Chapter 7
Sustaining Biodiversity:
The Species Approach
Chapter 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?
Updates Online
The latest references for topics covered in this section can be found at
the book companion website. Log in to the book’s e-resources page at
www.thomsonedu.com to access InfoTrac articles.
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InfoTrac: Domestic cats serve as add-on predators.
Paducah Sun (Paducah, KY), July 26, 2006.
InfoTrac: Invasion of the habitat snatchers. Wichita
Eagle, August 6, 2006.
InfoTrac: Group pulls for native Denali plants.
Anchorage Daily News, June 26, 2006.
Union of Concerned Scientists: Invasive Species
PBS: Strange Days on Planet Earth
USGS: Nonindigenous Aquatic 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.
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.
Passenger pigeon
Great auk
Dodo
Dusky seaside
sparrow
Aepyornis
(Madagascar)
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.
Grizzly bear
Utah prairie dog
Kirkland’s
warbler
Knowlton
cactus
Florida
manatee
Swallowtail
butterfly
Humpback
chub
Golden lion
tamarin
African elephant
Siberian tiger
Giant panda Black-footed Whooping
crane
ferret
Mountain gorilla Florida
panther
California
condor
Northern
spotted owl
Hawksbill
sea turtle
Blue whale
Black
rhinoceros
SPECIES
EXTINCTION
 Some
species
have
characteristics
that make them
vulnerable to
ecological and
biological
extinction.
Characteristic
Low reproductive
rate
(K-strategist)
Specialized niche
Narrow distribution
Examples
Blue whale, giant panda,
rhinoceros
Blue whale, giant panda,
Everglades kite
Many island species,
elephant seal, desert pupfish
Feeds at high trophic Bengal tiger, bald eagle,
grizzly bear
level
Fixed migratory
patterns
Blue whale, whooping crane,
sea turtles
Rare
Many island species,
African violet, some orchids
Commercially
valuable
Snow leopard, tiger,
elephant, rhinoceros,
rare plants and birds
Large territories
California condor, grizzly
bear, Florida panther
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.
SPECIES EXTINCTION
 Percentage
of various species types
threatened with premature extinction from
human activities.
34% (51% of freshwater species)
Fish
25%
Mammals
20%
Reptiles
Plants
Birds
14%
12%
SPECIES EXTINCTION
 Scientists
use
models to
estimate the risk
of particular
species becoming
extinct or
endangered.
Number
of species
existing
5 million
14 million
50 million
100 million
Effects of a 0.1% extinction rate
5,000 extinct per year
14,000 extinct per year
50,000 extinct per year
100,000 extinct per year
Number of years until one million
species are extinct
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.
Habitat
Pollution
Overfishing
loss
Habitat degradation
Commercial hunting
Climate change
and fragmentation
and poaching
Sale of exotic
Introducing nonnati
Predator and pest control
ve species
pets and decorative
plants
Secondary Causes
• Population growth
• Rising resource use
• No environmental
accounting
• Poverty
Basic Causes
HABITAT LOSS, DEGRADATION,
AND FRAGMENTATION
 Reduction
in
ranges of four
wildlife species,
mostly due to
habitat loss
and
overharvest.
Indian Tiger
Range 100 years ago
Range today
(about 2,300 left)
Black Rhino
Range in 1700
Range today
(about 3,600 left)
African Elephant
Probable range 1600
Range today
Asian or Indian Elephant
Former range
Range today
(34,000–54,000 left)
Case Study:
A Disturbing Message from the Birds
 Human
activities are causing serious declines
in the populations of many bird species.
Cerulean warbler
Florida scrub jay
Sprague’s pipit
California
gnatcatcher
Bichnell’s thrush Black-capped
vireo
Kirtland’s warbler Henslow’s
sparrow
Golden-cheeked
warbler
Bachman’s warbler
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.
Number of
bird species
609
400
200
1
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.
INVASIVE SPECIES
 Many
invasive species have been introduced
intentionally.
INVASIVE SPECIES
 Many
invasive species have been introduced
unintentionally.
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)
Accidentally Introduced Species
Sea lamprey
Argentina
(attached to lake trout) fire ant
Formosan termite
Zebra mussel
Brown tree
snake
Asian longhorned beetle
Eurasian ruffe
Asian tiger
mosquito
Common pigeon
(Rock dove)
Gypsy moth larvae
INVASIVE SPECIES
 The Argentina
fire
ant was introduced
to Mobile, Alabama
in 1932 from South
America.


Most probably from
ships.
No natural
predators.
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.
What Can You Do?
Invasive Species
• Do not allow wild animals to escape.
• Do not spread wild plants to other areas.
• Do not dump the contents of an aquarium into waterways,
wetlands, or storm drains.
• When camping use wood near your campsite instead of bringing
firewood from somewhere else.
• Do not dump unused bait into the water.
• After dogs visit woods or the water brush them
them home.
before taking
• After each use clean your vehicle, mountain bike, surfboard,
kayaks, canoes, boats, tent, hiking boots, and other gear before
heading for home.
• Empty all water from canoes, kayaks, dive gear, and other
outdoor equipment before heading home.
• Plant a variety of trees, shrubs, and other plants in your yard to
reduce losses from invasive species.
• Do not buy plants from overseas or swap them with others using
the Internet.
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
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.
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
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.
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.
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.
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
Endangered Species
 Because
of
scarcity of
inspectors,
probably no
more than 1/10th
of the illegal
wildlife trade in
the U.S. is
discovered.
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?
To conduct an instant in-class survey using a classroom response
system, access “JoinIn Clicker Content” from the PowerLecture main
menu for Living in the Environment.
 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.
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.
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.