Understanding Biodiversity

Biodiversity Overview

• Enormous diversity of life amazes and baffles observers

Examples of Biodiversity

• Over 20,000 ant species exist
• There are approximately 300,000 beetle species
• Fish species number around 28,000
• Almost 20,000 orchid species are recognized

Key questions ecologists and evolutionary biologists are trying to answer

• Why are there so many species?
• Has great diversity always existed?
• How did diversification happen?
• Why is diversity important to the biosphere?
• Would a less diverse biosphere function differently?
• How do humans benefit from biodiversity?

Defining Biodiversity

• Sociobiologist Edward Wilson popularized the term biodiversity
• Biodiversity includes diversity at all levels of biological organization, from macromolecules in cells to biomes
• Immense diversity (or heterogeneity) exists in the biosphere

Genetic Diversity

• A single species displays high diversity at the genetic level across its distribution
• Rauwolfia vomitoria shows genetic variation in Himalayan ranges regarding the potency and concentration of reserpine chemical it produces
• India has over 50,000 genetically different rice strains
• There are 1,000 mango varieties in India

Species Diversity

• The Western Ghats have greater amphibian species diversity than the Eastern Ghats

Ecological Diversity

• India has greater ecosystem diversity than Norway
• Indian ecosystems include deserts, rainforests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows

Importance of Biodiversity

• It took millions of years of evolution to accumulate nature's diversity
• Current rates of species loss could deplete this diversity in less than two centuries
• Biodiversity and its conservation are vital issues of international concern
• Biodiversity is critically important for survival and well-being on earth

Documented Species

• Slightly more than 1.5 million plant and animal species described so far according to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004)

Estimates of Total Species

• Estimates of the total number of species vary widely
• Many species inventories are more complete in temperate countries
• Based on temperate-tropical species richness comparisons, a statistical comparison of insects has been used

Estimates of Global Species

• Estimates range from 20 to 50 million
• A conservative, scientifically sound estimate by Robert May puts global species diversity at about 7 million

Species Breakdown

• Animals comprise over 70% of recorded species
• Plants (including algae, fungi, bryophytes, gymnosperms, angiosperms) account for no more than 22%
• Insects are the most species-rich taxonomic group, making up over 70% of total
• 7 of every 10 animals are insects highlighting their diversification
• Fungi species outnumber combined fish, amphibian, reptile, and mammal species

Prokaryotic Species Estimates

• Estimates do not give figures for prokaryotes
• Conventional taxonomic methods unsuitable for identifying microbial species
• Many microbial species are non-culturable in labs
• Biochemical or molecular criteria could place their diversity in the millions
• India possesses 2.4% of the world's land area, but has 8.1% of global species diversity

Status of Species in India

• Almost 45,000 plant species recorded in India
• Animal species are twice as numerous compared to plant species
• Considering May's estimates, only 22% of species have been recorded so far

Estimated Undiscovered Species in India

• Over 100,000 plant species
• Over 300,000 animal species

Threatened Species

• A large fraction of species faces extinction before discovery

Latitudinal Gradients

• Plant and animal diversity isn't uniform globally
• Species diversity generally decreases from equator to poles except in the tropics which lie between 23.5° N to 23.5° S

Species Examples

• Colombia has nearly 1,400 bird species
• New York has 105 bird species at 41° N
• Greenland has only 56 bird species at 71° N

India's biodiversity

• Has over 1,200 bird species due to most of land in tropical latitudes
• Ecuadorian forests can have 10 times more vascular plant species than equal area temperate forests in the Midwest USA
• The largely tropical Amazonian rainforest in South America holds greatest biodiversity, containing over:
  • 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

Hypotheses for Greater Tropics' Biological Diversity

• Speciation is a function of time as tropical latitudes remained undisturbed for millions of years unlike the glaciated temperate regions
• Tropical environments are less seasonal and more constant/predictable promoting niche specialization and greater diversity
• More solar energy in tropics leads to higher productivity that also contributes to greater diversity

Species-Area Relationships

• Alexander von Humboldt noted in South American jungles that species richness increased with area

Species Richness and Area Relation

• Relation between species richness and area for angiosperm plants, birds, bats, freshwater fishes is a rectangular hyperbola.
• Logarithmic scale shows straight line: log S = log C + Z log A

Formula Variables

• S = Species richness
• A = Area
• Z = slope of line (regression coefficient)
• C = Y-intercept

Slope Values

• Z ranges from 0.1 to 0.2 regardless of taxonomic group or region
• Larger areas like continents will have steeper lines with Z between 0.6 to 1.2
• Frugivorous birds / mammal slope in tropical forests has a slope of 1.15.
• An important question ecologists have asks:
  • Does the number of species in a community matter to the functioning of the ecosystem?

Traits of a Stable Community

• Does not show much variation in productivity from year to year
• Resistant or resilient to natural or man-made disturbances
• Resistant to alien species invasions

Studies

• David Tilman's experiments showed plots with more species have less year-to-year biomass variation and increased diversity also results in higher productivity.

Effects of Losing Species

• Rich biodiversity is essential for ecosystem health and survival of the human race
• Losing species is occurring at an alarming rate
• Paul Ehrlich (Stanford ecologist) used the 'rivet popper hypothesis'
  • The proper functioning of an ecosystem relies on its species as a plane relies on its rivets to function correctly. Removing species one by one (rivets) could dangerously weaken the ecosystem (the plane) leading to its collapse.

Biodiversity Loss

• There are continuing losses though speciation is occurring
• Biological wealth is declining rapidly due to humans

Loss Statistics

• Colonization of tropical Pacific Islands led to extinction of >2,000 native bird species
• IUCN Red List (2004) documents extinction of 784 species in last 500 years

Examples of Extinctions

• Dodo (Mauritius)
• Quagga (Africa)
• Thylacine (Australia)
• Steller’s Sea Cow (Russia)
• Bali, Javan, Caspian tiger subspecies

Species Loss Statistics

• The last 20 years have witnessed the disappearance of 27 species
• Extinctions are not random

Extinction Vulnerability

• Amphibians are especially vulnerable

• 15,500 species face threat of extinction

Threat of Extinction By Group

• 12% of bird species
• 23% of mammal species
• 32% of amphibian species
• 31% of gymnosperm species

Earth's Extinction History

• There have been 5 episodes of mass extinction
• The 'Sixth Extinction' has rates 100 to 1,000 times faster than pre-human times and our activities or responsible for the acceleration
• Current trends may wipe out half of Earth's species in the next 100 years

Consequences of Biodiversity Loss

• Leads to decline in plant production
• Leads to lowered resistance to drought
• Leads to increased ecosystem variability

Causes of Biodiversity Loss

• Accelerated rates of species extinctions due to human activities is know as 'The Evil Quartet'

Habitat Loss and Fragmentation

• The most important cause for animal/plant extinction
• Tropical rain forests were previously over 14% of Earth's land but now they are 6%
• 1000 more hectares of rainforest may be lost by completion of reading this book
• Amazon rainforest is being cut/cleared for cultivating soybeans or raising beef cattle

Habitat Degradation

• Pollution threatens species survival
• Breaking habitats into small fragments impacts mammals/birds and animals with migratory habits leading to population declines

Over-exploitation

• Over-exploitation results from need turning to greed
• Many extinctions in last 500 years are due to human overexploitation
• Marine fish populations are over harvested endangering species

Alien Species Invasions

• Alien species introduced intentionally or unintentionally can cause decline or extinction of indigenous species
• Nile perch introduction in Lake Victoria led to extinction of ecologically unique cichlid fish
• Invasive weed species like carrot grass, Lantana, water hyacinth cause environmental damage
• Illegal African catfish introduction threatens rivers' indigenous catfish

Co-extinctions

• Extinction of a species leads to extinction of associated species
• Host fish extinction leads to the extinction of parasites
• Extinction of one invariably leads extinction of the other in coevolved plant-pollinator mutualism

Reasons To Conserve Biodiversity

• There are many important reasons, some obvious while others are not as obvious
• These reasons can be grouped into three categories:
  • Narrowly utilitarian
  • Broadly utilitarian
  • Ethical

Narrowly Utilitarian Perspective

• Obvious; humans derive direct economic benefits
• Various plant species offer 25% of drugs sold worldwide and contribute to traditional medicines

Unexplored Resources

• Unknown how many more medicinally useful plants are in tropical rainforests will be explored for bioprospecting (exploring molecular, genetic/ species level diversity for economic importance)

Broadly Utilitarian Perspective

• Biodiversity plays major roles in many ecosystems
• The dwindling Amazon produces -20% of Earth's oxygen through photosynthesis

Ecological Services

• Pollination (pollinators are bees, bumblebees, birds, bats)

Ethical Perspective

• Relates to owes to millions of plants/animal /microbe species
• Need to realize every species has its own value needing moral care and for passing biological legacy for future generations

Conserving Biodiversity - In situ

• Conserving all levels of an ecosystem, example saving a whole forest to save and protect the tiger
• Situations where an animal or plant is endangered, urgent for conservation, and facing a very high risk of extinction in the future.

Conserving Biodiversity - Ex situ

• Off-site conservation is the most desirable approach
• Requires an understanding of the conflicts between development and conservation, and finding it unrealistic and not feasible
• Globally addressed by conservationists that identified 'biodiversity hotspots' containing high levels of species richness and high endemism
• 25 biodiversity hotspots are on the list

Hotspots

• Biodiversity hotspots are regions of accelerated habitat loss
• 3 Hotspots that cover India’s high biodiversity regions
  • The Western Ghats
  • Sri Lanka
  • Indo-Burma
  • Himalaya

Hotspot Conservation

• Hotspots cover less than 2% of earth’s land area
• A high level and strict protection of these hotspots could help reduce mass extinction by 30%.

India's Conservation Efforts

• Protected as biosphere reserves, national parks, and sanctuaries
• 14 biosphere reserves, 90 national parks, and 448 wildlife sanctuaries
• Religious/cultural traditions emphasized protection of nature
• Sacred groves are tracts that are venerated and given protection that are found in: -Khasi -Jaintia Hills (Meghalaya) -Aravalli Hills (Rajasthan) -Western Ghat -Karnataka -Maharashtra -Sarguja, Chanda/Bastar areas (Madhya Pradesh) -Meghalaya (sacred groves are last refuges for plants that are threatened)

Ex situ Conservation

• Threatened animals and are taken out from their environment for special care where they can be given special care
• Served by Zoos, botanical gardens, etc
• Animals have become extinct in the past have remained in Zoos
• Gametes can be preserved with cryopreservation, eggs can be fertilized by in vitro, and culture can be propagated with tissue

Biodiversity - Collective Responsibility

• Biodiversity has no political border, so the conservation of it is the responsibility of all countries
• Earth Summit called on all nations to take measurement for the conservation of biodiversity and sustainable utilization and benefits of it
• 190 countries pledged commitments to biodiversity loss with the World Summit of Sustainable Development