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Geography

Biodiversity Loss — The 6th Mass Extinction

Major Environmental Issues

Paper II · Unit 3 Section 5 of 11 0 PYQs 37 min
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Biodiversity Loss — The 6th Mass Extinction

4.1 Biodiversity and its Significance

Biodiversity (from "biological diversity") is the variety of life at three levels:

  • Genetic diversity: Variation within species (breeds, varieties)
  • Species diversity: Variety of species in an ecosystem
  • Ecosystem diversity: Variety of habitats, communities, and ecological processes

Why does biodiversity matter?

  1. Ecosystem services: Pollination (~$235 billion/year), water purification, soil formation, flood regulation, carbon storage, climate regulation
  2. Food security: ~80% of human caloric intake from just 12 plant species; wild relatives of crops provide genetic reservoir for breeding disease-resistant, drought-resistant varieties
  3. Medicine: ~50% of pharmaceutical drugs derive from natural products; ~70% of cancer drugs derived from nature
  4. Cultural and spiritual value: Indigenous peoples' identity and knowledge systems
  5. Intrinsic value: Each species has a right to exist

4.2 Current State of Biodiversity

IUCN Red List (2024): The most comprehensive biodiversity assessment:

  • 157,190 species assessed (of ~8.7 million estimated species — coverage still limited)
  • 44,016 species threatened with extinction = 28% of assessed species
  • 902 species confirmed extinct since 1500 CE; many more "functionally extinct" (too few to maintain healthy populations)

Category breakdown (of threatened species):

  • Critically Endangered (CR): 8,943 species (immediate risk)
  • Endangered (EN): 14,590 species
  • Vulnerable (VU): 20,483 species

Group-specific crisis:

  • Amphibians: ~41% of assessed species threatened — most at-risk group (UV sensitivity, dual-habitat, skin permeable to pollutants)
  • Freshwater fish: ~37% threatened — most freshwater ecosystems degraded
  • Sharks and rays: ~33% threatened — slow reproduction + intensive fishing
  • Mammals: ~26% threatened — habitat loss dominant
  • Birds: ~14% threatened — still concerning given sensitivity as indicator species

WWF Living Planet Report 2022: Average vertebrate population sizes declined 69% since 1970 (not species count but population abundance).

4.3 Causes of Biodiversity Loss

1. Habitat destruction (primary cause — 80% of threatened species):

  • Deforestation: Tropical forests (Amazon, Congo, SE Asia) house ~50% of all species on just 6% of land
  • Agricultural expansion: Monoculture replaces diverse natural ecosystems
  • Urban sprawl
  • Wetland draining: ~35% of world's wetlands lost since 1970

2. Overexploitation:

  • Overfishing: 33% of global fish stocks overfished; 60% at maximum sustainable levels
  • Poaching: Illegal wildlife trade (~$23 billion/year) — 2nd largest illegal trade after drugs
  • India: Tiger poaching (Bengal tiger — ~3,167 in 2022); elephant, rhinoceros, pangolin trafficking

3. Invasive Species:

  • Species introduced to new environments outcompete native species
  • Islands most vulnerable — 50% of documented extinctions on islands due to invasives
  • India: Water Hyacinth (Eichhornia crassipes, American origin) chokes wetlands; Lantana camara (Central American shrub) invades forests; Nile Tilapia threatens native fish

4. Pollution:

  • Pesticides (DDT — bioaccumulation, caused eagle eggshell thinning; now banned); nitrogen pollution (dead zones); microplastics; heavy metals
  • Eutrophication: Excess nitrogen/phosphorus → algal blooms → oxygen depletion → dead zones (Gulf of Mexico dead zone: ~22,700 km²)

5. Climate Change:

  • Projected to become the dominant driver of extinction by 2050
  • Bleaching of coral reefs; timing mismatches (species life cycles out of sync with seasonal food availability); range shifts; extreme events

4.4 Conservation Efforts

In-situ Conservation (in natural habitat):

  • Protected Areas (PAs): Currently ~17% of land and ~8% of ocean protected
  • Biosphere Reserves: Core + buffer + transition zones (UNESCO Man and Biosphere Programme)
  • Wildlife Corridors: Connect fragmented habitats (e.g., Terai Arc Landscape in India)

Ex-situ Conservation (outside natural habitat):

  • Zoos and botanical gardens: Breeding programmes for critically endangered species
  • Seed Banks: Svalbard Global Seed Vault (Norway, 78°N Arctic, 850 m underground) — stores 1.3 million crop varieties
  • Cryopreservation: Freezing genetic material (cells, gametes) of endangered species

International Agreements:

  • Convention on Biological Diversity (CBD, 1992): 196 parties; three objectives: conservation, sustainable use, benefit-sharing
  • Nagoya Protocol (2010): Access and Benefit-Sharing (ABS) — local communities get benefits from commercialisation of their genetic resources
  • Kunming-Montreal Global Biodiversity Framework (GBF, 2022, COP15):
    • "30×30" target: Protect 30% of land and 30% of ocean by 2030
    • Halt human-induced extinctions; restore 30% of degraded ecosystems
    • $200 billion/year biodiversity financing by 2030 (from $0 baseline in public and private)

India's biodiversity status:

  • Biodiversity hotspot: 2 of world's 36 hotspots — Indo-Burma (NE India) and Western Ghats-Sri Lanka
  • Endemism: ~7,500 endemic plant species; ~62% of mammal species in NE India are endemic to Asia
  • Wildlife Protection Act (1972): Schedule I species (highest protection); Project Tiger (1973) — Bengal Tiger population now ~3,167 (2022); Project Elephant (1992); Project Dolphin (2020)
  • Biological Diversity Act (2002) — India's national implementation of CBD