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Sustaining Biodiversity:
The Species Approach
Overview Questions
 How
do biologists estimate extinction rates,
and how do human activities affect these
rates?
 Why should we care about protecting wild
species?
 Which human activities endanger wildlife?
 How can we help prevent premature
extinction of species?
 What is reconciliation ecology, and how can it
help prevent premature extinction of species?
Core Case Study:
The Passenger Pigeon - Gone
Forever
 Once
the most
numerous bird on earth.
 In 1858, Passenger
Pigeon hunting became
a big business.
 By 1900 they became
extinct from overharvest and habitat
loss.
Figure 11-1
SPECIES EXTINCTION
 Species



can become extinct:
Locally: A species is no longer found in an area
it once inhabited but is still found elsewhere in
the world.
Ecologically: Occurs when so few members of a
species are left they no longer play its ecological
role.
Globally (biologically): Species is no longer
found on the earth.
Global Extinction
 Some
animals have become prematurely
extinct because of human activities.
Figure 11-2
Lost natural capital: some animal species that have become
prematurely extinct largely because of human activities, mostly
habitat destruction and overhunting. The Great Auk became
extinct in 1844 from overhunting because of its willingness to
march up the boardwalks to ships. QUESTION: Why do you
think birds top this list?
Passenger pigeon
Great auk
Dodo
Dusky seaside
sparrow
Aepyornis
(Madagascar)
Fig. 11-2, p. 223
Endangered and Threatened
Species: Ecological Smoke Alarms
 Endangered
species: so few individual
survivors that it could soon become extinct.
 Threatened species: still abundant in its
natural range but is likely to become
endangered in the near future.
Figure 11-3
Endangered natural capital: species that
are endangered or threatened with premature
extinction largely because of human activities.
Almost 30,000 of the world’s species and
1,260 of those in the United States are
officially listed as being in danger of becoming
extinct. Most biologists believe the actual
number of species at risk is much larger.
Fig. 11-3, p. 224
Grizzly bear
Utah prairie dog
Kirkland’s
warbler
Knowlton
cactus
Florida
manatee
Swallowtail
butterfly
Humpback
chub
Golden lion
tamarin
African elephant
Siberian tiger
Fig. 11-3, p. 224
Giant panda Black-footed Whooping
crane
ferret
Mountain gorilla Florida
panther
California
condor
Northern
spotted owl
Hawksbill
sea turtle
Blue whale
Black
rhinoceros
Fig. 11-3, p. 224
SPECIES
EXTINCTION
 Some
species
have
characteristics
that make them
vulnerable to
ecological and
biological
extinction.
Figure 11-4
SPECIES EXTINCTION
 Scientists
use measurements and models to
estimate extinction rates.


The International Union for the Conservation of
Nature and Natural Resources (IUCN) publishes
an annual Red List, listing the world’s threatened
species.
The 2004 Red List contains 15,589 species at
risk for extinction.
Figure 11-5
SPECIES EXTINCTION
 Percentage
of various species types
threatened with premature extinction from
human activities.
Figure 11-5
SPECIES EXTINCTION
 Scientists
use
models to
estimate the risk
of particular
species becoming
extinct or
endangered.
Figure 11-6
IMPORTANCE OF WILD SPECIES
 We
should not cause the premature
extinction of species because of the
economic and ecological services they
provide.
 Some believe that each wild species has an
inherent right to exist.

Some people distinguish between the survival
rights among various types of species (plants vs.
animals).
HABITAT LOSS, DEGRADATION,
AND FRAGMENTATION
 Conservation
biologists summarize the most
important causes of premature extinction as
“HIPPO”:





Habitat destruction, degradation, and
fragmentation
Invasive species
Population growth
Pollution
Overharvest
HABITAT LOSS, DEGRADATION,
AND FRAGMENTATION
 The
greatest threat to a species is the loss,
degradation, and fragmentation of where it lives.
Figure 11-7
Natural capital degradation: underlying and
direct causes of depletion and premature
extinction of wild species. The major direct
cause of wildlife depletion and premature
extinction is habitat loss, degradation, and
fragmentation. This is followed by the
deliberate or accidental introduction of harmful
invasive (nonnative) species into ecosystems.
HABITAT LOSS, DEGRADATION,
AND FRAGMENTATION
 Reduction
in
ranges of four
wildlife species,
mostly due to
habitat loss
and
overharvest.
Figure 11-8
Indian Tiger
Range 100 years ago
Range today
(about 2,300 left)
Fig. 11-8a, p. 230
Black Rhino
Range in 1700
Range today
(about 3,600 left)
Fig. 11-8b, p. 230
African Elephant
Probable range 1600
Range today
Fig. 11-8c, p. 230
Asian or Indian Elephant
Former range
Range today
(34,000–54,000 left)
Fig. 11-8d, p. 230
Case Study:
A Disturbing Message from the Birds
 Human
activities are causing serious declines
in the populations of many bird species.
Figure 11-9
 Threatened
natural capital: the 10 most
threatened species of U.S. songbirds,
according to a 2002 study by the National
Audubon Society. Most of these species are
vulnerable because of habitat loss and
fragmentation from human activities. An
estimated 12% of the world’s known bird
species may face premature extinction from
human activities during this century. (Data
from National Audubon Society)
Case Study:
A Disturbing Message from the Birds
 The
majority of the
world’s bird species are
found in South
America.

Threatened with habitat
loss and invasive
species.
Figure 11-10
INVASIVE SPECIES
 Many
Kudzu vine was introduced in
the southeastern U.S. to
control erosion. It has taken
over native species habitats.
nonnative
species provide us
with food, medicine,
and other benefits
but a a few can wipe
out native species,
disrupt ecosystems,
and cause large
economic losses.
Figure 11-A
INVASIVE SPECIES
 Many
invasive species have been introduced
intentionally.
Figure 11-11
Deliberately Introduced Species
Purple loosestrife European starling African honeybee
(“Killer bee”)
Marine toad
(Giant toad)
Water hyacinth
Japanese
beetle
Nutria
Hydrilla
Salt cedar
(Tamarisk)
European wild boar
(Feral pig)
Fig. 11-11a, p. 234
INVASIVE SPECIES
 Many
invasive species have been introduced
unintentionally.
Figure 11-11
INVASIVE SPECIES
 The
Argentina fire
ant was introduced
to Mobile, Alabama
in 1932 from South
America.


Most probably from
ships.
No natural
predators.
Figure 11-12
INVASIVE
SPECIES
 Prevention
is the
best way to reduce
threats from
invasive species,
because once they
arrive it is almost
impossible to slow
their spread.
Figure 11-13
Characteristics of
Successful
Invader Species
• High reproductive rate,
short generation time
(r-selected species)
• Pioneer species
• Long lived
Characteristics of
Ecosystems Vulnerable
to Invader Species
• Climate similar to
habitat of invader
• Absence of predators
on invading species
• Early successional
systems
• High dispersal rate
• Release growth-inhibiting
chemicals into soil
• Low diversity of
native species
• Absence of fire
• Generalists
• High genetic variability
• Disturbed by human
activities
Fig. 11-13, p. 236
POPULATION GROWTH,
POLLUTION, AND CLIMATE
CHANGE
 Population
growth, affluenza, and pollution
have promoted the premature extinction of
some species.
 Projected climate change threatens a number
of species with premature extinction.
Pollution
 Each




Example of biomagnification
of DDT in an aquatic food
chain.
year pesticides:
Kill about 1/5th of the
U.S. honeybee
colonies.
67 million birds.
6 -14 million fish.
Threaten 1/5th of the
U.S.’s endangered
and threatened
species.
Figure 11-15
DDT in fish-eating
birds (ospreys)
25 ppm
DDT in large fish
(needle fish)
2 ppm
DDT in small
fish (minnows)
0.5 ppm
DDT in
zooplankton
0.04 ppm
DDT in water
0.000003 ppm,
or 3 ppt
Fig. 11-15, p. 237
OVEREXPLOITATION
 Some
protected species are killed for their
valuable parts or are sold live to collectors.
 Killing predators and pests that bother us or
cause economic losses threatens some
species with premature extinction.
 Legal and illegal trade in wildlife species
used as pets or for decorative purposes
threatens some species with extinction.
OVEREXPLOITATION
 Rhinoceros
are often
killed for their horns
and sold illegally on
the black market for
decorative and
medicinal purposes.
Figure 11-16
Case Study:
Rising Demand for Bushmeat in
Africa
 Bushmeat
hunting has
caused the local
extinction of
many animals in
West Africa.
 Can spread
disease such as
HIV/AIDS and
ebola virus.
Figure 11-17
PROTECTING WILD SPECIES:
LEGAL AND ECONOMIC
APPROACHES
 International
treaties have helped reduce the
international trade of endangered and
threatened species, but enforcement is
difficult.

One of the most powerful is the 1975 Convention
on International Trade of Endangered Species
(CITES).
• Signed by 169 countries, lists 900 species that cannot
be commercially traded.
Case Study:
The U.S. Endangered Species Act
 One
of the world’s most far-reaching and
controversial environmental laws is the 1973
U.S. Endangered Species Act (ESA).


ESA forbids federal agencies (besides defense
department) to carry out / fund projects that
would jeopardize an endangered species.
ESA makes it illegal for Americans to engage in
commerce associated with or hunt / kill / collect
endangered or threatened species.
Case Study:
The U.S. Endangered Species Act
 Biodiversity
hotspots in relation to the largest
concentrations of rare and potentially
endangered species in the U.S.
Figure 11-18
Top Six Hot Spots
1 Hawaii
2 San Francisco Bay
area
3 Southern
Appalachians
4 Death Valley
5 Southern California
6 Florida Panhandle
Concentration of rare species
Low
Moderate
High
Fig. 11-18, p. 241
Endangered Species
 Because
of
scarcity of
inspectors,
probably no
more than 1/10th
of the illegal
wildlife trade in
the U.S. is
discovered.
Figure 11-19
Endangered Species
 Congress
has amended the ESA to help
landowners protect species on their land.
 Some believe that the ESA should be
weakened or repealed while others believe it
should be strengthened and modified to focus
on protecting ecosystems.
 Many scientists believe that we should focus
on protecting and sustaining biodiversity and
ecosystem function as the best way to
protect species.
How Would You Vote?
 Should
the Endangered Species Act be
modified to protect and sustain the nation's
overall biodiversity?


a. No. Protecting entire habitats will only further
interfere with the rights of landowners.
b. Yes. Protecting endangered habitats is more
efficient and effective than saving individual
species.
PROTECTING WILD SPECIES: THE
SANCTUARY APPROACH
 The
U.S. has set aside 544
federal refuges for wildlife,
but many refuges are
suffering from environmental
degradation.
Pelican Island was the
nation’s first wildlife refuge.
Figure 11-20
PROTECTING WILD SPECIES: THE
SANCTUARY APPROACH
 Gene
banks, botanical gardens and using
farms to raise threatened species can help
prevent extinction, but these options lack
funding and storage space.
 Zoos and aquariums can help protect
endangered animal species by preserving
some individuals with the long-term goal of
reintroduction, but suffer from lack of space
and money.
RECONCILIATION ECOLOGY
 Reconciliation
ecology involves finding ways
to share places we dominate with other
species.



Replacing monoculture grasses with native
species.
Maintaining habitats for insect eating bats can
keep down unwanted insects.
Reduction and elimination of pesticides to protect
non-target organisms (such as vital insect
pollinators).
Using Reconciliation Ecology to
Protect Bluebirds
 Putting
up bluebird
boxes with holes too
small for (nonnative)
competitors in areas
where trees have
been cut down have
helped reestablish
populations.
Figure 11-B
What Can You Do?
Protecting Species
• Do not buy furs, ivory products, and other
materials made from endangered or threatened
animal species.
• Do not buy wood and paper products
produced by cutting remaining oldgrowth forests in the tropics.
• Do not buy birds, snakes, turtles, tropical fish,
and other animals that are taken from the wild.
• Do not buy orchids, cacti, and other plants that
are taken from the wild.
• Spread the word. Talk to your friends and
relatives about this problem and what they can
do about it.
Fig. 11-21, p. 246