Chapter 11
Sustaining Biodiversity:
The Species Approach
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
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
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
 Percentage
of various species types
threatened with premature extinction from
human activities.
Figure 11-5
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
HABITAT LOSS, DEGRADATION,
AND FRAGMENTATION
 Reduction
in
ranges of four
wildlife species,
mostly due to
habitat loss
and
overharvest.
Figure 11-8
The Greatest Threat to the Biosphere!
 But
one of the greatest threats to
biodiversity comes from the introduction of
non-native species
INVASIVE SPECIES
 Invasive (implies that it’s introduction has been a problem)
 Introduced
 Alien
 Exotic
 Nonindigenous
 Non-native (often applied to species that are more benign)
Figure 11-A
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
Kudzu
Kudzu

Kudzu was introduced from Asia multiple times.






Initially as an ornamental for trellises
Then as a potential fodder for livestock
And then finally as a cover for roadsides (during the 1950’ and 1960’s as the US
Eisenhower Interstate system was being built).
Kudzu is a vine and has a deep taproot (several meters). The vine grows like
crazy and will cover large expanses of bare soil (and everything else) within one
growing season (it can grow several inches per day). Unfortunately the ground
cover does nothing to prevent soil erosion- the vegetation rests on the ground
but it doesn’t stabilize the soil. It only has one tap root. Roadsides covered with
grass are more stable because the grasses have fibrous roots (a mesh of a root
system rather than a single taproot). Because of its inability to stop soil erosion it
was abandoned as a road cover. It was ignored for about a decade, but by the
1970’s kudzu grew out of control. Today it is extremely hard to manage.
Because it has a deep taproot, if you mow it or cut it it comes right back. Certain
herbicides will control it but you have to mix very concentrated solutions, which
kills the native vegetation and pollutes the watershed. Herbicides are not
feasible over the large range.
Goats do a pretty good job at keeping it at bay. Repeated weeding by people will
also significantly reduce kudzu populations but this is labor intensive and not
practical over large areas.
In its native Asia, Kudzu is used in many different ways, to make bred, wine,
paper, baskets, etc. Now in the Southeast, there are kudzu festivals that
attempt to convince the public to use the kudzu. The hypothesis is that if people
find kudzu useful (to be used as food, to make wine, or to use the vines for
baskets) they will start collecting it more, and this will help reduce kudzu
expansion.
Kudzu
INVASIVE SPECIES
 Many
invasive species have been introduced
intentionally.
Figure 11-11
INVASIVE SPECIES
 Many
invasive species have been introduced
unintentionally.
Figure 11-11
Brown Tree Snake, Guam
There is a lot of concern about this snake being introduced into Hawaii or
introduced within the warmer environments of the US (e.g. Florida or Louisiana).
San Salvador Island
Australian Pine on San Salvador
Island
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
San Salvador Island
Australian Pine on San Salvador
Island
Characteristics of Invasive Species
1)
2)
3)
4)
5)
6)
Introduced into similar environment
Reproduce easily and quickly
No/few natural predators
More efficient than natives at competing
for resources
Abundance of prey
Invaders are well-adapted to human
activity.
Aquatic Invasive Plants

Purple Loosestrife = escaped ornamental that is
spreading at a rate of 115,000 hectares per year.
Aquatic Invasive Plants

Alligator weed = similar to the purple loosestrife,
alligator weed is spreading throughout
Southeastern wetlands – forming monospecific
stands that block out light and out-compete the
native aquatics.
Aquatic Invasive Plants

Water Hyacinth = naturalized from the Orinoco,
introduced within many aquatic environments in
warmer climates. The introduction of Water
Hyacinth in Lake Victoria is especially
problematic. It is chocking the lake and killing off
many of the fish.
Application of Herbicides to control
water hyacinth
http://dbw.ca.gov/images/hyancith.jpg
Aquatic Invasive Animals

Zebra Muscle = introduced into the Great Lakes (GL) and St.
Lawrence from ship ballast water. The second reading has
a good review of the economic impact of zebra muscles.
Aquatic Invasive Animals

Lampreys = migrated into the GL during the construction of
the Welland Canal (1921), source = http://www.greatlakes.net/envt/flora-fauna/invasive/lamprey.html. The
lamprey prey on native fish.
Aquatic Invasive Animals

Nutria or nutria rat = Originally brought in from South
America for their fur, but they escaped into the salt marshes
of the Gulf Coast and Maryland. The nutria eat the salt
marsh grasses and are significantly increasing loss of
coastal wetlands.
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
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
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.
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
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).