Download Saving the Key Deer

Conservation Ecology
Chapter 6
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Saving the Key Deer
• Modern human culture and the rapidly growing
global human population have created a
biodiversity crisis
– There is a rapid decrease in
the variety of species on Earth
• The decline in Key deer
populations is an example of
this crisis
– The Key deer is a miniature
subspecies of the whitetail
deer found only in the Florida
Keys
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• The Key deer was nearly exterminated by
hunting in the early 1900s
• The National Key Deer Pine Refuge was
established on Big Pine Key island in 1957
– The deer population rebounded to 600-800
• The Key deer is still on the endangered species
list
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• The human population on Big Pine Key has
increased tenfold since 1967
– Development has reduced the Key deer
habitat
– Motorists have
become the
main threat
to the deer's
survival
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• Conservation biology is a goal-oriented science
that seeks to counter the biodiversity crisis
• Conservation biology relies on research from
all levels of ecology, from populations to
ecosystems
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THE BIODIVERSITY CRISIS: AN OVERVIEW
38.1 Habitat destruction, introduced species, and
overexploitation are the major threats to
biodiversity
• Human alteration of
habitats poses the
single greatest threat
to biodiversity
– The loss of tropical
rain forests and
marine habitats are
especially
devastating
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Figure 38.1A
• Competition with introduced species also
threatens many species in their native habitats
– Introduced species are those that have been
transferred to an area where they did not
occur naturally
– Examples: European starlings, pigeons, and
house sparrows
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• One of the largest rapid-extinction events ever
recorded occurred in Lake Victoria, East Africa
– 200 species of freshwater fish were lost due to
the introduction of the Nile perch
Figure 38.1B
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• Overexploitation of wildlife also threatens many
species
– Excessive commercial harvest or sport hunting
has reduced the numbers of many species
– Examples: whales, American bison, Galápagos
tortoises, and numerous fish
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38.2 Biodiversity is vital to human welfare
• Preservation of biodiversity is important to
humans for aesthetic, ethical and practical
reasons
• Biodiversity provides humans with food,
clothing, shelter, oxygen, soil fertility, etc.
• We evolved in Earth's ecosystem
– Large-scale changes in the ecosystem threaten
us as well as other species
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• Medicinal plants and
their derivatives play
an important role in
the pharmaceutical
industry
– The rosy periwinkle
of Madagascar
provides two
substances effective
in the treatment of
Hodgkin’s disease
Figure 38.2
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38.3 Connection: Technology and the population
explosion compound our impact on habitats
and other species
• The explosive growth of the human population
and of technology continues today
• Although the populations of developing
nations are growing the fastest, it is the
resource consumption of the less populous,
developed nations that puts a greater strain on
the biosphere
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Oil spills, acid rain,
ozone depletion, and
chemical pesticides
affect the entire world
Figure 38.3a
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• Chemical
pesticides are
concentrated in
food chains by
biological
magnification
DDT concentration:
increase of
10 million times
DDT in
fish-eating birds
25 ppm
DDT in
large fish
2 ppm
DDT in
small fish
0.5 ppm
DDT in
zooplankton
0.04 ppm
DDT in water
0.000003 ppm
Figure 38.3B
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38.4 Connection: Rapid global warming could alter
the entire biosphere
• Burning of fossil fuels is increasing the amount
of CO2 and other greenhouse gases, such as
methane in the air
Figure 38.4A
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Light
CO2
Heat
CO2
CO2
Figure 38.4B
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• Projected atmospheric temperatures indicate an
increase in greenhouse gases
Figure 38.4C
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Methane is a more potent (20 times) greenhouse
gas than CO2
• Major Sources:
– half frozen slush in the northern hemisphere's
tundra permafrost regions (contain 3,000 times
as much methane as is in the atmosphere)
– bottom of the sea
– cattle farming
– landfills
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Methane “Burp”
• A temperature increase of merely a few degrees
would cause the 400 gigatons of methane
locked in the frozen arctic tundra to volatilize
and "burp" into a chain reaction
• This cycle could result in runaway global
warming the likes of which even the most
pessimistic doomsayers aren't talking about.
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“Burping” Events
• 55 million years ago in what geologists call the
Paleocene-Eocene Thermal Maximum (PETM),
when methane burps caused rapid warming
and massive die-offs, disrupting the climate for
more than 100,000 years.
• 251 million years ago, at the end of the Permian
period, when a series of methane burps came
close to wiping out all life on Earth. More than
94 percent of the marine species present in the
fossil record disappeared suddenly as oxygen
levels plummeted and life teetered on the verge
of extinction.
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"Control of methane emissions turns out to be a
more powerful lever to control global warming
than would be anticipated."
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Temperature increase of about 10.8 degrees
Fahrenheit, about the upper range for the
average global increase today's models predict
can be expected from burning fossil fuels by
2100. But these models could be the tail
wagging the dog since they don't add in the
effect of burps from warming gas hydrates.
• “If we trigger this runaway release of methane,
there's no turning back. No do-overs. Once it
starts, it's likely to play out all the way.”
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• An increase in global temperature could have
many negative effects
– Change in climate patterns
– Melting of polar ice
– Flooding of coastal regions
– Increase in the rate of species loss
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
THE GEOGRAPHIC DISTRIBUTION OF
BIODIVERSITY
38.5 Some locations in the biosphere are especially
rich in biodiversity
• Environments are patchy
– As a result, species are not evenly distributed
• Geographic distribution patterns for many
species indicate an uneven density
– Example: terrestrial birds in North and Central
America
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• Density of bird
species
Figure 38.5A
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• Biodiversity hot spots are relatively small areas
with a large concentration of species
• Many species in these hot spots are endemic
– They are found nowhere else
• Biodiversity hot spots can also be hot spots of
extinction
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• Location of some biodiversity hot spots
Figure 38.5B
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• Endemic species are highly sensitive to habitat
degradation and thus prone to extinction
• Many migratory species, both terrestrial and
aquatic, require international protection
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• Monarch butterflies
migrate throughout
Canada and the United
States during the
summer months
– In the autumn months,
they migrate to local
sites in Mexico and
California
– Such overwintering
populations are
susceptible to habitat
disturbances
Figure 38.5C
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• Sea turtles, such as the loggerhead turtle, are
threatened in their ocean feeding grounds and
on land
Figure 38.5D
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings