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Transcript
Sustaining Biodiversity:
The Ecosystem Approach
Chapter 9
WHAT IS THE MOST
THREATENED ECOSYSTEM?
WHY?
Three big ideas
• The economic value of ecological services 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…
• We can sustain aquatic biodiversity by establishing
protected sanctuaries, managing coastal development,
reducing water pollution, and preventing overfishing.
Section 9-1
WHAT ARE THE MAJOR THREATS
TO FOREST ECOSYSTEMS?
Forests vary in their age, makeup, and origins
• Natural and planted forests occupy about 30% of
the Earth’s “tree-friendly” land surface.
• Two major types based on their age and structure:
– Old growth forest
– Second-growth forest
Forests vary in their age, makeup, and origins
• A tree plantation (tree farm, commercial forest), is
usually made up of how many species?
What ages of trees? How diverse? Good or Bad?
• Forests provide important economic and
ecological services.
– Help with global warming… HOW?
The short rotation cycle of cutting and
regrowth of a monoculture tree plantation
Forests provide many important
economic and ecological services
What services do they provide?
How do they
contribute to
economies?
Unsustainable logging is a major
threat to forest ecosystems
• Methods of harvesting trees:
– Selective cutting.
– Clear-cut.
– Strip cutting.
Unsustainable logging is a major
threat to forest ecosystems
• 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
waterways.
– Habitat fragmentation.
– Loss of biodiversity.
– Forest exposure to invasion by nonnative
pests, diseases, and wildlife species.
Three major tree harvesting
methods
Aerial view showing clear-cut
logging, Washington state
How about forest fires… are they good
or bad?!?!
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 escape.
– 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 world’s
forests have been cut down
• Deforestation is the temporary or permanent removal of
large expanses of forest for agriculture, settlements, or
other uses.
• Human activities have reduced the earth’s 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
world’s remaining intact forests will have been logged or
converted to other uses within two decades, if not
sooner.
Harmful effects of deforestation
Forest cover in the U.S.
Tropical forests are
disappearing rapidly
• Tropical forests cover about 6% of the earth’s land area.
• At least half of the world’s known species of terrestrial
plants and animals live in tropical forests.
• Brazil has more than 30% of the world’s remaining tropical
rain forest in its vast Amazon basin.
• At the current rate of global deforestation, 50% of the
world’s remaining old-growth tropical forests will be gone or
severely degraded by the end of this century.
Major underlying and direct causes of the
destruction and degradation of tropical forests
Section 9-2
HOW SHOULD WE MANAGE
AND SUSTAIN FORESTS?
We can manage forests more
sustainably
• Certification of sustainably grown timber
and of sustainably produced forest
products can help consumers.
• Removing government subsidies and tax
breaks that encourage deforestation would
also help.
Ways to grow and harvest trees
more sustainably
Ways to protect tropical forests
and use them more sustainably
Section 9-3
HOW SHOULD WE MANAGE
AND SUSTAIN GRASSLANDS?
Left of fence: overgrazed land
Right: lightly grazed land
Restoration via secondary
ecological succession
Section 9-4
HOW SHOULD WE MANAGE
AND SUSTAIN PARKS AND
NATURE RESERVES?
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.
What are the problems?!?
Costa Rica’s eight megareserves
CASE STUDY: Costa Rica—A
Global Conservation Leader
• Tropical forests once completely covered Costa
Rica, but between 1963 and 1983 much of the
country’s 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 Rica—A
Global Conservation Leader
• The country’s largest source of income is its $1billion-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 world’s highest
deforestation rates to having one of the lowest.
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.
Section 9-5
WHAT IS THE ECOSYSTEM
APPROACH TO SUSTAINING
BIODIVERSITY?
Biodiversity hotspots
Ways you can help sustain
terrestrial biodiversity
Section 9-6
HOW CAN WE HELP TO
SUSTAIN AQUATIC
BIODIVERSITY?
The collapse of Canada’s 500year-old Atlantic cod fishery
Before and after a trawler net
Major commercial fishing
methods
Ways to manage fisheries more sustainably
and protect marine biodiversity
Three big ideas
• The economic value of ecological services…
• We can sustain terrestrial biodiversity by …
• We can sustain aquatic biodiversity by…
Human activities are destroying
and degrading aquatic biodiversity
• Human activities have destroyed or degraded a
large portion of the world’s coastal wetlands,
coral reefs, mangroves, and ocean bottom, and
disrupted many of the world’s freshwater
ecosystems.
• Rising sea levels are likely to destroy many coral
reefs and flood some low-lying islands along
with their protective coastal mangrove forests.
• Loss and degradation of many sea-bottom
habitats caused by dredging operations and
trawler fishing boats.
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 world’s known marine
fish species and 71% of the world’s freshwater
fish species face premature extinction.
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 world’s fisheries are fully
exploited, 20% are moderately overexploited,
and 28% are overexploited or depleted.
Overfishing: gone fishing; fish
gone
• Overharvesting has led to the collapse of some
of the world’s major fisheries.
• When overharvesting causes larger predatory
species to dwindle, rapidly reproducing invasive
species can more easily take over and disrupt
ocean food webs.
CASE STUDY: Industrial Fish
Harvesting Methods
• Industrial fishing fleets dominate the world’s 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 fishes.
• 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 world’s annual fish catch by
weight consists of bycatch species, which are mostly
thrown overboard dead or dying.
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 world’s ocean area lies outside
the legal jurisdiction of any country and is thus
an open-access resource and subject to
overexploitation.
We can protect and sustain
marine biodiversity
• Several ways to protect and sustain
marine biodiversity:
– Protect endangered and threatened aquatic
species.
– Establish protected marine sanctuaries.
– Protect whole marine ecosystems within a
global network of fully protected marine
reserves.
Taking an Ecosystem Approach to
Sustaining Aquatic Biodiversity
• Strategies for applying the ecosystem
approach to aquatic biodiversity include:
– Complete the mapping of the world’s aquatic
biodiversity, identifying and locating as many
plant and animal species as possible.
– Identify and preserve the world’s 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 world’s 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.