Understanding Biodiversity

Biodiversity Overview

• Biodiversity refers to the diversity at all levels of biological organization

Levels of Biodiversity

• Genetic diversity is variation within a species, like reserpine concentration in Rauwolfia vomitoria
• India has over 50,000 rice strains and 1,000 mango varieties
• Species diversity refers to the variety of species, such as amphibians in the Western Ghats
• Ecological diversity is the variety of ecosystems, such as India's range from deserts to alpine meadows

Species Numbers

• Around 1.5 million plant and animal species have been described
• Robert May estimates global species diversity at about 7 million

Animal vs Plant Species Distribution

• More than 70% of recorded species are animals
• Plants make up no more than 22% of the total, including algae, fungi, bryophytes, gymnosperms, and angiosperms
• Insects are the most species-rich group, accounting for more than 70% of all animal species
• Fungi species outnumber the combined total of fish, amphibian, reptile, and mammal species

India's Biodiversity

• India holds 8.1% of global species diversity on only 2.4% of the world's land
• This makes India one of the 12 mega diversity countries
• Around 45,000 plant and twice as many animal species have been recorded in India
• Estimates suggest over 100,000 plant and 300,000 animal species remain to be discovered in India

Latitudinal Gradients

• Species diversity generally decreases from the equator towards the poles
• The tropics harbor more species than temperate or polar regions
• Colombia has nearly 1,400 bird species
• New York has 105 bird species
• Greenland has 56 bird species
• India has over 1,200 species of birds
• A tropical forest in Ecuador can have 10 times more vascular plant species than a US Midwest temperate forest
• The Amazon rainforest has the greatest biodiversity, including 40,000 plant species, 3,000 fish, 1,300 birds, 427 mammals, 427 amphibians, 378 reptiles, and over 125,000 invertebrates
• An estimated two million insect species remain unnamed there

Factors Affecting Diversification in the Tropics

• Tropical latitudes remained undisturbed for millions of years due to fewer glaciations
• This provided a longer evolutionary time for species diversification
• Tropical environments are less seasonal, more constant, and predictable
• This promotes niche specialization and species diversity
• More solar energy is available, contributing to higher productivity

Species-Area Relationships

• Alexander von Humboldt noted species richness increases with area explored, but up to a limit
• This relationship is a rectangular hyperbola, which on a logarithmic scale is a straight line: log S = log C + Z log A
  • S = Species richness
  • A = Area
  • Z = slope of the line (regression coefficient)
  • C = Y-intercept
  • Z typically ranges from 0.1 to 0.2, however for very large areas like continents, Z values range from 0.6 to 1.2

Ecosystem Stability

• It's believed communities with more species tend to be more stable, productive, and resistant to biological invasions

Rivet Popper Hypothesis

• Paul Ehrlich's analogy explains the impact of species loss on an ecosystem
• Each species is like a rivet in an airplane (ecosystem)
• Losing species (rivets) may initially seem inconsequential, but over time, it can weaken the ecosystem, risking its function

Biodiversity Loss

• Colonization of tropical Pacific Islands led to the extinction of over 2,000 native bird species
• The IUCN Red List (2004) documents 784 extinctions in the last 500 years
• Examples include:
  • Dodo (Mauritius)
  • Quagga (Africa)
  • Thylacine (Australia)
  • Steller's Sea Cow (Russia)
  • Three tiger subspecies (Bali, Javan, Caspian)
• Analysis shows some groups, like amphibians, are more vulnerable to extinction
• Over 15,500 species worldwide face extinction

Historical Extinction Rates

• The current species extinction rates are 100 to 1,000 times faster than pre-human times
• Human activities are responsible for the accelerated rates
• Predicted that nearly half of all species face extinction within 100 years if trends continue

Consequences of Biodiversity Loss

• Decline in plant production
• Lowered resistance to environmental perturbations
• Increased variability in ecosystem processes

Causes of Biodiversity Loss

• Habitat loss and fragmentation is the most important driver of extinctions
• Tropical rainforests once covered 14% of Earth’s land but now cover only 6%
• The Amazon is being cut down for soy cultivation and cattle ranching
• Pollution degrades habitats
• Fragmented habitats affect mammals, birds needing large territories, and migratory animals
• Over-exploitation from need turning to greed
  • Steller’s sea cow and passenger pigeon extinctions caused over exploitation
  • Marine fish populations being over harvested
• Alien species invasions cause decline or extinction of indigenous species
  • Nile perch introduction in Lake Victoria led to extinction of 200 cichlid fish species
  • Invasive species like Parthenium, Lantana, and Eichhornia damage native species
  • The African catfish Clarias gariepinus threatens indigenous catfish
• Co-extinctions happen when the extinction of one species leads to the extinction of other species
• Plant-pollinator mutualism is an example

Reasons to Conserve Biodiversity

• Narrowly utilitarian: Humans derive direct economic benefits
• Food (cereals, pulses, fruits)
• Firewood
• Fiber
• Construction material
• Industrial products
• Medicinal products
• Broadly utilitarian: Biodiversity plays a major role in ecosystem services
• Amazon forest produces 20% of Earth's oxygen
• Ethical: Every species has an intrinsic value and a moral duty to care for the planet

Biodiversity Conservation Methods

• In situ (on-site) conservation protects the whole ecosystem
• Ex situ (off-site) conservation is used when species are endangered, needing urgent measures
• Biodiversity hotspots are regions identified for maximum protection having high species richness and endemism
  • There are a total of 34 biodiversity hotspots
• Three hotspots covering India's high biodiversity regions are:
  • Western Ghats and Sri Lanka
  • Indo-Burma
  • Himalaya

Conservation Efforts within India

• India legally protects ecologically unique and biodiversity-rich regions as
  • Biosphere reserves
  • National parks
  • Sanctuaries
• It also has religious and cultural traditions that protect nature, like sacred groves- located in
  • Khasi and Jaintia Hills (Meghalaya)
  • Aravalli Hills (Rajasthan)
  • Western Ghats regions (Karnataka and Maharashtra)
  • Sarguja, Chanda, and Bastar areas (Madhya Pradesh)
• Ex situ conservation involves
  • Zoological parks
  • Botanical gardens
  • Wildlife safari parks
• Advanced techniques include:
  • Cryopreservation
  • In vitro fertilization
  • Tissue culture methods
  • Seed banks

Global Initiatives

• The Convention on Biological Diversity was held in Rio de Janeiro in 1992 ('The Earth Summit')
• In 2002, The World Summit on Sustainable Development was held in Johannesburg, South Africa, with 190 countries pledging commitment to reduce biodiversity loss by 2010