Conservation Biology

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Conservation Biology

• Chapter 57

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Outline

• Overview of the Biodiversity Crisis
• Species Endemism and Hotspots
• Losing Biodiversity
• Predicting Vulnerable Species
• Factors Responsible for Extinction
• Introduced Species
• Ecosystem Disruption
• Perils of Small Population Size
• Preserving Endangered Species
• Conservation of Ecosystems

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Overview of the Biodiversity Crisis

• More than 99 of all species known to science are
  now extinct.
• As much as 20 of the worlds biodiversity may be
  lost during the next 30 years.
• No more than 15 of the worlds eukaryotic
  organisms have been discovered and given
  scientific names.

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Overview of the Biodiversity Crisis

• Extinction due to prehistoric humans
• Shortly after humans arrived, 74-86 of megafauna
  became extinct.
• caused by hunting and habitat clearing
• Extinctions in historical time
• Historical extinction rates are best known for
  birds and mammals because they are relatively
  large and well studied.

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Overview of the Biodiversity Crisis

• Since 1600, 2.1 of known mammal species and 1.3
  of known birds have become extinct.
• majority of historic extinctions have occurred on
  islands

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Species Endemism and Hot Spots

• A species found naturally in only one geographic
  area is termed endemic.
• Isolated geographical areas, such as oceanic
  islands, often have many endemic species.
• Notable hotspots of endemism are
  Madagascar,eastern Himalayas, and Australia.
• many experiencing high rates of habitat
  destruction

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Population Growth in Hotspots

• By protecting just 1.4 of the worlds land
  surface, 44 of the worlds vascular plants and
  35 of its terrestrial vertebrates can be
  preserved.
• In 1995, these spots contained 20 of the worlds
  population.
• areas of intense commercial exploitation

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Losing Biodiversity

• Direct economic value
• sources of food, medicine, clothing, etc..
• gene prospecting
• Indirect economic value
• ecological functioning such as water
  purification, flood buffering, erosion buffers,
  and mineral cycling
• Ethical and aesthetic value
• valuable in its own right

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Extinction Crisis

• Factors responsible for extinction
• overexploitation
• introduced species
• disruption of ecological interactions
• pollution
• loss of genetic variability
• catastrophic disturbances

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Case Study Amphibian Declines

• Monteverde Cloud Forest Preserve in Costa Rica
• golden toads - Bufo periglenes
• Despite living in a well-protected ecosystem, the
  species appears to have gone extinct.

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Frogs in Trouble

• Cause for concern
• Many amphibian species all over the globe are
  declining.
• Amphibians are particularly sensitive to
  environmental contaminants due to moist skin.
• There appears to be no single cause for decline.

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Habitat Loss

• Natural habitats adversely affected by human
  influences in four ways
• destruction
• clear-cut tree harvesting
• pollution
• habitat degradation
• disruption
• park visitors

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Habitat Loss

• Habitat fragmentation
• fragmenting of population into unconnected
  patches..
• Edge effects can significantly alter the
  microclimate near the edge and may reduce
  appropriate habitat for many species.
• Expanding edges opens up opportunities for
  parasites and predators to invade new areas.

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Fragmentation of a Woodland Habitat
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Case Study - Songbirds

• In many areas of the eastern United States, more
  than three-quarters of tropical migrant bird
  species have experienced a significant decline in
  population size.
• habitat fragmentation and loss
• wooded summer nesting grounds
• winter habitat in Central and South America

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Overexploitation

• Case study whales
• Commercial whaling began in sixteenth century and
  reached its apex in early twentieth century.
• As whalers reduced the numbers of one species,
  they simply switched species.
• In 1974, the International Whaling Commission
  (IWC) banned hunting on all blue, gray, and
  humpback whales and instituted partial bans on
  others.
• 1986 - worldwide moratorium

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Introduced Species

• Detrimental effects
• Colonization and extinction as natural processes
• Colonization may bring together species with no
  previous history of interaction.
• Human influences
• Effects of introductions on humans has been
  enormous.
• Nonnative species cost US economy 140 billion
  annually.

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Human Influences

• Cause species extinction and habitat
  restrictions.
• Indirect effects
• food chain alterations
• Efforts to combat introduced species
• eradication
• difficult, expensive, time consuming, and
  potentially impossible
• prevention

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Case Study - Introduced Species

• Lake Victoria - Immense shallow freshwater sea in
  equatorial east Africa was home to over 300
  species of cichlid fish species.
• Nile perch introduced in 1954.
• Only made up 2 of fish harvested from the lake
  until 1978.
• Eutrophication appears to have increased cichlid
  populations, which in turn triggered perch to
  begin eating large numbers of cichlids.
• most Cichlids eliminated by 1986

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Ecosystem Disruption

• Species often become vulnerable to extinction
  when their web of ecological interactions becomes
  disrupted.
• sea otters off the Alaskan coast
• Commercial whaling initiated series of changes
  that led to orcas feeding on sea otters, causing
  disastrous effects on kelp forests.

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Preserving Keystone Species

• Keystone species are usually characterized by the
  strength of their impact on their community.
• community importance
• flying foxes

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Perils of Small Population Size

• Demographic factors
• By nature of their small size, small populations
  are ill equipped to withstand a catastrophic
  event.
• dusky seaside sparrow
• Lack of genetic variability
• Small populations are prone to the loss of
  genetic variation as a result of genetic drift.

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Case Study - Loss of Genetic Variation

• Greater prairie chicken in Illinois has undergone
  a population collapse over last six decades.
• Introduction of steel plow in 1837 allowed large
  areas of prairie to be cleared.
• Sanctuaries set-up in 1962 and 1967, but by 1980,
  wild populations were extinct and sanctuary
  populations in trouble.
• lost one-third of genetic diversity
• influx of genetic diversity reversing trends

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Preserving Endangered Species

• Preservation approaches
• habitat restoration
• pristine restoration
• removal of introduced species
• cleanup and rehabilitation
• captive breeding
• peregrine falcon
• California condors
• Yellowstone wolves

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Conserving Ecosystems

• Isolated patches of habitat lose species much
  more rapidly than large areas.
• Megareserves are large areas of land that contain
  a core of one or more undisturbed habitats.
• focus on preserving intact ecosystems

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Megareserve Design
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Summary

• Overview of the Biodiversity Crisis
• Species Endemism and Hotspots
• Losing Biodiversity
• Predicting Vulnerable Species
• Factors Responsible for Extinction
• Introduced Species
• Ecosystem Disruption
• Perils of Small Population Size
• Preserving Endangered Species
• Conservation of Ecosystems

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