Environment Notes 09

BIODIVERSITY

Biodiversity, or biological diversity, is the variety and variability of life on Earth. The term was popularised by sociobiologist Edward O. Wilson in 1986. The Convention on Biological Diversity (CBD), signed at the Earth Summit in Rio de Janeiro in 1992, legally defines it as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems.” It is typically considered at three levels:

• Genetic Diversity: The variation in genes within a single species. This is crucial for a species’ ability to adapt to environmental changes. For example, different varieties of rice or mango in India represent high genetic diversity.
• Species Diversity: The variety of different species (plants, animals, fungi, and microorganisms) within a region. It is often measured by species richness (the number of species) and species evenness (the relative abundance of species).
• Ecosystem Diversity: The variety of habitats, biotic communities, and ecological processes in the biosphere. This refers to the diversity of ecosystems like deserts, rainforests, mangroves, coral reefs, etc., in a given area. The functioning of these ecosystems is determined by a complex interplay of factors:
  • Climatic Conditions: Temperature and precipitation patterns are the primary determinants of the type of ecosystem, for example, the formation of tropical rainforests in high temperature and high rainfall zones.
  • Vegetation and Hydrological Characteristics: The type of flora and the availability and flow of water shape the habitat for fauna. For instance, the unique mangrove vegetation of the Sundarbans is adapted to its brackish water estuarine conditions.
  • Habitat Characteristics: The physical and chemical nature of the soil and water (e.g., salinity, pH) defines the niche for specific organisms.
  • Biotic Interactions: The complex web of interactions like predation, competition, and symbiosis between life forms and their environment creates stable and resilient ecosystems.

WORLD DISTRIBUTION OF BIODIVERSITY

The distribution of biodiversity across the globe is not uniform. It follows a distinct pattern, most notably the Latitudinal Diversity Gradient (LDG), where species richness increases from the poles towards the equator.

• Tropical Regions: Cradles of Diversity
  • The tropics, lying roughly between 23.5°N and 23.5°S latitude, harbor the vast majority of the world’s species.
  • Reasons for High Tropical Biodiversity:
    1. High Solar Energy and Productivity: The tropics receive more direct and intense solar radiation throughout the year. This, combined with abundant rainfall, leads to high primary productivity (rate of biomass generation), which can support a greater number of species and more complex food webs.
    2. Climatic Stability: Tropical regions have experienced a more stable climate over geological timescales compared to temperate and polar regions. The middle and high latitudes were subject to repeated glaciations during the Pleistocene epoch. As articulated by ecologist Alfred Russel Wallace (1878), this long period of stability in the tropics has allowed for uninterrupted evolution (‘speciation’) and diversification, acting as both a ‘cradle’ (where new species evolve) and a ‘museum’ (where old species persist). The tropics were largely free from catastrophic ice ages, allowing evolutionary processes to continue for longer periods.
    3. Habitat Heterogeneity: The structural complexity of tropical rainforests, with multiple canopy layers, provides a greater number of ecological niches, allowing for the co-existence of a large number of species.
  • Key Tropical Ecosystems:
    • Tropical Rainforests: These ecosystems, such as the Amazon in South America and the Congo Basin in Africa, cover less than 7% of the Earth’s land surface but are estimated to contain more than 50% of all terrestrial species. They are considered the world’s largest “gene pools.”
    • Coral Reefs: Often called the “rainforests of the ocean,” coral reefs are built by colonies of tiny animals (polyps). Found in warm, shallow tropical waters, they support an estimated 25% of all marine species, making them one of the most diverse ecosystems on the planet. The Great Barrier Reef in Australia is a prime example.
    • Wetlands: Tropical wetlands, including mangroves, estuaries, inter-tidal zones, and freshwater marshes, are exceptionally productive. The Millennium Ecosystem Assessment (2005), a major study initiated by the UN, reported that while wetlands cover about 7% of the world’s surface, they account for a staggering 45% of the total value of the world’s ecosystem services. They are critical habitats for a vast array of species, especially 41% of the world’s fish species.

BIODIVERSITY HOTSPOTS

The concept of biodiversity hotspots was first articulated by British ecologist Norman Myers in two articles in The Environmentalist (1988, 1990). It is a biogeographic region characterized both by exceptional levels of plant endemism and by serious levels of habitat loss. The concept was later adopted and refined by Conservation International (CI), a non-governmental organization.

• Criteria for a Hotspot:

  1. High Endemism: The region must contain at least 1,500 species of vascular plants (0.5% of the world’s total) as endemics. Endemic species are those found nowhere else on Earth.
  2. High Threat Level: The region must have lost at least 70% of its original natural vegetation. This signifies a high degree of threat to its unique biodiversity.

• Global Significance:

  • There are currently 36 recognized biodiversity hotspots.
  • These hotspots represent just 2.4% of the Earth’s land surface but support more than half of the world’s plant species as endemics and nearly 43% of bird, mammal, reptile, and amphibian species as endemics. Most hotspots are located in tropical regions.

• Biodiversity Hotspots of India:

  1. The Western Ghats (and Sri Lanka): A mountain chain running parallel to India’s western coast. It harbors over 5,000 vascular plant species, of which about 1,700 (over 30%) are endemic. It is home to iconic and threatened species like the Lion-tailed Macaque, Nilgiri Tahr, and the largest population of Asian Elephants. It is also home to numerous endemic amphibian species, making it a global amphibian hotspot.
  2. The Indo-Burma Region: One of the largest hotspots, it encompasses Northeast India (except Assam’s Brahmaputra valley), Myanmar, Thailand, Laos, Cambodia, Vietnam, and parts of southern China. It is noted for its high diversity of freshwater turtles and globally threatened bird species like the critically endangered White-eyed River Martin. It also hosts unique primate species and large mammals like the Saola. The Andaman Islands are part of this hotspot.
  3. The Himalayas: This hotspot includes the entire Himalayan range across Pakistan, Nepal, Bhutan, and the Indian states of Uttarakhand, Himachal Pradesh, Sikkim, and Arunachal Pradesh. It features remarkable altitudinal gradients in ecosystems, from subtropical forests to alpine meadows. It is home to large mammals like the Snow Leopard, Asian Elephant, Greater One-horned Rhinoceros, and unique ungulates like the Himalayan Musk Deer.
  4. Sundaland: This hotspot covers the western half of the Indo-Malayan archipelago, including parts of Indonesia, Malaysia (Sarawak and Sabah), Brunei, and India’s Nicobar Islands. It is renowned for its rich flora, with an estimated 15,000 endemic plant species. The region is famous for its megafauna, especially the critically endangered Bornean and Sumatran Orangutans, and the Sumatran Rhino. The primary threat to this hotspot is commercial forestry and the expansion of oil palm plantations.

MEGA BIODIVERSE REGIONS OF THE WORLD

This is a separate but related concept, also developed by Conservation International in 1998. It refers to a group of countries that harbor the majority of Earth’s species and are therefore considered extremely biodiverse.

• Criteria:
  1. Plant Endemism: Must have at least 5,000 endemic plant species.
  2. Marine Ecosystems: Must have marine ecosystems within its borders.
• List of Countries: There are 17 megadiverse countries, including Australia, Brazil, China, Colombia, Ecuador, India, Indonesia, Madagascar, Malaysia, Mexico, Papua New Guinea, Peru, Philippines, South Africa, USA, Venezuela, and the Democratic Republic of Congo. These nations together hold over 70% of the planet’s biodiversity.

IMPORTANCE OF BIODIVERSITY

The Millennium Ecosystem Assessment (2005) framework categorizes the services provided by biodiversity into four types:

• Provisioning Services: These are the direct products obtained from ecosystems.

  • Food: While humans have historically used about 7,000 plant species for food, today, only about 30 species provide 95% of human food energy needs. Wild relatives of these crops, found in diverse ecosystems, are crucial genetic resources for developing new, resilient, and high-yielding varieties.
  • Medicines: A vast number of modern pharmaceuticals are derived from natural compounds. For example, Quinine (from the Cinchona tree) treats malaria, Digitalis (from the Foxglove plant) is used for heart ailments, and Vincristine (from the Rosy Periwinkle) is an anti-cancer drug.
  • Fibre, Fuel, and Water: Biodiversity provides wood for fuel and construction, fibres like cotton and jute, and plays a vital role in maintaining the quality and supply of fresh water.

• Regulating Services: These are the benefits obtained from the regulation of ecosystem processes.

  • Climate Regulation: Forests and oceans act as major carbon sinks, absorbing atmospheric CO2 and mitigating climate change. Phytoplankton in the oceans are responsible for producing over 50% of the world’s oxygen.
  • Pollination: An estimated three-quarters of the world’s food crops depend on pollination by animals like bees, butterflies, birds, and bats. The economic value of this service is immense.
  • Water Purification and Flood Control: Wetlands act as natural filters, purifying water. Mangrove forests and coral reefs serve as natural barriers, protecting coastlines from storm surges and tsunamis.

• Supporting Services: These are necessary for the production of all other ecosystem services.

  • Nutrient Cycling: Decomposers like bacteria and fungi break down organic matter, recycling essential nutrients through the ecosystem.
  • Soil Formation: The interaction of organisms, climate, and parent rock creates fertile soil, the foundation of terrestrial life.
  • Primary Production: The process of photosynthesis by plants forms the base of almost all food chains.

• Cultural Services: These are the non-material benefits people obtain from ecosystems.

  • Spiritual and Religious Values: Many cultures have deep spiritual connections with nature. In India, sacred groves are patches of forest protected by local communities due to religious beliefs, which inadvertently conserves biodiversity.
  • Recreation and Ecotourism: Natural landscapes and wildlife provide opportunities for tourism, hiking, and other recreational activities, generating economic benefits.
  • Aesthetic and Educational Value: Biodiversity inspires art, music, and science, enriching human experience and knowledge.

• Ethical Dimension: This perspective argues for conservation based on the intrinsic value of life. It posits that every species has a right to exist, regardless of its utility to humans. This view, central to environmental ethics, suggests that humans, as the dominant species with the power to cause extinction, have a moral responsibility to act as stewards of the planet.

THREATS TO BIODIVERSITY

The current rate of species extinction is estimated to be 100 to 1,000 times higher than the natural background rate, primarily due to human activities. Ecologists often refer to the major threats using the acronym HIPPO (Habitat Destruction, Invasive Species, Pollution, Population, and Overharvesting).

• Habitat Loss, Fragmentation, and Degradation: This is universally considered the single greatest threat to biodiversity.

  • Loss: The outright conversion of natural habitats (forests, wetlands, grasslands) for agriculture, urbanization, and industrial development destroys the homes of countless species.
  • Fragmentation: Large, continuous habitats are broken into smaller, isolated patches by roads, dams, and farms. This restricts the movement of species, reduces the gene pool, and increases their vulnerability to extinction.
  • Degradation: Pollution (e.g., acid rain, oil spills), deforestation, and resource depletion reduce the quality of a habitat, making it unable to support its native species.

• Invasive Alien Species:

  • These are non-native species introduced, intentionally or unintentionally, into an ecosystem where they outcompete native species for resources. They often possess high phenotypic plasticity (the ability to thrive in a wide range of environmental conditions), rapid reproduction rates, and lack natural predators in their new environment.
  • Examples in India include Lantana camara, Water Hyacinth (Eichhornia crassipes), and Prosopis juliflora (Vilayati Babul), which have decimated native flora in many areas.

• Excessive Exploitation of Resources (Overharvesting):

  • The unsustainable harvesting of plants and animals for food, medicine, and trade pushes many species towards extinction.
  • Examples include overfishing, which has depleted global fish stocks, and excessive logging of tropical hardwoods. The “Tragedy of the Commons,” a concept popularized by ecologist Garrett Hardin (1968), explains how shared resources are often overexploited.

• Pollution:

  • Chemical pollutants from industries and agriculture (pesticides, fertilizers), plastic waste, and oil spills can have devastating effects on ecosystems, particularly aquatic ones. Bioaccumulation and biomagnification of toxins in the food chain can be lethal to top predators.

• Climate Change:

  • Global warming is altering temperature and rainfall patterns, forcing species to shift their ranges or adapt. Many species, like corals (which undergo bleaching due to warmer seas) and polar bears, are unable to adapt quickly enough and face a high risk of extinction.

• Illegal Wildlife Trade:

  • The trafficking of wildlife and their products (ivory, rhino horn, tiger skins) is a multi-billion dollar illicit industry that has driven many iconic species to the brink of extinction.

Prelims Pointers

• Biodiversity Hotspot Concept: Given by Norman Myers in 1988.
• Criteria for a Hotspot:
  1. At least 1,500 endemic species of vascular plants.
  2. Loss of at least 70% of its original habitat.
• Global Hotspots: There are 36 recognized hotspots, managed and updated by Conservation International.
• India’s Biodiversity Hotspots (4):
  1. The Western Ghats
  2. The Himalayas
  3. Indo-Burma Region (includes Andaman Islands)
  4. Sundaland (includes Nicobar Islands)
• Megadiverse Countries: Concept by Conservation International (1998). There are 17 such countries, and India is one of them.
• Latitudinal Diversity Gradient (LDG): Species diversity increases from the poles to the tropics.
• Ecosystem Productivity: Tropical rainforests and coral reefs have very high biodiversity.
• Wetlands: As per the Millennium Ecosystem Assessment (2005), they cover ~7% of the Earth’s surface but account for ~45% of its natural productivity.
• Endemic Species: Species found exclusively in a particular geographical area and nowhere else.
  • Lion-tailed Macaque: Endemic to the Western Ghats.
  • Nilgiri Tahr: Endemic to the Nilgiri Hills in the Western Ghats.
  • Orangutans (Bornean and Sumatran): Endemic to the Sundaland hotspot.
• Invasive Alien Species in India: Lantana camara, Water Hyacinth (Eichhornia crassipes), Prosopis juliflora.
• Key Reports/Organizations:
  • WWF: Publishes the Living Planet Report.
  • Conservation International: Identifies and manages biodiversity hotspots and megadiverse countries.
  • Millennium Ecosystem Assessment (2005): Categorized ecosystem services.
• Phenotypic Plasticity: The ability of an organism to change its phenotype in response to changes in the environment. Often high in invasive species.

Mains Insights

GS Paper I (Geography)

• Physical and Human Geography Interface: The distribution of biodiversity hotspots is directly linked to physical geography (climate, topography, isolation). For example, the Himalayan hotspot’s unique biodiversity is a result of its extreme altitudinal variation. However, threats to these hotspots are driven by human geography—population density, patterns of agriculture (like Jhum/shifting cultivation in the Indo-Burma region), urbanization, and infrastructure development (dams and roads in the Western Ghats).
• Climate Change Impact: Climate change acts as a ‘threat multiplier’. Analyze how rising temperatures and erratic monsoons could impact the endemic species of the Western Ghats, which are adapted to specific climatic niches. Discuss the phenomenon of species migrating to higher altitudes in the Himalayas, leading to inter-species conflict and ecosystem disruption.

GS Paper III (Environment & Economy)

• Development vs. Conservation Debate: This is a critical analytical theme. The criteria for hotspots (high endemism and high threat) inherently place them in areas of conflict with developmental activities. The Gadgil vs. Kasturirangan committee reports on the Western Ghats exemplify this debate. Analyze the need for a balanced approach that integrates conservation goals with sustainable development and local livelihood security.
• Economic Valuation of Biodiversity: Biodiversity is not just an environmental issue but a core economic asset. Discuss the concept of ‘ecosystem services’ and their economic valuation. The loss of biodiversity (e.g., decline of pollinators) has direct economic costs for agriculture. This perspective is crucial for convincing policymakers to invest in conservation. Link this to India’s Biological Diversity Act, 2002, which aims to ensure fair and equitable sharing of benefits arising from the use of biological resources.
• Causes and Consequences of Biodiversity Loss: Frame this in a cause-effect matrix. Causes: Habitat fragmentation, invasive species, climate change, unsustainable consumption patterns. Consequences: Disrupted food webs, loss of genetic resources for future food and medicine, increased vulnerability to natural disasters, loss of livelihoods for forest-dependent communities, and emergence of zoonotic diseases.

GS Paper IV (Ethics)

• Environmental Ethics: The conservation of biodiversity raises fundamental ethical questions. Is there a moral duty to protect other species? Discuss the anthropocentric (human-centered) versus ecocentric (nature-centered) ethical frameworks. An anthropocentric argument for conservation is based on its utility for humans (ecosystem services). An ecocentric argument is based on the intrinsic value and rights of every species to exist.
• The Concept of Stewardship: As the most intelligent and powerful species, do humans have a special responsibility to act as stewards or trustees of the planet’s biodiversity for future generations? This connects to the principle of inter-generational equity.
• Ethical Dilemmas in Conservation: Discuss ethical dilemmas such as ‘conservation-induced displacement’ where creating protected areas might lead to the displacement of indigenous communities, whose rights and traditional knowledge also need to be protected. This requires a just and equitable approach to conservation.