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ENVIRONMENTAL SCIENCE 13e
CHAPTER 8:
Sustaining Biodiversity:
The Species Approach
Core Case Study: Polar Bears
and Projected Climate Change
• 20,000 – 25,000 polar bears in Arctic
• Hunt seals on winter sea ice
• Global warming is quickly reducing the
amount of sea ice and how long it lasts in
winter
• Polar bears have less time to hunt and
store fat for summer fasting
• Projected 30-35% decline by 2050
• Potentially extinct from wild by 2100
8-1 What Role Do Humans Play in
the Premature Extinction of Species?
• Concept 8-1 Species are becoming
extinct 100 to 1,000 times faster than
they were before modern humans
arrived on earth, and by the end of
this century, the extinction rate is
expected be 10,000 times higher than
the background rate.
Human Activities and Extinction
• Background extinction rate
• Current rate is 100-1000 times
background extinction
• Rate likely to rise to 10,000 times
• Is a mass extinction coming?
Current Extinction Rate
Estimates Are Conservative
• Species and biodiversity decrease in
next 50–100 years
• Biodiversity hotspot rates higher than
global average
• Degrading, simplifying, and
destroying diverse environments
Science Focus: Estimating
Extinction Rates (1)
•
Three difficulties
1. Not easy to document – takes a long
time
2. Only 2 million species of 8-100 million
identified
3. Little is known about the 2 million
species
Science Focus: Estimating
Extinction Rates (2)
• Study records of post-human extinctions
with previous extinctions from the fossil
record
• DNA copying mistakes
• How habitat reduction increases extinction
• Mathematical models
• Inadequate data and models
• Normal: 1 million to 10 million years
• Humans have greatly accelerated this
Ecological Smoke Alarms
• Endangered species
• Threatened species
• The first to go: large, slow, tasty, or
have valuable parts
• Some behaviors make species prone
to extinction
Case Study: Extinction of the
Passenger Pigeon
• Audubon, 1813: 3 days for a flock to
pass over
• Extinct by 1900
– Good to eat
– Feathers good for pillows
– Bones good for fertilizer
– Easy to kill
8-2 Why Should We Care about
Preventing Species Extinction?
• Concept 8-2 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.
Value of Species
• Instrumental value of biodiversity
– Food crops
– Genetic information
– Medicine
– Bioprospectors
– Ecotourism
• Do not know what we lose when
species go extinct
Ethical Obligations
• Intrinsic (existence) value
• Stewardship viewpoint
8-3 How Do Humans Accelerate
Species Extinction?
• Concept 8-3 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.
Causes of Endangerment and
Premature Extinction (HIPPCO)
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Habitat destruction
Invasive species
Population growth
Pollution
Climate change
Overexploitation
Habitat Loss
• Deforestation of tropical areas
greatest eliminator of species
• Endemic species
• Habitat fragmentation
Case Study: Declining Bird
Species (1)
• Decline of ~70% of ~10,000 known
species
• 12% threatened with extinction
• Birds around humans benefited, but
forest species declined
• Long-distance migrants – greatest
decline
Case Study: Declining Bird
Species (2)
• Reasons
– Habitat loss
– Habitat fragmentation
– Climate change
• Birds are environmental indicators
• Perform economic and ecological
services
Species Introductions
• Most beneficial – food crops,
livestock, pest control
• 500,000 alien invader species
globally
• 50,000 nonnative species in the U.S.
• Some definitely not beneficial
Case Study: The Kudzu Vine
• Kudzu introduced to control erosion
• Prolific growth
• Uses
– Asians use powdered starch in
beverages
– Edible
– Source of tree-free paper
– Japanese kudzu farm in Alabama
Disruptions from Accidentally
Introduced Species
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Downside of global trade
Downside of traveling
Argentina fire ant
Burmese python
Zebra mussel
Prevention of Nonnative
Species (1)
• Identify characteristics of successful
invaders
• Detect and monitor invasions
• Inspect imported goods
• Identify harmful invasive species and
ban transfer
Prevention of Nonnative
Species (2)
• Ships discharge ballast waters at sea
• Introduce natural control organisms of
invaders
Human Choices Drive Extinction
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Human population growth
Excessive, wasteful consumption
Use of pesticides
Climate change
DDT and Bioaccumulation
• 1950s–1960s fish-eating bird
populations drop
• DDT biologically magnified in food
webs
• Bird’s eggshells thin and fragile
• Leads to unsuccessful reproduction
Case Study: Where Have All the
Honeybees Gone?
• Honeybees responsible for 80% of
pollination of insect-pollinated plants
• Population down 30% since the 1980s
– Pesticides
– Parasitic mites
– Invasive African honeybees
• 2008: 36% of honeybee colonies lost
– Colony collapse disorder
– New nicotine-based pesticides to blame?
Illegal Killing and Trading of
Wildlife
• Poaching endangers many larger
animals, rare plants
• Over two-thirds die in transit
• Illegal trade: $1.1 million per hour
• Wild species depleted by pet trade
• Exotic plants often illegally gathered
The Value of Wild Rare Species
• Declining populations increase black
market values
• Rare species valuable in the wild –
eco-tourism
• Some ex-poachers turn to ecotourism
Rising Demand for Bush Meat
• Demand increasing with population
growth
• Increased road access
• Loggers, miners, ranchers add to
pressure
• Local and biological extinctions
• Spread of HIV and Ebola virus
8-4 How Can We Protect Wild
Species from Premature Extinction?
• Concept 8-4 We can reduce species
extinction and help to protect overall
biodiversity by establishing and
enforcing national environmental laws
and international treaties, creating a
variety of protected wildlife
sanctuaries, and taking precautionary
measures to prevent such harm.
International Treaties
• Convention on International Trade of
Endangered Species (CITES)
• Convention on Biological Diversity
(CBD)
U.S. Endangered Species Act
(1)
• National Marine Fisheries Services –
ocean species
• U.S. Fish and Wildlife Service – other
species
• Listings based on biological factors
• Forbids federal agency projects that
jeopardize listed species or habitats
U.S. Endangered Species Act
(2)
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Fines violations on private land
Illegal to sell or buy listed species
1,318 species listed
USFWS and NMFS supposed to
prepare recovery plan – 86% species
in 2009
U.S. Endangered Species Act
(3)
• Successful recovery plans include
American alligator, grey wolf, and
bald eagle
• Lax enforcement of imports and
exports
• Amended to give private landowners
economic incentive to save species
Science Focus: Accomplishments
of the Endangered Species Act
• Biologists defend limited success
– Species listed only when gravely
threatened
– Takes long time for species to recover
– >50% endangered species improving
• Need more funding
• Develop recovery plans more quickly
• Core habitat established when listed
Protection of Marine Species
• ESA and international treaties protect
endangered marine reptiles and
mammals
• Challenges to protecting marine
species
– Limited knowledge of species
– Difficulty in monitoring and enforcing
treaties – open oceans
Sea Turtles Threatened
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Six species critically endangered
Loss or degradation of habitat
Illegal harvest of eggs
Threats from fishing methods
Protection measures have helped
Case Study: Protecting Whales
(1)
• Easy to kill
• International Whaling Commission
– Sets quotas
– Often ignored
– No enforcement powers
• 1986: Whaling ban, although violated,
greatly decreased whale kills
Case Study: Protecting Whales
(2)
• Key countries that violate whaling ban
– Japan
– Norway
– Iceland
Establish Wildlife Refuges
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National Wildlife Refuge System
Wetland refuges: ~75%
40 million American visitors
20% of listed species in refuge
system
• Many refuges in disrepair, and many
allow mining, oil drilling, and off-road
vehicles
Storing Genetic Information
• Gene or seed banks
• Botanical gardens and arboreta
• Farms – commercial sale of
endangered species removes
pressure
Zoos and Aquariums for
Protection
• Collect species with long-term goal of
returning them into habitat
• Egg pulling
• Captive breeding
• 100–500 captive individuals to avoid
extinction
• 10,000 individuals to maintain
capacity for biological evolution
Case Study: Trying to Save the
California Condor
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Last 22 individuals captured
Released a few at a time
2009: 167 condors in the wild
Threatened by lead poisoning from
animal carcasses and gut piles
The Precautionary Principle
• When substantial preliminary evidence
indicates an activity could harm humans or
the environment, we should take
precautionary measures to prevent or
reduce the harm
• Do even if cause-and-effect relationships
are not yet clearly established
• “Better safe than sorry”
Three Big Ideas from This
Chapter - #1
We are greatly increasing the
premature extinction of wild species
by destroying and degrading their
habitats, introducing harmful invasive
species, and increasing human
population growth, pollution,
contributing to projected climate
change, and over-exploitation.
Three Big Ideas from This
Chapter - #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.
Three Big Ideas from This
Chapter - #3
We can work to prevent the premature
extinction of species and to protect
overall biodiversity by using laws and
treaties, protecting wildlife
sanctuaries, and making greater use
of the precautionary principle.