Chapter 25: Extinction and Conservation

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Chapter 25 Extinction and Conservation

• Robert E. Ricklefs
• The Economy of Nature, Fifth Edition

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Take note

• Be sure to check the readings on the website
• They will be on the exam

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Human Impact on Earth

• The human impact on the earth is substantial
• in the year 2000, human population was 6 billion
• we are still growing at the robust rate of 2 per
  year
• humans control or indirectly affect much of the
  earths surface
• 35 of land area is used for crops or permanent
  pastures
• countless additional hectares are grazed by
  livestock
• tropical forests are being felled at 17 million
  hectares per year
• 2 of remaining forest is cut per year
• desertification is a widespread problem,
  especially in Africa
• air and water pollution are also widespread

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Human impacts on the planet can be reduced.

• Negative consequences of human impacts on natural
  systems are enormous
• deterioration of the environment
• will lead to a declining quality of life for all
  humans
• already affects the other life forms on the
  planet
• But there is cause for hope
• humans can live in a clean and sustaining world,
  but only by placing support for our own
  population into balance with preservation of
  other species and the ecological processes that
  nurture us

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Three Lessons from Ecology 1

• The science of ecology has much to tell us about
  living sustainably in a healthy world.
• Environmental problems cannot be solved until the
  human population is brought under control
• density-dependent control of the human population
  will mean untold suffering
• we must learn to value individual human
  experience over numbers of progeny

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Three Lessons from Ecology 2

• Individual consumption of energy, resources, and
  food produced at higher trophic levels must be
  reduced
• we have already exceeded the capacity of earth to
  support the current human population at a level
  enjoyed by the most affluent societies
• we can make contributions to sustainability by
• investing in and utilizing energy- and resource-
  efficient technologies
• eating lower on the food chain

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Three Lessons from Ecology 3

• Ecosystems should be maintained in as close to
  their natural state as possible to keep natural
  processes intact
• areas unsuitable for grazing or agriculture
  should not be converted to such uses
• these areas are best set aside for conservation
  and recreation
• living with nature is always preferable to, and
  less costly than, going against it

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Biological diversity is incompletely described.

• There may be as many as 10 to 30 million species
  of plants, animals, and microbes worldwide
• only 1,500,000 species have been catalogued
• although lists are important, they represent only
  one approach to the documentation of biological
  diversity or biodiversity, the many unique
  attributes of living things

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Proportions of named species
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Components of Biodiversity 1

• Ecological diversity
• each species has unique attributes and
  adaptations that define its place in the
  ecosystem
• plants, for example, vary in
• tolerances of environmental conditions
• defenses against herbivores
• growth form
• strategies for pollination and seed dispersal

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Components of Biodiversity 2

• Genetic diversity
• crucial to evolutionary responses of organisms to
  changing environments
• has both within- and between-species components
• Geographic diversity
• each region has different species composition and
  diversity
• endemic species are restricted to small
  geographic areas
• regions with many endemics possess high endemism

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Endemism

• Oceanic islands are well known for harboring
  endemic forms
• nearly all native birds, plants, and insects of
  isolated islands live nowhere else
• loss of such island species caused by habitat
  destruction, hunting, or alien species means
  worldwide extinction
• humans have caused many extinctions of island
  endemics

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Be sure to

• Spend some time here http//biodiversity.moe.gov.
  lb/

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Value of Biodiversity

• Current loss of species is at an all-time high in
  earths history
• some estimates place this rate in excess of one
  species per day
• Why should we be concerned about loss of species?
• many species are gone already
• extinction is a natural process

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Moral Responsibility

• Extinction raises important moral issues
• some feel that because humankind affects all of
  nature, it is our moral responsibility to protect
  nature
• if morality is intrinsic to life itself
• rights of nonhuman individuals and species are as
  legitimate as the rights of individuals in human
  society
• Environmental ethics

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• What is a man without the beasts? If all the
  beasts were gone, men would die from great
  loneliness of spirit, for whatever happens to the
  beasts also happens to man.Chief Seattle

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Economic Benefits

• Individual species have direct economic and
  recreation values for humankind
• food resources
• game species
• sources of forest and other natural products
• drugs and other organic chemicals
• about 25 of prescriptions filled in the United
  States / more than 100 important medicinal drugs
  / are extracted directly from flowering plants
• Assigning economic value to one species does
  not address conserving biodiversity in a general
  sense. Why not?

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Economic values of species can cause
environmental harm.

• Policies favoring certain species may harm
  others
• cultivated species displace other species viewed
  as having lesser value
• predators, such as wolves, are eliminated because
  of conflicts with livestock operations
• overexploitation of resources (such as fisheries)
  may lead to their demise

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Ecotourism

• Some species have high value because they attract
  tourists, in a practice known as ecotourism
• many countries have benefited from the
  willingness of tourists to visit game parks and
  preserves ecotourism
• often brings much-needed foreign currencies into
  developing countries
• is responsible for development of parks and
  preserves
• is expanding, but its potential is finite
• people have limited resources to devote to such
  activities
• many species and ecosystems are not attractive to
  ecotourists

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Giving monetary value

• Chief Seattle How can you buy or sell the sky,
  the warmth of the land? The idea is strange to
  us.
• If we do not own the freshness of the air and the
  sparkle of the water, how can you buy them?
• Only after the last tree has been cut down, Only
  after the last river has been poisoned, Only
  after the last fish has been caught, Only then
  will you find money cannot be eaten.
• Cree Prophecy

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Indication of Environmental Quality

• Individual species may have value as indicators
  of environmental change
• birds of prey declined during the 1950s and 1960s
  in the United States
• this decline was traced to pollution of aquatic
  habitats by breakdown products of DDT, which
• entered aquatic food chains and were concentrated
  at each step in the chain
• interfered with physiology and reproduction in
  birds
• identification of the problem led to banning of
  DDT and subsequent recovery of many species

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Broken eggshells in the nest of a brown pelican
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Maintenance of Ecosystem Function

• Diversity may help stabilize ecological systems
• the research of Tilman and Downing has shown that
  biomass production was less affected by drought
  on high-diversity plots
• with many species present, some can assume key
  roles when environmental conditions change
• such switching is less likely in less diverse
  systems

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Decrease in plant biomass after event related
to plants species richness before event
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Plant biomass increases w/ number of plant guilds
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Extinction is natural, but its present rate is
not.

• Extinction is of concern because evolutionary
  lineages are lost forever.
• The relatively low rate of natural extinction is
  called background extinction
• life span of most species in the fossil record is
  1 to 10 million years
• analysis of the fossil record indicates a
  background extinction rate of 1 species per year

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Other Types of Extinction

• Mass extinctions are caused by natural
  catastrophes, such as meteor impacts
• such bolide impacts are thought to occur at
  intervals of 10 to 100 million years
• may have been responsible for mass extinctions at
  the end of the Paleozoic and Mesozoic eras
• Anthropogenic extinctions are caused by humans
• such preventable extinctions have brought the
  modern extinction rate to far in excess of
  natural levels

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Humans cause extinctions by several mechanisms.

• Populations disappear because deaths exceed
  births over a prolonged period
• extinction may be viewed as a failure to adapt to
  changing conditions
• a recent survey has revealed the principal causes
  of population decline for endangered U.S.
  species
• habitat reduction and modification (67 of cases)
• small population size
• introduction of exotic species
• overexploitation

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Habitat Reduction and Fragmentation

• Habitat reduction and fragmentation threaten many
  species
• some habitats are reduced or eliminated
  altogether
• fragmentation creates a suite of additional
  problems
• small areas may not be able to support viable
  populations of larger species, such as mammals
• small populations are subject to stochastic local
  extinction
• fragmentation increases edges, exposing forest
  interior species to increased parasitism and
  predation
• species of fragmented habitats may be unable to
  migrate with changing climate induced by global
  warming

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Atlantic coastal forests of Brazil reduced to a
small fraction
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Fragmented habitats

• support smaller populations
• Becomes a biological island

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Small Population Size

• Stochastic extinction is a risk that increases
  dramatically for the smallest populations.
• Reduced genetic variation in small populations
  may further increase the probability of
  extinction
• founder effects, inbreeding, genetic drift, and
  population bottlenecks all pose problems
• some species, notably the northern elephant seal,
  have survived severe population bottlenecks
  successfully

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Introductions of Exotic Species

• Decreases in habitat quality are frequently the
  consequence of introduced predators, competitors,
  or disease organisms
• many species arrive accidentally and others are
  introduced intentionally
• islands seem to be most vulnerable to introduced
  species (Hawaiian Islands have suffered greatly
  from introduced species)
• aquatic systems are also vulnerable to effects of
  exotics
• continental areas are not immune to effects of
  exotics

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Overexploitation

• Many species have succumbed to effects of direct
  exploitation by humans
• efficient hunting and fishing may drive species
  to extinction
• humans have a long history of overexploitation
• arrival of humans in North America was
  accompanied by rapid extinction of 56 species in
  27 genera of large mammals

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Overexploitation changes the species composition
of a community
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Vulnerability to extinction is poorly understood.

• Why some species are more vulnerable to
  extinction than others is hard to determine.
• Some attributes that predispose species to
  extinction include
• species attractive for exploitation
• species that have evolved in the absence of
  hunting
• species that have evolved in the absence of
  diverse disease organisms
• species with limited geographic range, restricted
  habitat distribution, and small local population
  size

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Conservation Planning

• Successful planning for conservation must include
  adequate habitat for a self-sustaining
  population
• in practice, conservation planning must consider
• ecological requirements of the species
• amount of space needed to support a minimum
  viable population

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Minimum Viable Populations

• The minimum viable population (MVP) is the
  smallest population that can sustain itself in
  the face of environmental variation.
• MVPs must be large enough to remain out of danger
  from stochastic extinction.
• Other minimal attributes include
• wide distribution, such that local catastrophes
  cannot affect the entire species
• some degree of population subdivision that can
  prevent the spread of disease

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More on Conservation Planning

• Migrations complicate conservation planning
• seasonal movements or different seasonal habitat
  needs are difficult to satisfy
• the entire Serengeti ecosystem of East Africa is
  needed to accommodate seasonal movements of
  wildlife
• long-distance migrants may face multiple
  challenges in breeding and wintering grounds
• It is not feasible to plan for the conservation
  of every species
• focus is increasingly on habitat conservation

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What could happen
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• Removed the buffalo exterminated the buffalo
  (why?)
• Replaced buffalo grass
• Planted wheat cows
• What happened?

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Black Sunday
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Critical Areas for Conservation

• What are the most valuable areas for conservation
  of species?
• the focus is on areas serving as havens for the
  largest numbers of species not represented
  elsewhere
• such biodiversity hotspots typically combine
  local diversity and endemism
• in continental areas, the objective is to target
  habitats and areas of special biological
  interest
• several small preserves may be more effective
  than one large preserve
• adding more area to preserves becomes
  increasingly expensive

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Challenges of Tropical Conservation 1

• Many tropical countries have large tracts of
  uncut forest and other undisturbed tropical
  habitats
• it may be relatively easy to set aside parks on
  paper, but many conflicts remain
• rapid growth of human populations
• increased exploitation of forest products
• illegal or questionable activities of poachers,
  squatters, miners, and logging concessions

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Challenges of Tropical Conservation 2

• The price of conservation is rising worldwide.
• Conservation must be an international effort,
  with wealth of the developed countries shared
  globally to protect biodiversity
• involving local people in the design and
  management of parks is especially important
• the benefits of conservation must be tangible and
  economically compelling

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Design of Nature Preserves 1

• Ecological principles derived from the theory of
  island biogeography can be helpful
• the species-area relationship
• larger areas support more species than smaller
  by
• reducing likelihood of stochastic extinction
• promoting genetic diversity
• buffering populations against disturbances
• the avoidance of edge effects
• the effects of habitat alteration extend for some
  distance
• freedom to migrate

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Design of Nature Preserves 2

• General recommendations exist for creation of
  preserves from large expanses of uniform habitat
• larger is better than smaller
• one large area is better than several smaller
  that add to the same size
• corridors connecting isolated areas are desirable
• circular areas are better than elongate areas
  with more edge

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Design of Nature Preserves 3

• Several small areas in different habitats may be
  more effective than one large area in uniform
  habitat.
• Nature preserves must be designed with the
  habitat requirements of their inhabitants in
  mind
• migratory needs must be accommodated through
  incorporation of diverse habitats linked by
  corridors
• roads and pipelines interfering with movements
  must be bridged in some fashion

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Check

• http//www.newscientist.com/blog/environment/2008/
  05/iron-curtain-becomes-nature-haven.html

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Endangered species have been rescued from the
brink.

• The California condor is a success story with
  several important lessons
• the condor population had dwindled to less than
  20 individuals in the 1980s
• the decision was made to bring the entire
  population into a captive breeding program
• this program has been very successful,
  highlighting the important role played by
  zoological parks
• the condor can now be released into habitat
  preserves purchased expressly for condor
  conservation

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California Condor

• Experienced gained through projects like that
  designed for the California condor will have many
  benefits
• experience gained will benefit similar programs
  in the future
• large tracts of natural habitat have been
  preserved
• such projects heighten the publics awareness of
  conservation issues
• condor populations are compatible with other land
  uses (recreation, hunting, ranching), so long as
  appropriate precautions are taken

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Condor Conservation

• Concessions to condors are neither difficult nor
  expensive. Making them simply depends on
  instilling values that acknowledge natural
  systems as an integral part of the environment of
  humankind.

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Summary 1

• Humankind has an enormous impact on earth and its
  natural resources. These impacts will continue
  to grow as the population grows beyond 6 billion.
• Resolving the environmental crisis will require
  cessation of population growth, conservation of
  energy and resources, and taking ecological
  values into consideration.
• Biodiversity has ecological, genetic, and
  geographic components.

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Summary 2

• The value of species is rooted in moral,
  aesthetic, and economic considerations. Species
  also have value as indicators of environmental
  quality. Diversity may also help stabilize
  ecosystem function.
• Background extinction may be estimated from the
  fossil record. Mass extinctions are associated
  with catastrophic events, while anthropogenic
  extinction has increased dramatically.

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Summary 3

• Habitat reduction may hasten a populations
  decline toward extinction. Introduction of
  exotic species is also a substantial cause of
  extinctions.
• Optimal design of nature preserves takes
  advantage of biodiversity hotspots, and
  principles elucidated in the theory of island
  biogeography.
• Species may be brought back from the brink of
  extinction. Such efforts highlight conservation
  problems and may also conserve natural habitats.