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Sustaining Biodiversity:
The Species Approach
Chapter 9
Core Case Study:
The Passenger Pigeon: Gone Forever
 Once the most numerous
bird on earth.
 In 1858, Passenger Pigeon
hunting became a big
 By 1900 they became
extinct from over-harvest
and habitat loss.
9-1 What Role Do Humans Play in the
Premature Extinction of Species?
 Concept 9-1A We are degrading and
destroying biodiversity in many parts of the
world, and these threats are increasing.
 Concept 9-1B Species are becoming extinct
100 to 1,000 times faster than they were before
modern humans arrived on the earth (the
background rate), and by the end of this century,
the extinction rate is expected to be 10,000
times the background rate.
Extinctions Are Natural But
Sometimes They Increase Sharply
 Background extinction and Mass extinction
• Discussed in Chapter 4
 Extinction rate – the percent of species that go
extinct in a given time period.
• Background extinction
• 1/1,000,000 per year = 0.0001%
• Mass extinction
• 50 – 95% of all living things on the planet
Extinctions Are Natural But
Sometimes They Increase Sharply
 Species can become extinct in three ways:
• Local Extinction:
• A species is no longer found in an area it once
inhabited but is still found elsewhere in the world.
• Typically the result of habitat destruction and affects
more than one species.
• Ecological Extinction:
• Occurs when so few members of a species are left
they no longer play its ecological role.
• Biological Extinction (Global Extinction):
• Species is no longer found on the earth.
• Biological extinction is FOREVER.
Some Human Activities Cause Premature
Extinctions; the Pace Is Speeding Up
 Estimates of current annual extinction rate:
• 0.01-1.0%
• 100 to 1,000 times greater than the background
extinction rate of 0.0001%
 Experts predict extinction rates will increase over
the next 50-100 years.
 Reason = US!!
Animal Species Prematurely Extinct
Due to Human Activities
 Many animals have become prematurely extinct
because of human activities.
• Development, habitat destructions, hunting, etc.
Animal Species Prematurely Extinct
Due to Human Activities
“The first animal species to go are the big,
the slow, the tasty, and those with
valuable parts…”
– Edward O. Wilson
(biodiversity expert)
Endangered Natural Capital:
Species Threatened with Premature Extinction
 Threatened (vulnerable) species:
• Still abundant in its natural range but is likely to
become endangered in the near future.
 Endangered species:
• So few individual survivors that it could soon
become extinct.
Endangered Natural Capital:
Species Threatened with Premature Extinction
 Extinct Ex.: Dodo, Passenger Pigeon
 Extinct in the wild Ex.: Alagoas Curassow
• Captive individuals survive, but there is no free-living, natural population
 Critically endangered Ex.: Ivory-billed Woodpecker, Javan Rhino
• Faces an extremely high risk of extinction in the immediate future
 Endangered Ex.: Cheetah, Blue Whale, Snow Leopard
 Vulnerable Ex.: Lion, Wolverine
 Conservation Dependent Ex.: Leopard Shark, Bristlecone Fir
• Would be threatened without active conservation programs.
 Near Threatened Ex.: California Red-legged Frog, Silvery Woolly Monkey
• Likely to qualify as threatened soon.
 Least Concern Ex.:Brown Rat, Rock Pigeon, Common Juniper
• No immediate threat to the survival of the species.
Endangered Natural Capital:
Species Threatened with Premature Extinction
Endangered Natural Capital:
Species Threatened with Premature Extinction
Characteristics of Species That Are Prone to
Ecological and Biological Extinction
 Some species have
characteristics that
make them more
vulnerable to ecological
and biological extinction.
 These characteristics
make survival harder
when environmental
conditions change or
when humans interfere.
Percentage of Various Species
Threatened with Premature Extinction
Science Focus:
Estimating Extinction Rates Is Not Easy
 Three problems with estimating extinction rate:
• Hard to document due to length of time
• Only 1.8 million species identified
• Little known about nature and ecological roles of
species identified
9-2 Why Should We Care about Preventing
Premature Species Extinction?
 Concept 9-2 We should prevent the premature
extinction of wild species because of the
economic and ecological services they provide
and because they have a right to exist
regardless of their usefulness to us.
Species Are a Vital Part
of the Earth’s Natural Capital
 Instrumental value – Usefulness in terms of economic
and ecological services
• Use value – economic goods or services
• Ecotourism: wildlife tourism
• Genetic information
• Nonuse value
• Existence value – happy knowing they are around
• Aesthetic value – pleasing to the eye
• Bequest value – available for future generations
 Ecological value – vital component of the ecosystem
9-3 How do Humans Accelerate
Species Extinction?
 Concept 9-3 The greatest threats to any
species are (in order) loss or degradation of its
habitat, harmful invasive species, human
population growth, pollution, climate change,
and overexploitation.
Loss of Habitat Is the Single Greatest
Threat to Species: Remember H.I.P.P.C.O.
 H.I.P.P.C.O. – the most important causes of
premature extinction:
• Habitat destruction, degradation, and
• Invasive (nonnative) species
• Population and resource use growth
• Pollution
• Climate change
• Overexploitation
 Habitat loss is the GREATEST threat to biodiversity
on this planet.
Degradation of coral reefs
Draining wetlands
Plowing grasslands
 Habitat fragmentation – when a large continuous
habitat is divided into smaller, scattered patches.
• By roads, agriculture, urban developed, etc.
 Reduction in
ranges of four
wildlife species,
mostly due to
habitat loss and
 Endemic Species
• Only live in one specific place (geographic location
or habitat type – usually islands)
• Very vulnerable to extinction as a result of habitat
loss or degradation.
 Many nonnative species are beneficial:
• Food, Medicine, Aesthetic enjoyment
 However, a few can wipe out native species, disrupt
ecosystems, and cause large economic losses.
 Nonnative species can become a problem since
they may have no natural:
• Predators
• Competitors
• Pathogens/Diseases
Kudzu vine was introduced to the southeastern U.S. in the 1930’s to
control erosion. Since then, it has taken over native species habitats.
 Many invasive species have been introduced intentionally…
…other invasive species have been introduced unintentionally.
Characteristics of Invader Species and
Ecosystems Vulnerable to Invading Species
 Prevention is the best way to reduce threats from invasive species,
because once they arrive it is almost impossible to slow their spread.
 Humans have increased the species extinction rate
by approximately 1,000 times.
 Experts predict that these rates will continue, or
accelerate, in the future.
 Human activities can pollute the water, soil, or air on
both on a local and global scale:
• Water – sewage, fertilizers, toxic chemicals and oil
• Soil – pesticides, waste, herbicides and toxic chemicals
(which may be washed from the land into water)
• Air – smoke and gases such as SO4, CO2, CH4 or other
gases that can lead to climate change
 In the 1950’s and 1960’s populations of fish
eating birds plummeted to dangerously low levels
• Cause? The pesticide known as DDT
• Banned in the U.S. in 1972
 Bioaccumulation
• DDT is fat soluble and can
accumulate in tissues
 Biomagnification
• the concentration of DDT in
tissues increases as you go
up the trophic levels
 Climate change caused by global warming
could lead to the extinction of up to 25% of all
land plants and animals by the year 2100.
 Many (but not all) extinctions will take place in
the upper latitudes:
• Polar bears
• 17 Penguin species
 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.
 Bush meat – indigenous people sustainably
hunting for food…more people = more hunting
 Rhinoceros are killed for their horns and sold
illegally on the black market.
 Elephants are killed for their ivory tusks
 Tigers and other “cats” killed for their pelts
9-4 How Can We Protect Wild Species
from Premature Extinction?
 Concept 9-4A We can use existing environmental laws
and treaties and work to enact new laws designed to
prevent species extinction and protect overall biodiversity.
 Concept 9-4B We can help to prevent species extinction
by creating and maintaining wildlife refuges, gene banks,
botanical gardens, zoos, and aquariums.
 Concept 9-4C According to the precautionary principle,
we should take measures to prevent or reduce harm to the
environment and to human health, even if some of the
cause-and-effect relationships have not been fully
established, scientifically.
International Treaties Can Help
Protect Species
 International treaties have helped reduce the trade of
endangered and threatened species.
 The 1975 Convention on International Trade of
Endangered Species (CITES)
• Lists 900 species that cannot be commercially
traded as live specimens or wildlife products
• Signed by 172 countries
• Enforcement is difficult
• Probably only 10% of illegal trade in the U.S. is caught
Case Study:
The U.S. Endangered Species Act
 One of the world’s most far-reaching and controversial
environmental laws:
 The 1973 U.S. Endangered Species Act (ESA)
• Overall goal is to identify and protect endangered
species in the U.S. and abroad.
• ESA makes it illegal for Americans to engage in
commerce associated with, or hunt / kill / collect,
endangered or threatened species.
• ESA forbids federal agencies (besides defense
department) to carry out or even fund projects that
would jeopardize an endangered species.
Case Study:
The U.S. Endangered Species Act
 Accomplishments:
• More than half of the species listed are stable or improving
• 99% of all listed species are still living
 Challenges:
• Very small budget
• Species are listed when faced with serious threat of extinction
• It can take decades to bring a species’ populations up
 Suggested changes to ESA:
• Increase the budget
• Develop recovery plans more quickly
• Establish a core of the endangered organism’s survival habitat
Gene Banks, Botanical Gardens, and Wildlife
Farms Can Help Protect Species
 Gene banks and botanical gardens to raise
threatened species can help prevent extinction.
 Zoos and aquariums can help protect endangered
animal species by preserving some individuals with
the long-term goal of reintroduction.
Gene Banks, Botanical Gardens, and Wildlife
Farms Can Help Protect Species
 Techniques for preserving endangered terrestrial
animal species:
Egg pulling
Captive breeding
Artificial insemination
Embryo transfer
Use of incubators
The Precautionary Principle
 The Precautionary Principle
• When preliminary evidence indicates that an
activity can harm the environment or human health,
we should take precautionary measures to prevent
or reduce such harm, even if we don’t fully
understand the cause/effect relationship.
• “Better Safe Than Sorry”
 Scientists use the precautionary principle to argue
for the:
• Preservation of species
• Preservation of ecosystems