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).

Mathematical Problems on Species-Area Curve:

• Step-by-step guide to solving problems:

  1. Identify the given values: Determine the values of S, A, Z, and C provided in the problem.
  2. Choose the correct formula: Use S = CA^Z for direct calculation or log S = log C + Z log A for logarithmic problems.
  3. Substitute the values: Plug the known values into the chosen formula.
  4. Solve for the unknown: Perform the calculation to find the missing variable.

• Understanding the Regression Coefficient (Z):

  • The value of Z represents the slope of the species-area relationship on a logarithmic scale and indicates how rapidly species richness increases with area.
  • Z = 0.1 to 0.2: This is a typical range for small, relatively uniform areas. It suggests a slower rate of increase in species richness with area.
  • Z = 0.6 to 1.2: This steeper slope is characteristic of very large areas, like entire continents. The rapid increase in species richness is due to the greater variety of habitats over a larger geographical area.
  • Z > 1.2: A very steep slope is often found in island ecosystems, where isolation leads to unique evolutionary paths and a high degree of endemism, causing species richness to increase rapidly with area.

Additional Mathematical Examples:

1. Calculate Species Richness (S):

   • Question: Calculate the species richness (S) for a place having an area of 3400 sq. km, a Y-intercept (C) of 20, and a regression coefficient (Z) of 1.
   • Solution:
     • Given: A = 3400, C = 20, Z = 1
     • Formula: S = CA^Z
     • Calculation: S = 20 * (3400)^1 = 68000
     • Answer: The species richness (S) is 68,000.

2. Calculate Species Richness (S) with a smaller Z:

   • Question: Find the number of species (S) in a 1000 sq. km forest area if the Y-intercept (C) is 15 and the regression coefficient (Z) is 0.2.
   • Solution:
     • Given: A = 1000, C = 15, Z = 0.2
     • Formula: S = CA^Z
     • Calculation: S = 15 * (1000)^0.2 = 15 * 3.98 ≈ 59.7
     • Answer: The species richness (S) is approximately 60.

3. Calculate the Y-intercept (C):

   • Question: A survey of a 500 sq. km area reveals 120 species of birds. If the regression coefficient (Z) for birds in that region is 0.8, what is the Y-intercept (C)?
   • Solution:
     • Given: S = 120, A = 500, Z = 0.8
     • Formula: C = S / (A^Z)
     • Calculation: C = 120 / (500)^0.8 = 120 / 148.6 ≈ 0.807
     • Answer: The Y-intercept (C) is approximately 0.807.

4. Calculate the Regression Coefficient (Z):

   • Question: An ecologist found 80 species of ferns in a 200 sq. km plot. The Y-intercept (C) for this type of vegetation is 10. What is the regression coefficient (Z)?
   • Solution:
     • Given: S = 80, A = 200, C = 10
     • Formula: Z = (log S - log C) / log A
     • Calculation: Z = (log(80) - log(10)) / log(200) = (1.903 - 1) / 2.301 = 0.903 / 2.301 ≈ 0.392
     • Answer: The regression coefficient (Z) is approximately 0.392.

5. Using the Logarithmic Equation:

   • Question: For a particular group of insects, the species-area relationship is given by log S = log(5) + 0.7 log A. How many species would you expect in an area of 10,000 sq. km?
   • Solution:
     • Given: C = 5, Z = 0.7, A = 10,000
     • Formula: log S = log C + Z log A
     • Calculation: log S = log(5) + 0.7 * log(10000) = 0.699 + 0.7 * 4 = 3.499. S = 10^3.499 ≈ 3155
     • Answer: Approximately 3,155 species are expected.

6. Effect of Area Loss on Species Richness:

   • Question: If the species-area relationship for a continent is S = 2.5 * A^0.9, and 50% of the forest area is lost, what is the percentage loss in species richness?
   • Solution:
     • Let the initial area be A1. The new area A2 = 0.5 * A1.
     • S1 = 2.5 * (A1)^0.9
     • S2 = 2.5 * (0.5 * A1)^0.9 = 2.5 * (0.5^0.9) * (A1)^0.9 = (0.5^0.9) * S1
     • Calculation: 0.5^0.9 ≈ 0.536. So, S2 ≈ 0.536 * S1.
     • Percentage loss = ((S1 - S2) / S1) * 100 = ((S1 - 0.536*S1) / S1) * 100 = 0.464 * 100 = 46.4%
     • Answer: A 50% loss in area results in approximately a 46.4% loss of species.

7. Predicting Species on an Island:

   • Question: An island of 50 sq. km has a Z value of 1.3 and a C value of 3. How many species are predicted to be on this island?
   • Solution:
     • Given: A = 50, C = 3, Z = 1.3
     • Formula: S = CA^Z
     • Calculation: S = 3 * (50)^1.3 = 3 * 153.0 ≈ 459
     • Answer: Approximately 459 species are predicted.

8. Calculating Species Loss from Habitat Destruction:

   • Question: A region with S = 40 * A^0.15 is being considered for a dam that will flood 1,000 sq. km of the original 4,000 sq. km area. How many species are expected to be lost?
   • Solution:
     • Initial Area (A1) = 4000. Final Area (A2) = 3000.
     • Initial Species (S1) = 40 * (4000)^0.15 = 40 * 3.31 ≈ 132
     • Final Species (S2) = 40 * (3000)^0.15 = 40 * 3.16 ≈ 126
     • Species Lost = S1 - S2 = 132 - 126 = 6
     • Answer: Approximately 6 species are expected to be lost.

9. Shannon Diversity Index (H):

   • Question: A community has three species with populations: Species A: 50, Species B: 30, Species C: 20. Calculate the Shannon Diversity Index (H).
   • Solution:
     • Total individuals (N) = 100. Proportions (pi): pA = 0.5, pB = 0.3, pC = 0.2.
     • Formula: H = -Σ(pi * ln(pi))
     • Calculation: H = -[(0.5 * ln(0.5)) + (0.3 * ln(0.3)) + (0.2 * ln(0.2))]
     • H = -[(-0.347) + (-0.361) + (-0.322)] = -[-1.03] = 1.03
     • Answer: The Shannon Diversity Index (H) is 1.03.

10. Comparing Diversity with Shannon Index:

    • Question: Compare the diversity of two communities. Community 1: 95 individuals of species A, 5 of species B. Community 2: 50 individuals of species A, 50 of species B.
    • Solution:
      • Community 1: N=100. pA=0.95, pB=0.05. H1 = -[(0.95*ln(0.95)) + (0.05*ln(0.05))] = -[(-0.049) + (-0.150)] = 0.199
      • Community 2: N=100. pA=0.5, pB=0.5. H2 = -[(0.5*ln(0.5)) + (0.5*ln(0.5))] = -[(-0.347) + (-0.347)] = 0.694
      • Answer: Community 2 (H=0.694) is more diverse than Community 1 (H=0.199) because it has greater species evenness.

Importance: Utilitarian, Ethical, and the Rivet Popper Hypothesis

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.

3. Rivet Popper Hypothesis:

   • Proposed by Stanford ecologist Paul Ehrlich.
   • This analogy compares an ecosystem to an airplane and species to the rivets holding it together.
   • The Hypothesis:
     • If passengers on a plane start popping rivets (representing species extinction), the plane (ecosystem) may not be affected initially.
     • However, as more rivets are removed, the plane becomes progressively weaker and eventually crashes.
     • The loss of a "key" rivet (a keystone species) on the wing could lead to a catastrophic failure, even if other rivets are intact.
   • Conclusion: This hypothesis highlights that every species plays a role in the ecosystem's health, and the continuous loss of species can lead to a sudden and dramatic collapse of the entire system.

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 and Co-evolution:

   • Co-extinction: 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.
   • Co-evolution: The process where two or more species reciprocally influence each other's evolution.
     • This is a "reciprocal evolutionary change" in interacting species, driven by natural selection.
     • Example: Ophrys and Bees (Sexual Deceit):
       • The Mediterranean orchid Ophrys uses sexual deceit to ensure pollination by a specific species of bee.
       • One of its petals has evolved to resemble the female of the bee in size, color, and markings.
       • The male bee, mistaking the petal for a female, attempts to "pseudocopulate" with it.
       • During this process, the bee is dusted with pollen. When it visits another Ophrys flower, it transfers the pollen, thus pollinating the flower.
       • This highly specific relationship means that if the bee species were to become extinct, the Ophrys orchid would also face extinction.

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 a resource (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).