5/19/14 1 1 Conservation Biology Chapter 59 2 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 3 Biodiversity Crisis
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Conservation Biology Chapter 59
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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
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Biodiversity Crisis
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Biodiversity Crisis • The majority of recent extinctions have
occurred in the past 150 years • Increased rate of extinction is worsening • Half of Earth’s plant species may be
threatened • 2/3 of vertebrate species could perish by
the end of this century
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Biodiversity Crisis • Majority of extinctions have occurred on
islands – Of 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
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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
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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
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Biodiversity Crisis
Some species under imminent extinction threat
Silversword
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Biodiversity Crisis
Hotspots: areas where species have high endemism and are disappearing at a rapid rate. Red areas are hotspots.
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Biodiversity Crisis
25 hotspots have been identified Contain nearly half of all terrestrial
species in the world
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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
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Biodiversity Crisis
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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
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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
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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
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Value of Biodiversity • Rosy Periwinkle:
vinvlastine and vincristine effectively treat common forms of childhood leukemia – Increase chances
of survival from 20% to over 95%
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Value of Biodiversity
Cancer-fighting drugs like taxol, have been developed from the bark of the Pacific yew
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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
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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
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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
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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
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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 ?
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Factors Responsible • Causes of extinction: direct or indirect
– Overexploitation – Habitat loss – Introduced species – Disruption of ecosystem interactions – Pollution – Loss of genetic variation – Catastrophic disturbances
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Factors Responsible
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Factors Responsible • Habitat loss devastates species