GS Notes

5. Environment Notes 07

25 min read

Elaborate Notes

Desert Biomes

A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. They are characterized by extreme aridity and temperature fluctuations. Based on their geographical location and climatic conditions, they are broadly classified into Hot Deserts and Mid-Latitude (Cold) Deserts.

  • Basic Characteristics:

    • Aridity and Precipitation: Deserts are defined by their lack of precipitation, typically receiving less than 250 mm (10 inches) of rainfall annually. This leads to extreme dryness.
    • Hydrology: Permanent rivers are absent. Water flow is ephemeral, occurring in temporary streams or channels called ‘wadis’ or ‘arroyos’ only after rare rainfall events.
    • Vegetation: Plant life is sparse and highly specialized. These plants, known as xerophytes, are adapted to survive in arid conditions. Large, woody trees are generally absent, with vegetation dominated by shrubs, cacti, and grasses.

  • Classification:

    • Hot Tropical Deserts: Located in tropical and subtropical regions (roughly between 15° and 30° North and South latitude), primarily on the western margins of continents due to offshore trade winds. Examples include the Sahara in North Africa, the Thar in India/Pakistan, and the Kalahari in Southern Africa. These deserts experience extremely high daytime temperatures.
    • Middle Latitude/Cold Deserts: Found in temperate regions, often in the interior of continents or in the rain shadow of high mountains. They experience hot summers but extremely cold winters. The Gobi Desert in Mongolia and China is a prime example, a result of the rain-shadow effect of the Himalayas.

  • Adaptations of Flora (Xerophytes): Organisms in deserts have evolved remarkable adaptations to cope with water scarcity and temperature extremes.

    • Water Conservation:
      • Leaves are often reduced to spines (like in cacti) or are small and waxy to minimize water loss through transpiration. This thick outer layer is the cuticle.
      • Photosynthesis is often carried out by the green, fleshy stems (e.g., Opuntia or Prickly Pear Cactus), a modification that reduces the surface area for water loss. Many desert plants use Crassulacean Acid Metabolism (CAM) photosynthesis, where stomata open only at night to absorb CO2, further conserving water.
    • Water Storage: Succulent plants like cacti and aloes store water in their stems, leaves, or roots.
    • Root System: Plants develop extensive and deep root systems to tap into underground water sources, or wide, shallow roots to quickly absorb surface water after rainfall.
    • Dormancy (Hibernation): Some plants, like ephemeral annuals, have a very short life cycle. Their seeds remain dormant for long periods and germinate, grow, flower, and produce new seeds within a few weeks of a rain event. Algae and lichens can dry up and enter a state of inactivity, reviving when moisture is available.
    • Stress Tolerance: Shrubs like the Wild Date Palm (Phoenix dactylifera) have high tolerance to water stress and salinity.

  • Adaptations of Fauna:

    • Behavioral Adaptations: Many animals are nocturnal, remaining in cooler burrows or shaded areas during the heat of the day and emerging at night to hunt and forage. This includes predators like the Fennec fox.
    • Physiological Adaptations: Animals like the camel are famed for their ability to withstand dehydration. Rodents and reptiles often have highly efficient kidneys that produce concentrated urine to conserve water.
    • Life Cycle: Many insects and amphibians have a very short larval or pupal stage (accelerated metamorphosis). This rapid development ensures they reach adulthood before temporary water sources dry up.
    • Diversity: Despite the harsh conditions, deserts host a surprising diversity of life, including a large insect population, reptiles (lizards, snakes), and birds of prey like owls and eagles that feed on them.

  • Geomorphological Features:

    • Oasis: A fertile area in a desert where the water table is near the surface, supporting vegetation and human settlement.
    • Salt Flats (Playas): When temporary desert lakes (playa lakes) evaporate, they leave behind deposits of salt and other minerals, creating vast salt flats. The high salt content in desert soils is due to:
      1. Capillary Action: Intense evaporation pulls mineral-rich groundwater to the surface. The water evaporates, leaving the salts behind in the topsoil.
      2. Insufficient Leaching: Low rainfall means there is not enough water to dissolve these salts and wash them down into deeper soil layers.
      3. Aeolian Deposition: Wind (the primary agent of erosion and deposition in deserts) can transport salt particles from other areas and deposit them.

Marine Biome

The marine biome is the largest biome on Earth, covering over 70% of the planet’s surface. It is characterized by saline water and is a continuous body, with all oceans being interconnected.

  • Zonation based on Light Penetration:

    • Photic (or Euphotic) Zone: The upper layer of the ocean (down to ~200 meters) where sunlight penetrates, allowing for photosynthesis. This zone is home to the vast majority of marine life and primary producers.
    • Aphotic Zone: The region below the photic zone where sunlight does not reach. This zone includes the twilight (dysphotic) zone and the perpetually dark deep ocean. Organisms here rely on chemosynthesis or on organic matter sinking from above (marine snow).

  • Zonation based on Depth and Location:

    • Littoral Zone (Intertidal Zone): The area between high and low tide marks, characterized by extreme fluctuations in temperature, salinity, and moisture.
    • Neritic Zone: Extends from the low tide mark to the edge of the continental shelf (~200m deep). It is part of the photic zone and is highly productive.
    • Oceanic Zone: The vast open ocean beyond the continental shelf. It is further divided by depth:
      • Bathyal Zone (Midnight Zone): 200m to 4,000m.
      • Abyssal Zone (The Abyss): 4,000m to 6,000m. Characterized by high pressure, low temperatures, and darkness.
      • Hadal Zone: The deepest parts of the ocean, found in oceanic trenches (>6,000m). Life here is adapted to immense pressure and consists mainly of chemosynthetic bacteria, detritivores like sea cucumbers, and unique fish species.

  • Classification of Marine Lifeforms:

    • Phytoplankton: Microscopic, free-floating photosynthetic organisms like diatoms and algae. They form the base of the marine food web and are the ocean’s primary producers. Ecologically, they are crucial for global carbon cycling, absorbing vast amounts of atmospheric CO2, a concept termed the ‘biological pump’.
    • Zooplankton: Microscopic or small animals that drift with ocean currents. They are primary consumers, feeding on phytoplankton. Examples include protozoans, krill, and the larval stages of larger animals like fish and corals.
    • Nekton: Actively swimming organisms that can move against currents. This group is dominated by vertebrates such as fish, whales, and turtles, as well as invertebrates like squid.
    • Benthos: Organisms that live on or in the seabed. This includes sessile (attached) organisms like corals and sea anemones, and motile organisms like crabs, starfish, and sea cucumbers.
    • Periphyton: Organisms that are attached to surfaces, such as rocks or the shells of other animals. This includes many species of algae and barnacles. They are a subset of benthic life.
    • Neuston: Organisms that live at the air-water interface. This includes organisms that float on the surface (e.g., Portuguese Man o’ War) or live just beneath it.

Forest and Forest Ecosystem

A forest is a complex ecosystem dominated by trees, forming a closed or nearly closed canopy, and supporting a vast array of life forms.

  • Definitions:

    • Administrative (ISFR): As per the India State of Forest Report (ISFR) 2021, ‘Forest Cover’ is defined as all land, more than one hectare in area, with a tree canopy density of more than 10 percent, irrespective of ownership and legal status. This includes orchards, bamboo, and palms.
    • Ecological: A forest is a community of plants and animals characterized by the dominance of trees, a significant degree of ground shade, vertical stratification (canopy, understory, shrub, and ground layers), and high biodiversity.

  • Ecological Functions of Forests:

    • Pedogenesis (Soil Formation): Forests are critical soil builders.
      • The decomposition of litter (fallen leaves, branches) by microorganisms forms humus, enriching the soil with nutrients.
      • The intricate root systems of trees bind the soil, preventing erosion, while also creating channels that improve aeration and water infiltration.
      • By slowing surface runoff, forests allow more water to percolate into the ground, accelerating the chemical weathering of parent rock, a fundamental process of soil formation.
    • Climate Regulation:
      • Carbon Sequestration: Forests act as major carbon sinks, absorbing atmospheric CO2 through photosynthesis and storing it in biomass and soil. As documented by the IPCC, this is a vital mechanism for mitigating global warming.
      • Albedo Effect: Forests have a lower albedo (reflectivity) than bare ground, but a higher albedo than oceans. The typical albedo of a forest is around 18%, meaning it absorbs a significant amount of solar radiation. However, through transpiration, they have a net cooling effect on the local and regional climate.
      • Hydrological Cycle: Through transpiration, a mature tree can release several hundred liters of water vapor into the atmosphere daily. This process, termed evapotranspiration, contributes significantly to local humidity and rainfall, creating self-sustaining weather patterns, as seen in the Amazon rainforest.
    • Hydrological Regulation:
      • Forests act as natural sponges. The forest floor, rich in humus, has high water-retention capacity. They absorb rainfall, reduce surface runoff, and facilitate groundwater recharge.
      • This sustained release of water from forest catchments maintains the perennial flow of rivers. The Shola forests of the Western Ghats are a classic example, serving as the critical catchment area for peninsular rivers like the Kaveri and Vaigai. The degradation of these forests has been directly linked to the reduced water flow in these rivers.
    • Habitat and Biodiversity: Forests provide habitats for an estimated 80% of the world’s terrestrial biodiversity. The structural complexity and stratification of forests create numerous ecological niches for a wide variety of plants, animals, and microorganisms.
    • Hazard Mitigation: By binding soil and slowing water flow, forests are the most effective natural defense against soil erosion, landslides (especially on steep slopes), and flash floods.

Deforestation and Forest Degradation

  • Definitions:

    • Deforestation: The permanent conversion of forested land to other non-forest uses, such as agriculture, pasture, or urban development. The loss is permanent as there is no provision for regeneration.
    • Forest Degradation: A reduction in the canopy cover or density of a forest, diminishing its capacity to provide ecological services. The land remains forested but in a poorer state. Shifting cultivation (or Jhum) is a primary example, where a forest patch is cleared and cultivated for a few years and then left fallow to regenerate. While traditionally sustainable, increasing population pressure has shortened fallow cycles, leading to permanent degradation.

  • Historical Trends and Data (Source: Our World in Data, FAO):

    • The planet has lost approximately one-third of its original forest cover since the end of the last ice age, around 10,000 years ago.
    • The rate of loss accelerated dramatically with the onset of the Industrial Revolution and colonialism.
      • 1850-1920: Loss of ~30 million hectares per decade, driven by industrialization and agricultural expansion in Europe and North America.
      • 1920-1980: Deforestation shifted to the tropics, with losses reaching ~120 million hectares per decade.
      • 1980s: This peaked at around 150 million hectares per decade.
    • Current Status: While the net rate of deforestation has slowed, it remains alarmingly high at 5-6 million hectares per year. According to the FAO’s Global Forest Resources Assessment, over 90% of this loss occurs in the tropics, particularly in South America (Amazon) and Southeast Asia.

  • Causes of Deforestation:

    1. Agricultural Expansion: The leading driver globally, accounting for the majority of deforestation. This includes conversion for commodity crops (palm oil, soy), subsistence farming, and cattle ranching. The conversion of the Cerrado savanna in Brazil for soy cultivation is a prominent modern example.
    2. Commercial Logging: Selective and clear-felling for timber contributes significantly to both deforestation and degradation, particularly in tropical regions where valuable hardwoods are extracted.
    3. Infrastructure and Development Projects: Large-scale projects such as dams (e.g., the Three Gorges Dam in China), mining operations, and transportation networks (e.g., the Trans-Amazonian Highway) lead to direct forest loss and fragment habitats.
    4. Overgrazing: In semi-arid and savanna ecosystems, excessive grazing by livestock can destroy vegetation cover, leading to soil compaction and desertification. The desertification of the Sahel region in Africa is a well-documented case, exacerbated by colonial-era land use changes and population growth.
    5. Forest Fires: While a natural part of some forest ecosystems, the frequency and intensity of wildfires have increased due to climate change and human activities (arson, land clearing), causing widespread degradation.

Prelims Pointers

  • Desert Biome:

    • Characterized by < 250 mm annual rainfall.
    • Vegetation type: Xerophytes.
    • Plant Adaptation: CAM photosynthesis, waxy leaves (cuticle), spines, deep roots, dormancy.
    • Animal Adaptation: Nocturnal behavior, efficient kidneys, accelerated metamorphosis.
    • Hot Deserts: Sahara, Thar, Kalahari, Arabian.
    • Mid-Latitude/Cold Deserts: Gobi, Patagonian.
    • Oasis: A fertile spot in a desert where water is found.
    • Desert soil is saline due to high evaporation, capillary action, and low leaching.

  • Marine Biome:

    • Photic Zone: Top layer of the ocean with sunlight (~200m).
    • Aphotic Zone: Layer without sunlight.
    • Nekton: Active swimmers (e.g., fish, whales).
    • Benthos: Bottom-dwellers (e.g., corals, crabs).
    • Plankton: Drifters; Phytoplankton (producers, e.g., diatoms) and Zooplankton (consumers, e.g., krill).
    • Periphyton: Attached to surfaces (e.g., barnacles).
    • Neuston: Live at the air-water interface.
    • Hadal Zone: Deepest ocean zone, located in trenches (>6000m).
    • Phytoplankton are responsible for the ocean’s ‘biological pump’, absorbing significant atmospheric CO2.

  • Forest Ecosystem:

    • ISFR Definition of Forest Cover: Land > 1 ha, canopy density > 10%.
    • Ecological Functions: Pedogenesis (soil formation), carbon sequestration, climate regulation, hydrological cycle maintenance.
    • Albedo of Forest: Approximately 18%.
    • Shola Forests: Tropical montane forests in the Western Ghats, crucial for perennial rivers like Kaveri.
    • National Forest Policy (1988) Target: 33% of geographical area under forest/tree cover (66% in hills, 20% in plains).

  • Deforestation:

    • Deforestation: Permanent conversion of forest to non-forest land.
    • Forest Degradation: Reduction in forest density and health.
    • Shifting Cultivation (Jhum): A form of agriculture often leading to forest degradation.
    • Primary Driver of Deforestation: Agricultural expansion (cattle ranching, soy, palm oil).
    • Sahel Region (Africa): An example of desertification caused by overgrazing and climate change.

Mains Insights

  • GS Paper I (Geography):

    • Distribution of World’s Deserts: The location of hot deserts on the western margins of continents in the subtropics is a direct consequence of atmospheric circulation patterns (subtropical high-pressure belts) and the influence of cold ocean currents, which inhibit moisture formation. Mid-latitude deserts like the Gobi are caused by extreme continentality and the rain-shadow effect of major mountain ranges.
    • Forest-River Linkage: The case of the Shola forests and Peninsular rivers provides a powerful example of the intricate link between ecosystems and water security. Deforestation in catchment areas directly impacts river regimes, turning perennial rivers into seasonal ones, thereby affecting agriculture, drinking water supply, and regional climate.

  • GS Paper III (Environment & Economy):

    • Development vs. Conservation Debate: Deforestation is often a direct consequence of economic development activities (mining, infrastructure, agriculture). This creates a conflict between short-term economic gains and long-term ecological sustainability. The challenge lies in integrating the principles of Sustainable Development, where the economic value of ecosystem services (e.g., water purification, carbon storage provided by forests) is recognized and incorporated into development planning.
    • Drivers of Deforestation - A Multi-faceted Analysis:
      1. Proximate Causes: Agricultural expansion, logging, infrastructure.
      2. Underlying Causes: Population growth, poverty (reliance on forests for subsistence), market demands (global commodity trade), weak governance and land tenure laws, and undervaluing of forest ecosystems in national accounting. Addressing deforestation requires tackling these root causes.
    • Forests and Climate Change Mitigation: Forests are central to India’s climate action plan (Nationally Determined Contributions - NDCs) under the Paris Agreement. The goal to create an additional carbon sink of 2.5 to 3 billion tonnes of CO2 equivalent through additional forest and tree cover by 2030 highlights their importance. This requires robust policies on afforestation, regeneration of degraded forests (e.g., CAMPA funds), and preventing deforestation.
    • Ocean as a Carbon Sink and its Vulnerability: While the marine biome, particularly phytoplankton, absorbs a significant portion of anthropogenic CO2, this service is under threat. Increasing CO2 absorption leads to ocean acidification, which harms marine life, especially shell-forming organisms like corals and mollusks. This illustrates that ecosystems have a finite capacity to buffer human impacts.

Previous Year Questions

Prelims

  1. Which of the following are the reasons for the formation of tropical deserts on the western margins of continents? (UPSC CSE 2013 - adapted)

    1. They are located in the subtropical high-pressure belts.
    2. Presence of warm ocean currents along the western coasts.
    3. They are under the influence of offshore Trade Winds.

    Select the correct answer using the code given below: (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3

    Answer: (c) 1 and 3 only. Explanation: Tropical deserts are formed under subtropical high-pressure belts where air subsides, leading to dry conditions. The Trade Winds in these regions are offshore, blowing from land to sea, thus carrying no moisture. Statement 2 is incorrect; it is the presence of cold ocean currents (e.g., Benguela, Peruvian) along the western coasts that stabilizes the air and inhibits rainfall.

  2. In the context of ecosystems, which of the following is/are considered as producer(s)? (UPSC CSE 2021 - adapted)

    1. Algae
    2. Diatoms
    3. Cyanobacteria

    Select the correct answer using the code given below: (a) 1 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3

    Answer: (d) 1, 2 and 3. Explanation: Producers (or autotrophs) are organisms that produce their own food, typically through photosynthesis. Algae, diatoms (a type of algae), and cyanobacteria are all capable of photosynthesis and form the base of aquatic food webs.

  3. Consider the following statements regarding Shifting Cultivation: (UPSC CSE 2020 - adapted)

    1. It is a practice of deforestation where land is permanently converted for agriculture.
    2. It leads to a reduction in soil fertility in the long run if fallow periods are shortened.
    3. It is a major driver of forest degradation in the tropical regions of India’s Northeast.

    Which of the statements given above is/are correct? (a) 1 and 2 only (b) 2 and 3 only (c) 3 only (d) 1, 2 and 3

    Answer: (b) 2 and 3 only. Explanation: Statement 1 is incorrect. Shifting cultivation is typically a form of forest degradation, not permanent deforestation, as the land is left to regenerate after a few years of cultivation. However, shortened fallow cycles due to population pressure prevent full regeneration, leading to loss of soil fertility and permanent degradation. It is a prevalent practice in Northeast India.

  4. The term ‘Nekton’ in an aquatic ecosystem refers to: (UPSC CSE 2022 - adapted) (a) Organisms that float on the surface of the water. (b) Microscopic plants drifting in the water column. (c) Animals that are active swimmers. (d) Organisms that live on the seabed.

    Answer: (c) Animals that are active swimmers. Explanation: Nekton are aquatic animals that can move independently of water currents. This group includes most fish, marine mammals, and squid. Organisms on the surface are Neuston, drifters are Plankton, and bottom-dwellers are Benthos.

  5. Which of the following best describes the ecological function of forests in regulating the hydrological cycle? (UPSC CSE 2019 - adapted) (a) They increase surface runoff, leading to faster river flow. (b) They absorb rainfall, reduce runoff, and facilitate groundwater recharge. (c) They primarily contribute to the water cycle through evaporation from the canopy. (d) They prevent water from percolating into the soil, preserving it on the surface.

    Answer: (b) They absorb rainfall, reduce runoff, and facilitate groundwater recharge. Explanation: The dense canopy and litter-covered floor of a forest intercept rainfall, slow down surface runoff, and increase infiltration into the soil. This process recharges groundwater and ensures a steady, perennial flow in rivers, acting as a natural sponge.

Mains

  1. Discuss the causes and consequences of deforestation. What measures, in your opinion, are needed to effectively curb this menace in India? (UPSC CSE 2020 - adapted)

    Answer: Deforestation refers to the permanent removal of forest cover for conversion to non-forest land use. It is a critical environmental issue with far-reaching consequences.

    Causes of Deforestation:

    • Agricultural Expansion: The primary driver, including conversion for cash crops, subsistence farming, and pasture land.
    • Infrastructure Development: Projects like highways, dams, and urban expansion lead to large-scale forest clearing.
    • Mining and Industrial Activities: Extraction of minerals and setting up industries often require clearing vast tracts of forest land.
    • Logging: Both legal and illegal timber extraction for commercial purposes contribute significantly.
    • Forest Fires: Increased frequency and intensity due to climate change and human negligence.
    • Underlying Drivers: Population pressure, poverty, weak governance, and unclear land tenure rights exacerbate the problem.

    Consequences of Deforestation:

    • Biodiversity Loss: Destruction of habitats leads to the extinction of plant and animal species.
    • Climate Change: Reduces the Earth’s capacity to absorb CO2, releasing stored carbon into the atmosphere and contributing to global warming.
    • Disruption of Hydrological Cycles: Leads to irregular rainfall patterns, reduced groundwater recharge, and increased instances of floods and droughts.
    • Soil Erosion and Desertification: The removal of tree cover exposes soil to erosion by wind and water, leading to loss of fertility and desertification.
    • Impact on Livelihoods: Affects indigenous and forest-dependent communities who rely on forest resources for their survival.

    Measures to Curb Deforestation in India:

    1. Strengthening Policy and Legal Frameworks: Strict enforcement of the Forest (Conservation) Act, 1980, and the Wildlife Protection Act, 1972.
    2. Promoting Sustainable Agriculture: Encouraging agroforestry and efficient farming practices to reduce the need for agricultural expansion.
    3. Community Participation: Empowering local communities through Joint Forest Management (JFM) and the Forest Rights Act, 2006, to make them stakeholders in conservation.
    4. Afforestation and Reforestation Programs: Scaling up initiatives like the National Afforestation Programme and using CAMPA funds effectively for regenerating degraded forests.
    5. Technological Integration: Using remote sensing and GIS for better monitoring of forest cover, detecting illegal activities, and managing forest fires.
    6. Valuing Ecosystem Services: Integrating the economic value of forests into national planning to create incentives for conservation over conversion.

    A multi-pronged approach involving robust policy, community engagement, and technological innovation is essential to balance development needs with the imperative of forest conservation.

  2. Desertification is a major environmental challenge. Examine the causes, both natural and anthropogenic, of desertification and its impact on India. (UPSC CSE 2021 - adapted)

    Answer: Desertification is the process of land degradation in arid, semi-arid, and dry sub-humid areas, resulting from various factors, including climatic variations and human activities. It leads to the loss of the land’s biological productivity.

    Causes of Desertification:

    • Natural Causes:

      • Climate Change: Changes in rainfall patterns, prolonged droughts, and increasing temperatures stress ecosystems.
      • Geological Processes: Natural soil erosion by wind and water can contribute to land degradation over long periods.

    • Anthropogenic (Human-induced) Causes:

      • Deforestation: Removal of vegetation cover exposes soil to erosion.
      • Overgrazing: Excessive livestock grazing destroys vegetation, compacts the soil, and reduces its water-holding capacity.
      • Unsustainable Agricultural Practices: Over-cultivation, improper irrigation leading to salinization, and excessive use of chemical fertilizers degrade soil health.
      • Mining and Quarrying: These activities strip the land of its protective cover and often leave it barren and degraded.
      • Urbanization: Unplanned expansion of cities encroaches upon and degrades surrounding land.

    Impact on India: According to ISRO’s Desertification and Land Degradation Atlas (2021), about 29.7% of India’s total geographical area is undergoing land degradation.

    • Agricultural Loss: Reduced soil fertility leads to declining crop yields, threatening food security for millions.
    • Water Scarcity: Degraded land has poor water retention capacity, leading to reduced groundwater recharge and increased water stress.
    • Biodiversity Loss: Habitat destruction results in the loss of flora and fauna, disrupting ecosystems.
    • Economic Impact: Loss of agricultural productivity and the cost of land reclamation impose a significant economic burden.
    • Forced Migration: As land becomes unproductive, it can lead to distress migration from rural to urban areas, creating socio-economic pressures.

    Addressing desertification requires integrated land and water management, promoting sustainable agriculture and afforestation, and empowering local communities to manage their resources effectively.

  3. The world’s forests are critical ecosystems. Elaborate on the ecological functions performed by forests and their role in mitigating climate change. (UPSC CSE 2019 - adapted)

    Answer: Forests are complex, dynamic ecosystems that perform a range of vital ecological functions essential for planetary health and human well-being.

    Ecological Functions of Forests:

    1. Biodiversity Conservation: Forests are repositories of biodiversity, providing habitats for a vast majority of terrestrial species and supporting complex food webs.
    2. Regulation of Hydrological Cycles: They act as natural sponges, intercepting rainfall, promoting infiltration, and recharging groundwater. This maintains the flow of rivers and moderates floods and droughts.
    3. Soil Conservation and Formation: The root networks of trees bind the soil, preventing erosion. The decomposition of forest litter enriches the soil with organic matter, a process known as pedogenesis.
    4. Nutrient Cycling: Forests play a crucial role in biogeochemical cycles (carbon, nitrogen, phosphorus), ensuring the continuous availability of nutrients for the ecosystem.
    5. Climate Regulation: Through evapotranspiration, forests influence local and regional temperature and precipitation patterns.

    Role in Mitigating Climate Change: Forests are central to the global carbon cycle and play a two-fold role in climate change mitigation:

    1. Carbon Sequestration (Carbon Sinks): Through photosynthesis, trees absorb atmospheric carbon dioxide (CO2), a primary greenhouse gas, and store it in their biomass (trunks, branches, leaves, roots) and in the soil. Healthy, growing forests are powerful carbon sinks.
    2. Avoiding Emissions: Deforestation and forest degradation are major sources of greenhouse gas emissions. When forests are cleared or burned, the stored carbon is released back into the atmosphere. Therefore, preventing deforestation (initiatives like REDD+) is one of the most cost-effective ways to reduce global emissions.

    Recognizing this, India, under its Nationally Determined Contributions (NDCs), has pledged to create an additional carbon sink of 2.5-3 billion tonnes of CO2 equivalent by 2030 through afforestation and reforestation efforts. Protecting and restoring forests is thus indispensable for achieving the goals of the Paris Agreement and ensuring a stable climate.

  4. Discuss the concept of marine biomes and the major threats they face due to anthropogenic activities. (UPSC CSE 2022 - adapted)

    Answer: The marine biome, encompassing all oceanic and sea environments, is the largest biome on Earth, characterized by saline water. It is a continuous body, crucial for regulating global climate and supporting immense biodiversity. It is typically zoned based on light penetration (photic/aphotic) and depth (littoral, neritic, abyssal).

    Major Anthropogenic Threats to Marine Biomes:

    1. Pollution:
      • Plastic Pollution: Accumulation of plastic debris harms marine life through ingestion and entanglement. Microplastics contaminate the food chain.
      • Chemical and Nutrient Runoff: Runoff from agricultural fields (fertilizers, pesticides) and industrial effluents leads to eutrophication, creating ‘dead zones’ with low oxygen levels.
      • Oil Spills: Accidental spills cause immediate and long-term damage to marine ecosystems.
    2. Climate Change:
      • Ocean Warming: Rising sea temperatures cause coral bleaching, disrupt marine species’ life cycles, and alter ocean currents.
      • Ocean Acidification: The absorption of excess atmospheric CO2 by seawater increases its acidity. This hinders the ability of shell-forming organisms like corals, mollusks, and plankton to build their shells and skeletons, threatening the base of the marine food web.
    3. Overfishing: Unsustainable fishing practices have depleted fish stocks worldwide, disrupting marine food webs and threatening the livelihoods of coastal communities. Destructive methods like bottom trawling also damage seabed habitats.
    4. Habitat Destruction: Coastal development, dredging, and mangrove deforestation destroy critical nursery habitats for many marine species. Deep-sea mining poses a new and significant threat to fragile, unexplored ecosystems.

    Addressing these threats requires a concerted global effort, including reducing carbon emissions, implementing sustainable fishing practices (e.g., through UNCLOS), controlling land-based pollution, and establishing Marine Protected Areas (MPAs) to conserve critical habitats.

  5. What is shifting cultivation? Explain how it has become a major factor in forest degradation in recent times and suggest measures for its sustainable management. (UPSC CSE 2018 - adapted)

    Answer: Shifting cultivation, also known as slash-and-burn agriculture or ‘Jhum’ in Northeast India, is a traditional agricultural system where a patch of forest is cleared and burned, and the ash is used to fertilize the soil for cultivating crops. After a few years, as soil fertility declines, the plot is abandoned and left fallow for natural regeneration, and the farmer moves to a new patch.

    Transformation into a Driver of Forest Degradation: Traditionally, shifting cultivation was sustainable due to long fallow periods (15-20 years), which allowed forests to regenerate completely. However, in recent times, it has become a major driver of forest degradation due to:

    1. Increased Population Pressure: Growing populations have reduced the land-to-person ratio, forcing farmers to shorten the fallow cycle drastically (now often just 3-5 years).
    2. Shortened Fallow Period: Insufficient time for regeneration prevents the recovery of forest vegetation and leads to a progressive decline in soil fertility, biomass, and biodiversity.
    3. Loss of Traditional Knowledge: The erosion of traditional ecological knowledge regarding sustainable land management practices has contributed to its unsustainability.
    4. Commercialization: A shift from subsistence farming to cash crops can intensify land use, further degrading the soil.

    Measures for Sustainable Management:

    1. Improving Fallow Management: Introducing leguminous plants and fast-growing trees during the fallow period can help restore soil fertility more quickly.
    2. Promoting Agroforestry and Land-Use Diversification: Integrating trees with crops (agroforestry) and promoting horticulture or animal husbandry can provide alternative livelihoods and reduce pressure on land for cultivation.
    3. Securing Land Tenure: Providing formal land tenure rights to communities practicing shifting cultivation, as under the Forest Rights Act, 2006, can incentivize long-term sustainable management of their land.
    4. Technological and Financial Support: Providing farmers with access to improved crop varieties, bio-fertilizers, and markets can enhance productivity on existing land, reducing the need to clear new forests.

    Instead of an outright ban, which could harm the livelihoods of indigenous communities, a policy focus on modifying and improving the practice is essential for both ecological conservation and social equity.

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