Download 31.4 What Are The Major Threats To Biodiversity?

Chapter 31
Conserving Earth’s
Biodiversity
Lectures by
Gregory Ahearn
University of North Florida
Copyright © 2009 Pearson Education, Inc..
31.1 What Is Conservation Biology?
 Conservation biology is the branch of
science that seeks to understand and
conserve biological diversity (biodiversity)
and can be analyzed at different levels.
• Genetic diversity is the variety and relative
frequencies of different alleles in the gene
pool of a species.
• Species diversity is the variety and relative
abundance of different species.
• Ecological diversity is the variety of different
ecosystems.
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31.1 What Is Conservation Biology?
 Conservation biologists study and seek to
preserve biodiversity at all levels.
• They apply methods drawn from ecology,
genetics, and evolutionary biology to help
protect and maintain the diversity of life.
• If genetic diversity of a species is reduced, the
species may lack the genetic variability to
evolve adaptations to changing environments.
• If the species diversity of an ecosystem is
reduced, community interactions necessary to
maintain an ecosystem may be threatened.
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31.1 What Is Conservation Biology?
 Conservation biologists study and seek to
preserve biodiversity at all levels
(continued).
• If ecological diversity is reduced, the ability of
the biosphere to support species may be
compromised.
• The knowledge gained by conservation
biologists can help preserve biodiversity only if
it is used to inform actions that prevent
human-caused extinctions.
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31.2 Why Is Biodiversity Important?
 Ecosystem services: practical uses for
biodiversity
•
•
•
•
•
•
•
•
Purifying air and water
Replenishing atmospheric oxygen
Pollinating plants and dispersing their seeds
Providing wildlife habitat
Decomposing wastes
Limiting erosion and flooding
Controlling pests
Providing recreational opportunities
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31.2 Why Is Biodiversity Important?
 Ecosystem services
Ecosystem services
Directly used substances
• food plants and animals
• building materials
• fiber and fabric materials
• fuel
• medicinal plants
• oxygen replenishment
Indirect, beneficial services
• maintaining soil fertility
• pollination
• seed dispersal
• waste decomposition
• regulation of local climate
• flood control
• erosion control
• pollution control
• pest control
• wildlife habitat
• repository of genes
Fig. 31-1
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31.2 Why Is Biodiversity Important?
 Ecosystems provide goods directly.
• Healthy ecosystems provide a variety of
resources directly to people.
• Wild-caught fish enrich our diets.
• Hunting for food and sport is important to
the economy of many rural areas.
• Forests provide wood for housing and
furniture.
• Wild plants are a source of medicines.
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31.2 Why Is Biodiversity Important?
 Ecosystems also benefit people indirectly.
• Soil formation
• Soil, with its diverse community of
decomposers and detritus feeders, plays a
major role in breaking down wastes and
recycling nutrients.
• We rely on soils to decompose waste
products from industry, sewage, agriculture,
and forestry.
• Thus, soil serves some of the same
functions as a water purification plant.
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31.2 Why Is Biodiversity Important?
 Ecosystems also benefit people indirectly
(continued).
• Erosion and flood control
• Grassland and forest plants block winds
that would otherwise blow away soil.
• The plant’s roots stabilize the soil and
increase its ability to hold water, reducing
both soil erosion and flooding.
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31.2 Why Is Biodiversity Important?
 Conversion of forests to farmland can
greatly increase rain runoff and soil erosion,
resulting in flooding.
Fig. 31-2a
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31.2 Why Is Biodiversity Important?
 Erosion and flood control (continued)
• Wetland ecosystems (marshes) reduce
flooding because they act like enormous
sponges that absorb storm water.
• The loss of this protective function was
illustrated by the catastrophic flooding of New
Orleans during Hurricane Katrina in 2005.
• Prior to dredging the waters of the Mississippi
River, the river produced a natural silt-laden
wetlands that served as a natural barrier to the
force of incoming storms.
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31.2 Why Is Biodiversity Important?
 The levees built to replace this ecosystem
service did not hold during the hurricane,
and as a consequence, 80% of the city was
flooded.
Fig. 31-2b
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31.2 Why Is Biodiversity Important?
 Climate regulation
• By providing shade, moderating temperature,
and serving as windbreaks, plant communities
have a major impact on local climates.
• Forests have dramatic effects on the water
cycle, returning water to the atmosphere
through transpiration.
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31.2 Why Is Biodiversity Important?
 Genetic resources
• Our food supply depends on a small number
of domesticated species; 75% of human food
is supplied by only 12 food crops.
• Such heavy dependence on just a few species
leaves our food security vulnerable to pests or
disease epidemics that attack the key crops.
• The best protection against such a potential
catastrophe would be to increase food crop
diversity by developing wild plants into new
food sources.
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31.2 Why Is Biodiversity Important?
 Recreation
• Ecotourism, in which people travel to observe
unique biological communities, is a rapidly
growing industry worldwide.
• Examples of ecotourism destinations include
tropical coral reefs and rainforests, the
Galapagos Islands, the African savanna, and
even Antarctica.
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31.2 Why Is Biodiversity Important?
 Ecological economies recognizes the
monetary value of ecosystem services.
• The emerging discipline of ecological
economics attempts to establish the monetary
value of ecosystem services, and to assess
the economic trade-offs that occur when
ecosystems are damaged to make way for
profit-making activities.
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31.2 Why Is Biodiversity Important?
 Ecological economies recognizes the
monetary value of ecosystem services
(continued).
• A farmer planning to divert water from a
wetland to irrigate a crop would weigh the
monetary value of increased crop production
against the cost of the labor and machinery
needed to divert the wetland’s water.
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31.3 Is Earth’s Biodiversity Diminishing?
 Extinction is a natural process, but rates
have risen dramatically.
• The fossil record indicates that, in the absence
of cataclysmic events, extinctions occur
naturally at a very low rate.
• However, there are occasional mass
extinctions, in which many species were
eradicated in a relatively short time.
• Five such mass extinction episodes have
occurred; the most recent took place about 65
million years ago and abruptly ended the age
of the dinosaurs.
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31.3 Is Earth’s Biodiversity Diminishing?
 Extinction is a natural process, but rates
have risen dramatically (continued).
• The causes of mass extinction are uncertain,
but sudden changes in the environment, such
as would happen by enormous meteor
impacts or rapid climate change, are the most
likely explanations.
• Most biologists have concluded that we are
now in the midst of the sixth mass extinction—
this one caused by human activities.
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31.3 Is Earth’s Biodiversity Diminishing?
 Extinction is a natural process, but rates
have risen dramatically (continued).
• The World Conservation Union (IUCN)
estimates that the current extinction rate is
between 100 and 1,000 times greater than the
background rate expected in the absence of
people.
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31.3 Is Earth’s Biodiversity Diminishing?
 Increasing numbers of species are
threatened with extinction.
• Species may be described as critically
endangered, endangered, or vulnerable,
depending on how likely they are to become
extinct in the near future.
• Species that fall into any of the three
categories above are described as threatened.
• In 2007, 16,306 species were considered
threatened, including 12% of all birds, 20% of
mammals, and 29% of amphibians.
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31.4 What Are The Major Threats To
Biodiversity?
 The greatest hazards to biodiversity are
posed by habitat destruction,
overexploitation, invasive species, pollution,
and global warming.
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31.4 What Are The Major Threats To
Biodiversity?
 Habitat destruction is the most serious
threat to biodiversity.
• Habitat is destroyed as rivers are dammed,
wetlands are drained, and grasslands and
forests are converted to agriculture, roads,
housing, and industry.
• Since people began to farm around 11,000
years ago, Earth has lost about half of its
forests.
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31.4 What Are The Major Threats To
Biodiversity?
 Approximately half of all tropical rain forests
have been cut down in the past 50 years.
Fig. 31-4
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31.4 What Are The Major Threats To
Biodiversity?
 Even when a natural ecosystem is not
completely destroyed, it may become split
into small pieces surrounded by regions
devoted to human activities.
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31.4 What Are The Major Threats To
Biodiversity?
 This habitat fragmentation can be a serious
threat to wildlife by making populations that
are too small to survive.
Fig. 31-5
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31.4 What Are The Major Threats To
Biodiversity?
 To be functional, a preserve must support a
minimum viable population (MVP).
• This is the smallest isolated population that
can persist, despite the effects of inbreeding
and potential disruptions from disease, fires,
and floods.
• The MVP for a species is influenced by many
factors, including the quality of the
environment, the species’ average lifespan, its
fertility, and how many young usually reach
maturity.
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31.4 What Are The Major Threats To
Biodiversity?
PLAY
Animation—Habitat Destruction and Fragmentation
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31.4 What Are The Major Threats To
Biodiversity?
 Overexploitation threatens many species.
• Overexploitation refers to hunting or harvesting
natural populations at a rate that exceeds their
ability to replenish their numbers.
• Overexploitation has increased as growing
demand is coupled with technological advances
that greatly increase our efficiency at harvesting
wild animals and plants.
• The IUNC estimates that overexploitation
impacts about 30% of threatened mammals and
birds.
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31.4 What Are The Major Threats To
Biodiversity?
 Over-fishing is the single greatest threat to
marine life, causing dramatic declines of
many species, including cod, sharks, red
snapper, swordfish, and tuna.
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31.4 What Are The Major Threats To
Biodiversity?
 Most species of
marine turtles are
endangered as a
result of over
harvesting of both
adults and their
eggs.
Fig. 31-6
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31.4 What Are The Major Threats To
Biodiversity?
 On land, rapidly growing populations in lessdeveloped countries increase the demand
for wild animal products, as hunger and
poverty drive people to harvest all that can
be eaten or sold, legally or illegally, without
regard to its rarity.
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31.4 What Are The Major Threats To
Biodiversity?
 Invasive species displace native wildlife and
disrupt community interactions.
• Humans transport many species around the
world, and in many cases, they cause no
harm.
• But sometimes, non-native species become
invasive; they increase in number at the
expense of native species, competing for food
or habitat, or preying on them directly.
• Introduced species can make native species
vulnerable to extinction.
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31.4 What Are The Major Threats To
Biodiversity?
 Invasive species displace native wildlife and
disrupt community interactions (continued).
• Island species are particularly vulnerable to
competition and predation from introduced
species.
• In Hawaii, 99% of the 415 threatened plants
and all but one of its 42 threatened bird
species are endangered by invasive species.
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31.4 What Are The Major Threats To
Biodiversity?
 Mongoose were introduced in the 1800s
and now threaten Hawaii’s native birds.
Fig. 31-7
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31.4 What Are The Major Threats To
Biodiversity?
 Pollution is a multifaceted threat to biodiversity.
• Pollutants include synthetic chemicals such as
plasticizers, flame retardants, and pesticides that
enter the air, soil, and water and then accumulate to
toxic levels in animal tissues.
• Naturally occurring substances, such as mercury,
lead, and arsenic are also toxic to both people and
wildlife.
• Others become pollutants by disrupting
biogeochemical cycles, such as the release of
oxidized nitrogen and sulfur that takes place during
combustion of fossil fuels, causing acid rain.
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31.4 What Are The Major Threats To
Biodiversity?
 Global warming is an emerging threat to
biodiversity.
• The use of fossil fuels, coupled with
deforestation, has increased atmospheric
carbon dioxide levels.
• This increase has been accompanied by
increasing global temperatures.
• Global warming may be causing more
extreme weather, such as heat waves,
droughts, floods, and stronger hurricanes.
• Global warming is as great a threat to
biodiversity as is habitat destruction.
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Conservation biology is an integrated science.
• Effective conservation depends on consensus and
broad participation, so conservation biologists seek
expertise and support from people outside of science.
• These people include government leaders,
environmental lawyers, and ecological economists.
• Conservation biologists collaborate with social
scientists and educators who help the public
understand how ecosystems function and how people
can preserve them.
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Conserving wild ecosystems
• Core reserves preserve all levels of biodiversity.
• Core reserves are natural areas protected from
most human uses, except low-impact recreation.
• These reserves encompass enough space to
preserve ecosystems and all their biodiversity.
• To establish effective core reserves,
conservationists must know the minimum critical
areas required to sustain minimum viable
populations of the species that require the most
space.
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Corridors connect critical animal habitats.
• To compensate for limits on the size of core
reserves, it is necessary to establish wildlife
corridors, which are strips of protected land
linking core reserves.
• Such corridors allow animals to move freely
and safely between habitats that would
otherwise be isolated by human activities.
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Corridors effectively
increase the size of
core reserves by
connecting them.
Fig. 31-8
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Corridors connect critical animal habitats
(continued).
• A wildlife corridor can be as narrow as an
underpass beneath a highway.
• Studies showed that a cougar was using an
underpass to move between suitable habitats,
and it is now an official wildlife corridor and is
being restored to a more natural state,
encouraging cougars and other animals to
cross safely beneath the freeway.
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31.5 How Can Conservation Biology Help
To Preserve Biodiversity?
 Wildlife corridors
Fig. 31-9
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31.6 Why Is Sustainability The Key To
Conservation?
 Natural ecosystems share the following
features that allow the ecosystem to persist
and flourish.
• Diverse communities with rich, complex
community interactions
• Relatively stable population sizes
• Recycling and efficient use of raw materials
• Reliance on renewable sources of energy
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31.6 Why Is Sustainability The Key To
Conservation?
 Sustainable living and sustainable
development promote long-term ecological
and human well being.
• Respect for nature’s operating principles is
central to sustainability.
• In a landmark document, Caring for the Earth,
the IUCN states that sustainable development
“meets the needs of the present without
compromising the ability of future generations
to meet their own needs.”
• It explains that humanity must take no more
from nature than nature can replenish.
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31.6 Why Is Sustainability The Key To
Conservation?
 Sustainable living and sustainable
development promote long-term ecological
and human well being (continued).
• Commercial fishing is a prime example of
technology working outside of nature’s limits.
• Sustainable fishing requires that we preserve
spawning grounds, limit fish catches, and
improve technology to avoid unintended
damage.
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31.6 Why Is Sustainability The Key To
Conservation?
 As individuals and governments recognize
the need to change, there are increasing
numbers of projects that are intended to
meet human needs sustainably.
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31.6 Why Is Sustainability The Key To
Conservation?
 Biosphere reserves provide models for
conservation and sustainable development.
• A world network of biosphere reserves has
been designated by the United Nations.
• The goal of biosphere reserves is to maintain
biodiversity and to evaluate techniques for
sustainable human development while
preserving local cultural values.
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31.6 Why Is Sustainability The Key To
Conservation?
 Biosphere reserves consist of three regions.
• A central core reserve that while protected,
allows research and sometimes tourism, as
well as some sustainable traditional uses.
• A surrounding buffer zone permits low-impact
human activities and development.
• Outside the buffer zone is a transition area
that supports settlements, tourism, fishing,
and agriculture, all operated sustainably.
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31.6 Why Is Sustainability The Key To
Conservation?
 Biosphere reserves (continued)
• Biosphere reserves are entirely voluntary and
are managed by the countries and regional
areas where they are located.
• In many cases, much of the land in the buffer
and transition zones is privately owned, and
some landowners may be unaware of its
designation.
• The concept of the biosphere reserve is an
elegant model for conservation in the context
of sustainable development, and it provides a
framework for both present and future efforts.
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31.6 Why Is Sustainability The Key To
Conservation?
 Sustainable agriculture helps preserve
natural communities.
• The greatest loss of habitat occurs when
people convert natural ecosystems to
monoculture farming, in which large expanses
of land are devoted to single crops.
• Farmers face pressure to produce large
amounts of food at the lowest possible cost,
and in some cases, this has led to
unsustainable farming that interferes with
ecosystem services.
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31.6 Why Is Sustainability The Key To
Conservation?
 Sustainable agriculture helps preserve
natural communities (continued).
• Farmers are increasing recognizing that
sustainable agriculture ultimately saves
money while preserving the land.
• The no-till cropping technique, which leaves
the remains of harvested crops in the fields to
form mulch for the next year’s crops, is one
component of sustainable agriculture.
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31.6 Why Is Sustainability The Key To
Conservation?
 No-till crops
Fig. 31-10
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31.6 Why Is Sustainability The Key To
Conservation?
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31.6 Why Is Sustainability The Key To
Conservation?
 Sustainable agriculture helps preserve
natural communities (continued).
• Most no-till farmers still use herbicides and
pesticides.
• Organic farmers also often use no-till
methods, but do not use synthetic herbicides,
insecticides, or fertilizers.
• Organic farming relies on natural predators to
control pests, and on soil microorganisms to
degrade animal and crop wastes, thereby
recycling their nutrients.
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31.6 Why Is Sustainability The Key To
Conservation?
 Changes in lifestyle and use of appropriate
technologies are also essential.
• Government policies and institutional changes
are vital for a sustainable future, but individual
choices are also important.
• We can reduce our consumption of energy
and nonrenewable fossil fuels by conserving
and by using energy-saving technologies.
• Our choices as consumers can provide
markets for foods and durable goods that are
produced sustainably.
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31.6 Why Is Sustainability The Key To
Conservation?
 Human population growth is unsustainable.
• The root cause of environmental degradation is
simple: too many people using too many resources
and generating too much waste.
• Through technological advances and by depleting the
Earth’s ecological capital, we have achieved a
population that far exceeds being in balance with the
natural ecosystems on this planet.
• Adding 80 million more people to Earth every year is
incompatible with saving what is left of Earth’s
biodiversity for those who are yet to come.
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