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Silently read page 183 Core Case Study
The passenger Pigeon: Gone Forever
Chapter 9
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Passenger pigeon hunted to extinction by 1900
 Why?
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Commercial hunters used a "stool pigeon”
 What is a stool pigeon?

Archeological record shows five mass extinctions
 What caused them?

Human activities: hastening more extinctions?
 How many species will become prematurely extinct?
Objective 1
“The natural world is everywhere disappearing
before our eyes – cut to pieces, mowed down,
plowed under, gobbled up, replaced by human
artifacts.” –Edward O.Wilson

Humans have disturbed ½ & probably about 83%
of the earth’s land surface
 Most of this disturbance involved filling in wetlands
 Converting grasslands & forests to crop fields & urban
areas
 Such disturbances eliminate large numbers of species by
destroying or degrading habitats

Background extinction
 Eventually all species become extinct. For the 3.56 billion years life has existed
on earth, there has been continuous, low level rates of extinction

Extinction rate
 The percentage or number of species that go extinct within a certain timer
period
 Example
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1 extinction per million species per year =
1 / 1 x 106 =
1 x 10-6 x 100 = .0001%
Mass extinction
 The extinction of many species in a relatively short period of geologic time
 There have been 5 mass extinctions

Levels of species extinction
 Local extinction – a species in no longer found in an area, but is still found
elsewhere
 Ecological extinction- so few members of a species are left that it can no longer
play its ecological roles in communities where it is found
 Biological extinction – the species is no longer found anywhere on the earth

Premature extinctions due to
 Habitat destruction
 Overhunting

Conservative estimates of extinction = 0.01-1.0%

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100 to 1000 times the background rate of .0001%
Growth of human population will increase this loss
Rates are higher where there are more endangered species
Tropical forests and coral reefs, wetlands and estuaries—sites
of new species—being destroyed
Speciation crisis – in addition to increasing the rate of
extinction, we may be limiting the long-term recovery
of biodiversity by reducing the rate of speciation
Why do you think birds top the list of extinct species?
Figure 9-3 for
packet

Endangered species – has so few individual
survivors that the species could soon become
extinct over all or most of its natural range

Threatened species, a.k.a. vulnerable species
 Still abundant in its natural range but, because of
declining numbers, is likely to become endangered in
the near future.
Fig 9-4 of text / pg 187
Copy this chart and commit it to
memory
Fig 9-5 / page 188
Why do you
think fishes
top this list?


Read science focus on page 188
There are 3 problems when estimating rates
 Hard to document due to length of time
 Only 1.8 million species identified out of 4-100 million
 Little known about nature and ecological roles of
species identified
How would you improve the estimation of
extinction rates?
Objective 2

Instrumental value
 Use values
 Their usefulness in providing ecological and economic services
▪ Ecotourism: wildlife tourism generates 950,000-1.8 million/minute
▪ 1 male lion living to 7 generate $515,000 in tourist dollars in Kenya and only
$1,000 if killed for its skin.
▪ Each year Americans spends more than 3X as many hours watching wildlife as
they spend watching movies or professional sporting events
 Nonuse value
▪ Existence value – the satisfaction of knowing that a species exists
▪ Aesthetic value – appreciate it for its beauty
▪ Bequest value – people will pay to protect some forms of natural
capital for future generations

Ecological value – vital component of ecosystem
functions of energy flow, nutrient cycling, and
population control
About 2,100 of the 3,000 plants identified by the National Cancer
Institute as sources of cancer-fighting chemicals come from
tropical forest.


Read the Science Focus on page 191
1989 international treaty against poaching
elephants
 400,000 elephants remain in the wild
 Before treaty – 87,000 were killed a year for ivory
 The treaty reduced poaching, but did not stop it.
 Currently 25,000 elephants per year

On the flip side, elephant populations have
exploded in some areas and are destroying
vegetation
 An adult elephant devours up to 660lbs of vegetation a day

Elephants damaging areas of South Africa:
 Do you favor culling elephants in areas where large
populations are degrading vegetation?

Intrinsic value: existence value
 An inherent right to exist and play its ecological roles,
regardless of its usefulness to us

Edward O. Wilson: biophilia phenomenon
 Because of the billions of years of biological connections
leading to the evolution of the human species, we have
an inherent genetic kinship with the natural world.

Biophobia
 Fear of many forms of wildlife

Read Science focus on page 192

Vulnerable to extinction – 25% of the worlds bats are endangered or
threatened – Why?
 Slow to reproduce
 Live in huge colonies in caves and abandoned mines
▪ Humans close up which trap bats in

Important ecological roles – What do bats do for us?
 70% of bats feed on crop-damaging nocturnal insects
 Pollen-eaters = pollinate flowers
 Fruit-eaters = distribute plants

Unwarranted fears of bats – Should you fear bats?
 More Americans die from being hit by coconuts than bat-transmitted disease.
Objective 3

The greatest threats to any species are (in order)
1. Habitat destruction, degradation, & fragmentation
2. Invasive (nonnative) species
3. Population and resource use growth
4. Pollution
5. Climate change
6. Overexploitation
Figure 9-10 for packet
What are two direct causes that are related to each of the
underlying causes?

Read the Science Focus on page 195

Tropical rain forests typically consist of large numbers of different
tree species with only a few members of each species in an area.

Tropical Biologist Bill Laurance, et al. studies the effects of
increasing fragmentation of tropical rain forests.
Why are TRF being fragmented?
 Roads, crop plantations, settlements, and cattle grazing

How large must a forest fragment be in order to prevent the loss
of rare trees?
 Within 330 ft (100 meters) of the edge of a forest fragment, typically up to 36%
of the biomass of old-growth trees is lost within 10-17 years of fragmentation.

Habitat loss and fragmentation of the birds’ breeding habitats
 Forests cleared for farms, lumber plantations, roads, and development

Intentional or accidental introduction of nonnative species
 Eat the birds
Seabirds caught and drown in fishing equipment
 Migrating birds fly into power lines, communication towers, and
skyscrapers
 Other threats
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Oil spills
Pesticides
Herbicides
Ingestion of toxic lead shotgun pellets
Greatest new threat: Climate change
 Environmental indicators – because birds live in every climate and
biome, respond quickly to environmental changes in their habitats,
and are relatively easy to track and count.


Read the Science Focus on page 195

In 2004, the World Conservation Union placed 3 species of vultures
on the critically endangered list.
▪ In the 1990’s there were more than 40 million of these carcass-eating
vultures. Within a few years their populations had fallen by more than 97%.
▪ What happened to their numbers?

Vultures poisoned from diclofenac in cow carcasses
 Diclofenac is an anti-inflammatiry drug that reduces pain in cows and humans.
 Diclofenac caused kidney failure in vultures that feed on dead cows.
 When the vultures died off, the dead cow carcasses increased
 Wild dogs started eating the cow carcasses
 Wild dog population exploded = more rabies
 In 1997 more than 30,000 people died of rabies

Most species introductions are beneficial
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Food – corn, wheat, rice, cattle, & poultry (98% of our food)
Shelter
Medicine
Aesthetic enjoyment
Nonnative species may have no natural
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Predators
Competitors
Parasites
Pathogens
Why is this significant?
Over 7,000 harmful invasive species have been deliberately
or accidentally introduced into the USA
Fig. 9-14a, p. 199
Fig. 9-14b, p. 199

Imported from Japan in the 1930s
 Planted in the SE to control soil erosion
 “ The vine that ate the South”
 As our climate gets warmer, the kudzu spreads north

Could there be benefits of kudzu?
 A Japanese firm built a kudzu farm in the US and ships
extracted starch to Japan
▪ The starch is sold for beverages, confections, & herbal remedies
 Almost every part of the kudzu is edible

How do they get here?
 Downside of global trade
▪ Aircraft, ballast water of tankers and cargo ships, wooden packing crates, cars and
truck, boats, and tourists

Argentina fire ant: 1930s
 Shiploads of lumber or coffee imported from South America
 No natural predator
 Pesticide spraying in 1950s and 1960s worsened conditions
▪ Temporally reduced populations, but also wiped out native ants
▪ This reduced competition and encouraged genetic resistance

Burmese python
 Imported as a pet and dumped when they got too large
I hate
Argentina
Fire Ants!

Prevent them from becoming established in the 1st place!
BUT HOW ???
1. Learn the characteristics of invasive species (fig 9-17)
2. Increase ground surveys and satellite observations
▪ Detect and monitor species invasions
▪ Develop models on how they spread
3. Step up inspection of imported goods
4. Set up treaties to ban transfer of invader species
5. Require cargo ships to discharge ballast water before entering
ports
6. Try to find natural ways to control them
▪ Predators, parasites, bacteria, and viruses
Figure 9-17 for
packet
Which, if any of the
characteristics on
the right-hand side
could human
influence?
Discuss with your letter partner.
Which of these two actions do you think are the most important? Why?

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Population growth and overconsumption have greatly
expanded the human ecological footprint
Climate change could drive more than 25% of all land
animals and plants to extinction by the end of the
century
Pollution and Pesticides
 DDT: Banned in the U.S. in 1972
 Pesticides kill about 20% of the beneficial honeybees, more
than 67 million birds, and 6-14 million fish.
 Bioaccumulation – an increase in the concentration of a chemical in
specific organs or tissues
 Biomagnification – an increase in concentration of DDt, PCbs, and
other slowly degradable, fat soluble chemicals in organisms at higher
trophic levels
So What?

Indigenous people sustained
by bush meat
1.
Within 1 or 2 decades, the
Congo basin’s rain forest –
the world’s 2nd largest rain
forest – will contain few
large mammals
2.
Butchering and eating
some forms of bush meat
has helped to spread fatal
diseases such as HIV/AIDS
and Ebola to humans
Objective 4

We can use existing environmental laws and treaties and work to
enact new laws designed to prevent species extinction and protect
overall biodiversity.

1975: Convention on International Trade in Endangered Species
(CITES)
 Bans capturing and selling threated or endangers species.
 Lists 900 species that cannot be commercially traded
 Signed by 172 countries

Convention on Biological Diversity (BCD)
 Focuses on ecosystems (reverse global decline of biodiversity)
 Ratified by 190 countries (not the U.S.)

Endangered Species Act (ESA): 1973 & later
amended in 1982, 1983, &1985
 Write down the ESA suggestions on page 208

Identify and protect endangered species in the U.S.
and abroad

Hot Spots – many of the rarest and most imperiled
species are concentrated in a few areas

We can help to prevent species extinction by
creating and maintaining wildlife refuges, gene
banks, botanical gardens, zoos, and aquariums.
1. Wildlife refuges
 Most are wetland sanctuaries
 More needed to protect endangered plants
2. Gene or seed banks
 Preserve genetic material of endangered plants
 Storing seeds in refrigerated, low humidity
environments
 More than 100 seed banks around the world
3. Botanical gardens and arboreta
 Contain Living plants

Techniques for preserving endangered terrestrial
species
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Egg pulling
Captive breeding
Artificial insemination
Embryo transfer
Use of incubators
Cross-fostering
Problems
 Zoo and aquariums limited space and funds
 Critics say these facilities are prisons for the organisms
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.
In earlier times, many people viewed huge flocks of
passenger pigeons as pest that devoured grain and
left massive piles of their waste. Do you think this
justified the passenger pigeon’s premature
extinction? Explain.
Assume you believe that premature extinction of an
undesirable species is justified, what would be you
three top candidates? What might be some
harmful ecological effects of such extinctions?