Environment: previous-year questions
273 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 80 of them came in the last five papers.
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Questions per year, counted from the official papers.
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With reference to the ‘New York Declaration on Forests’, which of the following statements are correct?
- 1. It was first endorsed at the United Nations Climate Summit in 2014.
- 2. It endorses a global timeline to end the loss of forests.
- 3. It is a legally binding international declaration.
- 4. It is endorsed by governments, big companies and indigenous communities.
- 5. India was one of the signatories at its inception.
Select the correct answer using the code given below.
Answer (a) & explanation
Statements 1, 2 and 4 are correct (a). Statement 1 is right: the New York Declaration on Forests came out of the UN Climate Summit in September 2014. Statement 2 is right: it set a global timeline to halve natural forest loss by 2020 and end it by 2030. Statement 4 is right: it was endorsed by governments, big companies, NGOs and indigenous groups. Statement 3 is wrong: it is a voluntary, non-binding declaration. Statement 5 is wrong: India did not sign it at its launch.
Notice the later Glasgow Leaders' Declaration on Forests (COP26, 2021), which again pledged to end deforestation by 2030; India did not sign that either. Bonn Challenge targets land restoration.
"declaration" plus "legally binding" is a contradiction you can spot.
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Answer as per the official UPSC answer key.
Which of the following Protected Areas are located in Cauvery basin ?
- 1. Nagarhole National Park
- 2. Papikonda National Park
- 3. Sathyamangalam Tiger Reserve
- 4. Wayanad Wildlife Sanctuary
Select the correct answer using the code given below :
Answer (c) & explanation
Nagarhole, Sathyamangalam and Wayanad lie in the Cauvery basin (c). All three sit in the Nilgiri hill region, drained by Cauvery tributaries. Item 1 is right: Nagarhole (Karnataka) is drained by the Kabini. Item 3 is right: Sathyamangalam (Tamil Nadu) lies along the Moyar and Bhavani. Item 4 is right: Wayanad (Kerala) is drained by the Kabini and its streams. Item 2 is wrong: Papikonda National Park is on the Godavari in Andhra Pradesh, where the river cuts a gorge through the Eastern Ghats.
Notice the Nilgiri Biosphere Reserve (1986), India's first, which links Nagarhole, Bandipur, Mudumalai, Wayanad and Silent Valley. Other Cauvery tributaries include the Hemavati, Shimsha, Arkavathi and Amaravati.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. 36% of India’s districts are classified as “overexploited” or “critical” by the Central Ground Water Authority (CGWA).
- 2. CGWA was formed under the Environment (Protection) Act.
- 3. India has the largest area under groundwater irrigation in the world.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 1 is wrong per the key: assessments by the Central Ground Water Board classify blocks, not whole districts, as over-exploited or critical, and the figures did not match 36% of districts by the CGWA. Statement 2 is right: the Central Ground Water Authority was set up in 1997 under Section 3(3) of the Environment (Protection) Act, 1986, to regulate groundwater use. Statement 3 is right: India uses more groundwater than any other country and has the largest area irrigated by it.
Notice Atal Bhujal Yojana (2019), which works on community groundwater management in seven States. Punjab, Haryana and Rajasthan have the worst over-extraction.
CGWB and CGWA again. The Board assesses; the Authority regulates.
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Answer as per the official UPSC answer key.
With reference to India’s biodiversity, Ceylon frogmouth, Coppersmith barbet, Gray-chinned minivet and White-throated redstart are
Answer (a) & explanation
All four are birds (a). The Ceylon frogmouth is a night bird of the Western Ghats and Sri Lanka, named for its wide, frog-like mouth. The coppersmith barbet is a small green bird named for its call, which sounds like a smith hammering metal. The grey-chinned minivet is a bright songbird of hill forests. The white-throated redstart is a Himalayan bird of high scrub. None of them is a primate (b), reptile (c) or amphibian (d); the frogmouth's name is the only trap.
Notice how UPSC likes species with misleading names. Other bird examples: the Great Indian Bustard (Critically Endangered), the Jerdon's courser, and the Malabar trogon. Notice too the Asian Waterbird Census, held each January.
"frogmouth" pushes you towards amphibians.
Answer as per the official UPSC answer key.
Among the following Tiger Reserves, which one has the largest area under “Critical Tiger Habitat” ?
Answer (c) & explanation
Nagarjunsagar-Srisailam has the largest critical tiger habitat (c). Nagarjunsagar-Srisailam Tiger Reserve, in the Nallamala hills of Andhra Pradesh (with the adjoining Amrabad in Telangana), is India's largest tiger reserve. Its core or critical tiger habitat is about 2,600 sq km, larger than Corbett (a, about 820 sq km), Ranthambore (b, about 1,100 sq km) and Sunderbans (d, about 1,700 sq km). Critical tiger habitats are the core zones kept free of human use under Section 38V of the Wild Life (Protection) Act.
Notice Project Tiger (1973) and the NTCA (2006). India now has 58 tiger reserves (Madhav, 2025, the latest) and about 3,682 tigers (2022), around 75% of the world's wild tigers.
Answer as per the official UPSC answer key.
Which one of the following protected areas is well-known for the conservation of a sub-species of the Indian swamp deer (Barasingha) that thrives well on hard ground and is exclusively graminivorous ?
Answer (a) & explanation
Kanha protects the hard-ground barasingha (a). The swamp deer has three sub-species. The hard-ground barasingha (Rucervus duvaucelii branderi) lives in the sal forests and meadows of Kanha in Madhya Pradesh. It eats only grass (graminivorous) and, unlike its cousins, lives on firm ground. Kanha saved it from near extinction (about 66 animals in 1970). It is the state animal of Madhya Pradesh. Manas (b) holds the eastern swamp deer of Assam's wetlands. Mudumalai (c) has no barasingha. Tal Chhapar (d) in Rajasthan is famous for blackbuck.
Notice the other sub-species: the western swamp deer in the Terai (Dudhwa, Shuklaphanta) and the eastern one in Kaziranga. Kanha's mascot is "Bhoorsingh the Barasingha".
Answer as per the official UPSC answer key.
Steel slag can be the material for which of the following ?
- 1. Construction of base road
- 2. Improvement of agricultural soil
- 3. Production of cement
Select the correct answer using the code given below :
Answer (d) & explanation
Steel slag can be used for all three (d). Steel slag is the stony waste left over when lime is used to remove impurities from molten iron in steel-making. Use 1 is right: crushed slag is hard and strong, so it is used in road base and sub-base layers; India's first steel slag road was built in Surat (2022). Use 2 is right: slag is rich in lime (calcium) and some silicates, so it can correct acidic soils. Use 3 is right: granulated blast furnace slag is ground into Portland Slag Cement, cutting the need for clinker.
Notice the idea of a circular economy: turning industrial waste into resources. Fly ash from power plants is reused the same way, in bricks and cement.
Answer as per the official UPSC answer key.
Which of the following are the most likely places to find the musk deer in its natural habitat ?
- 1. Askot Wildlife Sanctuary
- 2. Gangotri National Park
- 3. Kishanpur Wildlife Sanctuary
- 4. Manas National Park
Select the correct answer using the code given below :
Answer (a) & explanation
Askot and Gangotri are the likely homes of musk deer (a). The Himalayan musk deer lives in high alpine forests and scrub, usually above 2,500 metres. Item 1 is right: Askot Wildlife Sanctuary in Pithoragarh, Uttarakhand, was set up partly to protect musk deer. Item 2 is right: Gangotri National Park lies in the high Garhwal Himalaya. Item 3 is wrong: Kishanpur is in the Terai of Uttar Pradesh, part of Dudhwa Tiger Reserve, too low and warm. Item 4 is wrong: Manas is in the lowland Assam plains.
Notice that males are poached for musk, a gland used in perfume and medicine; the species is Endangered and in Schedule I. The alpine musk deer is the state animal of Uttarakhand.
Answer as per the official UPSC answer key.
In rural road construction, the use of which of the following is preferred for ensuring environmental sustainability or to reduce carbon footprint ?
- 1. Copper slag
- 2. Cold mix asphalt technology
- 3. Geotextiles
- 4. Hot mix asphalt technology
- 5. Portland cement
Select the correct answer using the code given below :
Answer (a) & explanation
Copper slag, cold mix asphalt and geotextiles are preferred (a). Item 1 is right: copper slag reuses an industrial waste in place of natural sand and aggregate. Item 2 is right: cold mix asphalt is laid without heating, saving fuel and emissions, and it works in rain and cold hill areas. Item 3 is right: geotextiles, such as jute or coir mats, strengthen the road and control erosion with less material. Item 4 is wrong: hot mix asphalt needs heating to about 150 °C, which burns fuel. Item 5 is wrong: making Portland cement releases a lot of CO₂.
Notice PMGSY (Pradhan Mantri Gram Sadak Yojana, 2000), which promotes green technologies in rural roads, including waste plastic, fly ash and these materials.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Coal ash contains arsenic, lead and mercury.
- 2. Coal-fired power plants release sulphur dioxide and oxides of nitrogen into the environment.
- 3. High ash content is observed in Indian coal.
Which of the statements given above is/are correct ?
Answer (d) & explanation
All three statements are correct (d). Statement 1 is right: coal fly ash carries toxic metals such as arsenic, lead and mercury, which can leak into water and soil from ash ponds. Statement 2 is right: burning coal releases sulphur dioxide (SO₂) and oxides of nitrogen (NOₓ), which cause acid rain and smog, along with particulate matter. Statement 3 is right: most Indian coal is low grade, with 30–45% ash, far more than imported coal, so plants produce huge amounts of ash.
Notice the response: Flue Gas Desulphurisation (FGD) units to cut SO₂, and rules for 100% fly ash use in bricks, cement and roads. Indian coal is low in sulphur, which is one benefit.
Answer as per the official UPSC answer key.
What is the use of biochar in farming ?
- 1. Biochar can be used as a part of the growing medium in vertical farming.
- 2. When biochar is a part of the growing medium, it promotes the growth of nitrogen-fixing microorganisms.
- 3. When biochar is a part of the growing medium, it enables the growing medium to retain water for longer time.
Which of the statements given above is/are correct ?
Answer (d) & explanation
All three statements are correct (d). Biochar is a charcoal made by heating crop waste or wood with little oxygen (pyrolysis). Statement 1 is right: biochar can be mixed into the soil-less growing media used in vertical farming, along with cocopeat and others. Statement 2 is right: its porous body gives a home to useful microbes, including nitrogen-fixing bacteria. Statement 3 is right: those same pores hold water and nutrients, so the medium stays moist for longer.
Notice its climate benefit: biochar locks carbon in the soil for hundreds of years, a form of carbon sequestration. Turning crop stubble into biochar is also proposed as an alternative to stubble burning in Punjab and Haryana.
Answer as per the official UPSC answer key.
Consider the following pairs :
| International agreement / set-up | Subject
| 1. Alma-Ata Declaration | Healthcare of the people
| 2. Hague Convention | Biological and chemical weapons
| 3. Talanoa Dialogue | Global climate change
| 4. Under2 Coalition | Child rights
Which of the pairs given above is/are correctly matched ?
Answer (c) & explanation
Pairs 1 and 3 are correct (c). The Alma-Ata Declaration (1978), from a WHO–UNICEF conference in Kazakhstan, set the goal of primary health care for all (1). The Talanoa Dialogue (2018), named after a Fijian word for open, inclusive talk, was a UNFCCC stock-take of climate action (3). Pair 2 is wrong because biological and chemical weapons are covered by the Biological Weapons Convention (1972) and the Chemical Weapons Convention (1993), not a "Hague Convention". Pair 4 is wrong because the Under2 Coalition is a group of state and regional governments working to keep warming under 2°C, not on child rights.
Notice the Astana Declaration (2018), which renewed Alma-Ata's goal. India's Ayushman Arogya Mandirs (health and wellness centres) carry the primary health care idea forward.
"Under2" sounds like "under 2 years", but it means keeping warming under 2°C.
Answer as per the official UPSC answer key.
If a particular plant species is placed under Schedule VI of The Wildlife Protection Act, 1972, what is the implication ?
Answer (a) & explanation
A licence is needed to cultivate that plant (a). Schedule VI of the Wild Life (Protection) Act, 1972 listed specified plants, such as the red vanda, blue vanda, ladies' slipper orchid and pitcher plant. They could be grown, but only with a licence from the Chief Wildlife Warden, so that plants taken from the wild could not be passed off as cultivated ones. Option (b) is wrong: cultivation is allowed under licence. Option (c) is wrong: GM crops are regulated by the GEAC. Option (d) is wrong: the schedule protects rare plants, it does not list invasive ones.
Notice the 2022 amendment, which cut the schedules from six to four: specified plants are now in Schedule III, and CITES species in Schedule IV.
Answer as per the official UPSC answer key.
Which of the following are the reasons/factors for exposure to benzene pollution ?
- 1. Automobile exhaust
- 2. Tobacco smoke
- 3. Wood burning
- 4. Using varnished wooden furniture
- 5. Using products made of polyurethane
Select the correct answer using the code given below :
Answer (a) & explanation
Factors 1, 2 and 3 are correct in UPSC's key (a). Benzene is released when carbon-rich material burns incompletely. Major sources are vehicle exhaust (1), as benzene is in petrol and is formed during burning; tobacco smoke (2), the main source for smokers; and wood burning (3), including stoves and forest fires. Benzene is a known cause of leukaemia and other blood cancers. UPSC's key leaves out varnished furniture (4) and polyurethane products (5), which give off other volatile organic compounds such as formaldehyde.
Notice India's limits: BS-VI fuel (from 2020) limits benzene in petrol to 1%, and the National Ambient Air Quality Standards set a yearly limit of 5 µg/m³. Petrol pumps use vapour recovery systems.
Answer as per the official UPSC answer key.
Which one of the following statements best describes the term ‘Social Cost of Carbon’ ?
It is a measure, in monetary value, of the
Answer (a) & explanation
It measures the long-term damage from one tonne of CO₂ (a). The social cost of carbon puts a money value on the harm caused by emitting one more tonne of CO₂ in a given year: lost crops, health damage, floods, heat and lower productivity, added up over time. Governments use it to weigh the costs and benefits of climate policies and regulations. Option (b) describes a country's fossil fuel demand, not damage. Option (c) describes the burden on a climate refugee. Option (d) describes an individual's carbon footprint.
Notice the related ideas of carbon pricing: a carbon tax and emissions trading. India launched its Carbon Credit Trading Scheme in 2023 under the Energy Conservation Act.
Answer as per the official UPSC answer key.
With reference to Indian elephants, consider the following statements :
- 1. The leader of an elephant group is a female.
- 2. The maximum gestation period can be 22 months.
- 3. An elephant can normally go on calving till the age of 40 years only.
- 4. Among the States in India, the highest elephant population is in Kerala.
Which of the statements given above is/are correct ?
Answer (a) & explanation
Statements 1 and 2 are correct (a). Statement 1 is right: an elephant herd is led by the oldest female, the matriarch, who remembers routes and water sources. Adult males usually live alone or in small groups. Statement 2 is right: pregnancy lasts about 22 months, the longest of any mammal. Statement 3 is wrong: female elephants can calve into their fifties and beyond, not just till 40. Statement 4 is wrong: Karnataka has the largest elephant population in India, followed by Assam and Kerala.
Notice that the Asian elephant is Endangered on the IUCN Red List and is in Schedule I of the Wildlife Protection Act. Project Elephant began in 1992. World Elephant Day is 12 August.
"40 years only": the word "only" makes 3 easy to reject.
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Answer as per the official UPSC answer key.
With reference to India’s Desert National Park, which of the following statements are correct ?
- 1. It is spread over two districts.
- 2. There is no human habitation inside the Park.
- 3. It is one of the natural habitats of Great Indian Bustard.
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1 and 3 are correct (c). Statement 1 is right: Desert National Park covers parts of Jaisalmer and Barmer districts in Rajasthan, about 3,162 sq km. Statement 2 is wrong: several villages and herders' settlements lie inside the park, which makes conservation harder. Statement 3 is right: it is the last major stronghold of the Great Indian Bustard, which is Critically Endangered with only about 150 birds left in the wild.
Notice the main threat to the bustard: collisions with overhead power lines, which led the Supreme Court to order lines to go underground in key areas. The park also holds fossils at Akal Wood Fossil Park. The bustard is the state bird of Rajasthan.
Answer as per the official UPSC answer key.
In the context of which one of the following are the terms ‘pyrolysis and plasma gasification’ mentioned?
Answer (d) & explanation
These are waste-to-energy technologies (d). Pyrolysis heats waste, such as plastics or biomass, to high temperatures without oxygen. Instead of burning, the material breaks down into pyrolysis oil, gas (syngas) and char. Plasma gasification uses a plasma torch, at several thousand degrees, to break waste down into syngas (mainly hydrogen and carbon monoxide), leaving a glassy, harmless slag. Both turn waste into fuel or power and reduce the load on landfills. They are not used for extracting rare earths (a) or natural gas (b), and they are not hydrogen car technology (c), though syngas can yield hydrogen.
Notice India's rules: the Solid Waste Management Rules, 2016 (being updated) promote waste-to-energy, and the SATAT scheme backs compressed biogas from waste.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Agricultural soils release nitrogen oxides into environment.
- 2. Cattle release ammonia into environment.
- 3. Poultry industry releases reactive nitrogen compounds into environment.
Which of the statements given above is/are correct?
Answer (d) & explanation
All three statements are correct (d). These are all sources of reactive nitrogen, meaning nitrogen in forms other than inert N₂ gas. Statement 1 is right because fertilised farm soils give off nitrous oxide (N₂O), a powerful greenhouse gas, and nitric oxide, as microbes act on extra urea. Statement 2 is right because cattle dung and urine release ammonia. Statement 3 is right because poultry farms release ammonia and other nitrogen compounds from droppings. The Indian Nitrogen Assessment (2017) named all three, with cereals and livestock as the main sources.
Notice the solutions: neem-coated urea (mandatory since 2015), nano urea by IFFCO, and soil health cards. India's 2019 UNEA resolution on sustainable nitrogen management was adopted.
Answer as per the official UPSC answer key.
Which of the following are in Agasthyamala Biosphere Reserve?
Answer (a) & explanation
Option (a) lists the parts of Agasthyamala (a). The Agasthyamala Biosphere Reserve, set up in 2001 at the southern tip of the Western Ghats on the Kerala–Tamil Nadu border, includes the Neyyar, Peppara and Shendurney wildlife sanctuaries in Kerala and the Kalakad Mundanthurai Tiger Reserve in Tamil Nadu. It joined UNESCO's World Network of Biosphere Reserves in 2016. It is home to the Kani tribe, known for the Arogyapacha herb. Option (b) describes the Nilgiri Biosphere Reserve, India's first (1986). Options (c) and (d) list protected areas of Andhra Pradesh and Telangana, with Mukurthi wrongly added from the Nilgiris.
India has 18 biosphere reserves, of which 13 are in the UNESCO network. Notice that Cold Desert (Himachal) joined in 2025.
(b) is a real biosphere reserve set, so it looks right; it is the Nilgiri one.
Answer as per the official UPSC answer key.