(a) proteins
(b) amino acids
(c) carbohydrates
(d) vitaminsIn NCERT's food chain "paddy → beetle → frog → snake → hawk", which organism is the top carnivore?
(a) Beetle
(b) Frog
(c) Snake
(d) HawkConsider the following statements, according to NCERT: 1. In the sedimentary cycle the main reservoir of nutrients is the atmosphere. 2. Ninety per cent of fixed nitrogen is biological. 3. Only about 0.1 per cent of the solar energy reaching the earth's surface is fixed in photosynthesis. Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Mains (practice, 150 words each):
- What are biogeochemical cycles? Explain how nitrogen is fixed. (old NCERT Ex. 3(i))
- What is ecological balance? Discuss the important measures needed to prevent ecological imbalance. (old NCERT Ex. 3(ii))
- Each year a large amount of plant material, cellulose, is deposited on the earth's surface. What natural processes does it undergo before it yields carbon dioxide and water? Approach: decomposition by micro-organisms in the carbon cycle (Table 4).
Short answers (old NCERT Ex. 2, about 30 words): a food chain is the sequence of eating and being eaten with the transfer of energy (grazing chain: paddy, beetle, frog, snake, hawk); a food web is food chains interlocked because carnivores eat several kinds of prey; a biome is a large plant and animal community whose boundaries are set mainly by climate.
📦 Revision Capsule
Hard Facts
- "Life on the Earth" (old ch 15) was dropped in the rationalised edition; the current Unit VI has only ch 14, Biodiversity and Conservation
- Ecology: Greek oikos; first used by Ernst Haeckel (oekologie), 1869
- Ecosystem = abiotic + biotic (producers, consumers: primary, secondary, tertiary; decomposers)
- NCERT food chain: paddy, beetle, frog, snake, hawk; 3–5 levels; energy lost through respiration, excretion, decomposition
- Five biomes: forest (equatorial, deciduous, temperate, boreal), desert (hot, semi-arid, coastal, cold), grassland (savannah, steppe), aquatic (freshwater, marine), altitudinal
- 0.1% of surface insolation fixed in photosynthesis
- Cycles: water, carbon, oxygen, nitrogen (gaseous); other minerals (sedimentary)
- Nitrogen 78% of air; 90% of fixed nitrogen biological; denitrification returns N₂
- Global mean CO₂: 422.8 ppm (2024); 425.6 ppm projected for 2025 (Global Carbon Budget 2025)
- Human CO₂ emissions 11.6 GtC in 2024: fossil 10.3, land-use change 1.3; ocean sink 3.4, land sink 1.9 GtC
Core Concepts
- Climate decides vegetation and vegetation decides animals, so the biome map follows the climate map
- Energy flows one way and is lost at each level; matter is recycled by decomposers
- Ecological balance is kept by competition and cooperation; disturbance brings succession
- Human emissions exceed what ocean and land sinks absorb, so atmospheric CO₂ rises
Confused Pairs
- Energy flow (one-way) vs nutrient cycling (circular)
- Food chain (one line) vs food web (interlinked chains)
- Grazing food chain (starts with plants) vs detritus food chain (starts with dead matter)
- Gaseous cycle (reservoir: air, ocean) vs sedimentary cycle (reservoir: soil, rocks)
- Savanna (tropical grassland) vs steppe (temperate grassland)
PYQ Pattern
- Mains GS3 has asked about the decomposition of cellulose and the carrying capacity of ecosystems; GS1 about dead zones in the oceans; Prelims about biomagnification in a food chain and India's biodiversity hotspots.
Sources
- NCERT, Fundamentals of Physical Geography, Class XI, ch 15 "Life on the Earth", 2019-20 edition (dropped in the rationalised edition), via the Wayback copy of the book: kegy2dd.zip, 4 May 2019; current ch 14 "Biodiversity and Conservation", Reprint 2026-27: kegy214.pdf.
- NCERT, Biology, Class XII, ch 12 "Ecosystem" (10 per cent law): lebo112.pdf.
- Friedlingstein, P. et al., "Global Carbon Budget 2025", Earth System Science Data 18, 3211–3288, published 13 May 2026, doi:10.5194/essd-18-3211-2026: essd.copernicus.org.
- NCERT, Science, Class X, Chapter 13 "Our Environment", Reprint 2026-27: jesc113.pdf.
- Zhang, N., Yasunari, T. and Ohta, T., "Dynamics of the larch taiga-permafrost coupled system in Siberia under climate change", Environmental Research Letters 6, 024003 (2011): doi.org.
- Rantanen, M. et al., "The Arctic has warmed nearly four times faster than the globe since 1979", Communications Earth & Environment 3, 168 (2022): doi.org.
- IPBES, Global Assessment media release, 6 May 2019: ipbes.net.
- PIB (MoEFCC), India at the IUCN World Conservation Congress, 9 October 2025: pib.gov.in; PIB (MoEFCC), fauna checklist of 104,561 species, 26 June 2024: pib.gov.in.
- CEPF, "Biodiversity Hotspots" and the Sundaland and North American Coastal Plain hotspot pages: cepf.net.
- Flanders Marine Institute (VLIZ), "Fossil fuel CO2 emissions hit record high in 2025", 12 November 2025 (Global Carbon Project key findings): vliz.be.
