Study Notes on Biodiversity and Conservation

Encountered diversity in life forms on Earth
- An alien would be amazed at the variety of organisms on the planet.
- Over 20,000 species of ants, 300,000 species of beetles, 28,000 species of fishes, and nearly 20,000 species of orchids.
Questions raised by ecologists and evolutionary biologists:
- Why are there so many species?
- Did such great diversity exist throughout Earth’s history?
- How did this diversification come about?
- Importance of biodiversity to the biosphere and its impact on human life.

Definition of biodiversity:
- Term popularized by sociobiologist Edward Wilson to describe the combined diversity at all levels of biological organization.
Types of biodiversity:
1. Genetic Diversity:
  - Variation within a single species across its distribution.
  - Example: Medicinal plant Rauwolfia vomitoria has variations in potency and concentration of the active compound (reserpine) across different Himalayan ranges.
  - India has over 50,000 genetically different rice strains, and 1,000 varieties of mango.
2. Species Diversity:
  - Example: Greater amphibian species diversity in Western Ghats compared to Eastern Ghats.
3. Ecological Diversity:
  - India has diverse ecosystems such as deserts, rainforests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows, surpassing the ecological diversity of places like Norway.

Biodiversity is vital for survival and well-being; loss of species can happen rapidly.

Published records indicate over 1.5 million described species.
Estimates for undiscovered species:
- Vary widely, educated guesses suggest between 20 to 50 million species.
- Conservative estimate (Robert May) suggests about 7 million total species.
Distribution specifics:
- Species inventories are more complete in temperate regions than in tropical ones, where many undiscovered species likely exist.

Animal species: Over 70% of recorded species are animals, with insects comprising over 70% of that.
Plants: Not more than 22% of the total species recorded are plants.
Fungi: More species than combined fishes, amphibians, reptiles, and mammals.
Prokaryotic species: Uncertain due to challenges in identification and culturing.

India has 2.4% of the world’s land area but 8.1% of global species diversity.
Approximately 45,000 plant species and twice as many animal species recorded; estimates suggest over 100,000 plant species and over 300,000 animal species remain undiscovered.

Diversity generally decreases from the equator to the poles.
- Example: Colombia (1,400 bird species) vs. New York (105 species) and Greenland (56 species).
- Tropical regions (23.5° N to 23.5° S) have more species than temperate or polar regions.
- Amazon rainforest hosts the highest biodiversity on Earth with 40,000 plant species, 3,000 fish, and 1,300 birds.

Longer evolutionary time in tropics (unstable temperate regions vs. stable tropics).
Less seasonal, more predictable environments promote niche specialization.
More solar energy leads to higher productivity and indirectly promotes greater diversity.

Species richness increases with explored area, becoming a rectangular hyperbola.
Equation: $ext{log } S = ext{log } C + Z ext{ log } A$
- Where ( S ) = Species richness, ( A ) = Area, ( Z ) = slope (regression coefficient), ( C ) = Y-intercept.
Z values: Generally range from 0.1 to 0.2 for many taxonomic groups, steeper (0.6 to 1.2) for larger areas.

Relationship between species richness and ecosystem functioning is under study.
Historically, more diverse communities tend to be more stable.
- Stability defined as less year-to-year productivity variation, resilience to disturbances, and resistance to invasions.
David Tilman found plots with more species showed less variation in biomass and higher productivity.

Analogy of the “rivet popper hypothesis” illustrates species roles in ecosystems.
Removal of species (rivets) impacts ecosystem integrity over time.

Information on extinction rates:
- IUCN Red List documents extinction of 784 species since the last 500 years (including 338 vertebrates, 359 invertebrates, 87 plants).
Recent species extinctions: dodo, quagga, thylacine, Steller’s Sea Cow.
- 27 species extinct in the last 20 years.

Habitat loss and fragmentation:
- Principle driver; rainforests lost drastically.
- Example: Destruction of the Amazon for agriculture.
Over-exploitation:
- Excessive collection of species; examples include Steller’s Sea Cow, passenger pigeon; current threats to marine life.
Alien species invasions:
- Introduction of non-native species disrupts ecosystems.
- Example: Nile perch in Lake Victoria leading to extinctions of cichlid fishes.
Co-extinctions:
- Interconnectedness of species leads to cascading effects upon extinction; e.g., extinction of a host fish leading to the extinction of its parasites.

Importance of biodiversity conservation can be categorized into:
- Narrowly Utilitarian: Direct economic benefits (food, medicine, etc.).
- Example: 25% of current drugs from plants.
- Broadly Utilitarian: Role in ecosystem services (pollination, oxygen production).
- Ethical: Moral duty to protect all species regardless of current usefulness.

Protecting species in their natural habitats.
- Identified biodiversity hotspots for priority protection (34 total including three in India).
- Significant legal protections in India (biosphere reserves, national parks, wildlife sanctuaries).
- Use of sacred groves in cultural conservation.

Species are removed from natural habitats for protection and breeding.
- Examples: Zoological parks, botanical gardens, gamete cryopreservation, and in vitro fertilization.

Summary of biodiversity concept and importance of conservation efforts.
Greater awareness of the need for biodiversity conservation amidst alarming extinction rates due to human activities.
Need for international collaboration on biodiversity conservation efforts.