Unit 5: Ecology and Environment - Chapter 3: Biodiversity and Conservation

5.3 Biodiversity and Conservation

Concept and Types: Genetic, Species, Ecosystem

Biodiversity (or biological diversity) is the variety of life on Earth at all its levels, from genes to ecosystems, and the ecological and evolutionary processes that sustain it. The term was popularized by Edward Wilson.

Types of Biodiversity:

1. Genetic Diversity:

   • Refers to the diversity in the genetic makeup within a species.
   • It is the variation of genes within the same species.
   • Allows a species to adapt to changing environmental conditions.
   • Example: The genetic variation in Rauwolfia vomitoria (Himalayan medicinal plant) in terms of the potency and concentration of the active chemical reserpine.
   • Example: India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

2. Species Diversity:

   • Refers to the variety of species within a region.
   • It is measured by:
     • Species Richness: The number of different species present in an area.
     • Species Evenness: The relative abundance of each species in an area.
   • Example: The Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

3. Ecosystem Diversity:

   • Refers to the variety of different types of ecosystems within a geographical area.
   • It includes the diversity of habitats, biotic communities, and ecological processes.
   • Example: India, with its deserts, rainforests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows, has a greater ecosystem diversity than a Scandinavian country like Norway.

Patterns: Latitudinal Gradient, Species-Area Curve

Patterns of Biodiversity:

1. Latitudinal Gradient:

   • Species diversity generally decreases as we move away from the equator towards the poles.
   • Tropics (equatorial regions) harbor more species than temperate or polar regions.
   • Reasons for higher diversity in tropics:
     • Stable Climate: Tropics have remained undisturbed for millions of years, leading to longer evolutionary time for species diversification.
     • Less Seasonal Variation: More constant and predictable environment, promoting niche specialization and avoiding frequent disturbances.
     • Higher Productivity: Greater solar energy availability, leading to higher productivity, which can support a greater diversity of life forms.

2. Species-Area Curve:

   • Proposed by the German naturalist and geographer Alexander von Humboldt.
   • States that within a region, species richness increases with increasing explored area, but only up to a certain limit.
   • The relationship between species richness (S) and area (A) is a rectangular hyperbola.
   • Equation: log S = log C + Z log A
     • S = Species richness
     • A = Area
     • Z = Slope of the line (regression coefficient)
     • C = Y-intercept
   • On a logarithmic scale, the relationship is a straight line.
   • The value of Z (slope) is generally 0.1 to 0.2 for small areas (e.g., within a continent). However, for very large areas (e.g., entire continents), the slope is much steeper (0.6 to 1.2).

Importance: Utilitarian, Ethical

Importance of Biodiversity:

1. Utilitarian Reasons:

   • Direct Utilitarian: Directly derived economic benefits from biodiversity.
     • Food: Cereals, pulses, fruits, vegetables, meat, fish.
     • Medicines: Over 25% of drugs are derived from plants (e.g., morphine from Papaver somniferum, quinine from Cinchona).
     • Industrial Products: Timber, fibers, dyes, resins, gums, rubber.
     • Ecotourism: Recreation, aesthetic pleasure.
   • Indirect Utilitarian: Ecosystem services provided by biodiversity.
     • Pollination by bees, birds, and bats.
     • Pest control by natural predators.
     • Climate regulation (e.g., Amazon rainforest).
     • Nutrient cycling.
     • Water purification.
     • Soil formation and erosion prevention.

2. Ethical Reasons:

   • Every species has an intrinsic value, regardless of its economic or utilitarian worth.
   • We have a moral obligation to protect and pass on our biological legacy to future generations.
   • The philosophical argument that all life forms have a right to exist.

Loss: Extinction (Dodo, Thylacine, Tigers), Causes (Habitat Loss, Overexploitation, Alien Species, Co-extinction)

Biodiversity Loss:

• The current species extinction rates are 100 to 1000 times faster than in pre-human times.
• Examples of Extinct Species:
  • Dodo: A flightless bird from Mauritius, extinct due to human hunting.
  • Thylacine (Tasmanian Tiger): A carnivorous marsupial from Australia, extinct due to hunting and habitat loss.
  • Steller's Sea Cow: A large, herbivorous marine mammal, extinct due to overexploitation.
  • Quagga: A subspecies of zebra from South Africa, extinct due to hunting.
  • Three subspecies of Tiger (Bali, Javan, Caspian) have become extinct.

Causes of Biodiversity Loss (The Evil Quartet):

1. Habitat Loss and Fragmentation:

• The most important cause.
• Destruction of natural habitats (e.g., deforestation for agriculture, urbanization, industrialization) leads to the loss of species.
• Fragmentation of large habitats into smaller, isolated patches affects species that require large territories (e.g., tigers, elephants).
• Example: The Amazon rainforest (lungs of the planet) is being cut and cleared for cultivating soybeans or for conversion to grasslands for raising beef cattle.

2. Over-exploitation:

   • When biological resources are harvested at a rate faster than they can replenish.
   • Examples: Overfishing, overhunting, over-harvesting of medicinal plants.
   • Examples of extinct species due to over-exploitation: Steller's Sea Cow, Passenger Pigeon.

3. Alien Species Invasions:

   • When non-native (alien) species are introduced (intentionally or unintentionally) into an ecosystem, they can become invasive and outcompete native species, leading to their decline or extinction.
   • Examples:
     • Nile Perch introduced into Lake Victoria (East Africa) led to the extinction of more than 200 species of cichlid fish.
     • Parthenium (carrot grass), Lantana, and Eichhornia (water hyacinth) are invasive weed species that pose a threat to native species.
     • African Catfish (Clarias gariepinus) for aquaculture purposes is posing a threat to indigenous catfish in Indian rivers.

4. Co-extinctions:

   • When one species becomes extinct, the species associated with it in an obligatory relationship also becomes extinct.
   • Examples:
     • When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
     • The extinction of a plant pollinator can lead to the extinction of the plant species if it is the only pollinator.

Conservation: In Situ, Ex Situ, Hotspots, Ramsar Sites, Red Data Book, Conventions

Biodiversity Conservation:

1. In Situ Conservation (On-site Conservation):

   • Conservation of genetic resources in natural populations of plant or animal species, such as forest genetic resources in natural forest ecosystems.
   • Advantages: Cost-effective, preserves the entire ecosystem.
   • Methods:
     • Biosphere Reserves: Large protected areas for conservation of biodiversity and cultural diversity, promoting sustainable use of resources (e.g., Nilgiri Biosphere Reserve).
     • National Parks: Areas reserved for wildlife where no human activity is permitted (e.g., Jim Corbett National Park, Kaziranga National Park).
     • Wildlife Sanctuaries: Areas where only wild animals are protected, and some human activities (like timber harvesting) may be allowed (e.g., Periyar Wildlife Sanctuary).
     • Sacred Groves: Patches of forest that are protected by local communities due to religious or cultural beliefs. Found in Meghalaya, Western Ghats, Aravalli Hills, etc.

2. Ex Situ Conservation (Off-site Conservation):

   • Conservation of components of biological diversity outside their natural habitats.
   • Advantages: Useful for endangered species, allows for breeding programs.
   • Methods:
     • Zoological Parks (Zoos): Wild animals are kept in captivity for public display, breeding, and conservation.
     • Botanical Gardens: Collections of living plants for scientific study, conservation, and public display.
     • Wildlife Safari Parks: Provide a natural habitat for animals, allowing visitors to observe them in a semi-wild environment.
     • Gene Banks/Seed Banks: Store viable seeds, gametes, and tissues of endangered species under controlled conditions (e.g., cryopreservation).
     • Cryopreservation: Preservation of gametes of threatened species in viable and fertile condition for long periods at very low temperatures (-196°C in liquid nitrogen).

Other Important Concepts in Conservation:

• Biodiversity Hotspots:

  • Regions with high levels of species richness and a high degree of endemism (species found nowhere else) that are also under significant threat of habitat loss.
  • Initially 25, now 36 hotspots identified worldwide.
  • In India: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya are biodiversity hotspots.

• Ramsar Sites:

  • Wetlands of international importance designated under the Ramsar Convention (Convention on Wetlands).
  • Aims to conserve and wisely use wetlands and their resources.

• Red Data Book:

  • Maintained by the International Union for Conservation of Nature (IUCN).
  • A catalog of taxa that are facing risk of extinction.
  • Provides information on the conservation status of species (e.g., Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, Data Deficient, Not Evaluated).

International Conventions for Biodiversity Conservation:

• Earth Summit (Rio de Janeiro, 1992):

  • Convened by the United Nations Conference on Environment and Development (UNCED).
  • Called upon all nations to take appropriate measures for the conservation of biodiversity and sustainable utilization of its benefits.
  • Led to the Convention on Biological Diversity (CBD).

• World Summit on Sustainable Development (Johannesburg, 2002):

  • Held in Johannesburg, South Africa.
  • Pledged to achieve a significant reduction in the current rate of biodiversity loss by 2010 (which was not fully met).