Chapter 23: Sustaining Terrestrial Biodiversity: The Ecosystem
23-1: Land Use in the World and the United States
Comparison of land use by percentage:
World United States
Forest 32% 30%
Rangeland/Pasture 26% 29%
Cropland 11% 17%
Desert/Tundra/Wetlands 29% 13%
Parks n/a 9%
Urban 2% 2%
The United States is very similar to the world averages in forest,
rangeland/pasture, and urban. The U.S. has a significantly higher percentage
of croplands and parks, and a significantly lower percentage of unusable lands
55% of the land in the United States is privately owned.
35% of the land is owned by the federal government. 95% of the federal land is
west of the Mississippi River and most of that is in Alaska.
Federally owned lands can be divided into three categories based on how the
land is used.
A. Multiple-Use Lands
National Forest System – managed by the U.S. Forest Service
These forests are used for many purposes, including logging, mining, farming,
hunting and recreation. The closest National Forest to us is Sumter National
Forest which is located between Simpsonville and Columbia. There are also
several National Forests in Western North Carolina.
National Resource Lands – managed by Bureau of Land Management
These are areas of land in the Western U.S. and Alaska that are used for
strategic resources and loaned to farmers for rangeland.
B. Moderately Restricted-Use Lands
National Wildlife Refuges – managed by the U.S. Fish & Wildlife Service
The primary purpose of these protected lands is to provide habitats for plants
and animals, especially birds. Wildlife refuges can also be used for the same
purposes as restricted-use lands, but usually on a lesser scale. There are 5
wildlife refuges in South Carolina, most of them coastal.
C. Restricted-Use Lands
National Park System – managed by the National Park Service
There are 56 major national parks and over 200 smaller sites. Only
recreational activities such as hiking, camping, fishing, boating (and
snowmobiling) are permitted.
Congaree National Park near Columbia is the only National Park in South
Carolina, designated in 2003. It is a swampy forest.
Great Smoky Mountains National Park on the North Carolina/Tennessee border
is only about 3 hours away. It is the most visited national park in the U.S.
Other popular national parks include Yellowstone, Yosemite, and Grand
National Wilderness Preservation System – split management
These are areas within other land units that are designated for recreational
activities only. The term “wilderness” specifically means no roads or
motorized vehicles are allowed.
How should U.S. public lands be managed?
Conservationist viewpoint (based on Leopold’s Land Ethic):
Protect habitats and biodiversity
Fair compensation for use of land (no subsidies)
Users of public lands should be held accountable for environmental
Opposition viewpoint (Sagebrush Rebels):
Convert public lands to private ownership
Save money by cutting funding for governmental regulation
Modify Endangered Species Act to open up more land for developing
Extremist opposition viewpoint (Wise-Use Movement)
Convert all federal land to multiple-use
Cut all old growth forests and replace with tree plantations
Convert national parks to private theme parks
23-2: Managing and Sustaining Forests
Ecological Importance of Forests:
Provides habitats for wildlife
Plays a vital role in nutrient cycles
Acts like a sponge (hold water, slow runoff, reduce erosion)
Influences climate (transpiration)
Economic Importance of Forests:
Medicines – many modern prescription drugs are based on the natural
chemical defenses of plants and animals
Forests can be divided into groups based on climate:
Polar (boreal or taiga)
South Carolina is on the border between subtropical and temperate climates.
Forests can be divided into groups based on level of disturbance:
A. Old-growth Forests: forests that have not been cut or significantly
altered by human activities for hundreds of years, enough time to reach
a mature community.
B. Second-growth Forests: forests that have regenerated through the
process of secondary succession following either human disturbance
(farm) or natural disturbance (lightning-based forest fire).
C. Tree plantations (tree farms): forests with a monoculture specifically
planted for commercial harvesting.
Since the agricultural revolution began, it is estimated that the world’s
forest cover has been reduced by 50%. Another 30% of the forests have
been significantly fragmented.
Currently, 90-95% of the forest reduction occurs in developing countries of
the tropics, specifically Latin America, Asia, and Africa.
The primary reasons for deforestation of tropical forests are:
Land for housing an increasing population
Croplands to feed an increasing population
Wood to burn for fuel
Wood to sell for profit
Forest Management Styles:
A. Even-aged: trees are harvested in large groups, replanted and allowed
to grow for 6-100 years before being harvested as a group again. The
tendency to plant fast-growing trees quickly saps the soil of necessary
B. Uneven-aged: mature trees are harvested selectively, not as a group.
This leads to a lower rate of economic return, but is more sustainable in
The process of harvesting a forest begins with building logging roads. The
introduction of roads to a wilderness community is the key step in facilitating
environmental damage through:
Opening previously inaccessible areas to lots of people
Increasing exposure to nonnative species
Fragmenting the forest into small sections
Methods of Harvesting Trees:
1. Selective Cutting: the cutting of trees as individuals or small groups.
This is generally a positive method of harvesting, unless the process of
high-grading is occurring. High-grading means removing only the largest
and most desirable individuals from the forest.
2. Shelterwood Cutting: the removal of all mature trees in a series of 2 or
3 cuts over the span of a decade.
3. Seed-tree Cutting: the removal of a majority of trees, leaving behind
uniformly distributed seed trees to replenish the area.
4. Clear-cutting: the removal of all of the trees in a given area in a single
5. Strip-cutting: a variation of clear cutting in which narrow strips of trees
are removed and allowed to replenish before another strip is cut.
Clear cutting techniques have many advantages economically, but also
many drawbacks environmentally.
How Can Forests be Managed More Sustainably?
A. Longer rotations between harvests
B. Use selective cutting instead of clear-cutting
C. Leave dead trees/fallen timber for habitats
D. Increase use of tree farms
*More intensive use of tree farms may actually be a benefit to forests as a
whole. If timber demand can be satisfied through a small number of
intensively grown tree farms, pressure to cut existing old-growth and second-
growth forests may be reduced.
Effect of Pathogens/Insects
A. Nonnative tree diseases
Chestnut blight has wiped out almost all chestnut trees
Dutch elm disease
Hickory trees have also been very susceptible to fungus
B. Nonnative pests: several examples, but the most damaging has been the
gypsy moth, whose caterpillars strip deciduous trees bare, rendering
them unable to photosynthesize.
Many ecosystems rely on intermittent fires to burn away low vegetation/brush.
Chaparral (Southern California)
Southern Pine Forests
Some species even require fire to germinate. The seeds are not released from
the cone until extremely high temperatures are reached.
Types of Forest Fires
A. Surface Fires: burn the undergrowth/leaf litter. They spare most
mature trees and wild animals. Occasional surface fires are generally a
good thing for most ecosystems.
B. Crown Fires: burn entire trees/forests. They usually occur in forests
where a surface fire has not occurred in several years. Crown fires
cause massive destruction as the fire jumps from the canopy of one tree
to the next.
Educational programs such as Smokey the Bear have convinced Americans that
all forest fires are bad, which is not necessarily true.
A prescribed fire is a controlled surface fire that decreases the likelihood of a
destructive crown fire occurring in the future.
The U.S. Forest Service/National Park Service policy involving fires on public
land is to allow naturally caused forest fires to burn themselves out as long as
they do not threaten:
Several destructive crown fires occur annually in the Western United States
because of naturally dry conditions and the lack of regular surface fires to burn
up the underbrush.
Major forest fires burned up much of the forested areas of Yellowstone Park in
1988 and again in 1994.
One potential solution to this problem is to hire logging companies to
selectively cut trees on public lands to thin them out, reducing the chances
that a fire would spread from one tree to the next (lower the tree density).
23.3: Forest Resources and Management in the United States
Status of American Forests:
Forest land has increased from a century ago, primarily due to
secondary succession on abandoned farmland.
Forests are generally healthier than a century ago due to
restrictions on air pollution.
Over 90% of original old growth forest in the United States has
already been cut at least once.
Increasing dependence on tree farms creates large areas with very
Urban sprawl/suburban growth continues to increase, placing
demand on wooded areas for housing/commercial development.
How Should U.S. National Forests Be Managed?
About 20% of the forest in the United States is owned by the government.
The U.S. Forest Service has two main management philosophies:
1. Sustained Yield: do not cut down the trees faster than they can be
2. Multiple Use: national forests should be used for a variety of
Perennial conflict exists between timber companies and conservationists as to
how best to use the national forest resources.
From 1930-1988, timber harvesting from national forests grew sharply. One
reason for this is a law allocating 25% of the money received from timber sales
to the local counties, which has led local governments to encourage sales.
Overall, the National Forest Service does not make a profit for the government
on the timber it sells. When the cost of transportation, administration, road
construction, and wood preparation are factored in, the result is a net loss.
It is estimated that between 1978 and 1998, the U.S. Forest Service lost about
seven billion dollars in potential profits by selling timber for less than market
Under the Clinton administration the policy of the U.S. Forest Service stated
that the “ecological sustainability of resources be the overall goal of forest
management”. Timber harvests from federal lands dropped sharply.
One of Clinton’s last acts in office was to block road construction in several
areas of national forests, making them eligible for protection as Wilderness
The Bush administration lifted the ban on road construction (grrr) and favors
giving more control to local governments as to the use of their part of the land
within the national forests. Since local governments profit directly from
timber sales, harvesting would likely increase under this plan (timber sales are
up 40% since Bush took office).
How can we reduce the need to harvest so many trees?
Demand for trees could be reduced by limiting paper use by:
1. Reducing excess packaging and junk mail
2. Increasing paper recycling programs
3. Making paper from other agricultural materials
Paper use by percentage:
TP/Paper towels (8%)
In China, 60% of their paper is already made tree-free, primarily through the
use of agricultural wastes such as rice straw.
23-4: Tropical Deforestation and the Fuelwood Crisis
Tropical forests have decreased by approximately 50% since 1950. At current
deforestation rates, the total will be halved again in another 50 years.
The Amazon rain forest in Brazil has half of the world’s remaining tropical rain
forest. 30% of the plant and animal species in the world live in the Amazon
Several countries have already deforested over 80% of their original land area
of tropical forest, e.g. Haiti and the Philippines.
Madagascar is an example of a country that is currently experiencing a fast rate
of deforestation. The vast deforestation is causing visible erosion problems,
leading to a loss of productive topsoil. Madagascar’s case is important because
85% of the species on the island are endemic, meaning they are found only on
the island of Madagascar.
Why Does Tropical Deforestation Occur?
Population growth requires forest clearing
Poverty makes timber value enticing
Governments benefit by selling land to developed nations
The Downward Spiral of Tropical Forest Degradation
1. A logging road is built to access the timber
2. High grade timber is selectively-cut and exported to developed nations
3. Land is sold to ranchers, whose animals graze unsustainably
4. Land is sold to local settlers, who use slash-and-burn techniques to
complete the deforestation
5. Crops are grown for a few years until the nutrients are depleted from
6. Settlers move on to another area
7. Original land area grows back through succession as grasslands due to
lack of water from transpiration, or even worse, becomes desertified.
How to Reduce the Effects of Deforestation
A. Provide education on the long-term benefit of sustainable agriculture
B. Offer financial incentives for governments to protect forests (debt for
C. Certify timber grown through sustainable practices
D. Put more effort into the rehabilitation of degraded forest areas
80% of the wood harvested in developing countries is used as fuelwood, usually
as heat or for cooking.
Because of overpopulation, fuelwood is being harvested faster than it can be
How can the fuelwood crisis be averted?
A. Switching to other fuels, such as root-fuel plants
B. Planting specific types of fast-growing fuelwoods
C. Improve the efficiency of the burning methods
23-5: Managing and Sustaining National Parks
99% of the national parks in developing countries are considered to be “paper
parks”, meaning they are protected in name only. Their borders are constantly
invaded by and resources abused by loggers, poachers, etc.
In the United States, the primary problem faced by national parks is their own
popularity, or how to strike a balance between the conflicting goals of
preserving nature and making it more available to the public.
The policy used by the National Park Service to manage their land is natural
regulation, the idea that the parks are basically wilderness areas that can
regulate themselves if left alone.
23-6: Establishing, Designing, and Managing Nature Reserves
Conservationists state that ideally nature reserves should be established over
about 20% of the land in a country, including multiple biomes.
Two countries which have done a good job creating nature reserves are Brazil
and Costa Rica, which set aside eight megareserves to preserve biodiversity.
How to Design a Nature Reserve
Circular shape, if possible, with a buffer zone around the park
Large reserves work the best because many species require a large range
Heterogeneous reserves include many different habitats within a single
Biodiversity “hot spots” are areas with both a high level of biodiversity and a
large number of endemic species. These are the ideal places to build nature
reserves because they offer the most protection for the least amount of cost.
Unfortunately, 19 of 25 “hot spots” are located in areas of rapidly growing
population, making it less likely that effective reserves can be established
The U.S. Wilderness Act of 1964 allows undeveloped lands to be set aside and
protected, both on their own and within the confines of other land types.
Wilderness is described as a place where “man is a visitor who does not
remain.” 75% of U.S. Wilderness Lands are located in Alaska.
Creating wilderness areas is definitely a preservationist ideal. One knock on
them is that they do not include enough different biomes. Most grasslands or
wetlands are not preserved at wilderness areas because they agricultural or
Preservationists advocate using the “Leave No Trace” wilderness ethic,
meaning that the wilderness area should look exactly the same before and
after your visit.
Most wilderness areas are believed to be too small to truly be effective
because they are too small to guard against effects from the outside (nonnative
species, pollution, etc.)
23-7: Ecological Restoration
Restoration is the process of trying to restore a habitat to its predegraded
Rehabilitation is the attempt to restore partial function to an ecosystem
(replanting, pollution clean up).
Replacement is changing an ecosystem to a different, but still productive,
ecosystem than it was originally (tree farm).
Artificial ecosystems are man-made attempts to recreate actual ecosystems in
locations where they are needed (artificial reefs).