UPSC 2025 Environment and Ecology Questions with Answers
14 previous year UPSC Prelims questions on Environment and Ecology in the UPSC 2025 Prelims. Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 1–10 of 14 questions
Browse Environment and Ecology chapters
UPSC 2025Environment and Ecology · Pollution
Q1. Consider the following: 1. Cigarette butts 2. Eyeglass lenses 3. Car tyres How many of them contain plastic?
Explanation
Plastics are synthetic polymers widely used in modern products due to their versatility, durability, and cost-effectiveness. Cigarette Butts: Cigarette butts, made of cellulose acetate, are the most littered plastic waste worldwide, with 4.5 trillion butts discarded annually--66% of the 6 trillion cigarettes smoked. Each releases about 15,000 microplastic fibers, leaching nicotine, arsenic, and lead, and takes up to 10 years to degrade. Eyeglass Lenses: Eyeglass lenses are now mostly plastic-- CR-39, polycarbonate (used in 90% of glasses), Trivex, and high-index plastics--preferred for being lightweight, shatter-resistant, and optically clear. Improper disposal contributes to plastic waste, but recycling remains limited. Car Tyres: Car tyres contain 24% synthetic rubber, 19% natural rubber, carbon black, and synthetic fibers like nylon and polyester. Tyre wear particles (TWPs) contribute 10-28% of oceanic microplastics, totaling 1.2-2.8 million tonnes annually. Hence, option (c) is correct.
Additional insight:
Microplastics, fragments of plastic less than 5 mm, originate from primary sources (e.g., microbeads in cosmetics) or secondary sources (e.g., breakdown of larger plastics like synthetic fabrics or tyres). They are a global pollution threat, found in oceans, air, soil, food, and even human organs, contributing to environmental and health concerns.
Exam tip:
You can try, The "NOT" approach for all statements, this tests the improbability of negating a statement--if denying its impact seems highly unlikely, the statement is plausibly true. For example: Saying "Cigarette butts, Eyeglass lenses or car tyres do not contain plastic" seems highly implausible, suggesting that all three do contain plastic.
UPSC 2025Environment and Ecology · Pollution
Q2. Consider the following statements: Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries. Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals. Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content. Which one of the following is correct in respect of the above statements?
Explanation
Statement I is correct: Activated carbon is an effective, versatile adsorbent for removing pollutants from effluent streams like wastewater and industrial discharges, widely used in textile, pharmaceutical, and petrochemical industries. It removes organic compounds (e.g., phenols, dyes), heavy metals (e.g., lead, mercury), and VOCs with 90-99% efficiency. The EPA classifies it as a Best Available Technology (BAT) for wastewater treatment.
Statement II is correct: Its large surface area (500-1500 m²/g) and microporous structure (<2 nm pores) offer abundant adsorption sites. Surface functional groups (e.g., hydroxyl, carboxyl) enhance binding of cadmium, chromium, lead, and mercury, with 95-99% removal efficiency. High BET surface area and pore volume (0.5-2 cm²/g) explain its adsorption efficiency, reinforcing Statement I.
Statement III is correct: Activated carbon can be synthesized from environmental wastes (e.g., coconut shells, rice husks, bagasse, fruit peels, sewage sludge) via pyrolysis (400-800°C) and chemical/physical activation. Coconut shells yield >1000 m²/g, bagasse 800-1200 m²/g. This cost-effective, sustainable process supports its use in pollutant removal and aligns with circular economy goals
UPSC 2025Environment and Ecology · Climate Change
Q3. Consider the following statements: Statement I: Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions. Statement II: Silica-bearing clay is mixed with limestone while manufacturing cement. Statement III: Limestone is converted into lime during clinker production for cement manufacturing. Which one of the following is correct in respect of the above statements?
Explanation
Statement I is Correct: It is estimated that around 4-8 percent of the world’s carbon dioxide (CO₂) emissions come from the manufacture of cement, making it a major contributor to global warming
Statement II is correct but doesn’t explain statement I: Silica-bearing clay is mixed with limestone while manufacturing cement. Limestone, primarily composed of calcium carbonate (CaCO₃)₃), begins to decompose at temperatures around 825°C (1517°F). This process, called calcination, breaks down the limestone into calcium oxide (CaO) and carbon dioxide (CO₂). Thus the step of mixing Silica bearing clay and limestone contribute to the Carbon dioxide emission from cement industry.
Statement III is correct and explains Statement I: A significant portion of the emissions are an intrinsic part of the production of clinker. In the process of making cement clinker, limestone, which is primarily calcium carbonate (CaCO₃)₃), is heated to high temperatures (1450°C or 2640°F) in a kiln. This process, called calcination, decomposes the limestone into calcium oxide (CaO), commonly known as lime, and carbon dioxide (CO₂). The lime then reacts with other raw materials like clay and silica to form the clinker, which is the main ingredient in cement.
UPSC 2025Environment and Ecology · Climate Change
Q4. Consider the following statements: Statement I: At the 28th United Nations Climate Change Conference (COP28), India refrained from signing the ‘Declaration on Climate and Health’. Statement II: The COP28 Declaration on Climate and Health is a binding declaration; and if signed, it becomes mandatory to decarbonize health sector. Statement III: If India’s health sector is decarbonized, the resilience of its health-care system may be compromised. Which one of the following is correct in respect of the above statements?
Explanation
COP 28 was held in Dubai, UAE in December 2023. It introduced the COP28 Declaration on Climate and Health to reduce health sector greenhouse gas emissions, enhance climate-resilient health systems, and address climate-related health risks like air pollution and extreme weather. $1 billion was pledged by entities like the Rockefeller Foundation and Green Climate Fund for climate-health initiatives.
Statement I is correct: India abstained from signing due to concerns over reducing greenhouse gas emissions from cooling systems critical for healthcare infrastructure, especially in remote areas. Highlighted that cooling systems for vaccines and medicines ensure healthcare resilience, and decarbonization could disrupt service delivery. This aligned with India’s G20 presidency (2023) focus on resilient healthcare.
Statement II is incorrect: The COP28 Declaration is non-binding, encouraging voluntary actions like assessing health sector emissions, developing action plans, and promoting low-carbon health systems, active mobility, and sustainable diets. It operates outside UNFCCC/Paris Agreement frameworks, not mandating decarbonization. India raised concerns about cooling-related emissions feasibility, not mandatory requirements.
Statement III is correct: India argued that decarbonizing the health sector, particularly cooling systems for vaccine storage and hospitals, could compromise healthcare resilience in tropical climates and remote areas. A Kenyan delegate noted India’s concern that emission reductions could hinder medical demands in underserved regions. India’s G20 priorities (2023) emphasized healthcare access, medical countermeasures, and digital health platforms, supported by its low per-capita emissions (<4% of global GHG emissions) and developing nation status.
Exam tip:
For S2, UN Declarations (like COP outcomes) are typically non-binding. These are soft law instruments -- they express intent and global consensus but do not carry legal enforcement mechanisms. If a global declaration were legally binding, it would require parliamentary ratification, feature enforcement clauses, and likely cause wider international debate. Since none of that happened, the statement makes an extreme and unrealistic claim. Giving option C as correct.
UPSC 2025Environment and Ecology · Climate Change
Q5. Consider the following statements: Statement I: Article 6 of the Paris Agreement on climate change is frequently discussed in global discussions on sustainable development and climate change. Statement II: Article 6 of the Paris Agreement on climate change sets out the principles of carbon markets. Statement III: Article 6 of the Paris Agreement on climate change intends to promote inter-country non-market strategies to reach their climate targets. Which one of the following is correct in respect of the above statements?
Explanation
Article 6 of the Paris Agreement (2015, COP21) provides a framework for international cooperation to achieve climate goals through market-based and non-market-based mechanisms, enabling countries to meet their Nationally Determined Contributions (NDCs). It’s central to discussions on climate finance, GHG reduction, and SDG alignment.
Statement I is correct:
Article 6 is a cornerstone of the Paris Agreement, frequently discussed at COP summits--COP26 (Glasgow, 2021) and COP29 (Baku, 2024). It enables international cooperation for NDCs, addresses carbon markets and non-market approaches (NMAs), and mobilizes up to $1 trillion in climate finance by 2050. Highlighted by the World Bank and UNFCCC, it ensures environmental integrity and supports sustainable development. In India, with <4% of global GHG emissions, Article 6 is key in climate negotiations. Delays in rule finalization--e.g., COP25 (Madrid, 2019)--due to concerns like double counting underscore its importance.
Statement II is correct:
Article 6.2 allows bilateral trading of ITMOs with corresponding adjustments to avoid double counting. Article 6.4 sets up a UN-supervised Paris Agreement Crediting Mechanism (PACM), succeeding the Kyoto Protocol’s CDM, issuing A6.4ERs with 2% cancellation and 5% share for the Adaptation Fund. As per the World Bank and IISD, these rules--finalized at COP26 and advanced at COP29--enhance market integrity and climate finance. This explains Statement I, as carbon markets drive debates on market integrity, double counting, and private sector investment (e.g., $1 trillion potential by 2050).
Statement III is correct:
Article 6.8 promotes non-market approaches (NMAs) like tech transfers, policy coordination, and adaptation finance. Recognized by UNFCCC and Legal Response International, NMAs support equity, climate resilience, and SDGs, especially for nations like India, making Article 6 central in climate talks. This also explains Statement I, as NMAs address equity and cooperation, key topics in climate negotiations, especially for developing nations like India
UPSC 2025Environment and Ecology · Environmental Organisations
Q6. Which one of the following launched the Nature Solutions Finance Hub for Asia and the Pacific’?
Explanation
The Nature Solutions Finance Hub for Asia and the Pacific was launched by the Asian Development Bank (ADB) on December 4, 2023, during COP28 in Dubai to mobilize $2 billion by 2030 for nature-based solutions such as reforestation, mangrove restoration, and sustainable agriculture. It aims to address climate change and biodiversity loss using blended finance, guarantees, and impact-linked payments to attract private capital, supporting SDG 13 (Climate Action) and SDG 15 (Life on Land). Partners include the OPEC Fund, AFD, Saudi Fund for Development, ASEAN Catalytic Green Finance Facility, IUCN, WWF, and Conservation International. ADB’s Mandate:
Established in 1966, headquartered in Manila, with 68 members (49 from Asia-Pacific). Provides $22 billion annually, committed $100 billion for climate finance (2019-2030). In 2023, 40% of approvals were climate-focused, including $434.25 million for Assam Solar Park and Rs 2,346 crore for the Ahmedabad Peri-Urban Project. Supports ecosystem restoration, biodiversity conservation, and sustainable development. Global Context: Nature-based solutions absorb 55% of carbon through forests, oceans, and land ecosystems, vital for the Asia-Pacific, where 2/3 of GDP is nature-dependent. India’s Context: India, an ADB member, benefits from climate finance (e.g., $434.25 million for Assam solar park, Rs 2,346 crore for Ahmedabad Peri-Urban Project).Challenges include land acquisition issues, highlighting social safeguards. Options (b), (c) & (d) are incorrect: (b) AIIB (est. 2016, Beijing) focuses on infrastructure, not involved in this ADB-led hub. (c) NDB (est. 2015, BRICS, Shanghai) supports green energy but not linked to the hub. (d) IBRD (World Bank, est. 1944, Washington D.C.) supports climate goals but not part of this initiative.
UPSC 2025Environment and Ecology · Climate Change
Q7. With reference to Direct Air Capture’, an emerging technology, which of the following statements is/are correct? I. It can be used as a way of carbon sequestration. II. It can be a valuable approach for plastic production and in food processing. III. In aviation, it can be a source of carbon for combining with hydrogen to create synthetic low-carbon fuel. Select the correct answer using the code given below.
Explanation
Direct Air Capture (DAC) is an emerging negative emission technology that extracts carbon dioxide (CO₂) directly from the atmosphere. It is gaining attention for its potential to mitigate climate change by enabling carbon sequestration, utilization in products, and synthetic fuel production
Statement I is correct:
DAC uses chemical processes with liquid solvents (e.g., potassium hydroxide) or solid sorbents to extract CO₂ from the atmosphere. Captured CO₂ is sequestered in deep geological formations like saline aquifers or depleted oil/gas reservoirs for permanent storage, preventing atmospheric release. As of 2024, 27 DAC plants capture about 0.01 Mt CO₂/year, with plans for 130 facilities targeting 65 Mt CO₂/year by 2030 (IEA Net Zero Emissions scenario). DACCS is critical for carbon dioxide removal (CDR), essential to limit warming to 1.5°C (NASA, IPCC). Especially important for hard-to-abate sectors (e.g., aviation). India’s low per-capita emissions (<4% global GHG) make DACCS a strategic offset tool.
Statement II is correct:
CO₂ is a feedstock for industrial uses:
Plastics production (polycarbonates, polyurethanes) locks CO₂ for decades to centuries, offering durable sequestration. Food processing: carbonation of beverages, modified atmosphere packaging, with a global CO₂ market of 230 Mt/year. WRI highlights CO₂ use in plastics/concrete as more durable than short-term uses like beverages. DAC CO₂ use supports India’s food processing sector (Make in India focus). Despite costs ($400-740/tCO), policy support (e.g., US 45Q tax credits) enhances viability.
Statement III is correct:
DAC CO₂ combined with renewable hydrogen produces synthetic kerosene (power-to-liquid fuels) via processes like Fischer-Tropsch. SAFs are drop-in fuels compatible with existing aircraft, helping decarbonize aviation. DACCU mitigates CO₂ and non-CO₂ effects (contrails). Costs currently $1.50-4.50/gallon, expected to fall by 2050. India emits about 2% global aviation GHG, potentially benefiting from SAF adoption to meet CORSIA goals.
Additional insight:
DAC uses fans to pull air over sorbents/solvents; CO₂ is released with heat (~600°C). High energy use (6-10 GJ/tCO) is mitigated by renewable energy integration. Global DAC plants include Stratos (USA), Mammoth (Iceland), Kollsnes (Norway); India could deploy DAC in solar-rich states like Gujarat and Rajasthan. Key challenges: High costs, energy intensity; policy incentives like US 45Q tax credit ($20/tCO sequestration, $10/tCO enhanced oil recovery) and carbon markets drive adoption. India’s renewable energy push (450 GW target by 2030) and growing industrial sectors align with DAC for decarbonization.
Exam tip:
You can try, The "NOT" approach for all statements, this tests the improbability of negating a statement--if denying its impact seems highly unlikely, the statement is plausibly true. For example: Can DAC CO₂ be used in manufacturing? Yes --captured CO₂ is being tested in synthetic polymers, carbonated beverages, and even lab-grown food products. Denying its utility in these areas seems too rigid and ignores experimental applications. Similarly apply this in all three statements and observe that all are likely true.
UPSC 2025Environment and Ecology · Species
Q8. Regarding Peacock tarantula (Gooty tarantula), consider the following statements: I. It is an omnivorous crustacean. II. Its natural habitat in India is only limited to some forest areas. III. In its natural habitat, it is an arboreal species. Which of the statements given above is/are correct?
Explanation
Peacock Tarantula Overview Scientific Name: Poecilotheria metallica, also Gooty tarantula. Status: Critically Endangered, IUCN Red List. Description: Arboreal spider, Theraphosidae family (Arachnida, Araneae), known for vibrant metallic blue coloration. Habitat: Endemic to <100 sq km of deciduous forests in Andhra Pradesh (Nandyal, Giddalur, Seshachalam Biosphere Reserve) and Tamil Nadu (Pakkamalai Reserve Forests, Villupuram, Tirumala foothills). Threats: Habitat loss from deforestation, logging, firewood harvesting, and illegal pet trade. Protection: CITES Appendix II (2019) bans export without permits. Diet and Behavior:
Carnivorous, feeds on flying insects (moths, crickets) and occasionally small vertebrates (mice, small birds). Photosensitive, flees bright light, may bite if provoked with medically significant venom causing pain, nausea, dizziness (no fatalities). Constructs asymmetric funnel webs in tree holes. Spiderlings start terrestrial, transition to arboreal.
Statement I is incorrect: The Peacock tarantula is an arachnid (class Arachnida, order Araneae, family Theraphosidae), not a crustacean (class Crustacea, e.g., crabs, shrimp).
Statement II is correct: Is endemic to a small area (<100 sq km) of deciduous forests in Andhra Pradesh and Tamil Nadu.
Statement III is correct: Poecilotheria metallica is an arboreal spider, living in tree holes and constructing asymmetric funnel webs to capture flying insects.
UPSC 2025Environment and Ecology · Climate Change
Q9. Consider the following statements: I. Carbon dioxide (CO₂) emissions in India are less than 0.5 t CO₂/capita. II. In terms of CO₂ emissions from fuel combustion, India ranks second in Asia-Pacific region. III. Electricity and heat producers are the largest sources of CO₂ emissions in India. Which of the statements given above is/are correct?
Explanation
India, the third-largest global CO₂ emitter (2.8 Gt CO₂, 2023), has low per capita emissions (1.9-2.0 t CO₂/capita, 2022-2023) due to its 1.43 billion population (2022). Coal dominates power sector (75-76% electricity generation), followed by industry and transport.
Statement I is incorrect: Per capita CO₂ emissions measure annual emissions per person. IEA (2024) reports India’s at 2.0 t CO₂/capita (2023), Statista (2024) cites 1.89-2.0 t CO₂/capita (2022-2023), up from 1.79 t CO₂/capita (2021) due to economic growth and coal reliance. Our World in Data (2022) confirms 1.9 t CO₂/capita, below global average (4.6 t CO₂/capita) but above 0.5 t CO₂/capita. Worldometer (2022) notes 1.89 t CO₂/capita, historically 0.44 t (1980). Low emissions reflect large population and biomass use (13% lack electricity, Carbon Brief).
Statement II is correct: CO₂ emissions from fuel combustion (coal, oil, natural gas) reached 2.8 Gt CO₂ (2023, IEA), making India the second-largest emitter in Asia-Pacific after China (12.6 Gt CO₂). Emissions grew 7.2% (2023) due to coal-powered electricity (75% generation) and industrial growth (steel, cement).
Statement III is correct: Electricity and heat production, driven by coal-fired power plants (75% generation, 1,317 TWh, 2023, CEA Annual Report 2023-24), is India’s largest CO₂ source, contributing over 50% emission increase (1.4 Gt COe, Statista). Carbon intensity is 713 g CO₂/kWh, above global average (480 g CO₂/kWh). Industrial processes (cement, steel) and transport (oil-based) are secondary sources.
Exam tip:
The figure ‘less than 0.5 t CO₂/capita’ doesn’t align with India’s current scale of industrial activity, power consumption, and global rankings. Less than 0.5 tons is too low. Hence more probable to be false. Eliminating options A and D.
UPSC 2025Environment and Ecology · Ecology, Ecosystem and Functions of Ecosystem
Q10. With reference to the planet Earth, consider the following statements: I. Rain forests produce more oxygen than that produced by oceans. II. Marine phytoplankton and photosynthetic bacteria produce about 50% of world’s oxygen. III. Well-oxygenated contains surface water several folds higher oxygen than that in atmospheric air. Which of the statements given above is/are correct?
Explanation
Oxygen production is critical for Earth’s atmosphere, primarily driven by photosynthesis in marine and terrestrial ecosystems.
Statement I is incorrect: Oceans, not rainforests (Amazon, Congo), are the primary oxygen producers. NOAA estimates 50-80% of global oxygen from marine phytoplankton in the photic zone (top 200 meters). NASA cites 50-85%, with Prochlorococcus (a cyanobacterium) contributing 5-20%. Rainforests produce ~28% (National Geographic, WWF), with other terrestrial plants adding ~2%. Oceans’ dominance stems from 71% Earth’s surface and phytoplankton’s rapid turnover (days vs. decades for trees).
Statement II is correct: Marine phytoplankton (diatoms, dinoflagellates) and photosynthetic bacteria (cyanobacteria, e.g., Prochlorococcus) are the main oceanic oxygen producers. NOAA and Smithsonian confirm 50-80% of global oxygen from oceanic photosynthesis, with NASA and WWF estimating 50-85%, including 5-20% from Prochlorococcus. Photosynthesis in the photic zone uses sunlight, CO₂, and nutrients, supporting the marine food web and atmospheric oxygen. The ~50% estimate is conservative but accurate.
Statement III is correct: Well-oxygenated surface water has high dissolved oxygen (DO) (5-10 mg/L, up to 12-15 mg/L in cold, turbulent conditions, per USGS). Atmospheric air contains 21% oxygen (~210,000 ppm, 210 g/L). Surface water’s DO (0.015 g/L) is ~14,000 times less than air, due to low oxygen solubility, confirming it cannot hold "several folds higher" oxygen.
Answer key for these questions
Q
UPSC year
Correct answer
1
2025
(c) All the three
2
2025
(a) Both Statement II and Statement III are correct and both of them explain Statement I
3
2025
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
4
2025
(c) Only one of the Statements II and III is correct and that explains Statement I
5
2025
(a) Both Statement II and Statement III are correct and both of them explain Statement I
6
2025
(a) The Asian Development Bank (ADB)
7
2025
(c) I, II and II
8
2025
(d) II and III
9
2025
(c) II and III only
10
2025
(b) II only
Frequently asked questions
How many previous year UPSC questions are there on Environment and Ecology?
This page covers 14 previous year UPSC Prelims GS Paper-I questions on Environment and Ecology in the UPSC 2025 Prelims, asked from 1996 to 2025. Each has the correct answer and an explanation.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Environment and Ecology?
Questions on Environment and Ecology in the UPSC 2025 Prelims are available for 22 years, from 1996 to 2025. Use the Year filter to practise a single paper.
