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Sustaining Biodiversity: The Ecosystem Approach


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Title: Sustaining Biodiversity: The Ecosystem Approach

Sustaining Biodiversity The Ecosystem Approach
  • Chapter 9

What are the major threats to forest ecosystems?
  • Section 9-1

Forests vary in their age, make-up, and origins
  • Natural and planted forests occupy about 30 of
    the earths land surface (excluding Greenland and
  • Two major types based on their age and structure
  • Old growth forest Uncut or regenerated primary
    forest that has not been seriously disturbed by
    human activities or natural disasters for several
    hundred years or more.
  • Second-growth forest A stand of trees resulting
    from secondary ecological succession that
    develops after the trees in an area have been
    removed by human activities such as clear-cutting
    for timber or cropland or by natural forces such
    as fire, hurricanes, or volcanic eruption.

Forests vary in their age, make-up, and origins
  • A tree plantation (tree farm, commercial forest),
    is a managed tract with uniformly aged trees of
    one or two genetically uniform species that
    usually are harvested by clear-cutting as soon as
    they become commercially valuable.
  • Forests provide important economic and ecological
  • Forests remove CO2 from the atmosphere and store
    it in organic compounds (biomass) through
  • Forests help to stabilize the earths temperature
    and slow projected climate change.

The short rotation cycle of cutting and regrowth
of a monoculture tree plantation
Weak trees removed
25 yrs
Clear cut
30 yrs
15 yrs
Years of growth
Seedlings planted
5 yrs
10 yrs
Fig. 9-3a, p. 176
Forests provide many important economic and
ecological services
Unsustainable logging is a major threat to forest
  • The first step in harvesting trees is to build
    roads for access and timber removal, but they can
    cause the following problems
  • Increased erosion and sediment runoff into
  • Habitat fragmentation.
  • Loss of biodiversity.
  • Forest exposure to invasion by nonnative pests,
    diseases, and wildlife species.

Unsustainable logging is a major threat to forest
  • Methods of harvesting trees
  • Selective cutting.
  • Clear-cut.
  • Strip cutting.

Three major tree harvesting methods
(a) Selective cutting
Clear stream
Fig. 9-6a, p. 179
(b) Clear-cutting
Muddy stream
Fig. 9-6b, p. 179
(c) Strip cutting
Cut 1 year ago
Dirt road
Cut 310 years ago
Clear stream
Fig. 9-6c, p. 179
Aerial view showing clear-cut logging, Washington
Fire can threaten or benefit forest ecosystems
  • Surface fires usually burn only undergrowth and
    leaf litter on the forest floor.
  • Kills seedlings and small trees but spares most
    mature trees and allows most wild animals to
  • Burns away flammable ground material and may help
    to prevent more destructive fires.
  • Frees valuable mineral nutrients tied up in
    slowly decomposing litter and undergrowth.

Fire can threaten or benefit forest ecosystems
  • Releases seeds from the cones of lodgepole pines.
  • Stimulates the germination of certain tree seeds
    (e.g. giant sequoia and jack pine).
  • Helps to control tree diseases and insects.
  • Crown fires are extremely hot fires that leap
    from treetops, burning whole trees.
  • Can destroy most vegetation, kill wildlife,
    increase soil erosion, and burn or damage human
    structures in their paths.

Surface fires and crown fires
Almost half of the worlds forests have been cut
  • Deforestation is the temporary or permanent
    removal of large expanses of forest for
    agriculture, settlements, or other uses.
  • Human activities have reduced the earths
    original forest cover by about 46, with most of
    this loss occurring in the last 60 years.
  • If current deforestation rates continue, about
    40 of the worlds remaining intact forests will
    have been logged or converted to other uses
    within two decades, if not sooner.

Almost half of the worlds forests have been cut
  • Clearing large areas of forests, especially
    old-growth forests, has important short-term
    economic benefits, but it also has a number of
    harmful environmental effects.
  • The net total forest cover in several countries
    changed very little or even increased between
    2000 and 2007. Some due to natural reforestation
    by secondary ecological succession on cleared
    forest areas and abandoned croplands, or the
    spread of tree plantations.
  • Concern about the growing amount of land occupied
    by commercial tree plantations, because
    replacement of old-growth forests by these
    biologically simplified tree farms represents a
    loss of biodiversity, and possibly of stability,
    in some forest ecosystems.

Harmful effects of deforestation
CASE STUDY Many Cleared Forests in the United
States Have Grown Back
  • Forests that cover about 30 of the U.S. land
    area provide habitats for more than 80 of the
    countrys wildlife species and supply about
    two-thirds of the nations surface water.
  • Today, forests in the U.S. cover more area than
    they did in 1920, primarily due to secondary
  • Every year, more wood is grown in the U.S. than
    is cut and the total area planted with trees
  • Protected forests make up about 40.
  • Since the mid-1960s, an increasing area of the
    nations remaining old-growth and fairly diverse
    second-growth forests has been cut down and
    replaced with biologically simplified tree

Forest cover in the U.S.
Tropical forests are disappearing rapidly
  • Tropical forests cover about 6 of the earths
    land area.
  • At least half of the worlds known species of
    terrestrial plants and animals live in tropical
  • Brazil has more than 30 of the worlds remaining
    tropical rain forest in its vast Amazon basin.
  • At the current rate of global deforestation, 50
    of the worlds remaining old-growth tropical
    forests will be gone or severely degraded by the
    end of this century.

Causes of tropical deforestation are varied and
  • There are a number of interconnected underlying
    and direct causes.
  • Pressures from population growth and poverty,
    push subsistence farmers and the landless poor
    into tropical forests, where they try to grow
    enough food to survive.
  • Government subsidies can accelerate the direct
    causes such as logging and ranching by reducing
    the costs of timber harvesting, cattle grazing,
    and the creation of vast plantations of crops
    such as soybeans.

Causes of tropical deforestation are varied and
  • Tropical forests in the Amazon and other South
    American countries are cleared/burned for cattle
    grazing and large soybean plantations.
  • In Southeast Asia, tropical forests are being
    replaced with vast plantations of oil palm, whose
    oil is used in cooking, cosmetics, and biodiesel
    fuel for motor vehicles.
  • In Africa, people struggle to survive by clearing
    plots for small-scale farming and by harvesting
    wood for fuel, which is causing deforestation on
    that continent.

Major underlying and direct causes of the
destruction and degradation of tropical forests
How should we manage and sustain forests?
  • Section 9-2

We can manage forests more sustainably
  • Certification of sustainably grown timber and of
    sustainably produced forest products can help
  • Removing government subsidies and tax breaks that
    encourage deforestation would also help.

Ways to grow and harvest trees more sustainably
We can improve the management of forest fires
  • In the United States, the Smokey Bear educational
    campaign has
  • prevented countless forest fires, saved many
    lives and prevented billions of dollars in loss
    of trees, wildlife, and human structures.
  • convinced the public that all forest fires are
    bad and should be prevented or put out.
  • Trying to prevent all forest fires can make
    matters worse by increasing the likelihood of
    destructive crown fires due to the accumulation
    of highly flammable underbrush and smaller trees
    in some forests.

We can improve the management of forest fires
  • Strategies for reducing fire-related harm
  • Prescribed burns are small, contained surface
    fires to remove flammable small trees and
    underbrush in the highest-risk forest areas.
  • Allow some fires on public lands to burn, thereby
    removing flammable underbrush and smaller trees,
    as long as the fires do not threaten human
    structures and life. Protect houses/buildings in
    fire-prone areas by thinning a zone of about 60
    meters (200 feet) around them and eliminating the
    use of flammable building materials such as
    wooden shingles.
  • Thin fire-prone areas by clearing small
    fire-prone trees and underbrush under careful
    environmental controls.

We can reduce the demand for harvested trees
  • Reduce inefficient use of construction materials,
    excess packaging, overuse of junk mail,
    inadequate paper recycling, and failure to reuse
    or find substitutes for wooden shipping
  • Paper can be made from fiber that does not come
    from trees.

Ways to reduce tropical deforestation
  • Debt-for-nature swap can make it financially
    attractive for countries to protect their
    tropical forests.
  • Conservation concessions occur when governments
    or private conservation organizations pay nations
    for agreeing to preserve their natural resources.

Ways to reduce tropical deforestation
  • Consumers can reduce the demand for products that
    are supplied through illegal and unsustainable
    logging in tropical forests.
  • For building projects, use recycled waste lumber
    or wood alternatives, such as recycled plastic
    building materials and bamboo.
  • Reduce the use of throwaway paper products and
    replace them with reusable plates, cups, and
    cloth napkins and handkerchiefs.
  • Individuals can plant trees.

Ways to protect tropical forests and use them
more sustainably
How should we manage and sustain grasslands?
  • Section 9-3

Some rangelands are overgrazed
  • Grasslands provide many important ecological
    services, including soil formation, erosion
    control, nutrient cycling, storage of atmospheric
    carbon dioxide in biomass, and maintenance of
  • Rangelands are unfenced grasslands in temperate
    and tropical climates that supply forage, or
    vegetation, for grazing (grass-eating) and
    browsing (shrub-eating) animals.

Some rangelands are overgrazed
  • Livestock also graze in pastures, which are
    managed grasslands or enclosed meadows usually
    planted with domesticated grasses or other
  • Overgrazing occurs when too many animals graze
    for too long and exceed the carrying capacity of
    a rangeland area.
  • Limited data from surveys in various countries
    indicate that overgrazing by livestock has caused
    a loss in productivity in as much as 20 of the
    worlds rangeland.

Left of fence overgrazed landRight lightly
grazed land
We can manage rangelands more sustainably
  • Control the number of grazing animals and the
    duration of their grazing in a given area so the
    carrying capacity of the area is not exceeded.
  • Rotational grazing confine cattle to one area
    via portable fencing for a short time (12 days)
    and then moved.
  • Provide supplemental feed at selected sites and
    strategically locate water holes and tanks and
    salt blocks to reduce overgrazing.
  • Suppress the growth of unwanted invader plants by
    use of herbicides, mechanical removal, or
    controlled burning or use controlled, short-term
    trampling by large numbers of livestock.

Restoration via secondary ecological succession
How should we manage and sustain parks and nature
  • Section 9-4

National parks face many environmental threats
  • More than 1,100 major national parks are located
    in more than 120 countries.
  • Most too small to sustain many large animal
  • Many parks suffer from invasions by nonnative
    species that compete with and reduce the
    populations of native species.
  • Some parks are so popular that large numbers of
    visitors are degrading the natural features that
    make them attractive.
  • Parks in less-developed countries have the
    greatest biodiversity of all parks, but only
    about 1 of these parklands are protected.

CASE STUDY Stresses on U.S. Public Parks
  • The U.S. national park system, established in
    1912, includes 58 major national parks, along
    with 335 monuments and historic sites. States,
    counties, and cities also operate public parks.
  • Popularity is one of the biggest problems. Noisy
    and polluting vehicles degrade the aesthetic
    experience for many visitors, destroy or damage
    fragile vegetation, and disturb wildlife.
  • Many suffer damage from the migration or
    deliberate introduction of nonnative species.
  • Native speciessome of them threatened or
    endangeredare killed or removed illegally.

Nature reserves occupy only a small part of the
earths land
  • As of 2010, less than 13 of the earths land
    area was strictly or partially protected in
    nature reserves, parks, wildlife refuges,
    wilderness, and other areas.
  • No more than 5 of the earths land is strictly
    protected from potentially harmful human
  • Conservation biologists call for full protection
    of at least 20 of the earths land area in a
    global system of biodiversity.
  • Developers and resource extractors oppose
    protection and contend that these areas might
    contain valuable resources that would add to
    current economic growth.

Nature reserves occupy only a small part of the
earths land
  • Ecologists and conservation biologists view
    protected areas as islands of biodiversity and
    natural capital that help to sustain all life and
    economies and serve as centers of evolution.
  • The buffer zone concept strictly protects an
    inner core of a reserve and establishes buffer
    zones in which local people can extract resources
    sustainably without harming the inner core.
  • By 2010, the United Nations had used this
    principle to create a global network of 553
    biosphere reserves in 109 countries.

CASE STUDY Costa RicaA Global Conservation
  • Tropical forests once completely covered Costa
    Rica, but between 1963 and 1983 much of the
    countrys forests were cleared to graze cattle.
  • Costa Rica is a superpower of biodiversity, with
    an estimated 500,000 plant and animal species.
  • Costa Rica now has a system of nature reserves
    and national parks that, by 2010, included about
    a quarter of its land.
  • Costa Rica now devotes a larger proportion of its
    land to biodiversity conservation than does any
    other country

CASE STUDY Costa RicaA Global Conservation
  • The countrys largest source of income is its
    1-billion-a-year tourism industry, almost
    two-thirds of which involves ecotourism.
  • To reduce deforestation, the government has cut
    subsidies for converting forest to rangeland.
  • The government pays landowners to maintain or
    restore tree cover.
  • Between 2007 and 2008, the government planted
    nearly 14 million trees.
  • Went from having one of the worlds highest
    deforestation rates to having one of the lowest.

Costa Ricas eight megareserves
Caribbean Sea
Costa Rica
Pacific Ocean
National parkland
Buffer zone
Fig. 9-20, p. 191
Protecting wilderness is an important way to
preserve biodiversity
  • One way to protect undeveloped lands is to set
    them aside as wilderness, land officially
    designated as an area where natural communities
    have not been seriously disturbed by humans and
    where human activities are limited by law.
  • Some critics oppose protecting large areas for
    their scenic and recreational value for a
    relatively small number of people.
  • Conservation biologists support protecting
    wilderness in order to preserve biodiversity and
    as centers for evolution.

CASE STUDY Controversy over Wilderness
Protection in the United States
  • Conservationists have been trying to save wild
    areas from development since 1900.
  • The Wilderness Act (1964) allowed the government
    to protect undeveloped tracts of public land from
    development as part of the National Wilderness
    Preservation System.
  • Only about 2 of the land area of the lower 48
    states is protected, most of it in the West.

What is the ecosystem approach to sustaining
  • Section 9-5

Here are four ways to protect ecosystems
  • Most biologists and wildlife conservationists
    believe that the best way to keep from hastening
    the extinction of wild species through human
    activities is the ecosystems approach, which
    protects threatened habitats and ecosystem

Here are four ways to protect ecosystems
  • Four-point plan of the ecosystems approach
  • Map the worlds terrestrial and aquatic
    ecosystems and create an inventory of the species
    contained in each of them and the ecosystem
    services they provide.
  • Locate and protect the most endangered ecosystems
    and species, with emphasis on protecting plant
    biodiversity and ecosystem services.
  • Seek to restore as many degraded ecosystems as

Protecting global biodiversity hotspots is an
urgent priority
  • Some biodiversity scientists urge adoption of an
    emergency action strategy to identify and quickly
    protect biodiversity hotspots, areas especially
    rich in plant species that are found nowhere else
    and are in great danger of extinction .
  • These hotspots cover only a little more than 2
    of the earths land surface, they contain an
    estimated 50 of the worlds flowering plant
    species and 42 of all terrestrial species.
  • These hotspots are home for a large majority of
    the worlds endangered or critically endangered
    species, and one-fifth of the worlds population.

Biodiversity hotspots
We can rehabilitate and restore ecosystems that
we have damaged
  • Almost every natural place on the earth has been
    affected or degraded to some degree by human
  • We can at least partially reverse much of this
    harm through ecological restoration the process
    of repairing damage caused by humans to the
    biodiversity and dynamics of natural ecosystems.
  • Examples of restoration include
  • replanting forests

We can rehabilitate and restore ecosystems that
we have damaged
  • restoring grasslands
  • restoring coral reefs
  • restoring wetlands and stream banks
  • reintroducing native species
  • removing invasive species
  • freeing river flows by removing dams.

We can rehabilitate and restore ecosystems that
we have damaged
  • Four steps to speed up repair operations include
    the following
  • Restoration.
  • Rehabilitation.
  • Replacement.
  • Creating artificial ecosystems.

We can rehabilitate and restore ecosystems that
we have damaged
  • Researchers have suggested a science-based,
    four-step strategy for carrying out most forms of
    ecological restoration and rehabilitation
  • Identify the causes of the degradation.
  • Stop the abuse by eliminating or sharply reducing
    these factors.
  • If necessary, reintroduce key species to help
    restore natural ecological processes.
  • Protect the area from further degradation and
    allow secondary ecological succession to occur.

We can share areas we dominate with other species
  • Reconciliation ecology is the science that
    focuses on inventing, establishing, and
    maintaining new habitats to conserve species
    diversity in places where people live, work, or
  • Examples include
  • Protecting local wildlife and ecosystems can
    provide economic resources for their communities
    by encouraging sustainable forms of ecotourism.

We can share areas we dominate with other species
  • Protecting vital insect pollinators such as
    native butterflies and bees by reducing the use
    of pesticides, planting flowering plants as a
    source of food for pollinating insect species,
    and building structures which serve as hives for
    pollinating bees.
  • Protecting bluebirds within human-dominated
    habitats where most of the bluebirds nesting
    trees have been cut down by using nesting boxes
    and keeping house cats away from nesting

Ways you can help sustain terrestrial biodiversity
How can we help to sustain aquatic biodiversity?
  • Section 9-6

Human activities are destroying and degrading
aquatic biodiversity
  • Human activities have destroyed or degraded a
    large portion of the worlds coastal wetlands,
    coral reefs, mangroves, and ocean bottom, and
    disrupted many of the worlds freshwater
  • Rising sea levels are likely to destroy many
    coral reefs and flood some low-lying islands
    along with their protective coastal mangrove
  • Loss and degradation of many sea-bottom habitats
    caused by dredging operations and trawler fishing

Human activities are destroying and degrading
aquatic biodiversity
  • In freshwater aquatic zones, dam building and
    excessive water withdrawal from rivers for
    irrigation and urban water supplies destroy
    aquatic habitats, degrade water flows, and
    disrupt freshwater biodiversity.
  • The deliberate or accidental introduction of
    hundreds of harmful invasive species threatens
    aquatic biodiversity.
  • Thirty-four percent of the worlds known marine
    fish species and 71 of the worlds freshwater
    fish species face premature extinction.

Before and after a trawler net
Overfishing gone fishing fish gone
  • A fishery is a concentration of a particular wild
    aquatic species suitable for commercial
    harvesting in a given ocean area or inland body
    of water.
  • The fishprint is defined as the area of ocean
    needed to sustain the consumption of an average
    person, a nation, or the world.
  • Fifty-two percent of the worlds fisheries are
    fully exploited, 20 are moderately
    overexploited, and 28 are overexploited or

Overfishing gone fishing fish gone
  • Overharvesting has led to the collapse of some of
    the worlds major fisheries.
  • When overharvesting causes larger predatory
    species to dwindle, rapidly reproducing invasive
    species can more easily take over and disrupt
    ocean food webs.

The collapse of Canadas 500-year-old Atlantic
cod fishery
Fish landings (tons)
Fig. 9-25, p. 197
CASE STUDY Industrial Fish Harvesting Methods
  • Industrial fishing fleets dominate the worlds
    marine fishing industry, using global satellite
    positioning equipment, sonar fish-finding
    devices, huge nets and long fishing lines,
    spotter planes, and gigantic refrigerated factory
    ships that can process and freeze their catches.
  • Trawler fishing is used to catch fish and
    shellfish by dragging a funnel-shaped net held
    open at the neck along the ocean bottom.
  • Purse-seine fishing, is used to catch
    surface-dwelling fish by using a spotter plane to
    locate a school the fishing vessel then encloses
    it with a large net called a purse seine.

CASE STUDY Industrial Fish Harvesting Methods
  • Longlining involves lines up to 130 kilometers
    (80 miles) long, hung with thousands of baited
    hooks to catch open-ocean fish species or bottom
  • Drift-net fishing catches fish with huge drifting
    nets that can hang as deep as 15 meters (50 feet)
    below the surface and extend to 64 kilometers (40
    miles) long.
  • Drift-nets can trap and kill large quantities of
    unwanted fish, called bycatch, along with marine
    mammals, sea turtles, and seabirds.
  • Almost one-third of the worlds annual fish catch
    by weight consists of bycatch species, which are
    mostly thrown overboard dead or dying.

Major commercial fishing methods
Fish farming in cage
Trawler fishing
Spotter airplane
Purse-seine fishing
Drift-net fishing
Long line fishing
lines with hooks
Deep sea aquaculture cage
Fish caught by gills
Fig. 9-26, p. 198
We can protect and sustain marine biodiversity
  • Protecting marine biodiversity is difficult for
    several reasons.
  • The human ecological footprint and fishprint are
    expanding so rapidly into aquatic areas that it
    is difficult to monitor the impacts.
  • Much of the damage to the oceans and other bodies
    of water is not visible to most people.

We can protect and sustain marine biodiversity
  • Many people incorrectly view the seas as an
    inexhaustible resource that can absorb an almost
    infinite amount of waste and pollution and still
    produce all the seafood we want.
  • Most of the worlds ocean area lies outside the
    legal jurisdiction of any country and is thus an
    open-access resource and subject to

We can protect and sustain marine biodiversity
  • Several ways to protect and sustain marine
  • Protect endangered and threatened aquatic
  • Establish protected marine sanctuaries.
  • Protect whole marine ecosystems within a global
    network of fully protected marine reserves.

Ways to manage fisheries more sustainably and
protect marine biodiversity
Taking an Ecosystem Approach to Sustaining
Aquatic Biodiversity
  • Strategies for applying the ecosystem approach to
    aquatic biodiversity include
  • Complete the mapping of the worlds aquatic
    biodiversity, identifying and locating as many
    plant and animal species as possible.
  • Identify and preserve the worlds aquatic
    biodiversity hotspots and areas where
    deteriorating ecosystem services threaten people
    and other forms of life.

Taking an Ecosystem Approach to Sustaining
Aquatic Biodiversity
  • Create large and fully protected marine reserves
    to allow damaged marine ecosystems to recover and
    to allow fish stocks to be replenished.
  • Protect and restore the worlds lakes and river
    systems (the most threatened ecosystems of all).
  • Initiate worldwide ecological restoration
    projects in systems such as coral reefs and
    inland and coastal wetlands.
  • Find ways to raise the incomes of people who live
    in or near protected lands and waters so that
    they can become partners in the protection and
    sustainable use of ecosystems.

Taking an Ecosystem Approach to Sustaining
Aquatic Biodiversity
  • The harmful effects of human activities on
    aquatic biodiversity and ecosystem services could
    be reversed over the next 2 decades if an
    ecosystem approach is implemented, at a cost one
    of penny per cup of coffee consumed in the world
    each year.

Three big ideas
  • The economic values of the important ecological
    services provided by the worlds ecosystems are
    far greater than the value of raw materials
    obtained from those systems.
  • We can sustain terrestrial biodiversity by
    protecting severely threatened areas, protecting
    remaining undisturbed areas, restoring damaged
    ecosystems, and sharing with other species much
    of the land we dominate.
  • We can sustain aquatic biodiversity by
    establishing protected sanctuaries, managing
    coastal development, reducing water pollution,
    and preventing overfishing.