UPSC Prelims 2023
Environment & Ecology Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 3 — All three

Green hydrogen, produced from renewable energy sources through electrolysis, is a versatile clean fuel that can be utilized in multiple ways. All three statements regarding its applications are correct.

✅ Statement 1 – Correct: Green hydrogen can be used directly as a fuel in modified internal combustion engines, replacing conventional fossil fuels.
✅ Statement 2 – Correct: Green hydrogen can be blended with natural gas (up to 20% in existing pipelines) and used for heating, power generation, and industrial applications.
✅ Statement 3 – Correct: Green hydrogen is used in hydrogen fuel cells to generate electricity for running electric vehicles, offering zero-emission transportation.

📝 Short Notes: Green Hydrogen

• Definition: Hydrogen produced through electrolysis of water using renewable energy sources (solar, wind, hydro), resulting in zero carbon emissions.
• Production Method: Water (H₂O) is split into hydrogen (H₂) and oxygen (O₂) using electricity from renewable sources in an electrolyzer.
• Color Coding: Green (renewable energy), Grey (fossil fuels without carbon capture), Blue (fossil fuels with carbon capture), Brown/Black (coal).
• Applications: Transportation (fuel cell vehicles), industrial processes (steel, ammonia production), energy storage, power generation, and heating.
• India's Initiatives: National Green Hydrogen Mission (2023) targeting 5 MMT annual production by 2030; focus on making India a global hub for green hydrogen production and export.
• Advantages: Zero emissions at point of use, high energy density, long-term storage capability, and versatile applications across sectors.
• Challenges: High production costs, energy-intensive electrolysis process, storage and transportation infrastructure requirements, and need for renewable energy scale-up.

Detailed Explanation:

Answer: Option 2 — Only two

Community Reserves are protected areas in India that act as buffer zones or migration corridors between established national parks and wildlife sanctuaries. Among the four statements given, only two are correct regarding the governance and permitted activities in Community Reserves.

❌ Statement 1 – Incorrect: The Chief Wildlife Warden does not become the governing authority. As per Section 36D of the Wildlife Protection Act, the State Government constitutes a Community Reserve Management Committee which is the responsible authority for managing the community reserve. The committee elects a Chairman who acts as the Honorary Wildlife Warden.

✅ Statement 2 – Correct: Hunting is strictly prohibited in Community Reserves once an area is notified as such under the Wildlife Protection Act.

✅ Statement 3 – Correct: People living in and around Community Reserves are permitted to collect non-timber forest produce (NTFP) as part of their traditional rights and livelihood activities.

❌ Statement 4 – Incorrect: Traditional agricultural practices, including shifting cultivation (jhum), are not allowed in Community Reserves to protect the ecological integrity of these areas.

📝 Short Notes: Community Reserves under Wildlife Protection Act

Detailed Explanation:

Answer: Option 3 — Both 1 and 2

Both statements correctly describe the role and powers of Biodiversity Management Committees (BMCs) in India under the Biological Diversity Act, 2002, which implements the Nagoya Protocol objectives at the local level.

✅ Statement 1 – Correct: BMCs are indeed key institutional mechanisms for realizing Nagoya Protocol objectives in India by ensuring local-level implementation of Access and Benefit Sharing (ABS) provisions and involving local communities in biodiversity governance.

✅ Statement 2 – Correct: BMCs have statutory powers to determine access to biological resources within their jurisdiction and levy collection fees on such access, as mandated under the Biological Diversity Act, 2002 and Biological Diversity Rules, 2004.

📝 Short Notes: Biodiversity Management Committees (BMCs) and Nagoya Protocol

Detailed Explanation:

Answer: Option 3 — Honeybees

The waggle dance is a unique form of communication performed by worker honeybees to inform other members of the colony about the direction and distance to food sources. This remarkable behavior was decoded by Austrian scientist Karl von Frisch, who won the Nobel Prize for this discovery. The direction of the dance relative to the vertical indicates the angle to the food source in relation to the sun, while the duration of the waggle portion indicates the distance.

📝 Short Notes: Honeybee Waggle Dance

• Discovered by: Karl von Frisch (Austrian ethologist, Nobel Prize 1973)
• Purpose: Communication among worker bees about food source location (nectar, pollen, water)
• Direction indication: Angle of the waggle run relative to vertical = angle to food source relative to the sun's position
• Distance indication: Duration and number of waggles indicate distance to the source (longer dance = farther distance)
• Round dance: Performed for food sources very close to the hive (within 50-100 meters)
• Significance: Demonstrates complex social communication in insects and symbolic language in non-human species

Detailed Explanation:

Answer: Option 2 — Only two

Two out of three statements regarding mercury pollution are correct. Gold mining activities and coal-based thermal power plants are both significant sources of mercury pollution globally. However, the claim that there is "no known safe level" is scientifically inaccurate, as regulatory bodies like WHO have established reference doses and tolerable intake levels for mercury exposure.

✅ Statement 1 – Correct: Gold mining, especially artisanal and small-scale mining, uses liquid mercury to amalgamate with gold particles, releasing significant mercury into water bodies and forests, notably in regions like the Amazon.

✅ Statement 2 – Correct: Coal-based thermal power plants (TPPs) are the largest anthropogenic source of mercury emissions, releasing mercury through fly ash and flue gases; studies show TPPs contribute over 80% of mercury emissions in countries like India.

❌ Statement 3 – Incorrect: While mercury is highly toxic, regulatory and scientific bodies establish safe exposure thresholds; WHO's Provisional Tolerable Weekly Intake for methylmercury is 1.6 µg/kg body weight/week, and drinking water limit is 1 µg/litre, demonstrating that safe levels do exist below which health risks are minimal.

📝 Short Notes: Mercury Pollution

• Sources of Mercury Pollution: Coal-fired power plants (largest source), artisanal gold mining, chlor-alkali industry, waste incinerators, cement production, and volcanic eruptions.
• Mercury in Environment: Converts to toxic methylmercury in aquatic systems through bacterial action; bioaccumulates in fish and biomagnifies up the food chain.
• Health Effects: Damages nervous system, kidneys, and developing fetuses; causes Minamata disease (severe neurological syndrome); particularly harmful to children and pregnant women.
• Minamata Convention: Global treaty (2013) to protect human health and environment from anthropogenic mercury emissions and releases; India ratified in 2018.
• Safe Exposure Levels: WHO guidelines: 1.6 µg/kg body weight/week for methylmercury; 1 µg/litre for drinking water; concept of "dose makes the poison" applies.
• Mercury from Coal Plants: Indian coal contains 0.05-0.5 ppm mercury; released during combustion; fly ash disposal in ponds creates aquatic ecosystems contaminated with mercury.

Detailed Explanation:

Answer: Option 2 — Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I

Carbon markets are indeed widely recognized as crucial market-based mechanisms under the Paris Agreement (Article 6) for achieving emission reduction targets cost-effectively. Carbon markets do facilitate resource transfers from private sector to the State, particularly through auction-based cap-and-trade systems where governments sell emission permits. However, the widespread adoption of carbon markets stems from their economic efficiency and flexibility in reducing emissions, not primarily from their revenue generation function for governments.

✅ Statement-I – Correct: Carbon markets (cap-and-trade systems, voluntary carbon credits) are recognized globally as key tools for climate mitigation, allowing cost-effective emission reductions through price signals.
✅ Statement-II – Correct: In many carbon market schemes, particularly cap-and-trade systems with auctioned permits, private entities pay the government for emission allowances, transferring resources to the State.
However, Statement-II does not explain Statement-I: The prominence of carbon markets arises from their economic efficiency in achieving climate goals, not from their revenue-transfer function.

📝 Short Notes: Carbon Markets

• Carbon Markets: Market-based mechanisms that put a price on carbon emissions to incentivize emission reductions through economic instruments.
• Cap-and-Trade Systems: Government sets an emission cap; permits are allocated/auctioned; entities can trade permits, creating market price for emissions.
• Carbon Offset Markets: Voluntary or compliance-based systems where emission reductions from one activity offset emissions elsewhere through tradable credits.
• Paris Agreement Article 6: Establishes frameworks for international cooperation through market and non-market mechanisms to achieve Nationally Determined Contributions (NDCs).
• Resource Transfer Mechanism: When governments auction emission permits, private emitters pay for allowances, generating public revenue while creating emission reduction incentives.
• Key Advantage: Achieves emission targets at lowest economic cost by allowing flexibility—entities that can reduce emissions cheaply do so and sell permits to those facing higher reduction costs.

Detailed Explanation:

Answer: Option 3 — All three

All three activities mentioned are recognized methods for carbon capture and sequestration (CCS) that are actively discussed in climate mitigation strategies.

✅ Activity 1 – Correct: Spreading finely ground basalt rock on farmlands (enhanced weathering) captures atmospheric CO₂ through chemical weathering reactions that form stable carbonates, effectively sequestering carbon in the soil.

✅ Activity 2 – Correct: Increasing ocean alkalinity by adding lime enhances the ocean's natural capacity to absorb and store atmospheric CO₂ by shifting the carbonate equilibrium, making oceans a more effective carbon sink.

✅ Activity 3 – Correct: Capturing industrial CO₂ emissions and storing them as carbonated water in abandoned subterranean mines is a direct carbon capture and storage (CCS) technique that prevents greenhouse gases from entering the atmosphere.

📝 Short Notes: Carbon Capture and Sequestration Methods

• Enhanced Weathering: Accelerates natural rock weathering by spreading silicate minerals (like basalt) on land; reacts with CO₂ to form stable carbonates that lock carbon for thousands of years.
• Ocean Alkalinization: Adding alkaline substances (lime, olivine) to oceans increases pH and carbonate concentration, enhancing CO₂ absorption capacity and counteracting ocean acidification.
• Geological Sequestration: Industrial CO₂ is captured at source, compressed, and injected into deep geological formations (depleted oil/gas fields, saline aquifers, mines) where it mineralizes or remains trapped.
• Other CCS Methods: Afforestation, soil carbon sequestration, biochar application, direct air capture (DAC), and bioenergy with carbon capture and storage (BECCS).
• Global Significance: CCS technologies are essential for achieving net-zero emissions targets and limiting global warming to 1.5-2°C as outlined in the Paris Agreement.

Detailed Explanation:

Answer: Option 3 — Statement-I is correct but Statement-II is incorrect

This question tests understanding of India's groundwater usage patterns and the primary purposes of extraction. Statement-I correctly cites the UN World Water Development Report 2022 data, while Statement-II incorrectly attributes the high extraction primarily to drinking water and sanitation needs.

✅ Statement-I – Correct: According to the UN World Water Development Report 2022, India extracts approximately 251 km³ of groundwater annually from an estimated 20 million wells and tube wells, which indeed represents more than a quarter (about 25-26%) of the world's total groundwater withdrawal.

❌ Statement-II – Incorrect: While India does need to cater to approximately 18% of the world's population, the major reason for high groundwater extraction is not drinking water and sanitation. Approximately 89% of India's groundwater extraction is used for irrigation purposes, not for drinking water and sanitation. Agriculture is the primary driver of groundwater depletion in India.

📝 Short Notes: India's Groundwater Usage

• Total Annual Extraction: Approximately 251 km³, the highest in the world (>25% of global extraction)
• Sectoral Distribution: ~89% for irrigation, ~9% for domestic use, ~2% for industrial use
• Infrastructure: Over 20 million wells and tube wells across the country
• Critical Concern: Unsustainable extraction rates leading to groundwater depletion, particularly in northwestern and southern India
• Key States Affected: Punjab, Haryana, Rajasthan, Gujarat, Tamil Nadu, and Karnataka face severe groundwater stress
• Recharge Gap: Extraction rates significantly exceed natural recharge rates in many regions, especially in agricultural belts

Detailed Explanation:

Answer: Option 1 — The International Union for Conservation of Nature

The Invasive Species Specialist Group (ISSG) is a global network of scientific and policy experts on invasive species, organized under the auspices of the Species Survival Commission (SSC) of the International Union for Conservation of Nature (IUCN). The ISSG develops and maintains the Global Invasive Species Database, which is a comprehensive resource on alien and invasive species that threaten biodiversity and ecosystems worldwide.

📝 Short Notes: IUCN and Its Specialist Groups

• IUCN (International Union for Conservation of Nature): Founded in 1948, it is the world's oldest and largest global environmental organization, working on biodiversity conservation and sustainable use of natural resources.
• Species Survival Commission (SSC): The largest of IUCN's six commissions, comprising over 10,000 experts organized into ~160 Specialist Groups focused on various species and conservation issues.
• Invasive Species Specialist Group (ISSG): Established in 1994, it aims to reduce threats to natural ecosystems and native species by increasing awareness of invasive alien species and providing tools for prevention and management.
• Global Invasive Species Database: Maintained by ISSG, it contains information on over 1,000 invasive species, including their ecology, distribution, impacts, and management strategies.
• IUCN Red List: Another major IUCN initiative that assesses the conservation status of species globally, widely recognized as the most comprehensive inventory of biological diversity.

Detailed Explanation:

Answer: Option 3 — Statement-I is correct but Statement-II is incorrect

This question tests knowledge about the biogeographical distribution of marsupials and their ecological adaptations. Statement I correctly identifies that marsupials are not naturally found in India, while Statement II incorrectly restricts their habitat requirements.

✅ Statement I – Correct: Marsupials are indeed not naturally found in India. They are primarily native to Australia (kangaroos, koalas, wombats), the Americas (opossums), and Papua New Guinea. India falls outside the natural distribution range of marsupials.

❌ Statement II – Incorrect: This statement is factually wrong on multiple counts. Marsupials do not require montane grasslands exclusively and can thrive in diverse habitats including forests, deserts, savannas, wetlands, and even urban areas. They also coexist with various predators in their natural habitats (e.g., dingoes in Australia). The claim that they can thrive "only" in montane grasslands with no predators is completely false.

📝 Short Notes: Marsupials - Distribution and Ecology

• Definition: Marsupials are mammals characterized by giving birth to relatively undeveloped young that continue development in a pouch (marsupium).
• Primary Distribution: Australia (~70% of all marsupial species), Americas (opossums), Papua New Guinea, and nearby islands.
• Habitat Diversity: Marsupials occupy varied habitats - rainforests (tree kangaroos), deserts (bilbies), grasslands (kangaroos), forests (koalas), and wetlands (water opossums).
• Examples: Kangaroos, wallabies, koalas, wombats, Tasmanian devils, possums, and opossums.
• Evolutionary Significance: Marsupials represent an ancient mammalian lineage that thrived in Gondwanaland before continental drift isolated populations.
• Indian Context: No native marsupials exist in India due to biogeographical separation and different evolutionary pathways in the Indian subcontinent.

Detailed Explanation:

Answer: Option 2 — Only two

This question tests understanding of biofilter functions in Recirculating Aquaculture Systems (RAS). Out of three statements, two are correct regarding waste treatment and ammonia conversion, while the statement about phosphorus is incorrect.

✅ Statement 1 – Correct: Biofilters provide waste treatment by removing uneaten fish feed and organic matter, as beneficial bacteria on biofilter media break down these wastes.

✅ Statement 2 – Correct: Biofilters convert toxic ammonia from fish waste to less harmful nitrate through the nitrification process performed by beneficial bacteria (ammonia → nitrite → nitrate).

❌ Statement 3 – Incorrect: Biofilters do not increase phosphorus levels in water; their primary role is waste removal and ammonia conversion, while phosphorus management is handled through feed formulation and water quality control.

📝 Short Notes: Recirculating Aquaculture System (RAS) and Biofilters

• RAS Definition: A technology for farming fish in tanks where water is filtered and recirculated, minimizing water usage and waste discharge.
• Biofilter Function: Core component of RAS that hosts beneficial bacteria for biological filtration and waste treatment.
• Nitrification Process: Two-step bacterial process where Nitrosomonas bacteria convert ammonia (NH₃) to nitrite (NO₂⁻), then Nitrobacter bacteria convert nitrite to nitrate (NO₃⁻).
• Waste Removal: Biofilters remove solid wastes including uneaten feed, fish feces, and other organic matter through bacterial decomposition.
• Phosphorus Management: Controlled through fish feed formulation, mechanical filtration, and water exchange, not through biofilters.
• Benefits of RAS: Water conservation, reduced environmental impact, disease control, and intensive fish production in limited space.

Detailed Explanation:

Answer: Option 3 — All three

Green hydrogen, produced through electrolysis of water using renewable electricity, is expected to play a significant role in decarbonizing all three heavy industries mentioned. It offers a clean alternative to fossil fuels in energy-intensive industrial processes, thereby reducing carbon emissions substantially.

1. Fertilizer plants: Green hydrogen can replace natural gas in ammonia synthesis, which is the primary feedstock for fertilizer production. This eliminates the carbon-intensive steam methane reforming process currently used.

2. Oil refineries: Refineries use hydrogen for hydrocracking and desulfurization processes. Green hydrogen can replace the hydrogen currently produced from fossil fuels, reducing the refinery's carbon footprint.

3. Steel plants: Green hydrogen can replace coal and coke in the direct reduction of iron ore (DRI process), eliminating one of the largest sources of industrial CO₂ emissions. Several pilot projects globally are already testing hydrogen-based steelmaking.

📝 Short Notes: Green Hydrogen and Industrial Decarbonization

• Green Hydrogen: Hydrogen produced via electrolysis of water using electricity from renewable sources (solar, wind, hydro). It is carbon-free if the electricity is 100% renewable.
• Fertilizer Industry: Uses hydrogen to produce ammonia (NH₃) via the Haber-Bosch process. Currently, ~1-2% of global energy and CO₂ emissions come from ammonia production using fossil fuel-derived hydrogen.
• Oil Refining: Refineries consume significant hydrogen for upgrading heavy crude, hydrocracking, and removing sulfur. Green hydrogen can directly substitute fossil-fuel-derived hydrogen.
• Steel Industry: Traditional blast furnace method uses coke (from coal) as a reducing agent. Green hydrogen-based Direct Reduced Iron (DRI) technology can replace this, producing water instead of CO₂.
• National Green Hydrogen Mission (India): Launched in 2023 with ₹19,744 crore outlay to make India a global hub for green hydrogen production and export by 2030.
• Challenges: High production cost, infrastructure development, storage and transportation issues, and scaling up electrolyzer manufacturing capacity.

Detailed Explanation:

Answer: Option 2 — Orangutan

Orangutans are highly intelligent great apes known for their remarkable tool-use capabilities. They have been extensively observed using sticks to scrape and extract insects from holes in trees and logs, probe for honey, and even fashion leaves into gloves or napkins. This behavior demonstrates their advanced cognitive abilities and problem-solving skills, making them one of the most tool-proficient non-human primates.

📝 Short Notes: Tool Use in Animals

• Orangutans: Use sticks to extract insects, honey, and seeds; use leaves as umbrellas, gloves, and napkins; found in Borneo and Sumatra.
• Chimpanzees: Use sticks to fish for termites, stones to crack nuts, and leaves as sponges for drinking water.
• Crows: Craft hooked tools from twigs to extract insects; demonstrate advanced problem-solving abilities.
• Sea Otters: Use rocks as anvils to crack open shellfish while floating on their backs.
• Elephants: Use branches to swat flies, scratch themselves, and modify sticks to reach food.
• Dolphins: Use marine sponges to protect their rostrums while foraging on the seabed.

Detailed Explanation:

Answer: Option 1 — Only one

Among the three fauna listed, only the Malabar Civet is a nocturnal animal, being primarily active during the night. The Lion-tailed Macaque is a diurnal species, active during the day, while the Sambar Deer is crepuscular, most active during dawn and dusk rather than after sunset.

Analysis of Each Species:
🦁 Lion-tailed Macaque: Diurnal primate found in Western Ghats, active during daylight hours.
🐆 Malabar Civet: Nocturnal carnivore endemic to Western Ghats, most active after sunset. ✅
🦌 Sambar Deer: Crepuscular herbivore, most active at dawn and dusk, not strictly nocturnal.

📝 Short Notes: Activity Patterns in Animals

Detailed Explanation:

Answer: Option 2 — Only two

The question tests knowledge about the behavioral ecology of Indian squirrels. Out of the three statements, two are correct (statements 2 and 3), while statement 1 is incorrect as Indian squirrels are primarily arboreal and build tree nests rather than ground burrows.

❌ Statement 1 – Incorrect: Indian squirrels like the Indian Palm Squirrel (Funambulus) and Malabar Giant Squirrel (Ratufa indica) are arboreal species that build nests (dreys) in tree branches, hollows, or crevices using twigs and leaves, not ground burrows.

✅ Statement 2 – Correct: Indian squirrels exhibit scatter hoarding behavior, burying nuts and seeds in shallow ground locations for later retrieval, which also aids in seed dispersal and forest regeneration.

✅ Statement 3 – Correct: Squirrels are opportunistic omnivores; while their primary diet includes seeds, nuts, fruits, and fungi, they also consume insects, caterpillars, bird eggs, and occasionally small vertebrates.

📝 Short Notes: Indian Squirrels - Ecology & Behavior

• Common Species: Indian Palm Squirrel (Funambulus palmarum), Three-striped Palm Squirrel (F. tristis), Malabar Giant Squirrel (Ratufa indica), and Indian Giant Squirrel (Ratufa macroura)
• Habitat: Predominantly arboreal (tree-dwelling); found in forests, urban parks, gardens, and agricultural landscapes
• Nesting: Build dreys (leaf and twig nests) in tree branches or use tree hollows; do not make ground burrows unlike ground squirrels found in other regions
• Food Storage: Practice scatter hoarding - bury food items in multiple scattered locations rather than one central cache; excellent spatial memory for retrieval
• Diet: Omnivorous - primarily herbivorous (nuts, seeds, fruits, flowers, bark) but also consume insects, bird eggs, and occasionally small animals
• Ecological Role: Important seed dispersers for many tree species; forgotten caches germinate into new plants, aiding forest regeneration
• Conservation Status: Most species are Least Concern, but habitat specialists like the Malabar Giant Squirrel face threats from habitat fragmentation

Detailed Explanation:

Answer: Option 3 — Only three

Hydrofluorocarbons (HFCs) are synthetic compounds primarily used as replacements for ozone-depleting substances. Among the given applications, HFCs are used in aerosols (as propellants), foam agents (for blowing plastic foams), and fire retardants (as clean fire suppressants), but NOT in lubricants.

✅ Aerosols – Correct: HFCs serve as non-flammable propellants in aerosol products like hairsprays, deodorants, and cleaning sprays.
✅ Foam agents – Correct: HFCs are widely used as foam-blowing agents in manufacturing polyurethane and polystyrene foams for thermal insulation.
✅ Fire retardants – Correct: HFCs (such as HFC-227ea) are used as "clean agents" in fire suppression systems, replacing ozone-depleting Halons.
❌ Lubricants – Incorrect: Lubricants are formulated from mineral oils, synthetic hydrocarbons (polyalphaolefins), or esters, not HFCs.

📝 Short Notes: Hydrofluorocarbons (HFCs)

• Nature: Synthetic organic compounds containing hydrogen, fluorine, and carbon atoms; do not contain chlorine.
• Ozone Impact: HFCs do not deplete the ozone layer (unlike CFCs and HCFCs) as they lack chlorine and bromine.
• Climate Impact: Potent greenhouse gases with high Global Warming Potential (GWP), ranging from hundreds to thousands of times that of CO₂.
• Common Uses: Refrigeration and air conditioning, aerosol propellants, foam-blowing agents, fire suppression systems, and solvent applications.
• Regulatory Framework: Controlled under the Kigali Amendment (2016) to the Montreal Protocol, which mandates phased reduction of HFC production and consumption.
• India's Commitment: India ratified the Kigali Amendment in 2021, committing to reduce HFC use by 85% by 2047.
• Alternatives: Natural refrigerants (ammonia, CO₂, hydrocarbons), HFOs (hydrofluoroolefins) with lower GWP.