Download Genetic diversity

Species diversity
• Species Diversity = the number or variety of
species in the world or in a particular region
- 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
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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 inferior offspring
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Ecosystem diversity
• Ecosystem diversity = the number and variety of
ecosystems
• Also encompasses differing communities and
habitats
• Rapid vegetation change and varying landscapes
within an ecosystem promote higher levels of
biodiversity
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Measuring biodiversity is not easy
• Out of the estimated 3 - 100 million species on Earth,
only 1.7 - 2 million species have been successfully
catalogued
• Very difficult to identify species
- Many remote spots on Earth remain unexplored
- Small organisms are easily overlooked
- Many species look identical until thoroughly examined
• Entomologist Terry Erwin found 163 beetle species
specialized on one tree species
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Biodiversity is unevenly distributed
• Living things are
distributed unevenly across
Earth
• Latitudinal gradient =
species richness increases
towards the equator
Canada has 30 - 100 species of
breeding birds, while Costa Rica
has more than 600 species
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Latitudinal gradient has many causes
• Climate stability, high plant productivity, and no glaciation
• Tropical biomes support more species and show more species
evenness
- Diverse habitats increase species diversity
• Human disturbance can increase habitat diversity
- But only at the local level
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Biodiversity provides 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
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Biodiversity helps 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
- If the species can be functionally replaced by others, it
may make little difference
- Extinction of a keystone species may cause other species
to decline or disappear
• “To keep every cog and wheel is the first precaution of
intelligent tinkering” (Aldo Leopold)
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Biodiversity enhances food security
• Genetic diversity within crops is enormously
valuable
- Turkey’s wheat crops received $50 billion
worth of disease resistance from wild wheat
• Wild strains provide disease resistance and have
the ability to grow back year after year without
being replanted
• New potential food crops are waiting to be used
- Serendipity berry produces a sweetener 3,000
times sweeter than sugar
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Some potential new food sources
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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
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Biodiversity generates economic benefits
• People like to experience protected natural areas,
creating economic opportunities for residents,
particularly in developing countries
- 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 on native
species
• But, too many visitors to natural areas can degrade
the outdoor experience and disturb wildlife
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People value and seek out 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
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Do we have ethical obligations to other
species?
• Humans are part of nature and need resources to survive
• But, we also have conscious reasoning ability and can
control our actions
- Our ethics have developed from our intelligence and
our ability to make choices
• Many people feel that other organisms have intrinsic
value and an inherent right to exist
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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
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Extinction is a natural process
• Paleontologists estimate 99% of all species that ever
lived are now extinct
• Background rate of extinction = natural extinctions for
a variety of reasons
- 1 extinction per 1 to 10 million species for mammals
and marine species
- 1 species out of 1,000 mammal and marine species
would go extinct every 1,000 to 10,000 years
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What makes a species vulnerable to extinction?
• Specialized niche
• Low reproductive rate
- Blue whales, giant panda, rhinoceros
• Feeds at high trophic level
- Bengal tiger, bald eagle
• Fixed migratory patterns
- Blue whale, whooping crane, sea turtles
• Commercially valuable
- Snow leopard, tigers, elephants, rare birds, orchids
• Rare/Narrow Distribution (island species)
• Need Large Territory
- Condor, Florida panther
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Earth has experienced five mass
extinctions
• In the past 440 million years, mass extinctions have
eliminated at least 50% of all species
• After every mass extinction the biodiversity returned to or
exceeded its original state
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The current mass extinction is human
caused
• During this Quaternary period, we may lose more
than half of all species
- Hundreds of human-induced species
extinctions, and multitudes of others, teeter on
the brink of extinction
• The current global extinction rate is 100 to 1,000
times greater than the background rate
- This rate will increase tenfold in future decades
due to human population growth and resource
consumption
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Human Impacts on Ecosystems
• Fragmenting and degrading habitat (stop)
- e.g. Tropical forests being cut at a rate of 0.6 to 2% per year
- Half of remaining forests lost or degraded in 25 to 83yrs
• Simplifying natural ecosystems
- Creating monocultures
• Using, wasting, or destroying an increasing percentage of earth’s NPP (27% of
total)
• Strengthening some populations of pest species and disease causing bacteria by
causing genetic resistance through overuse of pesticides & antibiotics
• Eliminating some key predators
• Deliberately or accidentally introducing exotic species
• Over harvesting of renewable resources
• Interfering with normal cycling and flows of energy in ecosystems
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Causes of Premature Extinction of Wild Species
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Fig. 12-6 p. 231
People have hunted species to extinction for
millennia
Extinctions followed human arrival on islands and continents
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Poaching often = Extinction
CITIES Treaty
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Endangered vs. Threatened
• Endangered:
- So few left that species could soon become extinct over all or
most of its range
• Threatened:
- Still relatively abundant but b/c of declining numbers is likely
to become endangered in the near future
• WWF study: 30k Under threat of extinction
- 34% of world’s fish
- 25% of world’s amphibians
- 24% of world’s mammals
- 20% of world’s reptiles
- 14% of world’s plant species
- 12% of world’s bird species
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Current extinction rates are higher than
normal
• The Red List = an updated list of species facing high
risks of extinctions
- 23% of mammal species
- 12% of bird species
- 31 - 86% of all other species
• Since 1970, 58 fish species, 9 bird species, and 1
mammal species has 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
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Biodiversity loss is more than extinction
• Decreasing numbers are
accompanied by smaller
species’ 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%
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Biodiversity loss has many causes
• Reasons for biodiversity losses are multifaceted,
complex, and hard to determine
- Factors may interact synergistically
• Four primary causes of population decline are:
- Habitat alteration
- Invasive species
- Pollution
- Overharvesting
• Global climate change now is the fifth cause
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Threats from Nonnative Species
Fig. 12-12 p. 238
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Invasive species cause biodiversity loss
• Introduction of non-native species to new environments
- Accidental: zebra mussels
- Deliberate: food crops
• Island species are especially vulnerable
• Invaders have no natural predators, competitors, or parasites
• Cost billions of dollars in economic damage
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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
• The damage to wildlife and ecosystems caused by
pollution can be severe
- But it tends to be less than the damage caused
by habitat alteration or invasive species
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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
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
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Climate change causes biodiversity
loss
• Emissions of greenhouse gases warms 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
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Warming has been the greatest in the Arctic
The polar bear is being considered for the endangered
species list
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Biodiversity loss has a variety of causes
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Conservation biology responds to
biodiversity loss
• Conservation biology =
devoted to understanding
the factors that influence
the loss, protection, and
restoration of biodiversity
- Arose as scientists
became alarmed at the
degradation of natural
systems
- An applied and goaloriented science
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Conservation scientists work at multiple
levels
• Conservation biologists integrate evolution and
extinction with ecology and environmental systems
- Design, test, and implement ways to mitigate
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
• Metapopulations = a network of subpopulations
- Small populations are most vulnerable to extinction
and need special attention
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Preserving Biodiversity
The Species Approach
The Ecosystem Approach
Goal
Goal
Protect species from
premature extinction
Protect populations of
species in their natural
habitats
Strategies
• Identify endangered
species
• Protect their critical
habitats
Tactics
• Legally protect
endangered species
• Manage habitat
Strategy
Preserve sufficient areas
of habitats in different
biomes and aquatic
systems
Tactics
• Protect habitat areas
through private purchase or
government action
• Propagate endangered
species in captivity
• Eliminate or reduce
populations of alien species
from protected areas
• Reintroduce species into
suitable habitats
• Manage protected areas to
sustain native species
• Restore degraded
ecosystems
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PRESERVE “HOT
SPOTS”
Fig. 7-2, pg. 136
Protecting Wild Species: The Sanctuary Approach
 Wildlife refuges and protected areas
 Gene banks, botanical gardens, and farms
 Zoos and Aquariums
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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 habitat is so fragmented, a species cannot survive
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Protecting biodiversity
• Cloning – a technique to create more individuals and
save species from extinction
- 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
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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 animals 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
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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 2007, the U.S. had 1,312 species listed as
endangered or threatened
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US Endangered Species Act (1973—Nixon!)
• Provides a program for the conservation of threatened and endangered
plants and animals and the habitats in which they are found
- Dept of Interior maintains the list of 632 endangered species (over
50% plants) and 190 threatened species
- Anyone can petition the US F&WS to add a species to the list
(if it is in danger of extinction in all or most of its range)
- Can be listed b/c of habitat destruction, overexploitation,
disease/predation, inadequacy of existing regulations, any
human threat to its continued existence
• Law prohibits any action (either administrative or “real”) that results in
the “taking” of a listed species OR ADVERSELY AFFECTS
HABITAT
- Illegal to take, possess, sell, transport listed sp.
- Recovery Plan is written for each species
- Provides for acquire land that preserves these species
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The ESA is controversial
• Many Americans support protection of 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
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Despite opposition, the ESA has had
successes
• Peregrine falcons, brown pelicans, bald eagles,
and others have recovered and are no longer listed
• 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
- In recent years, political forces have attempted
to weaken the ESA
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The Lacey Act
•
Overview. This Act authorizes the Secretary of the Interior to adopt measures to aid in
restoring game and other birds in parts of the U.S. where they have become scarce or
extinct and to regulate the introduction of birds and animals in areas where they had not
existed. All sections but one of the original 1900 Act have been repealed and either
restated in or reenacted by other code provisions. This is a summary of the one remaining
section of the original Lacey Act.
•
Game and Wild Bird Preservation. The purposes of the Act are to aid in the restoration
of game and other wild birds in parts of the U.S. where they have become scarce or
extinct and to regulate the introduction of American or foreign birds or animals in
localities where they have not previously existed. The duties and powers of the
Department of the Interior include the preservation, distribution, introduction and
restoration of game and other wild birds.
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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
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International conservation efforts
• UN Convention on International Trade in Endangered
Species of Wild Fauna and Flora (1973) (CITES) –
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 2007, 188 nations had signed on
- Iraq, Somalia, the Vatican, and the U.S. did not join
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Habitat alteration causes biodiversity loss
• The greatest cause of biodiversity loss
- Farming simplifies communities
- Grazing modifies the grassland structure and species
composition
- Clearing forests removes resources organisms need
- Hydroelectric dams turn rivers into reservoirs upstream
- Urbanization and suburban sprawl reduce natural
communities
- A few species (i.e., pigeons, rats) benefit from changing
habitats
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Habitat alteration has occurred in every
biome
Particularly in tropical rainforests, savannas, and tropical
dry forests
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Island biogeography
• 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
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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
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Island Biogeography
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Small “islands” of forest rapidly lose
species
• Forests are fragmented by
roads and logging
• Small forest fragments lose
diversity fastest
- Starting with large species
• Fragmentation is one of the
prime threats to biodiversity
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The species-area curve
• Large islands contain more species than small islands
- They are easier to find and have lower extinction rates
- They possess more habitats
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Biodiversity hotspots
• Biodiversity hotspots – prioritizes regions most
important globally for biodiversity
- Support a great number of 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
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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
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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
- Protecting land deprives people access to resources
- But, it can guarantee that these resources will not be
used up or sold to foreign corporations and can instead
be sustainably managed
• Many projects have succeeded
- But, others have not, due mainly to funding problems
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Innovative economic strategies
• Debt-for-nature swap = a conservation organization
pays off a portion of a developing country’s international
debt
- In exchange for a promise by the country to set aside
reserves
- Fund environmental education, and
- Better manage protected areas
• Conservation concession = conservation organizations
pay nations to conserve, and not sell, resources
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Conclusion
• Loss of biodiversity will result in a mass extinction
• 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
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