Chapter 10
Sustaining Terrestrial Biodiversity: The Ecosystem Approach
Summary
1.
Conservation biology attempts to slow down the rate at which we are destroying and degrading the earth’s
biodiversity through the use of rapid response strategies. Hot spots, the most endangered and species-rich
ecosystems, receive emergency action to slow down/stop the loss of biodiversity in these systems.
Bioinformatics manages, analyzes, and communicates basic biological and ecological information to help
sustain biodiversity.
2.
Forests provide important ecological and economic services, are storehouses of biodiversity, and affect weather
and climate throughout the world. Forest resource management varies according to the type of forests. In
diverse forests, the age and size of trees are preserved to foster natural regeneration. Government policies will
primarily determine the future of forests, including old-growth forests.
3.
Forests in the United States should be managed so as to retain as much of the forests as possible. Clear-cutting
and seed-tree cutting methods of harvesting are scourges on the forest; selective cutting is the most reasonable
way to harvest trees.
4.
Deforestation is one of the most serious ecological problems of this century. The earth’s forests have been
reduced by 20–50% and the destruction continues to this day. Deforestation has many harmful environmental
effects: reduces ecological services of forests, releases large amounts of carbon dioxide in the air, produces a
drier and hotter climate; reduces the control of water movements, and increases soil erosion.
5.
Tropical deforestation is one of the biggest threats to world economic health and climate. To help sustain
tropical forests, nations of the world must unite to discourage deforestation and degradation.
6.
Problems affecting parks run from little/no protection from their governments or being too small to sustain
large animal species, to being too popular and, therefore, overused by people. Some methods for managing
parks include: limiting the number of visitors, raising entry fees to provide funds for maintenance and
management, managing parks in reference to nearby federal lands, discouraging development around already
established parks, and providing more volunteers and better paid employees to maintain the parks.
7.
Only about 7% of the world’s terrestrial areas are protected from potentially harmful human activities; these
areas need to be expanded throughout the world. In order to adequately conserve biodiversity, at least 20% of
the earth’s land area should be protected in a global network of reserves.
8.
Wilderness is an amount of land legally set aside to prevent/minimize harm from human activities. This is land
where human beings may visit but not remain. Wilderness areas are important for: (1) their natural beauty, (2)
their natural biological diversity, (3) their enhancement of mental and physical health of visitors, and (4) their
contributions to biodiversity and to evolutionary possibilities.
9.
Ecological restoration is the process of repairing damage caused by humans to the biodiversity and dynamics
of natural ecosystems.
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10. Initiatives that would help to sustain the earth’s biodiversity include:
– Immediately preserving the world’s biological hot spots
– Protecting the remaining old-growth forests
– Mapping the world’s terrestrial and aquatic biodiversity
– Identifying and taking action for the world’s marine hot spots, just as for the terrestrial hot spots
– Protecting and restoring the world’s lakes and river systems
– Developing a global conservation strategy that protects the earth’s terrestrial and aquatic ecosystems
– Making conservation profitable
– Initiating ecological restoration projects worldwide
Key Questions and Concepts
10-1 What are the major threats to forest ecosystems?
CORE CASE STUDY: Gray wolves once roamed in abundance throughout the United States. By 1900, most
of their population had been decimated. In 1974 the wolf was listed as endangered. Its declining population
had many effects at the ecosystem level. Decreased predation allowed for growth in populations of grazing
animals, which had devastating effects on vegetation as well as other animal populations. Beginning in 1995,
wolves were reintroduced to Yellowstone National Park. Since then, their population has increased and they
have been removed from protection under the ESA.
A. Forests with at least 10% tree cover occupy about 30% of the earth’s surface, excluding Greenland and
Antarctica.
B. Forests are classified according to their age and structure into three major types.
1. Old growth/frontier forests are those that have not been seriously disturbed by human activities/natural
disasters for hundreds of years. These forests are storehouses of biodiversity because of the ecological
niches they provide for wildlife species.
2. Second-growth forests develop in an area after human activities or natural forces have removed them.
3. Tree plantations/tree farms replant and clear-cut one species of trees in a regular cycle.
C. Harmful effects of deforestation (temporary/permanently removing trees) are given below:
1. Deforestation reduces biodiversity and the ecological services that forests provide.
2. Deforestation can change regional climate, and forests will not regenerate.
3. Deforestation emits carbon dioxide, which affects global climate change.
D. The presence of logging roads has many negative consequences.
1. Logging roads increase erosion and sediment runoff, fragment habitats, and contribute to loss of
biological diversity.
2. They expose forest to invasion by nonnative pests, diseases, and wildlife species.
E. Different harvesting methods affect the continuing growth of forests.
1. In selective cutting, intermediate-aged/mature trees are cut singly or in small groups.
2. Clear-cutting removes every single tree in one cutting.
3. Strip cutting removes a strip of trees along the contour of the land and spreads the cutting out over
several decades.
SCIENCE FOCUS: Researchers have attempted to devise a method to place a monetary value on
ecosystem services. They hope that these efforts will make people aware that: ecosystem services are
essential for humans and their economies, the economic value of ecosystem processes is substantial, and
sustainably managed ecosystems are a long-term source of income.
F. Three types of fires affect forest ecosystems.
1. Surface fires usually burn underbrush, leaf litter, and small seedlings, but most wild animals survive.
They have benefits such as burning flammable ground material to prevent more destructive fires and
release nutrients, stimulate germination of some seeds, and control pathogens and insects.
2. Crown fires are extremely hot and leap from treetop to treetop. Buildup of ground litter increases
likelihood of crown fires that result in greater destruction and soil erosion.
3. Protection of forest resources from fire includes fire prevention and prescribed burning.
G. Accidental and deliberate introductions of forest diseases and insects are a major threat to forests.
H. Climate change threatens many forests.
1. Some species are sensitive to heat.
2. Insects and disease may move into forests where they weren’t previously found.
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3. Drier conditions exacerbate the risk of fire.
I. Deforestation is widespread across the planet and is continuing.
1. World Resources Institute surveys indicate that original forest cover has decreased by about 46%.
2. Global deforestation is occurring by at least 0.2–0.5% per year, with most losses taking place in
developing countries.
3. If conditions don’t change within the next 10–20 years, 40% of the world’s remaining forests will have
been logged or converted to other uses.
CASE STUDY: Forests cover about 30% of the land area in the United States. Early in the nation’s
history, forests were decimated. Today, however, forests cover more land area in the U.S. than they did in
1920. Much of this is second growth. In addition, much of the nation’s old-growth forest has been replaced
with simplified tree plantations.
H. Tropical forests make up 6% of the earth’s land area.
1. They once covered twice as much area. Most destruction has occurred since 1950.
2. Brazil and Indonesia lead the world in tropical forest loss.
3. At least half of the world’s terrestrial plant and animal species are found in tropical rainforests.
4. Annual tropical forest loss is estimated to be between 50,000 and 170,000 square kilometers.
K. Four primary causes of tropical forest destruction are:
1. Population growth and poverty drive subsistence farmers to tropical forests where they attempt to farm.
2. Government subsidies make tropical forest resources cheap—relative to their full ecological value.
3. Degradation begins when roads are cut into the forest for logging. Selective cutting removes the best
timber (high grade).
4. Ranchers come in behind the timber cutters and overgraze land, they then move on and subsistence
farmers come in and practice slash-and-burn farming to complete the destruction of the land.
5. Healthy rain forests do not burn, but logging, settlements, grazing, and farming have fragmented the
forest; they dry out, making them more flammable for when lightning and people to start fires.
6. Burning contributes to global climate change, accounting for 20% of the annual greenhouse gas
emissions.
10-2 How should we manage and sustain forests?
A. Fire management can be improved.
1. The Smokey Bear educational campaign taught that fire is bad. Ecologists suggest that putting out all
fires increases the risk of a catastrophic fire event.
2. According to the Forest Service, severe fire could threaten 40% of federal forest lands due to fuel
buildup.
3. Risk can be reduced via prescribed fire, allowing natural fires to burn, and clearing vegetation from
around structures.
SCIENCE FOCUS: Scientific Certification Systems (SCS) is part of the Forest Stewardship Council (FSC),
which certifies timber and products generated from environmentally sound and sustainable practices. Since
1995, the area of the world’s forests that meets these standards has grown 16-fold. Still, less than 10% of the
world’s forested area is certified.
B. Improving the efficiency of wood use would reduce pressure to harvest trees on public and private land.
1. Up to 60% of wood consumed in the U.S. is wasted due to inefficient use of construction materials,
excess packaging and overuse of junk mail, inadequate paper recycling, and failure to reuse wooden
shipping containers.
C. Use of tree-free fibers for papermaking is another way to reduce pressure on tree harvest.
1. Use of fibers from agricultural residues and crops such as kenaf are alternatives to tree fibers.
CASE STUDY: About half the wood harvested each year in the U.S., and three-fourths of that in
developing countries, is used for fuel. Rings of deforested land surround cities, and the demand for
fuelwood in urban areas exceeds the sustainable yield of nearby forests. Community forestry projects
involve local people in planting small plantations of fast-growing fuelwood trees in community
woodlots.People can use more efficient, less polluting woodstoves, solar ovens, or electric hotplates
powered by windpower to reduce the demand for fuelwood.
D. In order to reduce deforestation and degradation of tropical forests:
1. We must help settlers learn methods to practice in small-scale sustainable agriculture and forestry.
2. We must harvest sustainable fruits and nuts in the rain forests.
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3. We should consider using debt-for-nature swaps, which allow countries that owe foreign aid/foreign
debt to act as custodians of protected forest reserves in order for debt to be forgiven.
4. We must develop an international system for evaluating and certifying that tropical timber has been
produced by sustainable methods.
5. Loggers can harvest trees more gently: canopy vines being cut saves damage to nearby trees; use the
most open paths to remove felled trees.
10-3 How should we manage and sustain grasslands?
A. Grasslands provide many important ecological services yet are the second-most altered ecosystem.
B. Livestock often overgraze on rangelands (non-managed grasslands) and pastures (managed grasslands),
causing soil and erosion and exploitation by invasive plants.
C. Grasslands also suffer from undergrazing, which can reduce the net primary productivity of the area.
D. To utilize grasslands in a sustainable way, we must control the number and distribution of livestock.
E. Ranchers, ecologist, and environmentalists in the United States are working together to protect grasslands
by rotating livestock.
F. Invasive plants can be combated with herbicides, mechanical removal, and controlled burning.
CASE STUDY: Since 1980, there has been a population surge in the ranch country in the Southwestern
United States. This has led to uncontrolled urban development. Now, ranchers and environmentalists are
working together to conserve ranchland as a means of sustaining the remaining grassland habitats. One
strategy is to pay ranchers for conservation easements, which bar future owners from developing land.
10-4 How should we manage and sustain parks and nature reserves?
A. There are more than 1,100 national parks in more than 120 countries.
1. Parks in developing countries possess the greatest biodiversity, but are least protected.
CASE STUDY: The U.S. National Park system includes 58 major national parks. Their popularity brings
pollution and associated problems with overuse. Non-native species threaten biodiversity in parks, which
are often isolated amidst development. Inadequate budgets add to the challenges faced by our national
parks.
SCIENCE FOCUS: Scientists are monitoring the gray wolves that have been reintroduced to Yellowstone
National Park. The effects of this reintroduction have been many. They are impacting the populations and
behaviors of large grazing animals. This has helped to restore riparian zones that were degraded by elk.
Coyote populations have also been decreased. It will take decades of research to understand the way these
animals impact the functioning of their ecosystem.
B. Conservation biologists call for strict protection of at least 20% of earth’s global system as biodiversity
reserves that include multiple examples of all the earth’s biomes.
C. Large reserves are usually the best way to protect biodiversity, but in some locales several well-placed,
medium-sized, isolated reserves may be a better way to protect a variety of habitats.
1. Buffer zones establish an inner zone of intact habitat.
2. The United Nations has established 529 biosphere reserves globally, based on this principle.
D. Establishment of habitat corridors helps to support more species and allows migration of vertebrates with
large ranges.
1. Migration of individuals can occur when environmental conditions deteriorate within a range.
2. They can also threaten isolated populations by allowing movement of pest species, disease, fire, and
exotic species between reserves.
3. They may be costly to acquire, protect, and maintain.
CASE STUDY: The most impressive country for conserving its land and natural resources has been Costa
Rica. It has established a system of reserves and national parks, and it devotes a larger portion of its land to
biodiversity conservation than any other country. It has consolidated its parks and reserves into eight
megareserves, which help generate a $1 billion per year in ecotourism industry. Costa Rica once had one of
the highest rates of deforestation and now has one of the lowest.
E. The wilderness concept provides for large tracts of undeveloped land.
CASE STUDY: The Wilderness Act was not passed in the U.S. until 1964. Only about 4.6% of U.S. land
is protected as wilderness, with almost three-fourths of it in Alaska. Only about 1.8% of the lower 48 states
are protected as wilderness. Only 81 of the 233 distinct ecosystems are protected in wilderness. Industries
see these areas as sources of increased profits and short-term economic growth. Protection of areas under
consideration for wilderness status was discontinued in 2003.
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10-5 What is the ecosystem approach to sustaining biodiversity?
A. We should focus on protecting ecosystems and their biodiversity rather than distinct species.
1. Map and inventory ecosystems.
2. Identify the most endangered ecosystems.
3. Restore degraded ecosystems.
4. Make development biodiversity-friendly via tax breaks.
B. Biodiversity hotspots are areas especially rich in species, and in great risk of extinction.
1. In all 34 hotspots, a total of 86% of habitat has been destroyed.
CASE STUDY: The Eastern Arc Mountains of Tanzania have the highest concentration of endangered
animals on earth. The area is a hotspot because of threats to habitat. So far, 70% of the ancient forests have
been cleared. The forest is now fragmented, but protected in government reserves, where people can still
forage and gather fuelwood.
C. Another approach to biodiversity conservation is to protect those areas where vital ecosystem processes are
being impaired.
D. Life-raft ecosystems are those in which people live in extreme poverty and must degrade ecosystem
processes to survive.
SCIENCE FOCUS: Guanacaste National Park in Costa Rica is the site of one of the world’s largest
ecological restoration projects. The project involves local community members in the restoration effort.
Many local students have been trained in restoration ecology. This project is guided by the belief that it will
ultimately fail unless the local communities see some economic benefit in its success.
E. Environmental degradation can be partially reversed through ecological restoration.
F. Scientists study how natural systems recover and are learning to speed up repair operations by the
following approaches:
1. Restoration returns a degraded habitat to a condition as close to its natural state as possible.
2. Rehabilitation involves trying to restore an ecosystem to a functional state rather than is original state.
3. Replacement is replacing a degraded ecosystem with a productive pasture or tree farm.
4. Creating artificial ecosystems is another possibility.
G. Applied Ecology: inventing, establishing, and maintaining new habitats for species to coexist with humans.
CASE STUDY: The Blackfoot River comprises a large and diverse watershed. It is also home to many
people who witnessed environmental degradation due to poor mining, logging, and grazing practices. This
stimulated activism at the community level. In 1993, community members organized the Blackfoot
Challenge. This resulted in drastic improvements, and became a classic example of reconciliation ecology.
Additional Video Resources
The Lorax (Animated, Dr. Seuss, 1972, Online)
Animated version of the classic book about an industrialist and the destruction of the environment.
Main Website: http://video.google.com/videoplay?docid=6650219631867189375
Activity: http://www.teacherweb.com/TN/WestValleyMiddle/TheLorax/
NOVA—Fire Wars
Main Website: http://www.pbs.org/wgbh/nova/fire/
Teacher’s Guide: http://www.pbs.org/wgbh/nova/teachers/programs/2908_fire.html
Major World Ecosystems; (Documentary, 2004)
Covers a variety of ecosystems, and what their requirements are.
http://www.amazon.com/Major-World-Ecosystems/dp/B00004T01Y
Valley at the Crossroads (Documentary, 2002)
The battle over sprawl in California's Central Valley, where 50% of America's fruits, and vegetables are grown.
http://www.bullfrogfilms.com/catalog/vac.html
Livable Landscapes. (Documentary, 2002)
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How growth and sprawl affect the quality of life in New England, and some possible solutions.
http://www.bullfrogfilms.com/catalog/ll.html
Web Resources
National Interagency Fire Center
http://www.nifc.gov/fire_info/nfn.htm
Has up-to-date information on wildfires as well as educational materials.
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Suggested Responses to Critical Thinking Questions
The following are examples of the material that should be contained in possible student answers to the end of
chapter Critical Thinking questions. They represent only a summary overview and serve to highlight the core
concepts that are addressed in the text. It should be anticipated that the students will provide more in-depth and
detailed responses to the questions depending on an individual instructor’s stated expectations.
1.
List three ways you could apply concept 10-5C to help sustain terrestrial ecosystems and biodiversity.
Answers will vary. However, three possible ways to apply concept 10-5C are landscaping with native
plants, purchasing only wood products that are made of sustainably harvested wood, and planting and
caring for trees.
2.
Do you support the program that reintroduced populations of the gray wolf in the Yellowstone ecosystem
in the United States (Core Case Study)? Explain. Do you think the reintroduction of wolves should be
expanded to areas outside of the park? Explain.
Yes, the introduction of the gray wolf helps to restore the natural ecological balance of the area. The gray
wolf, regarded as a keystone species, helps to sustain the biodiversity and restore balance to the ecosystem,
which prevents further degradation. I would be in favor of expanding these reintroduction efforts to areas
outside of the park, provided that there was a widespread education campaign as well as resources available
to people who need to fortify their own resources, such as livestock, against the reintroduction of this large
predator.
3.
Some argue that growing oil palm trees in plantations in order to produce biodiesel fuel will help us to
lessen our dependence on oil and will cut vehicle CO2 emissions. Do you think these benefits are important
enough to justify burning and clearing some tropical rain forests? Why or why not? Can you think of ways
to produce biofuels, other than cutting trees? What are they?
These benefits are not sufficient to justify the potential loss of biodiversity. There are potential other
sources of biofuels, as well as new alternative technologies that could be developed and exploited.
Biodiversity loss is an irreparable consequence of this extractive activity. Other ways to produce biofuels
range from first exhausting all waste oil resources, and then focusing on highly productive crops, such as
sugar cane, as well as new alternatives such as algae. Ultimately, energy conservation and a diversification
of sources may be the best alternative.
4.
In the early 1990s, Miguel Sanchez, a subsistence farmer in Costa Rica, was offered $600,000 by a hotel
developer for a piece of land that he and his family had been using sustainably for many years. The land
contained an old-growth rain forest and a black sand beach in an area under rapid development. Sanchez
refused the offer. What would you have done if you were a poor subsistence farmer in Miguel Sanchez’s
position? Explain your decision.
I would have refused the offer like Sanchez did. The family heritage on land owned by generations of the
same family is worth more than hard cash. Although many of these subsistence farmers are considered
“poor” by the standards of living in the developed world, they have in many ways a much “richer” life than
money alone can provide. Sanchez thought it important to continue in the sustainable ways of his family. I
agree.
5.
There is controversy over whether Yellowstone National Park in the United States should be accessible by
snowmobile during winter. Conservationists and backpackers, who use cross-country skis or snowshoes for
excursions in the park during winter, say no. They contend that snowmobiles are noisy, pollute the air, and
can destroy vegetation and disrupt some of the park’s wildlife. Proponents say that snowmobiles should be
allowed so that snowmobilers can enjoy the park during winter when cars are mostly banned. They point
out that new snowmobiles are made to cut pollution and noise. A proposed compromise plan would allow
no more than 950 of these new machines into the park per day, only on roads, and primarily on guided
tours. What is your view on this issue? Explain.
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Snowmobile access should not be allowed during the winter months in Yellowstone. Even new
environmentally-friendly, pollution-free snowmobiles will destroy vegetation and disrupt wildlife. During
this normally peaceful time during the year, the park should remain closed to motorized traffic in order for
the ecosystem to function without disruption for the season.
6.
In 2006, Lester R. Brown estimated that reforesting the earth and restoring the earth’s degraded rangelands
would cost about $15 billion a year. Suppose the United States, as the world’s most affluent country,
agreed to put up half this money, at an average annual cost of $25 per American. Would you support doing
this? Explain. What other part or parts of the federal budget would you decrease to come up with these
funds?
Yes, I would support this. The United States comprises less than 5 percent of the world’s population but we
are responsible for a much higher percentage use of the world’s resources and resulting environmental
degradation. Other countries should also kick in and help offset the costs. These funds could come out of
the military budget that the Pentagon receives.
7.
Should developed countries provide most of the money to help preserve remaining tropical forests in
developing countries? Explain.
Yes, developing countries need help from the developed world in order to preserve their remaining tropical
forests. Many of the countries in the developed world have been the driving force for much of the
deforestation that has occurred from oil, mineral, and other resource extraction in these areas. Many of the
developing countries cannot even afford to pay back the interest on the loans from the World Bank and the
IMF. In some cases they have entered into “debt for nature swaps.”
8.
9.
Are you in favor of establishing more wilderness areas in the United States, especially in the lower 48
states (or in the country where you live)? Explain. What might be some drawbacks of doing this?
Ensuring that current wilderness areas remain protected would be a main priority. Then an assessment of
what other potential wilderness areas in the nation could be protected should be conducted, and decisions
made on a case by case basis. Once an area has been given the designation of being a wilderness area, then
it should keep that designation and not have it removed by the next government administration. There are
drawbacks to this. Some people will be against protecting these areas and may wish to expand into them for
development or resource extraction. Others may wish this to occur as it may limit their own ability to use
the area as they would like to, for offroading for example.
Congratulations! You are in charge of the world. List the three most important features of your policies for
using and managing: (a) forests, (b) grasslands, (c) nature reserves such as parks and wildlife refuges, (d)
biological hotspots, and (e) areas with deteriorating ecosystems services.
(a) I would ensure that sustainable harvesting practices took place in forested areas in order to supply and
promote the production of sustainably grown wood products, manage the forests using best practices, and
replant areas that have been cut down.
(b) I would limit grazing rights on grasslands and remove subsidies that turn grasslands into cash cropyielding areas, and minimize habitat fragmentation by limiting road construction and development of these
areas.
(c) I would limit the yearly use of nature reserves by putting a cap on the number of visitors who could
access the area; increase the funding for park management and maintenance, and increase the amount of
area in and around the reserves by purchasing and protecting more land.
(d) I would limit development in biodiversity hotspots, and implement a habitat conservation plan to
protect as many threatened and endangered species as possible.
(e) Areas with deteriorating ecosystem services would be the focus of aggressive ecological restoration
programs. These would involve community members, so that the local population would feel connected
with the process. This would foster a cohesiveness that would help the projects to succeed.
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10. List two questions that you would like to have answered as a result of reading this chapter.
Student answers will vary and provide a good starting point for class discussion.
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