Biodiversity | Environment for UPSC CSE PDF Download

What Is Biodiversity?

Biodiversity is the variety and variability of life on Earth. It is commonly measured at three levels: genetic diversity, species diversity and ecosystem diversity. Terrestrial biodiversity is generally greater near the equator because warm climates and high primary productivity support more species. Conservation and sustainable use of biodiversity are fundamental to ecologically sustainable development. Biodiversity underpins human livelihoods, culture and wellbeing, and provides resources and services on which families, communities and nations depend.

1. Levels of Biodiversity

Biodiversity is usually considered at three interrelated levels:

Genetic diversity

• Definition: Variation in genes within a particular species.
• Importance: Genetic diversity allows populations to adapt to changing environments and disease pressures; it helps ensure long-term survival of species.
• Examples: Different varieties of crops, breeds of livestock, and the variation in colour, shape and size seen among butterflies, roses, parakeets and corals.
• Application: Conservation of genetic resources is essential for plant and animal breeding, and for maintaining resilience in agriculture and natural populations.

Species diversity

• Definition: The variety of living organisms (species) in a given area.
• Notes: Species are distinct genetically and do not usually interbreed in nature; closely related species share many hereditary traits (for example, about 98.4% of human and chimpanzee genes are similar).
• Measurement concept: Species diversity is influenced both by the number of species and by their relative abundances.
• Example: A forest with many tree and understorey species has high species diversity compared with a plantation of a single tree species.

Ecosystem (or community) diversity

• Definition: The variety of habitats, communities and ecological processes within a region. A habitat is the place where a species lives and is defined by climate, vegetation, soil and geography.
• Examples of ecosystems: Coral reefs, grasslands, wetlands, deserts, mangroves and tropical rainforests.
• Interaction: Changes in climate alter vegetation and habitats; species adapted to particular environments will become dominant where conditions suit them. Ecosystem diversity therefore influences species diversity and community composition.

2. Measurement of Biodiversity

Biodiversity measurement commonly uses two major components: species richness and species evenness. Quantitative indices provide standard ways to compare diversity across sites.

Species richness

• Definition: The number of species present in a community or sample.
• Scale-based concepts:
  • Alpha diversity - diversity within a particular site or ecosystem, usually expressed as the number of species (species richness).
  • Beta diversity - comparison of diversity between ecosystems; often measured as the change in species composition from one habitat to another.
  • Gamma diversity - overall diversity for different ecosystems within a larger region.

Species evenness

• Definition: The relative abundance of species in a site. Low evenness means a few species dominate; high evenness means abundances are more similar across species.

Common diversity indices (brief)

• Shannon-Wiener index: H' = -Σ p_i ln p_i, where p_i is the proportion of individuals belonging to species i; it combines richness and evenness.
• Simpson's index: D = Σ p_i²; expresses the probability that two individuals randomly selected from a sample belong to the same species (often reported as 1 - D to indicate diversity).
• Use: Engineers and ecologists use these indices when planning environmental impact assessments, restoration projects and monitoring programmes.

3. Biodiversity and Food Webs

• The basic chemical building blocks of plants, animals and humans include carbon, oxygen, nitrogen and hydrogen.
• These elements occur in air, water and soil. Green plants (producers) convert sunlight, water and carbon dioxide into organic matter by photosynthesis and take up some nutrients such as nitrogen from the soil.
• Animals and humans (consumers) obtain energy by eating plants or other animals. The links that transfer energy and nutrients among producers and consumers form food chains and, more realistically, complex food webs.
• Food chains and webs vary in complexity with the environment. For example, grass → grasshopper → frog → snake is a simple chain found in many habitats.
• Every species has a role in the network; removal or extinction of species can break links in the web and cause cascading effects on other species, including human communities.

4. Services Provided by Biodiversity

Biodiversity supplies a wide range of services essential for human survival and for the functioning of natural systems. These services are often grouped into four categories used in ecosystem assessments.

• Provisioning services: Food; fresh water; medicinal resources and pharmaceutical compounds; wood, fibre and other raw materials; genetic resources and breeding stock.
• Regulating services: Climate regulation; flood and erosion control; water purification and protection of water resources; pollination of crops; breakdown and absorption of pollution; pest and disease regulation.
• Supporting services: Soil formation and protection; nutrient storage and recycling; primary production that underpins food webs; maintenance of ecosystem structure and processes.
• Cultural services: Recreation and tourism; research and education; spiritual, aesthetic and cultural values that communities derive from nature.

5. Causes of Biodiversity Loss

Biodiversity loss happens when species die out or when habitats essential for their survival are altered or destroyed. Habitat destruction is the most common and pervasive cause, often linked to development and land-use change.

Natural causes

• Floods
• Earthquakes
• Landslides
• Interspecific rivalry and natural competition
• Lack of pollination and natural diseases

Human (man-made) causes

• Habitat destruction and fragmentation (for settlements, industry, infrastructure)
• Uncontrolled commercial exploitation of species
• Hunting and poaching
• Conversion of biodiverse sites for agriculture or urban use
• Pollution of air, water and soil
• Drainage and filling of wetlands
• Destruction of coastal habitats such as mangroves

6. Biodiversity Conservation

Conservation aims to maintain ecological diversity, preserve ecosystem services and ensure continuity of food chains and natural processes. Conservation measures include legal protection, habitat management, restoration, species recovery programmes and sustainable use policies.

Modes of conservation

Ex-situ conservation

• Definition: Conservation of species outside their natural habitats.
• Examples and practices: Zoological parks, botanical gardens, seed banks, captive breeding programmes, and rearing centres.
• Reintroduction: Reintroducing plants or animals into habitats from which they have become locally extinct is a form of ex-situ conservation. For example, the Gangetic gharial has been reintroduced in parts of Uttar Pradesh, Madhya Pradesh and Rajasthan.
• Role: Ex-situ conservation preserves genetic material, supports research, and provides stock for restoration and recovery.

In-situ conservation

• Definition: Protection of species within their natural habitats.
• Typical protected areas: National parks, wildlife sanctuaries, biosphere reserves, reserved forests and protected forests.
• Role: In-situ conservation maintains ecological processes and supports natural evolution and adaptation.

Constraints in biodiversity conservation

• Low priority for conservation of living resources in some development planning.
• Economic exploitation of natural resources without sustainable safeguards.
• Insufficient local knowledge and awareness about species and ecosystems.
• Unplanned urbanisation and uncontrolled industrialisation leading to habitat loss and pollution.

7. Botanical Gardens and Zoos

Botanical gardens

Definition: Scientifically planned collections of living plants (trees, shrubs, herbs, climbers and others) from different regions of the world.

• Purposes: Study of taxonomy and plant growth; introduction and acclimatisation of exotic plants; germplasm conservation; development of new hybrids; conservation of rare and threatened species.
• Role in ex-situ conservation: Botanical gardens hold seed banks, living collections and research facilities that support restoration and education.

Zoos

• Definition (legal context): A zoo is an establishment where captive animals are kept for public exhibition; the legal definition in many contexts includes rescue centres and excludes licensed dealers in captive animals.
• Evolution of role: Historically for entertainment; modern zoos function as centres for conservation, captive breeding, research and environmental education.
• Contribution: Zoos help save individual animals, support species recovery through captive breeding and engage the public in conservation awareness.

8. The Red Data Book

• Species considered threatened are listed in compilations produced by agencies and organisations; the most widely cited resource is the Red Data Book issued by the International Union for Conservation of Nature (IUCN), headquartered in Morges, Switzerland.
• The Red Data Book is a continually updated collection of information on the conservation status of many species. The IUCN's Special Survival Commission first issued the Red Data Book in 1966 to guide preservation and management efforts.
• Colour-coded pages are used to indicate urgency: for example, pink pages in some versions list critically endangered species, while green pages indicate species that were once threatened but have recovered. The content is updated as species' statuses change.
• The Red Data Book typically contains more extensive information for mammals and birds, but also covers many other taxa that face extinction.

9. IUCN Categories of Threat and Classification

The IUCN Red List classifies taxa according to their global extinction risk. The main categories are described below.

Extinct (EX)

• Definition: A taxon is Extinct when there is no reasonable doubt that the last individual has died. This designation follows exhaustive surveys in known and expected habitats at appropriate times.

Extinct in the Wild (EW)

• Definition: A taxon is Extinct in the Wild when it survives only in cultivation, in captivity, or as a naturalised population well outside its past range. This status follows exhaustive surveys in historical ranges.

Critically Endangered (CR)

• Definition: A taxon is Critically Endangered when the best available evidence indicates it meets any of the Critically Endangered criteria and thus faces an extremely high risk of extinction in the wild.
• Criteria examples: Reduction in population (greater than 90% over the last 10 years), population size fewer than 50 mature individuals, or quantitative analysis showing a ≥50% probability of extinction in the wild within 10 years.

Endangered (EN)

• Definition: A taxon is Endangered when it meets any Endangered criteria and is facing a very high risk of extinction in the wild.
• Criteria examples: Reduction in population (around 70% over the last 10 years), population size fewer than 250 mature individuals, or quantitative analysis showing a ≥20% probability of extinction in the wild within 20 years.

Vulnerable (VU)

• Definition: A taxon is Vulnerable when it meets the Vulnerable criteria and is considered to be facing a high risk of extinction in the wild.
• Criteria examples: Reduction in population (greater than 50% over the last 10 years), population size estimated to be fewer than 10,000 mature individuals, or a ≥10% probability of extinction in the wild within 100 years.

Near Threatened (NT)

• Definition: A taxon is Near Threatened when it is close to qualifying for a threatened category or is likely to qualify in the near future.

Least Concern (LC)

• Definition: A taxon is Least Concern when it does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened; widespread and abundant taxa are included in this category.

Data Deficient (DD)

• Definition: A taxon is Data Deficient when there is inadequate information to assess its risk of extinction. This does not imply low risk; it highlights the need for more research on distribution and abundance.

Not Evaluated (NE)

• Definition: A taxon is Not Evaluated when it has not yet been assessed against the IUCN criteria.

10. Example: Pit Vipers

Pit vipers possess a specialised sensory organ known as a pit located between the eye and the nostril. This organ detects infrared radiation (body heat) from other animals, creating a thermal "picture" of prey. Pit vipers often strike and envenomate prey and then release it; the snake follows the wounded animal using heat sensing until it can safely consume it. Many pit vipers hunt at night, when the contrast between the prey's body heat and the surrounding air is greatest. All rattlesnakes belong to the pit viper group.

11. Practical Measures and Policy Instruments

• Protected area networks: national parks, wildlife sanctuaries and biosphere reserves to conserve habitats and species.
• Legal protection and regulation: wildlife protection laws, trade controls and national policies on forests and wetlands.
• Community-based conservation and sustainable use: involving local people in management and benefit-sharing.
• Restoration ecology: active restoration of degraded habitats, reforestation, wetland rehabilitation and species reintroduction where feasible.
• Ex-situ facilities: seed banks, botanical gardens and captive-breeding centres for banking genetic resources and supporting recovery.
• Monitoring and research: regular biodiversity surveys, long-term ecological monitoring and updating of conservation status (for example, via the IUCN Red List).

Conclusion

Biodiversity is a multi-level concept essential for ecosystem function, human livelihoods and sustainable development. Measuring biodiversity requires understanding species richness and evenness and using standard indices. Threats arise from both natural events and human activities, with habitat destruction and exploitation being primary drivers. Conservation combines in-situ and ex-situ approaches, legal protection, scientific research and community engagement. For engineers and technologists, integrating biodiversity knowledge into planning, design and monitoring is central to building resilient and sustainable systems.