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Chapter 8
Biodiversity and
Conservation
Biology
This lecture will help you understand:
• The scope of
Earth’s biodiversity
• Background rates
and mass extinction
• Primary causes of
biodiversity loss
• The benefits of
biodiversity
• Conservation
biology
• Biodiversity
conservation efforts
Central Case: Saving the Siberian tiger
• Although tigers once roamed across Asia, today they are
exceedingly rare and approaching extinction.
• Siberian tigers are the largest cat in the world.
- The Russian Far East mountains house the last
remaining Siberian tigers.
- Historically, native people rarely killed tigers.
• Recently, the wild population approached extinction.
- Hunting, poaching, and habitat destruction from road
building, logging, and agriculture
• International conservation groups are working to save the
species from extinction.
- Research, education, zoos, and captive breeding
programs
Biodiversity encompasses several levels
• Humans are diminishing
Earth’s diversity of life.
• Biodiversity: sum total of all
organisms in an area
- Split into three specific
levels:
- Species diversity
- Genetic diversity
- Ecosystem diversity
Species diversity
• Species diversity: the number or variety of
species in the world or in a particular region
- Species richness: the number of species
- Evenness or relative abundance: extent
to which numbers of individuals of different
species are equal or skewed
- Speciation generates new species and
adds to species richness.
- Extinction reduces species richness.
The taxonomy of species
• Taxonomists: scientists
who classify species
- Common ancestry, ability
to interbreed
- Genera: related species
are grouped together
- Families: groups of
genera
• Every species has a twopart scientific name: genus
and species.
Subspecies: the level below a species
• Subspecies: populations of species that occur in different
areas and differ slightly from each other
- Divergence stops short of separating the species.
- Subspecies are denoted with a third part of the
scientific name.
Siberian tiger =
Panthera tigris altaica
Bengal tiger =
Panthera tigris tigris
All subspecies of tigers have
disappeared from 93% of
their historic range.
Genetic diversity
• Encompasses the differences in DNA among
individuals within species and populations
• The raw material for adaptation to local conditions
• Populations with higher genetic diversity can
survive.
- They can cope with environmental change.
• Populations with low genetic diversity are
vulnerable.
- To environmental change
- Disease
- Inbreeding depression: genetically similar
parents mate and produce defective offspring
Ecosystem diversity
• Ecosystem diversity: the number and
variety of ecosystems
• It also encompasses differing communities
and habitats.
- Sizes, shapes, and interconnectedness of
patches within habitats, communities, or
ecosystems
Some groups contain more species than
others
• Species are not evenly distributed among taxonomic
groups.
- Insects predominate over
all other life-forms.
- 40% of all insects are
beetles.
• Groups accumulate species
by:
- Adaptive radiation
- Allopatric speciation
- Low rates of extinction
Measuring biodiversity is not easy
• Species richness is a good gauge for overall
biodiversity.
• Out of our “best guess” estimates of 5–30 million
species on Earth, only 1.7–2 million species have
been identified and described.
• Very difficult to identify species
- Small organisms are easily overlooked.
- Many species look identical until closely
examined.
- Many remote spots on Earth remain unexplored.
Biodiversity is unevenly distributed
• Living things are distributed unevenly across Earth.
• Latitudinal gradient: species richness increases
toward the equator
- Equatorial regions have higher plant
productivity, stable climates, and no glaciation.
- Diverse habitats increase niches, which increase
species diversity.
- Ecotones (areas where habitats intermix) often
have higher diversity.
• Human disturbance can increase habitat diversity.
- But only at the local level
Biodiversity losses and species extinction
• Extinction: occurs when the last member of a species dies
and the species ceases to exist
• Extirpation: the disappearance of a particular population
from a given area, but not the entire species globally
- Can lead to extinction
• Paleontologists estimate 99% of all species are now extinct.
• Background rate of extinction: natural extinctions for a
variety of reasons
- Mammal and marine species: 1 species out of 1,000
become extinct every 1,000 to 10,000 years, which
translates to:
- 1 extinction per 1–10 million species
Earth has experienced five mass
extinctions
• In the past 440 million years, mass extinctions have
eliminated at least 50% of all species.
• Dinosaurs went extinct at the end of the Cretaceous
period (65 million years ago) from an asteroid impact.
The current mass extinction is human
caused
• During our modern era (Quaternary period),
we may lose more than half of all species.
• Today’s extinction event differs from others
because it is…
- Caused by humans, and
- Humans will suffer because of it
• The current global extinction rate is 100 to
1,000 times greater than the background rate.
- This rate will increase tenfold in future
decades.
People have hunted species to extinction for
millennia
Extinctions followed human arrival on islands and continents.
Current extinction rates are higher than
normal
• The Red List: an updated list of species facing high
risks of extinctions
- 22% of mammal species
- 12% of bird species
- 16–86% of all other species
• Since 1970, 58 fish species, 9 bird species, and 1
mammal species have gone extinct.
- In the U.S. in the last 500 years, 236 animal and
17 plant species are confirmed extinct.
- Actual numbers are undoubtedly higher.
Biodiversity loss is more than extinction
• Population is declining
- Accompanied by
shrinking
geographic ranges
• Genetic, ecosystem,
and species diversity
are being lost.
• The Living Planet
Index summarizes
trends in populations.
- Between 1970 and
2003, the Index fell
by 30%.
Biodiversity loss has many causes
• Reasons for biodiversity losses are
multifaceted, complex, and hard to determine.
• Four primary causes of population decline
are:
- Habitat alteration
- Invasive species
- Pollution
- Overharvesting
• Global climate change now is the fifth cause.
• Each factor is intensified by human
population growth and resource consumption.
Habitat alteration causes biodiversity loss
• The greatest cause of biodiversity loss
- Farming simplifies communities
- Grazing modifies grassland structure and species
composition
- Clearing forests removes resources that organisms
need.
- Hydroelectric dams turn rivers into upstream reservoirs
and affect floodplains downstream.
- Urbanization and suburban sprawl reduce natural
communities.
- A few species (i.e., pigeons, rats) benefit from changing
habitats.
Less than 1% of North America’s Great Plains remains, and
grassland bird populations have declined 82–99%.
Habitat alteration occurs in every biome
Particularly in tropical rainforests, tropical dry forests, and savannas
Invasive species cause biodiversity loss
• Introduction of non-native species to new
environments
- Accidental: zebra mussels
- Intentional: food crops
• Island species haven’t evolved defenses and are
very vulnerable.
- Invaders have no natural predators, competitors,
or parasites.
• Cost billions of dollars in economic damage each
year
Examples of exotic species causing problems
Pollution causes biodiversity loss
• Harms organisms in many ways
- Air pollution degrades forest ecosystems.
- Water pollution adversely affects fish and
amphibians.
- Agricultural runoff harms terrestrial and aquatic
species.
- The effects of oil and chemical spills on wildlife
are dramatic and well known.
• Although pollution is a substantial threat…
- It tends to be cause less damage than habitat
alteration or invasive species.
Overharvesting causes biodiversity loss
• Vulnerable species are large, few in number, long-lived, and
have few young (K-selected species).
- The Siberian tiger is hunted without rules and regulations.
- The early 1990s saw increased tiger poaching because of
powerful economic incentives.
- Many other species affected: Atlantic gray whale, sharks,
gorillas
Today the oceans contain
only 10% of the large
animals they once did.
Climate change causes biodiversity loss
• Our manipulation of earth’s climate system is
having global impacts on biodiversity.
• Emissions of greenhouse gases warm
temperatures.
- Modifies global weather patterns and
increases the frequency of extreme weather
events
- Increases stress on populations and forces
organisms to shift their geographic ranges
• Most animals and plants will not be able to
cope.
Warming has been the greatest in the Arctic
The polar bear has been listed on the U.S.
endangered species list.
Biodiversity loss has causes and consequences
Biodiversity benefits: free ecosystem
services
• Provides food, shelter, fuel
• Purifies air and water and detoxifies wastes
• Stabilizes climate, moderates floods, droughts, wind,
temperature
• Generates and renews soil fertility and cycles
nutrients
• Pollinates plants and controls pests and disease
• Maintains genetic resources
• Provides cultural and aesthetic benefits
• Allows us to adapt to change
The annual value of just 17 ecosystem services = $16 - 54 trillion per
year
Biodiversity benefits: maintain ecosystem
function
• Biodiversity increases the stability and
resilience of communities and ecosystems.
- Decreased biodiversity reduces a natural
system’s ability to function and provide
services to our society.
• The loss of a species affects ecosystems
differently.
- Extinction of a keystone species may cause
other species to decline or disappear.
Biodiversity benefits: enhanced food
security
• Genetic diversity in crops is
enormously valuable.
- Turkey’s wheat crops
received $50 billion worth of
disease resistance from wild
wheat.
• New potential food crops are
waiting to be used.
- Serendipity berry produces a
sweetener 3,000 times
sweeter than sugar.
- Salt tolerant grasses can be
irrigated with seawater.
Organisms provide drugs and medicines
• Each year
pharmaceutical
products owing their
origin to wild species
generate up to $150
billion in sales.
- The rosy periwinkle
produces
compounds that
treat Hodgkin's
disease and
leukemia.
Biodiversity benefits: economic benefits
• Biodiversity provides a source of income through
tourism.
- Ecotourism: people visit natural areas, creating
economic opportunity for residents living near
those areas
- Costa Rica: rainforests
- Australia: Great Barrier Reef
- Belize: reefs, caves, and rainforests
• A powerful incentive to preserve natural areas and
reduce impacts on the landscape and species
• But too many visitors to natural areas can degrade
the outdoor experience and disturb wildlife
Biodiversity benefits: people value nature
• Biophilia: connections that humans subconsciously seek
with life
- Our affinity for parks and wildlife
- Keeping of pets
- High value of real estate with views of natural lands
• Nature deficit
disorder:
alienation from
the natural
environment
- May be behind
the emotional
and physical
problems of
the young
Do we have ethical obligations to other
species?
• Many feel that living organisms have an innate right
to exist.
- Biodiversity conservation is justified on ethical
grounds.
- “If tigers aren’t worth saving, then what are we all
about? What is worth saving?”
• Despite our ethical convictions, and biodiversity’s
many benefits, the future of biodiversity remains far
from secure.
Conservation biology responds to
biodiversity loss
• Conservation biology: studies the factors that influence
the loss, protection, and restoration of biodiversity
- Scientists became alarmed at the degradation of natural
systems.
- Applied and goal-oriented, it tries to minimize human
impacts.
• Conservation geneticists: study genetic attributes of
organisms to infer the status of their population
- Minimum viable population: how small a population
can become before it runs into problems
• Conservation biologists try to learn how likely a population
is to persist or go extinct, particularly small and isolated
ones.
Island biogeography
• Protecting habitat and species requires thinking and
working at the landscape level.
• Equilibrium theory of island biogeography:
explains how species come to be distributed among
oceanic islands
- Also applies to “habitat islands” — patches of one
habitat type isolated within a “sea” of others
- Explains how the number of species on an island
results from an equilibrium between immigration
and extirpation
- Predicts an island’s species richness based on
the island’s size and distance from the mainland
Species richness results from island size and
distance
• Fewer species colonize an island far from the mainland.
• Large islands have higher immigration rates.
• Large islands have lower extinction rates.
The species-area curve
• Area effect: large islands contain more species than small
islands
- They are easier to find, and their larger populations
have lower extinction rates.
- They possess more habitats.
The number
of species
on an
island
doubles as
the island
size
increases
tenfold.
Small “islands” of habitat rapidly lose
species
• Forests are fragmented by
roads and logging.
• Small forest fragments lose
diversity fastest.
- Starting with large
species
Should conservation focus on endangered
species?
• Endangered Species Act (1973) (ESA): forbids the
government and private citizens from taking actions
that destroy endangered species or their habitats
- To prevent extinction
- Stabilize declining populations
- Enable populations to recover
• As of 2008, the U.S. had 1,046 species listed as
endangered and 307 listed as “threatened.”
Despite opposition, the ESA has had
successes
• Peregrine falcons, brown pelicans, bald eagles, and others
have recovered and are no longer listed as endangered.
• Intensive management has stabilized other species.
- The red-cockaded woodpecker
- 40% of declining populations are now stable.
• These successes occur despite underfunding of the U.S.
Fish and Wildlife Service and the National Marine Fisheries
Service.
- Recently, political forces have attempted to weaken the
ESA.
- In 2006, 5,700 U.S. scientists wrote letters of protest to
Congress.
The ESA is controversial
• Most Americans support protecting endangered
species.
• Opponents feel that the ESA values endangered
organisms more than the livelihood of people.
- Private land use will be restricted if an endangered
species is present.
- “Shoot, shovel, and shut up”: landowners conceal
the presence of endangered species on their land
• But the ESA has stopped few development projects.
- Habitat conservation plans and safe harbor
agreements: landowners can harm species if they
improve habitat for the species in other places
Other countries have their own version of
the ESA
• Species at Risk Act (2002): Canada’s endangered
species law
- Stresses cooperation between landowners and
provincial governments
- Criticized as being too weak
• Other nations’ laws are not enforced.
- The Wildlife Conservation Society has to help pay
for Russians to enforce their own anti-poaching
laws.
Protecting biodiversity
• Captive breeding: individuals are bred and raised with the
intent of reintroducing them into the wild
- Zoos and botanical gardens
• Some reintroductions are controversial.
Ranchers
opposed the
reintroduction of
wolves to
Yellowstone
National Park.
Some habitats
are so fragmented,
a species cannot
survive.
Protecting biodiversity
• Cloning: a technique to create more individuals
and save species from extinction
- DNA from an endangered species is inserted
into an egg, which is implanted into a surrogate
mother.
- Most biologists agree that these efforts are not
adequate to recreate the lost biodiversity.
• Ample habitat and protection in the wild are
needed to save species.
Umbrella species
• Conservation biologists use particular species as
tools to conserve communities and ecosystems.
- Protecting the habitat of these umbrella species
helps protect less-charismatic species that would
not have generated public interest.
• Flagship species: large and charismatic species
used as spearheads for biodiversity conservation
- The World Wildlife Fund’s panda bear
• Some organizations are moving beyond the single
species approach to focus on whole landscapes.
International conservation efforts
• UN Convention on International Trade in
Endangered Species of Wild Fauna and Flora
(CITES) (1973): protects endangered species by
banning international transport of their body parts
• Convention on Biological Diversity (1992):
- Seeks to conserve biodiversity
- Use biodiversity in a sustainable manner
- Ensure the fair distribution of biodiversity’s
benefits
- By 2008, 188 nations had signed on.
- Iraq, Somalia, the Vatican, and the U.S. did not
join.
Biodiversity hotspots
• Biodiversity hotspots:
an area that supports a
high number of species
- Endemic species:
species found
nowhere else in the
world
- The area must have
at least 1,500
endemic plant
species (0.5% of the
world total).
- It must have lost 70%
of its habitat due to
human impact.
There are 34 global biodiversity hotspots
2.3% of the planet’s land surface contains 50%
of the world’s plant species and 42% of all
terrestrial vertebrate species.
Community-based conservation
• Protecting habitats makes good sense, but this
affects people living in and near these areas.
• Community-based conservation: conservation
biologists actively engage local people in protecting
land and wildlife
- Projects provide education, retraining, and paid
salaries to protect animals from poachers.
- Protecting land protects resources from being
used up or sold to foreign corporations.
Conclusion
• Loss of biodiversity threatens to result in a mass
extinction event equivalent to mass extinctions of
the past.
• Primary causes of biodiversity loss are:
- Habitat alteration, invasive species, pollution,
overharvesting of biotic resources, and climate
change
• Human society cannot function without
biodiversity’s benefits.
• Science can help save species, preserve habitats,
restore populations, and keep natural ecosystems
intact.
QUESTION: Review
Which level is NOT included in the concept of
biodiversity?
a)
b)
c)
d)
Species
Genetics
Ecosystems
All of the above are included in this concept.
QUESTION: Review
What happens when a species experiences
“inbreeding depression”?
a) The species becomes too large for the resource
base
b) Genetically similar parents mate and produce
inferior offspring
c) Genetically similar parents mate and produce
superior offspring
d) The number and variety of species increases
e) An ecosystem’s biodiversity increases
QUESTION: Review
According to the concept of “latitudinal gradient,”
which of the following happens?
a) Species richness increases toward the equator
b) Species richness decreases toward the
equator
c) Species richness decreases over time
d) Countries like Canada have many more
species than expected
e) People in warmer climates protect species
better than people in colder climates
QUESTION: Review
Which of the following statements is FALSE?
a)
b)
c)
d)
Very small species are often overlooked.
Remote areas may have unidentified species.
We have identified almost all species on Earth.
There are more insect species than any other
type of species.
e) Ecotones often have high biodiversity.
QUESTION: Review
Which of the following is the major cause of
extinction?
a)
b)
c)
d)
e)
Invasive species
Pollution
Habitat loss
Overharvesting
These are pretty much equal in causing
extinction.
QUESTION: Review
Biodiversity does all of the following EXCEPT:
a)
b)
c)
d)
e)
Provide ecosystem services
Decrease food security
Maintain ecosystem function
Provide aesthetic benefits
Provide economic benefits
QUESTION: Review
According to the theory of island biogeography,
which island would have the LOWEST species
richness?
a)
b)
c)
d)
e)
A large island, close to the mainland
A large island, far from the mainland
A small island, close to the mainland
A small island, far from the mainland
None of these; islands don’t really have
species
QUESTION: Review
A “biodiversity hotspot” is:
a) An area located near the equator
b) An area that supports few, but large,
species
c) An area that contains naturally high
numbers of people
d) An area that contains a large number of
endemic species
e) An area where the wealthy can go on
vacation
QUESTION: Review
Which statement about the U.S. Endangered
Species Act is FALSE?
a) It forbids the government, but not private
citizens, from harming endangered species.
b) It lists endangered and threatened species.
c) It is designed to prevent extinction.
d) It is designed to enable populations to
increase.
e) It is designed to stabilize declining
populations.
QUESTION: Weighing the Issues
If a pharmaceutical company produces a medicine from a
plant found in Costa Rica that will earn millions of dollars,
who should reap the financial benefits?
a) The company, because it had to pay millions of dollars
to discover and produce the drug
b) Costa Rica, because it had the plant that produced the
drug
c) Taxpayers, because they fund lots of research through
their tax dollars
d) Native people in Costa Rica, because the company
would not have found the drug without their help
e) The native people, the company, and Costa Rica,
because all played a vital part in the drug’s discovery
and development
QUESTION: Weighing the Issues
Have you ever personally experienced
evidence of the biophilia hypothesis?
a)
b)
c)
d)
e)
Yes, I frequently feel a connection to other
living things and nature
Yes, sometimes, on a particularly lovely
day
Maybe, but I’m not sure
No, because I don’t get to experience
nature often enough
Definitely not, unless I was going to earn
money from using nature
QUESTION: Interpreting Graphs and Data
Where would ecotourists go to view the maximum
species richness on these islands?
a) Redonda
d) Hispaniola
b) Montserrat
e) Jamaica
c) Puerto Rico
QUESTION: Interpreting Graphs and Data
Which biome lost the most area by 1950? Which
biome lost the most area in recent decades?
a) Temperate
grassland,
tropical dry
forest
b) Desert,
savanna
c) Chaparral,
tundra
d) Temperate
grassland,
desert