UPSC Prelims Previous Year Questions 2025: Environment | Environment for UPSC CSE PDF Download

Ans: (b)
Oxygen on Earth primarily comes from photosynthesis, with marine phytoplankton playing a significant role. The statements provided are evaluated as follows:

• Statement I is false: Marine phytoplankton in oceans contribute more oxygen to the atmosphere than rainforests do.
• Statement II is true: Approximately half of the world's oxygen is produced by marine phytoplankton and photosynthetic bacteria.
• Statement III is false: Atmospheric air contains significantly more oxygen than surface water, not the other way around.

Thus, the correct answer is B.

Ans: (a)
Article 6 of the Paris Agreement is vital for fostering international collaboration to achieve climate goals through both carbon markets and non-market mechanisms.

• Statement I is true: Article 6 is frequently highlighted as it facilitates cooperation via market-based and non-market approaches to address climate change.
• Statement II is true: It establishes guidelines for carbon markets, including mechanisms for carbon trading and credits.
• Statement III is true: It supports non-market approaches, such as technology transfer and capacity building, to help meet climate objectives.

Therefore, the correct answer is A.

Ans: (c)
At COP28, India opted not to join the “Declaration on Climate and Health,” a decision driven by specific concerns about the declaration's implications.

• Statement I is true: India was among the countries that did not sign the COP28 Declaration on Climate and Health, which was endorsed by over 120 nations.
• Statement II is false: The declaration is a voluntary political commitment, not a legally binding obligation, so signing it does not require immediate decarbonization of the health sector.
• Statement III is true: India’s reluctance stems from concerns that rapidly decarbonizing its health sector could undermine healthcare accessibility and resilience, given its developmental and resource constraints.

Thus, only Statement III accurately explains India’s decision not to sign, while Statement II misrepresents the declaration’s non-binding nature.

Ans: (d)

The Peacock tarantula, also known as the Gooty tarantula, is a rare, tree-dwelling spider native to specific forest regions in India.

• Statement I is false: The Peacock tarantula is an arachnid (spider), not an omnivorous crustacean.
• Statement II is true: Its habitat is limited to certain forest areas in the Eastern Ghats of India.
• Statement III is true: It is an arboreal species, residing in trees and tree crevices.

Therefore, the correct answer is D.

Ans: (a)
Nature-based solutions leverage natural processes to address climate change and biodiversity loss, requiring targeted financial backing. The Asian Development Bank (ADB) introduced the Nature Solutions Finance Hub for Asia and the Pacific to provide funding for nature-based initiatives tackling climate and environmental issues in the region.

Ans: (a)
Cloud seeding, a technique to induce rainfall, relies on chemicals with specific crystalline structures to form ice nuclei.

• Option A is true: Silver iodide and potassium iodide are both used in cloud seeding due to their ability to promote ice nuclei formation, facilitating precipitation.
• Option B is false: Silver nitrate is not utilized in artificial rainmaking processes.
• Option C is false: Potassium nitrate is not employed in cloud seeding.
• Option D is false: Neither silver nitrate nor potassium chloride is used for inducing rainfall.

Thus, the correct answer is A.

Ans: (a)
Activated carbon is extensively utilized for pollutant removal due to its distinctive properties and environmentally friendly production methods.

• Statement I is true: Activated carbon efficiently removes pollutants from industrial effluents, leveraging its high adsorption capacity, making it a staple in water treatment and pollution control.
• Statement II is true: Its effectiveness stems from a vast surface area created by a porous structure, which enables it to capture heavy metals and other contaminants effectively.
• Statement III is true: Activated carbon can be sustainably and cost-effectively produced from carbon-rich agricultural wastes, such as coconut shells and rice husks, enhancing its eco-friendliness.

Therefore, Statements II and III are correct and collectively explain the validity of Statement I.

Ans: (c)
Statement I is incorrect: India's per capita CO₂ emissions are approximately 1.9–2.0 tonnes, which is significantly higher than the 0.5 tonnes per capita mentioned.
Statement II is correct: India is the second-largest emitter of CO₂ from fuel combustion in the Asia-Pacific region, following China.
Statement III is correct: The primary source of India’s CO₂ emissions is electricity and heat production, predominantly from coal-based power generation.
Thus, the correct answer is C.

Ans: (a)

A. The European Union: The Nature Restoration Law (NRL), adopted in 2024, is an EU law that establishes mandatory targets for ecosystem restoration, climate change mitigation, and biodiversity protection across EU member states. Correct.
B. The World Bank: This international financial institution provides loans and grants but does not have the authority to enact legislation like the NRL. Incorrect.
C. OECD: The Organisation for Economic Co-operation and Development focuses on economic cooperation and policy coordination, not on enacting binding environmental laws like the NRL. Incorrect.
D. FAO: The Food and Agriculture Organization, a UN agency, concentrates on addressing hunger and agricultural issues and does not enact regional legislation like the NRL. Incorrect.
Thus, the correct answer is A.

Ans: (b)

Statement I is incorrect: The World Bank's warning specifically addresses the dangers of wet-bulb temperatures, not flooding, cyclones, or droughts, which are separate climate-related threats.
Statement II is correct: A wet-bulb temperature above 35°C prevents the human body from cooling itself through sweating, as it cannot release heat, leading to potentially fatal conditions for humans and animals.
Thus, the correct answer highlights the critical impact of high wet-bulb temperatures on survival.

Ans: (c)

• Statement I is correct: Cigarette butts have filters made of cellulose acetate, a type of plastic.
• Statement II is correct: Eyeglass lenses are typically made from polycarbonate or CR-39, both plastic materials, rather than glass.
• Statement III is correct: Car tires include synthetic rubber, which contains plastic-based polymers.

Thus, all three items—cigarette butts, eyeglass lenses, and car tires—contain hidden plastics, confirming that the correct answer is that all statements are true.

Ans: (a)

• Statement I is correct: The circular economy reduces greenhouse gas emissions by minimizing waste and optimizing energy use.
• Statement II is correct: It conserves raw materials by promoting reuse, recycling, and extending product lifecycles.
• Statement III is correct: Sustainable design and efficient processes in the circular economy help reduce production waste.

Thus, all three statements are true, confirming that the circular economy effectively supports waste reduction, resource conservation, and emission cuts.

Ans: (b)

• Statement I is correct: The cement industry accounts for approximately 5-8% of global CO₂ emissions, establishing it as a significant contributor to greenhouse gases.
• Statement II is correct: In cement production, silica-bearing clay is combined with limestone to supply essential minerals such as silicon, aluminum, and iron, which are critical for the final cement product.
• Statement III is correct: During clinker production, limestone (calcium carbonate) is heated, transforming into lime (calcium oxide) and releasing CO₂ through a process called calcination, which is the primary source of carbon emissions in cement manufacturing.

While both Statements II and III are accurate, Statement III directly addresses the primary source of carbon emissions in cement production as described in Statement I.

Ans: (b)

• Statement I is correct: Cassava is a perennial woody shrub, accurately classified based on its growth form.
• Statement II is correct: Ginger is an herb with a pseudostem formed from tightly packed leaf bases, fitting its classification.
• Statement III is correct: Malabar spinach is an herbaceous climber with soft, climbing stems, correctly identified.
• Statement IV is incorrect: Mint is a perennial herb, not an annual shrub, as it lacks woody stems and persists across seasons.
• Statement V is incorrect: Papaya is a large herbaceous plant, not a woody shrub, as its stem is soft and not fully woody.

Thus, only the first three statements are correct, making the correct answer B (Only three).

Ans: (c)

• Statement I is correct: Direct Air Capture (DAC) technology extracts CO₂ from the atmosphere, enabling carbon sequestration to reduce greenhouse gas levels.
• Statement II is correct: The CO₂ captured through DAC can be utilized in industries, such as producing plastics and supporting food processing applications.
• Statement III is correct: DAC provides CO₂ that, when combined with hydrogen, can be used to create synthetic low-carbon aviation fuels, contributing to sustainable energy solutions.

Thus, all three statements are accurate, making the correct answer C.