Unit8

8.1 Introduction

  • Biodiversity Overview: Since life began 3.5 billion years ago, approximately 500 million kinds of organisms, including plants, animals, and microorganisms, have inhabited Earth.

  • Species Count: The UN Convention on Biological Diversity estimates around 13 million species still exist, with only 1.7 million identified. Many regions, particularly tropical rainforests, remain biologically unexplored.

  • Extinction Events: Nature experiences periodic mass extinctions. Five major events have been documented, often linked to catastrophic natural occurrences. Currently, human activities have escalated extinction rates, suggesting an impending sixth extinction.

8.2 Causes of Biodiversity Loss

Key Influences

  • Human-related factors such as habitat destruction, overexploitation, and global climate change.

  • The main causes include:

    • Habitat Loss: Alteration or destruction of habitats directly threatens species survival.

    • Human-Wildlife Conflict: Overutilization of certain species leads to declines.

    • Selective Species Destruction: Targeted eradication of certain species can destabilize ecosystems.

8.2.1 Habitat Loss

  • Definition: A habitat is the natural environment where species find food and shelter. Loss of habitat leads to forced adaptation, migration, or extinction.

  • Effects of Habitat Loss: Organisms may die, compete with local populations, or be pushed into unsuitable environments.

  • Fragile Habitats: Coral reefs, oceanic islands, and mountain tops are considered particularly vulnerable to extinction.

Case Study: Coral Reefs

  • Vulnerability: Sensitive to temperature changes and pollution.

  • Statistics: By 1992, 10% of coral reefs were damaged; another 30% were expected to decline within 20 years.

8.3 Human-Wildlife Conflict

  • Participants in nature resource use often exceed sustainable levels, such as overfishing and logging, threatening various species.

  • Commercial and Sport Hunting: Increased hunting pressures on large mammals such as elephants and rhinos, significantly impacted by the black market.

8.3.1 Selective Species Destruction

  • Example: The extinction of the Passenger pigeon, once numerous, due to overhunting.

  • Consequences: Highlighting the unintentional ecological impacts of eliminating individual species.

8.3.2 Domestication of Selective Species

  • Impacts: Loss of characteristics that allow wild survival; example: domesticated corn that cannot survive without human assistance.

8.3.3 Use of Pesticides

  • Harmful to pollinators and aquatic life; historical use of DDT as a prime example affecting bird populations.

8.3.4 Global Climate Change

  • Increased CO2 levels from fossil fuel combustion are expected to raise global temperatures and lead to extreme weather events impacting biodiversity.

8.4 Poaching of Wildlife

  • Unsustainable hunting practices, commercial hunting, and illegal wildlife trade threaten numerous species, particularly in the case of rhinos and elephants due to their valuable parts (horns and tusks).

8.5 Biological Invasion

  • Invasive Species: Non-native species introduced to new environments can disrupt ecosystems, often due to the lack of natural predators.

  • Examples include:

    • Water Hyacinth: Originating from Brazil, a nuisance plant damaging aquatic ecosystems.

    • Parthenium Hysterophorus: Introduced with food grains; causes allergies and proliferates uncontrollably.

8.6 Need for Conserving Biodiversity

  • Importance: Biodiversity supports ecosystems, provides resources, and holds ethical significance for future generations. Diverse ecosystems offer resilience against environmental changes.

8.7 Conservation of Biodiversity

In-situ Conservation

  • Focused on protecting existing species in their natural habitats, ensuring viable populations and maintaining ecological processes.

Ex-situ Conservation

  • Involves species conservation outside their natural habitats, such as botanical gardens and zoos.

  • Methods include:

    • Captive Breeding: Breeding endangered species in controlled environments.

    • Seed Banks and Tissue Culture: Storing genetic material for potential future restoration efforts.

8.8 Nature Reserves

  • Serve as critical zones for biodiversity preservation by balancing human needs with conservation efforts.

Biosphere Reserves

  • Established to foster sustainable use and conservation, enabling effective management of ecosystems.

8.9 Summary

  • Biodiversity loss is a result of multiple human activities and requires urgent conservation measures.

  • Key conservation strategies involve both in-situ and ex-situ methods, supported by protected areas, such as national parks and wildlife reserves.

8.10 and 8.11 Terminal Questions and Answers

  • Address the significance of biodiversity, methods of conservation, and the consequences of loss.

Further Readings

  • Suggested resources for deepening understanding of biodiversity and conservation practices.