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Conservation Biology Chapter 59 Biodiversity Crisis Extinction is a fact of life: all species become extinct eventually More than 99% of species known to science are now extinct Current accelerating loss of habitat 20% of present day species will be extinct by the middle of this century

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Conservation Biology Chapter 59

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biodiversity crisis
Biodiversity Crisis
  • Extinction is a fact of life: all species become extinct eventually
  • More than 99% of species known to science are now extinct
  • Current accelerating loss of habitat
    • 20% of present day species will be extinct by the middle of this century
    • 2000 of the world’s 8600 species of birds could go extinct
biodiversity crisis3
Biodiversity Crisis
  • Members of Homo sapiens wreaked havoc even in prehistoric times
  • Mammoths and mastodons, giant sloths, saber-toothed tigers
  • 74% - 86% of mega fauna thought to have been caused by human hunting
biodiversity crisis4
Biodiversity Crisis
  • 40,000 years ago Australia had mega sized marsupials
    • All disappeared at about the same time humans arrived
  • Madagascar human caused extinctions
    • 15 species of lemurs
    • Pigmy hippopotamus
    • Flightless elephant bird (3m tall), 13 species of moas, and more
biodiversity crisis5
Biodiversity Crisis

Why have African mega fauna survived ?

  • Perhaps because animals coevolved with humans there
  • Animals evolved counteradaptations to human predation
biodiversity crisis6
Biodiversity Crisis
  • The majority of recent extinctions have occurred in the past 150 years
  • Increased rate of extinction is worsening
  • Birds recognized as critically endangered increased from 8% in 1996 to 2000
  • Half of Earth’s plant species may be threatened
  • 2/3rds of vertebrate species could perish by the end of this century
biodiversity crisis7
Biodiversity Crisis
  • Majority of extinctions have occurred on islands
    • 85 species of mammals; 60% lived on islands
  • Why are islands so vulnerable ?
    • Evolved in the absence of predators
    • Humans introduced competitors, diseases
    • Island populations are usually small which increases their risk for extinction
biodiversity crisis8
Biodiversity Crisis
  • Current mass extinctions are notable because
    • It is the only such event triggered by a single species (Homo sapien)
    • A few million years is a long time to wait for recovery
    • It is not clear that biodiversity will rebound this time
  • Humans are utilizing resources that new species would need to evolve
biodiversity crisis9
Biodiversity Crisis
  • Endemic species: species found naturally in only one geographic area and no place else
    • Occupy restricted ranges
    • Example: Komodo dragon lives only in a few islands
    • Example: Mauna Kea Silversword only lives in a single volcano crater on the island of Hawaii
biodiversity crisis cont
Biodiversity Crisis (Cont.)

Some species under imminent extinction threat

biodiversity crisis12
Biodiversity Crisis

Hotspots: areas where species have high endemism and are disappearing at a rapid rate. Red areas are hotspots.

biodiversity crisis13
Biodiversity Crisis

25 hotspots have been identified

Contain nearly half of all terrestrial

species in the world

biodiversity crisis14
Biodiversity Crisis
  • Human population growth in hotspots
  • By protecting 1.4% of the world’s land surface
    • 44% of the worlds vascular plants
    • 35% of its terrestrial vertebrates can be preserved
  • In 1995, 20% of the human population were located in hotspots
  • Growth rate exceeds the average in 19 hotspots
biodiversity crisis16
Biodiversity Crisis

Why are species going extinct in hotspots ?

  • High rates of habitat destruction
    • Land cleared for agriculture, housing, economic development
  • More than 70% of the original area of each hotspot has already disappeared
  • Only 15% or less of original habitat remains in 14 hotspots
    • 90% Madagascar forest lost
    • 95% Brazilian forest lost
value of biodiversity
Value of Biodiversity
  • Why care about loss of biodiversity ?
    • Direct economic value of products we obtain from species: food and drugs
    • Indirect economic value of benefits produced by species without our consuming them
    • Ethical and aesthetic values
value of biodiversity18
Value of Biodiversity
  • Direct economic value includes resources for our survival
    • Food crop genetic variation
    • 40% of prescription and nonprescription drugs have active ingredients extracted from plants
      • Aspirin
      • Cancer fighting drugs
value of biodiversity19
Value of Biodiversity
  • Rosy Periwinkle: vinvlastine and vincristine effectively treat common forms of childhood leukemia
    • Increase chances of survival from 20% to over 95%
value of biodiversity20
Value of Biodiversity

Cancer-fighting drugs like taxol, have been developed from the bark of the Pacific yew

value of biodiversity21
Value of Biodiversity
  • Indirect economic value is derived from ecosystem services
    • Maintain chemical quality of natural water, buffer against storms and droughts
    • Prevent loss of minerals and nutrients
    • Moderate local and regional climate
    • Absorb pollution
    • Promote breakdown of organic wastes and cycling of minerals
value of biodiversity22
Value of Biodiversity

Mangroves in

Thailand are more

Valuable than

Shrimp farms

value of biodiversity23
Value of Biodiversity

Tropical rainforests provide more economic benefits if they are left standing than if they are destroyed and the land used for other purposes

value of biodiversity24
Value of Biodiversity

Case Study: New York City watershed

  • 90% of 9 million people’s water comes from the Catskill Mountains and Delaware River
  • Dilemma: Protect functioning ecosystem or construct filtration plants
    • To build plants cost $6 billon
    • Operating cost $300 million/year
    • Spend $1 billion over 10 years to preserve the ecosystem
value of biodiversity25
Value of Biodiversity

New York City’s water source

value of biodiversity26
Value of Biodiversity
  • Economic trade-offs
    • Ecosystem was beneficial when the United States was being settled
    • Habitat destruction today may be economically desirable
      • How many services will it provide
      • What are the negative effects
        • Increased flooding and pollution
        • Decreased rainfall
        • Vulnerability to hurricanes
value of biodiversity27
Value of Biodiversity
  • Consequences of removing a species could mean we are gambling with the future of an ecosystem we depend on
  • Problems of valuing ecosystems
    • Do not have a good estimate of the monetary value of services provided by ecosystems
    • People who gain the benefits of environmental degradation are often not the same people who pay the costs
value of biodiversity28
Value of Biodiversity
  • Ethical and aesthetic values are based on our conscience
    • Every species has a value of its own
    • Humans should act as guardians or stewards for the diversity of life around us
    • How do we place a value on beauty ?
      • What if it no longer existed ?
factors responsible
Factors Responsible
  • Causes of extinction: direct or indirect
    • Overexploitation
    • Habitat loss
    • Introduced species
    • Disruption of ecosystem interactions
    • Pollution
    • Loss of genetic variation
    • Catastrophic disturbances
factors responsible31
Factors Responsible
  • Case Study: Amphibians on the decline
  • 1963, Jay Savage Costa Rica
    • Many breeding toads, bright orange
      • Bufo periglenes
  • 1989, only a single male was observed
  • Today, no toads
  • They have gone


factors responsible33
Factors Responsible
  • Frogs in trouble
    • Frog populations that had once been abundant were now decreasing or entirely gone
    • 2005: 43% of amphibian species experienced decreases in population size
    • 1/3rd are threatened with extinction
factors responsible37
Factors Responsible

Why worry about amphibian declines ?

  • Many species have declined in pristine, well-protected habitats
  • Particularly sensitive to the state of the environment because of their moist skin
    • Chemicals pass into their body
    • Larval habitats are aquatic
factors responsible38
Factors Responsible
  • No single cause for amphibian decline is apparent
    • Different species are afflicted by different problems
    • Global environment is deteriorating in many different ways
factors responsible39
Factors Responsible
  • Habitat loss devastates species richness
  • Natural habitats may be adversely affected by humans
    • Destruction
    • Pollution
    • Disruption
    • Habitat fragmentation
factors responsible40
Factors Responsible
  • Destruction of habitat
    • Clear-cut harvesting of timber
    • Burning of tropical forests
    • Urban and industrial development
  • 10 fold increase in habitat area leads to ~ doubling in the number of species
  • Area reduced by 90% then half of all species will be lost
factors responsible41
Factors Responsible

Rain forest covering the eastern coast of Madagascar:

  • 90% habitat loss
  • many extinctions
  • 16 of 31 primate species threatened or extinct
factors responsible42
Factors Responsible

Extinction and Island Area

factors responsible43
Factors Responsible
  • Pollution
    • Species can no longer survive
    • Aquatic environments particularly vulnerable
    • Many lakes “sterilized” by acid rain
  • Disruption
    • Visitors to bat cave: four visits per month caused 86% - 95% declines in population size
factors responsible44
Factors Responsible
  • Habitat fragmentation: dividing the habitat up into small, unconnected areas
    • Low population numbers
    • Smaller populations in each fragment
    • Edge effects: changes in microclimate along the edge of a habitat
factors responsible45
Factors Responsible
  • Edge effects
    • Trees exposed to more sunlight
      • Hotter and drier conditions
      • Less biomass growth
    • Opportunities for parasite and predator species
    • Habitat fragmentation is blamed for local extinctions in a wide range of species
factors responsible46
Factors Responsible
  • Fragmentation of Wisconsin woodland habitat
  • Cover less than 1% of original area
factors responsible47
Factors Responsible
  • Landowners in Manaus, Brazil preserved patches of rain forest of different sizes to examine the effect of patch size on species extinction
  • Extinction rate was negatively related to patch size
  • Even the largest patches (100 hectares) lost half of their bird species in less than 15 years
factors responsible48
Factors Responsible

Manaus, Brazil

factors responsible49
Factors Responsible

Case Study: songbird declines

  • Year round residents prosper (robins)
  • Migrant songbirds have declined
    • Nest in northern forests in summer but spend winter in South or Central America or the Caribbean Islands
    • Rock Creek Park in Washington, DC lost 90% in the past 20 years
factors responsible50
Factors Responsible
  • Nation wide, American redstarts declined about 50% in 10 years
  • Only about has as many birds fly over the Gulf of Mexico each spring as in the 1960’s
  • Culprit:
    • habitat fragmentation and loss
    • Availability of winter habitat declined
factors responsible51
Factors Responsible

American Redstart

factors responsible52
Factors Responsible

Case Study: whales

  • Over fishing
  • IWC regulates commercial whale hunting
  • Was it too late ?
factors responsible53
Factors Responsible

Introduced species threaten native species and habitats

  • Colonization: process by which a species expands its geographic range
    • Birds are blown off course
    • Bird eats a fruit and defecates its seeds miles away
    • Lowered sea levels connect to isolated populations
factors responsible54
Factors Responsible
  • Colonization brings together species with no history of interaction
  • Ecological interactions may be strong because species have not evolved ways of adjusting to the presence of one another
  • Results:
    • Increase in species diversity
    • Extinction of species
factors responsible55
Factors Responsible
  • Human influence on colonization
    • Plants and animals can be transported in the ballast of large ocean vessels

Zebra mussels

factors responsible56
Factors Responsible
  • 50,000 species have been introduced in the United States
  • Effects:
    • $140 billion per year in economic costs
    • Human health: west nile fever
    • Hawaii: mosquitoes brought malaria
      • 70% native fauna extinct or restricted to high elevations
factors responsible57
Factors Responsible

Two thirds of Hawaiian birds are extinct or have reduced populations

factors responsible58
Factors Responsible
  • Effect may not be direct, but spread through the ecosystem
    • Argentine ant has spread through much of the southern US, reducing populations of native ant species
      • Negative effect on coast horned lizard which feeds on native ants
      • Native ants spread seeds, introduced ones do not
factors responsible59
Factors Responsible
  • Efforts to combat introduced species
    • Eradicating extremely difficult, expensive and time consuming
    • Prevent introduction
  • Case Study: Lake Victoria cichlids
    • 300 species of cichlid fishes: most extinct, endangered or threatened
    • Nile perch introduced in 1954
factors responsible60
Factors Responsible
  • How did cichlid extinctions occur?
    • Eutrophication, algal bloom, cichlid populations increased, oxygen levels dropped
    • Nile perch populations increased as cichlids populations increased
    • Nile perch ate many of the cichlids
    • Introduction of water hyacinth compounded the problem
factors responsible61
Factors Responsible

Disruption of ecosystems can cause an extinction cascade

factors responsible62
Factors Responsible
  • Loss of keystone species may disrupt ecosystems
    • Sea otters are a keystone species of kelp forest ecosystems
    • Keystone species is a qualitative concept
    • Flying fox bats are a keystone species
      • Pollinates plants
      • Key disperser of seeds
      • Elimination due to hunting and habitat loss is having a devastating effect
factors responsible63
Factors Responsible
  • Small populations are vulnerable to extinction
    • Demographic factors
      • Ill-equipped to withstand catastrophes
      • Heath hen
        • Once common in US: hunting pressure eliminated all but 1 population
        • Fire destroyed the preserve’s habitat
        • Population ravaged by predators
factors responsible64
Factors Responsible

Heath hen and dusky seaside sparrow

factors responsible65
Factors Responsible
  • Lack of genetic variability is a second dilemma small populations face
    • Genetic drift
  • Populations lacking variation composed of sickly, unfit or sterile individuals
  • More genetically variable individuals have greater fitness
factors responsible66
Factors Responsible

Case Study: Prairie chickens

  • Was abundant in midwestern prairies
  • 1837 introduction of agriculture in the prairies; population has collapsed
  • 1962 & 1967 sanctuaries established
    • Privately owned grasslands disappeared
    • 1990, egg hatching rate only 38%
    • One dominant male: genetic variation loss
factors responsible67
Factors Responsible
  • Tested genetic variation theory
    • Extracted DNA for stuffed birds collected in 1930s
    • Compared to birds living in the same place before 1970 population collapse
    • Genetic variation loss in population in Illinois
    • Transplant birds from other states
    • Hatching rates back up to 94% in 1994
factors responsible68
Factors Responsible

Prairie chicken, male mating ritual

preserving species
Preserving Species

Destroyed habitats can sometimes be restored

  • Restore plants and animals to abandoned farm lands
  • No restoration is ever truly pristine
preserving species70
Preserving Species

Removing introduced species

  • Cichlid fishes restoration
    • Breeding and restocking endangered species
    • Removal of water hyacinth and Nile perch populations
preserving species71
Preserving Species

Cleanup and rehabilitation

  • Clean up pollution
  • Nashua River in New England
    • Heavily polluted habitat
    • Returned to near pristine condition
preserving species72
Preserving Species

Case Study: Peregrine falcon

  • DDT banned in 1972
    • Captive breeding program began in 1970
    • 1986: over 850 birds released in 13 states
conservation of ecosystems
Conservation of Ecosystems
  • Habitat fragmentation is one of the most pervasive enemies of biodiversity conservation efforts
  • Focus on preserving pristine state in national parks and reserves
    • Amount of land preserved is limited
    • Not many areas completely protected
  • Also focus on surrounding areas with some level of human disturbance
conservation of ecosystems74
Conservation of Ecosystems
  • Key to management
    • Operate them in a way compatible with local land use
      • No economic activity in core pristine area
      • Remainder of land used for nondestructive harvesting of resources
      • Some hunting
      • Corridors of dispersal
conservation of ecosystems75
Conservation of Ecosystems
  • Corridors of dispersal
    • Link pristine areas
    • Increase population sizes
    • Allow recolonization due to catastrophe
    • Protection to species that move over great distances during the course of a year