UPSC Mains Previous Year Questions 2022: GS3 Environment & Ecology | Environment for UPSC CSE PDF Download

Q1: Each year a large amount of plant material, cellulose, is deposited on the surface of Planet Earth. What are the natural processes this cellulose undergoes before yielding carbon dioxide, water and other end products? (Environment and Ecology)
Ans: 

Cellulose: Considered the most abundant organic compound on Earth, cellulose has a chemical formula represented as (C₆H₁₀O₅)n when viewed as a chain. It serves as a crucial structural component in the primary cell wall of green plants, various forms of algae, and oomycetes. Additionally, certain bacteria secrete cellulose for biofilm formation.

Properties of Cellulose:

• Complex carbohydrate composed of oxygen, carbon, and hydrogen.
• A chiral, tasteless compound with no discernible odor.
• Biodegradable, insoluble in water, and most organic solvents.

Natural Processes of Cellulose:

• Biosynthesis: In plants, cellulose is synthesized at the plasma membrane by Rosette Terminal Complexes (RTCs) containing cellulose synthase enzymes.
• Breakdown (Cellulolysis): Cellulolysis involves breaking down cellulose into smaller polysaccharides (cellodextrins) or complete conversion into glucose units. Bacteria utilize these breakdown products for proliferation, and ruminants later digest the bacterial mass in their digestive systems.
• Breakdown (Thermolysis): At temperatures above 350 °C, cellulose undergoes thermolysis (pyrolysis), decomposing into solid char, vapors, aerosols, and gases like carbon dioxide. This process, occurring via a solid-to-liquid-to-vapor transition, yields maximum vapors condensing into a liquid known as bio-oil at 500 °C.

Applications of Cellulose:

• Primarily used in the production of paperboard and paper.
• Under development for conversion from energy crops to biofuels, such as cellulosic ethanol, representing a renewable fuel source.
• The potential biofuel production from cellulose holds significance in meeting India's targets in the Paris Climate Agreement.

Q2: Discuss in detail the photochemical smog emphasizing its formation, effects and mitigation. Explain the 1999 Gothenburg protocol. (Environment and Ecology)
Ans: Photochemical Smog: Also known as Los Angeles smog, photochemical smog is a form of air pollution resulting from the interaction of solar radiation with airborne mixtures of nitrogen oxides (NOx) and volatile organic compounds (hydrocarbons).

Formation:

• The formation of photochemical smog is closely linked to the concentration of primary pollutants (nitrogen oxides like nitric oxide, nitrogen dioxide, and nitrous oxide, along with most VOCs) in the atmosphere. In some cases, it is also associated with the concentration of secondary pollutants (aldehydes, tropospheric ozone, and PAN).
• Photochemical smog initiation involves nitrogen oxides absorbing visible or ultraviolet sunlight energy, forming nitric oxide (NO) and free oxygen atoms (O). These combine with molecular oxygen (O2) to create ozone (O3).
• Chemical reactions occur with hydrocarbons, certain organic compounds, and sunlight to generate photochemical smog.

Effects:

• Chemicals formed in photochemical smog, when combined with hydrocarbons, produce molecules causing eye irritation.
• Ground-level ozone can be highly toxic to humans, leading to symptoms like decreased vision and shortness of breath.
• Contributes to acid rain and eutrophication.

Mitigation:

• Usage of catalytic converters to reduce vehicle emissions of nitrogen, carbon dioxide, and hydrocarbons.
• Reduction of greenhouse gas and urban emissions through biofuels in transportation.
• Adoption of cleaner vehicle options, including hydrogen-powered and electric vehicles.

Gothenburg Protocol:

• Adopted on 30 November 1999 in Gothenburg (Sweden) by UNECE countries, the Gothenburg Protocol aims to Abate Acidification, Eutrophication, and Ground-level Ozone.
• Also known as the Multi-effect protocol, it sets emission ceilings for 2010 for four pollutants: Sulphur, NOx, VOCs, and ammonia.
• The protocol is currently under negotiation for a revised version, with an update in 2012 to include particulate matter and black carbon.

Q3: Discuss global warming and mention its effects on the global climate. Explain the control measures to bring down the level of greenhouse gases which cause global warming, in the light of the Kyoto Protocol, 1997. (Environment and Ecology)
Ans. Global warming refers to the prolonged heating of Earth's surface, observed since the pre-industrial period (between 1850 and 1900), primarily attributed to human activities such as fossil fuel burning. These activities elevate the levels of heat-trapping greenhouse gases in Earth's atmosphere.

Effects on Global Climate:

• Water Shortages: Early snowmelts, vanishing glaciers, and severe droughts contribute to increased water scarcity.
• Coastal Flooding: Rising sea levels result in heightened coastal flooding.
• Environmental Challenges: Heatwaves, intense rainfall, and elevated flooding pose challenges for agriculture, forests, and urban areas.
• Ecosystem Disruption: Coral reefs and alpine meadows face disruption, leading to potential extinction of numerous plant and animal species.
• Health Impact: Higher air pollution levels contribute to increased allergies, asthma, and infectious diseases.

Control Measures for Greenhouse Gases:

• Kyoto Protocol: An international treaty adopted in 1997, entering into force in 2005, committing states to policies that reduce greenhouse gas emissions.

• Targeted Gases: The Kyoto Protocol addresses six gases, including Carbon Dioxide (CO₂), Methane (CH₄), Nitrous Oxide (NO₂), Sulphur hexafluoride (SF₆), hydrocarbons (HCFs), and perfluorocarbons (PFCs).

• Mechanisms for Reduction:

  • The Clean Development Mechanism allows countries with emission-reduction commitments to implement projects in developing nations.
  • Carbon Credits, tradable certificates equal to one tonne of carbon dioxide, aim to limit greenhouse gas concentration growth through activities like afforestation and methane capture.
  • Joint Implementation enables countries with emission reduction commitments to earn units from emission reduction projects.
    Emission Trading allows countries to sell unused emission units to others exceeding their targets.
  • Principle and Binding Limits: The Kyoto Protocol operates based on the principle of common but differentiated responsibilities and stands as the only global treaty imposing binding limits on greenhouse gas emissions.

Q4: Explain the causes and effects of coastal erosion in India. What are the available coastal management techniques for combating the hazard? (Environment and Ecology)

Ans. Coastal erosion refers to the removal of coastal sand or land displacement caused by factors such as local sea level rise, strong wave action, and heavy intrusion of seawater in coastal regions. The Ministry of Earth Sciences reported to the Lok Sabha that a significant portion of the 6,907.18 km long Indian mainland coastline is experiencing varying degrees of coastal erosion.

Factors Responsible for Coastal Erosion:

Natural Reasons:

• Global Warming: The rise in CO₂ concentration in the atmosphere contributes to planet warming and glacier melting, leading to sea level rise and increased coastal erosion threats.
• Planetary Cycle: Earth and Moon's planetary positions cause fortnightly tides in the sea.
• Strong Winds: Winds generate energy, released by waves breaking rocks into sand over time.
• Warming of Sea Water: Increased cyclone formation in the Indian peninsula contributes to coastal area destruction.

Anthropological Reasons:

• Violation of Coastal Management Zones (CMZ) Rules: Builders violating CMZ rules contribute to coastal erosion.
• Energy Production: Activities like nuclear and tidal energy production near coastal areas.
• Dredging: Shallow water dredging near coasts.
• Reduced Sand Flow: Decreased sand flow from rivers into the ocean.

Effects of Coastal Erosion:

• Rise in Sea Level: Increases the threat of submergence for small islands.
• Habitat Destruction: Leads to the vulnerability of coastal flora and fauna.
• Loss of Income: Impacts income from coastal ecosystems.

Coastal Management Techniques:

• Natural Response:
  • Coastal Shelter Belts:
    (i) Mangroves, coral reefs, and lagoons act as natural defenses against sea storms and erosion, absorbing and deflecting storm energy.
    (ii) These habitats are crucial for shore protection and environmental conservation.
• Artificial Response:

  • Geo-synthetic Tubes / Bags: Tube-shaped bags filled with sand slurry and lined with geotextile create artificial coastal structures like breakwaters or dunes, reducing wave energy and preventing erosion.

  • Artificial Beach Nourishment: Adding sand or sediment to beaches combats erosion and increases beach width.

  • Groynes: Active structures extending into the sea catch and hold back sediment, reducing longshore erosion.

With the escalating threats of climate change, rising sea levels are an inevitable outcome. Considering the dense population of coastal areas in India, thoughtful coastal planning is crucial, including the option of relocating people to safer areas.