Biodiversity and Conservation

BIODIVERSITY AND CONSERVATION

13.1 BIODIVERSITY

**Biodiversity** (biological diversity) is a term popularized by sociobiologist Edward Wilson to describe the combined diversity at all levels of biological organization, ranging from macromolecules within cells to biomes. The term reflects the enormous variety of life forms on Earth and the genetic variation within species across different geographical regions.

Three Levels of Biodiversity

**1. Genetic Diversity**

Refers to variation in genetic composition within a single species across its distributional range

Different populations of the same species show variations in traits, enzyme production, and phenotypic characteristics

**Example:** Rauwolfia vomitoria (medicinal plant) growing in different Himalayan ranges shows variations in potency and concentration of reserpine (active chemical)

**Indian examples:** India possesses more than 50,000 genetically different strains of rice and 1,000 varieties of mango, demonstrating rich genetic diversity

This diversity is crucial for crop improvement and adaptation to environmental changes

**2. Species Diversity**

Refers to the variety and number of different species within a specific region or ecosystem

Measured by counting the total number of distinct species present

**Example:** Western Ghats have greater amphibian species diversity compared to Eastern Ghats

Species diversity is influenced by geographical location, climate, and ecological conditions

**3. Ecological Diversity**

Refers to the variety of different ecosystems and biomes within a geographical region

**Example:** India demonstrates high ecological diversity with deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows

**Comparison:** India has greater ecosystem diversity than Scandinavian countries like Norway due to varied geographical features

Ecological diversity supports multiple habitats for different organisms

Global Species Inventory

**Current Knowledge of Species on Earth:**

According to IUCN (2004), slightly more than **1.5 million** plant and animal species have been discovered and described

Conservative estimate by Robert May places global species diversity at approximately **7 million species**

Extreme estimates range from 20-50 million species

A significant proportion of undiscovered species exists in tropical regions, making accurate global estimates difficult

Biologists use species richness comparisons between temperate and tropical regions to extrapolate total species numbers

**Distribution of Known Species:**

More than 70% of all recorded species are animals

Plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22% of total species

Insects represent more than 70% of all animal species (meaning 7 out of every 10 animals on Earth are insects)

Fungi species number exceeds the combined total of fishes, amphibians, reptiles, and mammals

Prokaryotes are largely unaccounted for in these estimates; their diversity could run into millions if molecular/biochemical criteria are used for species delineation

**Biodiversity of India:**

India occupies only 2.4% of Earth's land area but holds 8.1% of global species diversity

Status as one of the **12 mega-diversity countries of the world**

Nearly 45,000 plant species and twice as many animal species have been recorded from India

If May's global estimate of 22% discovered species is applied to India, approximately **100,000+ plant species** and **300,000+ animal species** await discovery and description

Presents both tremendous opportunity and urgent conservation challenge as many species face extinction before discovery

13.1.2 Patterns of Biodiversity

**Latitudinal Gradients**

The diversity of plants and animals is not uniformly distributed globally; instead, it shows a distinctive pattern known as latitudinal gradient.

**Key Pattern:** Species diversity decreases as one moves away from the equator toward the poles.

**Scientific Observation:**

Tropics (latitudinal range 23.5° N to 23.5° S) harbor significantly more species than temperate or polar regions

**Comparative examples:**

Colombia (near equator): ~1,400 bird species

New York (41° N): 105 bird species

Greenland (71° N): 56 bird species

India (largely tropical): >1,200 bird species

Tropical forests contain up to 10 times more vascular plant species per unit area compared to temperate forests

**Amazon Rainforest Biodiversity (Greatest on Earth):**

40,000+ plant species

3,000 fish species

1,300 bird species

427 mammal species

427 amphibian species

378 reptile species

125,000+ invertebrate species

Estimated 2 million insect species awaiting discovery and naming

**Hypotheses Explaining Greater Tropical Diversity:**

1. **Evolutionary Time Hypothesis:** Tropical regions remained relatively undisturbed for millions of years without glaciations (unlike temperate regions subjected to frequent ice ages), providing extended evolutionary time for species diversification and speciation

2. **Environmental Stability Hypothesis:** Tropical environments are less seasonal, relatively constant, and predictable compared to temperate zones. This environmental stability promotes niche specialization and ecological resource partitioning, leading to greater species diversity

3. **Solar Energy Hypothesis:** Greater solar energy available in tropical regions contributes to higher primary productivity, which indirectly supports higher consumer diversity and overall species richness

**Species-Area Relationship**

German naturalist Alexander von Humboldt observed during his South American explorations that **species richness increases with increasing explored area** within a region, up to a limiting point. This relationship forms a rectangular hyperbola.

**Mathematical Expression:**

On logarithmic scale, the relationship is described as:

**log S = log C + Z log A**

Where:

**S** = Species richness (number of species)

**A** = Area explored

**Z** = Slope of regression line (regression coefficient)

**C** = Y-intercept

**Important Values:**

For regional areas (small to medium scales), **Z value ranges between 0.1 to 0.2** across all taxonomic groups and regions (plants in Britain, birds in California, mollusks in New York State)

For very large continental areas, **Z value ranges between 0.6 to 1.2** (steeper slope)

Example: For frugivorous (fruit-eating) birds and mammals in tropical forests of different continents, Z = 1.15

**Interpretation:** Steeper slopes for continental areas indicate that species diversity increases much more rapidly with area at larger geographical scales, suggesting that continental species pools are more differentiated from each other.

13.1.3 Importance of Species Diversity to Ecosystem Functioning

**Central Question:** Does the number of species in a community really matter to ecosystem functioning?

**Historical Ecological Perspective:**

For decades, ecologists hypothesized that communities with more species are generally more stable than species-poor communities

**Stability Definition:** A stable community should (a) not show excessive year-to-year variation in productivity, (b) be resistant or resilient to occasional disturbances (natural or human-induced), and (c) resist invasions by alien species

**Evidence from Tilman's Long-term Ecosystem Experiments:**

David Tilman conducted extended outdoor plot experiments demonstrating:

Plots with greater species richness showed **less year-to-year variation in total biomass**

Increased species diversity contributed to **higher ecosystem productivity**

These findings support the relationship between biodiversity and ecosystem stability

**Importance of Biodiversity to Human Survival:**

Rich biodiversity is essential for ecosystem health

Biodiversity is imperative for the very survival of human race on this planet

Current rates of species extinction pose serious risks to ecosystem functioning

**"Rivet Popper Hypothesis" (Paul Ehrlich, Stanford Ecologist):**

Analogy comparing ecosystem to an airplane:

**Ecosystem = Airplane** (biological system)

**Species = Rivets** (structural components)

When passengers remove rivets (species extinction), initial impact on flight safety (ecosystem function) may be minimal

However, as more rivets are removed (more species lost), the airplane becomes dangerously weak over time

**Critical distinction:** Loss of wing rivets (key species driving major ecosystem functions) poses greater threat than loss of rivets from seats or windows (less critical species)

**Implication:** Not all species contribute equally to ecosystem functioning; keystone species loss has disproportionate impacts

13.1.4 Loss of Biodiversity

**Current Extinction Crisis:**

While speciation rates are minimal, species are continuously being lost at alarming rates driven by human activities.

**Recent Extinction Examples:**

Dodo (Mauritius)

Quagga (Africa)

Thylacine (Australia)

Steller's Sea Cow (Russia)

Three tiger subspecies (Bali, Javan, Caspian)

Historical example: Colonization of tropical Pacific Islands led to extinction of >2,000 native bird species

**IUCN Red List Data (2004):**

**784 species** documented as extinct in last 500 years

338 vertebrates

359 invertebrates

87 plants

27 species disappeared in the last 20 years alone

**Current Extinction Threats:**

More than **15,500 species worldwide** face threat of extinction

12% of all bird species threatened

23% of all mammal species threatened

32% of all amphibian species threatened

31% of all gymnosperm species threatened

Amphibians appear particularly vulnerable to extinction

**"Sixth Extinction" vs. Previous Mass Extinctions:**

Fossil records reveal five previous episodes of mass extinction during Earth's history (>3 billion years since life's origin and diversification).

**Key Difference - Extinction Rates:**

Pre-human extinction rates: Natural background rate

Current extinction rates: **100 to 1,000 times faster** than pre-human times

**Cause:** Human activities directly responsible for accelerated rates

**Warning:** If present trends continue, nearly **half of all species on Earth might be extinct within next 100 years**

**Ecological Consequences of Biodiversity Loss:**

In-situ loss of biodiversity in a region leads to:

1. **Decline in plant production** (reduced primary productivity)

2. **Lowered resistance to environmental perturbations** (decreased resilience to drought and environmental stress)

3. **Increased variability in ecosystem processes** including plant productivity, water use, and pest/disease cycles

Causes of Biodiversity Loss: "The Evil Quartet"

Four major factors driving species extinction (collectively termed "The Evil Quartet"):

**1. Habitat Loss and Fragmentation**

**Definition:** Physical destruction, degradation, and breaking up of habitats into smaller, isolated fragments.

**Mechanisms of Impact:**

Most important single cause driving animals and plants to extinction

Habitat loss reduces available living space for species

Fragmentation prevents gene flow between isolated populations

Mammals and birds requiring large territories are severely affected

Migratory animals cannot complete migration routes

Leads to population decline and local extinction

**Dramatic Examples:**

Tropical rainforests originally covered **>14% of Earth's land surface**, now reduced to **~6%**

Amazon rainforest ("lungs of the planet") cleared for soybean cultivation and grasslands for cattle ranching

**Rate of loss:** 1,000 hectares of rainforest lost during reading of one chapter

Habitat degradation by pollution also threatens species survival

**2. Over-exploitation**

**Definition:** Excessive harvesting and use of natural resources beyond sustainable levels.

**Process:**

Humans have traditionally depended on nature for food and shelter (legitimate use)

When "need" converts to "greed," overexploitation occurs

Harvesting rates exceed reproductive capacity of species populations

**Historical and Current Examples:**

**Past extinctions:** Steller's sea cow, passenger pigeon

**Current threats:** Many marine fish populations globally are over-harvested, endangering commercially important species

Unsustainable hunting and fishing practices deplete wild populations

**3. Alien Species Invasions**

**Definition:** Introduction of non-native species that become invasive and outcompete or prey upon native species.

**Mechanisms:**

Alien species introduced unintentionally (in cargo) or deliberately (for agriculture, aquaculture, ornamental purposes)

Invasive species lack natural predators/competitors in new environment

Outcompete native species for resources or prey on them

Disrupt ecosystem balance and food chains

**Major Examples:**

**Nile perch introduction to Lake Victoria (East Africa):** Caused extinction of ecologically unique assemblage of >200 cichlid fish species

**Carrot grass (Parthenium):** Invasive weed threatening native vegetation in India

**Lantana:** Invasive plant degrading native ecosystems

**Water hyacinth (Eichhornia):** Aquatic invasive species choking water bodies

**African catfish (Clarias gariepinus):** Recently introduced to India for aquaculture; threatens indigenous catfish species

**4. Co-extinctions**

**Definition:** Extinction of a species triggers obligatory extinction of dependent species.

**Mechanism:**

When a species becomes extinct, its dependent plant and animal species also face extinction

Based on ecological relationships like predator-prey, host-parasite, mutualism

**Examples:**

**Host-parasite relationship:** Extinction of a host fish species leads to extinction of its unique parasite assemblage

**Plant-pollinator mutualism:** Extinction of a specialized pollinator leads to extinction of coevolved plant species (and vice versa)

Extinction cascade effects can remove multiple species from ecosystem

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13.2 BIODIVERSITY CONSERVATION

**Biodiversity conservation** encompasses strategies, policies, and practices aimed at protecting species, genetic diversity, and ecosystems from further loss and degradation.

13.2.1 Why Should We Conserve Biodiversity?

Multiple compelling reasons exist for biodiversity conservation, grouped into three conceptual categories:

**1. Narrowly Utilitarian Arguments**

**Basis:** Direct economic benefits derived from biological resources

**Examples:**

**Food sources:** Cereals, pulses, fruits, nuts

**Fuel:** Firewood and biomass energy

**Fiber and construction materials:** Wood, bamboo, cork

**Industrial products:** Tannins, lubricants, dyes, resins, perfumes

**Medicinal compounds:** Pharmaceutically active substances

**Statistical evidence:** More than 25% of drugs currently sold worldwide are plant-derived

**Traditional medicine:** 25,000 plant species contribute to traditional medicines used by native peoples globally

**Bioprospecting potential:** Tropical rainforests contain numerous undiscovered medicinal plants; nations with high biodiversity can gain substantial economic returns through bioprospecting (exploring molecular, genetic, and species-level diversity for economically valuable products)

**2. Broadly Utilitarian Arguments**

**Basis:** Biodiversity's critical role in ecosystem services provided by nature

**Ecosystem Services Provided by Biodiversity:**

**Oxygen production:** Amazon forest produces approximately 20% of total atmospheric oxygen through photosynthesis

**Economic valuation challenge:** How does one place economic value on atmospheric oxygen? (Consider hospital oxygen cylinder costs for perspective)

**Pollination services:** Ecosystems provide pollination services essential for plant reproduction; without pollinators, plants cannot produce fruits or seeds

**Water cycle regulation:** Vegetation and ecosystems regulate water infiltration, storage, and cycling

**Nutrient cycling:** Microorganisms and fauna facilitate decomposition and nutrient recycling

**Soil formation and maintenance:** Biological processes create and maintain fertile soils

**Climate regulation:** Vegetation influences local and global climate patterns

**Pest and disease control:** Natural predators and pathogens regulate pest populations

**Aesthetic and recreational value:** Natural areas provide tourism and recreational opportunities

**3. Ethical Arguments**

**Philosophical Basis:** Intrinsic value of life forms and moral responsibility

**Core Principles:**

All living organisms have inherent right to exist independent of human utility

Humans have moral responsibility to preserve biodiversity for its own sake

Future generations have right to inherit Earth's biological wealth

Biodiversity represents billions of years of evolutionary heritage

Extinction represents permanent loss of unique evolutionary experiments

Moral obligation to prevent species extinction caused by human activities

Ethical stewardship of Earth's living systems

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IUCN Red List Categories (Extinction Risk Assessment)

The International Union for Conservation of Nature and Natural Resources classifies species based on extinction risk:

**Extinct (EX):** No individual known to exist; species lost forever

**Critically Endangered (CR):** Extremely high risk of extinction in wild; fewer than 50 individuals or equivalent populations

**Endangered (EN):** High risk of extinction; fewer than 250 individuals remaining or equivalent populations

**Vulnerable (VU):** Moderate risk of extinction; population declining but not yet at critical levels

**Near Threatened (NT):** Population declining; may become threatened in near future

**Least Concern (LC):** Widespread species with stable populations; lowest extinction risk

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Biodiversity Hotspots

**Definition:** Geographical regions with exceptionally high species diversity combined with significant threat to biodiversity.

**Criteria for Hotspot Designation:**

High endemism (species found nowhere else on Earth)

Significant portion of habitat already lost or under threat

Requires immediate conservation action

**Global Hotspots:** 34 recognized biodiversity hotspots worldwide

**Indian Hotspots:**

**Western Ghats:** High amphibian diversity, unique flora, endemic species

Other regions of high biodiversity concentration

These regions require prioritized conservation efforts

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Conservation Strategies

In-Situ Conservation

**Definition:** Protection and conservation of species in their natural habitats and ecosystems.

**Major Types:**

**1. Biosphere Reserves**

Large protected areas encompassing multiple ecosystems

Core zone: Strictly protected, minimal human disturbance

Buffer zone: Permits controlled research and limited human activities

Transition zone: Allows sustainable resource use by local communities

Example: Sundarbans Biosphere Reserve (mangrove ecosystems and Bengal tiger)

**2. National Parks**

Government-protected areas with legal status

Entry restricted or regulated for visitors

Focus on protection of fauna, flora, and geological features

Habitat preservation for wildlife conservation

Example: Jim Corbett National Park (tiger conservation)

**3. Wildlife Sanctuaries**

Protected areas primarily focused on wildlife conservation

May permit certain human activities like grazing or forestry

Less strict protection than national parks

Local communities may have traditional rights

Example: Periyar Wildlife Sanctuary (Kerala)

**4. Sacred Groves**

Forest areas protected through religious and cultural beliefs

Traditional conservation by local communities

Often found in biodiversity-rich regions

Combine conservation with cultural preservation

Example: Sacred groves in Western Ghats and Northeast India

Ex-Situ Conservation

**Definition:** Protection of species outside their natural habitats, often in artificial conditions.

**Major Types:**

**1. Seed Banks**

Store seeds of plant species in controlled conditions

Enable preservation of genetic diversity

Allow future restoration of extinct or endangered populations

Example: National Seed Bank systems

**2. Zoological Parks and Botanical Gardens**

Maintain captive populations of endangered animals and plants

Provide research opportunities

Enable breeding programs for species recovery

Educate public about conservation

Example: Delhi Zoo, Indian Institute of Science Botanical Garden

**3. Cryopreservation**

Freezing of cells, tissues, or whole organisms at ultra-low temperatures (typically -196°C in liquid nitrogen)

Preserves genetic material indefinitely

Enables future resurrection of species or genetic recovery

Advanced biotechnology application

**4. DNA Banks/Genetic Resource Banks**

Storage of genetic material (DNA, cells, tissues) for future use

Preserves genetic information of extinct or endangered species

Enables molecular-level conservation

Supports research and breeding programs

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Key Conservation Concepts for CBSE Board Exam

**Megadiversity Countries:** Nations containing disproportionate share of global species diversity (12 worldwide); India is one.

**Ecosystem Services:** Benefits provided to humans by natural ecosystems (oxygen, water purification, pollination, climate regulation).

**Keystone Species:** Species whose impact on ecosystem functioning is disproportionate to their abundance; their loss causes ecosystem-wide consequences.

**Endemic Species:** Species found exclusively in one geographical region; particularly vulnerable to extinction.

**Habitat Fragmentation:** Breaking of continuous habitats into isolated patches, preventing gene flow and increasing extinction risk.

**Invasive Species:** Non-native species introduced to new environments that outcompete, prey upon, or otherwise negatively impact native species.

**Extinction Cascade:** Series of extinctions triggered by loss of single species, particularly keystone or mutualist species.

**Conservation Priority:** Biodiversity hotspots and regions of high endemism require prioritized protection due to unique species concentration and extinction risk.