Biodiversity

Chapter 5: Biodiversity

Definition of Biodiversity

  • Biodiversity: The sum total of all the variety and variability of life in a defined area.

  • Coined to emphasize complex variations within and among organisms at different levels.

  • Biological Diversity (UN Earth Summit Definition, 1992): Variability among living organisms from terrestrial, marine and aquatic ecosystems, including diversity within species, between species, and of ecosystems.

Levels of Biodiversity

5.1 Types

  1. Genetic Diversity

    • Variation in genetic composition within or among species.

    • Key for adaptability and natural selection; basis of speciation.

  2. Species Diversity

    • Defined by the variety of species and their interactions.

    • Includes species richness (number of species) and species evenness (distribution of individuals among species).

    • Taxonomic Diversity: The genetic relationship among species.

  3. Ecosystem Diversity

    • Encompasses all species and abiotic factors in a region (e.g., temperature, soil).

    • Reflects the number of niches, trophic levels, and ecological processes.

Gradients and Magnitude of Biodiversity

5.2 Gradients

  • Latitudinal Gradient: Biodiversity increases from the poles to the equator.

    • Tropics harbor more species than temperate or polar areas.

    • Example: Colombia (1,400 bird species) vs. New York (105 species).

  • Altitudinal Variation: Species diversity decreases with altitude.

5.3 Magnitude

  • Current estimates of species range from 2 to 10 million; 1.6 million described.

  • Over 70% of recorded species are animals, with insects being the most diverse group.

  • Biodiversity Hotspots: Areas with high endemism and loss of habitat (40% of plant species in hotspots).

Uses of Biodiversity

5.4 Ecosystem Services

  • Biodiversity maintains ecosystem services such as:

    • Gaseous composition of the atmosphere

    • Natural pest control and pollination

    • Water purification and nutrient cycling

5.5 Human Economic Value

  • Source of food (major crops) and medicinal compounds.

  • Wild biodiversity can buffer against agricultural failures.

Threats to Biodiversity

5.6 Major Threats

  1. Habitat Loss and Fragmentation: Destruction of natural habitats leading to species displacement.

  2. Introduction of Invasive Species: Non-native species can outcompete and cause harm to local ecosystems.

  3. Overexploitation: Excessive harvesting of species can lead to population declines.

  4. Climate Change and Pollution: Alters habitats and affects biodiversity.

Extinction of Species

5.7 Extinction Processes

  • Extinction is a natural process but currently exaggerated due to human activities.

  • The biodiversity crisis refers to the current high extinction rates compared to natural background rates.

5.8 Mass Extinctions

  • Notable mass extinctions occurred at the end of the Permian and Cretaceous periods.

  • Current extinction rates are significantly greater than background rates.

Conservation of Biodiversity

5.9 Global and National Efforts

  • Numerous international treaties (e.g., CBD, CITES) exist to protect biodiversity.

  • Protected Areas: Include national parks, wildlife sanctuaries, biosphere reserves to preserve habitats and species.

Biodiversity Conservation Strategies

5.10 In-Situ and Ex-Situ Conservation

  • In-Situ: Conservation within natural habitats (e.g., national parks).

  • Ex-Situ: Preservation outside natural habitats (e.g., seed banks, zoos).

Types of Protected Areas in India

  • National Parks, Wildlife sanctuaries, Marine protected areas, and Biosphere reserves.

  • Biosphere Reserves: Areas designed to conserve ecosystems while allowing sustainable development and research.