Transcript + Chapter 25: Extinction and Conservation Robert E. Ricklefs

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Robert E. Ricklefs
The Economy of Nature, Fifth Edition
Chapter 25: Extinction
and Conservation
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Take note
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Be sure to check the readings on the website
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They will be on the exam
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Human Impact on Earth
 The
 in
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human impact on the earth is substantial:
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
earth’s surface:
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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
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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
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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:
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investing in and utilizing energy- and resource- efficient
technologies
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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:
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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.
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There may be as many as 10 to 30 million species of plants,
animals, and microbes worldwide:
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only 1,500,000 species have been catalogued
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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
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Ecological diversity:
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each species has unique attributes and adaptations that define its
place in the ecosystem:
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plants, for example, vary in:
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tolerances of environmental conditions
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defenses against herbivores
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growth form
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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
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 Geographic
diversity:
each region has different species composition and
diversity
 endemic species are restricted to small geographic
areas
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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 …
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Spend some time here: http://biodiversity.moe.gov.lb/
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Value of Biodiversity
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Current loss of species is at an all-time high in earth’s
history:
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some estimates place this rate in excess of one species per day
Why should we be concerned about loss of species?
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many species are gone already
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extinction is a natural process
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Moral Responsibility
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Extinction raises important moral issues:
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some feel that because humankind affects all of nature, it is our
moral responsibility to protect nature
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if morality is intrinsic to life itself:
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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
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Individual species have direct economic and recreation
values for humankind:
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food resources
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game species
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sources of forest and other natural products
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drugs and other organic chemicals
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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?
+Economic values of species can
cause environmental harm.
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Policies favoring certain species may harm others:
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cultivated species displace other species viewed as having lesser
value
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predators, such as wolves, are eliminated because of conflicts
with livestock operations
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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:
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often brings much-needed foreign currencies into developing
countries
is responsible for development of parks and preserves
is expanding, but its potential is finite:
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people have limited resources to devote to such activities
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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:
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this decline was traced to pollution of aquatic habitats by
breakdown products of DDT, which:
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entered aquatic food chains and were concentrated at each
step in the chain
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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
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Diversity may help stabilize ecological systems:
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the research of Tilman and Downing has shown that biomass
production was less affected by drought on high-diversity plots:
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with many species present, some can assume key roles when
environmental conditions change
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such switching is less likely in less diverse systems
+ 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:
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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:
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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:
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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:
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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…
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…support smaller populations
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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:
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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
+ 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:
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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
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minimal attributes include:
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:
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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?)
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Replaced buffalo grass
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Planted wheat + cows
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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:
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such biodiversity hotspots typically combine local
diversity and endemism
in continental areas, the objective is to target habitats and
areas of special biological interest:
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several small preserves may be more effective than one large
preserve
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adding more area to preserves becomes increasingly
expensive
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+ Challenges of Tropical
Conservation 1
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Many tropical countries have large tracts of uncut forest and
other undisturbed tropical habitats:
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it may be relatively easy to set aside parks “on paper,” but many
conflicts remain:
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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:
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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:
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larger areas support more species than smaller by:
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reducing likelihood of stochastic extinction
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promoting genetic diversity
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buffering populations against disturbances
 the
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species-area relationship:
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…
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http://www.newscientist.com/blog/environment/2008/05/iro
n-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
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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 public’s 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 population’s
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.