Transcript Biodiversity Notes

Biodiversity
Finz 2012
A World Rich in Biodiversity
• Biodiversity, short for biological diversity, is
the variety of organisms in a given area, the
genetic variation within a population, the
variety of species in a community, or the
variety of communities in an ecosystem.
• Certain areas of the planet, such as tropical
rainforests, contain an extraordinary variety
of species.
• Humans need to understand and preserve
biodiversity for our own survival.
Unknown Diversity
• The study of biodiversity starts with
the unfinished task of cataloging all the
species that exist on Earth.
• The number of species known to science
is about 1.7 million, most of which are
insects. However, the actual number of
species on Earth is unknown.
• Scientists accept an estimate of
greater than 10 million for the total
number of species.
Unknown Diversity
Unknown Diversity
• New species are considered known when
they are collected and described
scientifically.
• Unknown species exist in remote
wilderness, deep oceans, and even in
cities.
• Some types of species are harder to
study and receive less attention than
large, familiar species.
Levels of Diversity
• Biodiversity can be studied and described
at three levels: species diversity,
ecosystem diversity, and genetic diversity.
• Species diversity refers to all the
differences between populations of
species, as well as between different
species.
• Ecosystem diversity refers to the variety
of habitats, communities, and ecological
processes within and between ecosystems.
Levels of Diversity
• Genetic diversity refers to all the
different genes contained within all
members of a population.
• A gene is a segment of DNA that is
located in a chromosome and that codes
for a specific hereditary trait.
Benefits of Biodiversity
• Biodiversity can affect the stability of
ecosystems and the sustainability of
populations.
• We depend on healthy ecosystems to
ensure a healthy biosphere that has
balanced cycles of energy and nutrients.
• Species are part of these cycles.
Species Are Connected to
Ecosystems
• When scientists study any species
closely, they find that it plays an
important role in an ecosystem.
• Every species is probably either
dependent on or depended upon by at
least one other species in ways that are
not always obvious.
• When one species disappears from an
ecosystem, a strand in a food web is
removed.
Species Are Connected to Ecosystems
• Some species are clearly critical to the
functioning of an ecosystem.
• A keystone species is a species that is critical
to the functioning of the ecosystem in which
it lives because it affects the survival and
abundance of many other species in its
community.
• An example is the sea otter. The loss of the
sea otter populations led to an unchecked sea
urchin population, which ate all the kelp
leading to the loss of kelp beds along the U.S.
Pacific Coast.
Species and Population
Survival
• The level of genetic diversity within
populations is a critical factor in species
survival.
• Genetic variation increases the chances
that some members of the population
may survive environmental pressures or
changes.
• Small and isolated populations are less
likely to survive such pressures.
Species and Population
Survival
• When a population shrinks, its genetic
diversity decreases as though it is
passing through a bottleneck.
• Even if such a population is able to
increase again, there will be inbreeding
within a smaller variety of genes.
• The members of the population may
then become more likely to inherit
genetic diseases.
Species and Population
Survival
Medical and Industrial Uses
• About one quarter of the drugs
prescribed in the United Sates are
derived from plants, and almost all of
the antibiotics are derived from
chemicals found in fungi.
• New chemicals and industrial materials
may be developed from chemicals
discovered in all kinds of species.
• The scientific community continues to
find new uses for biological material and
genetic diversity.
Medical Uses
Agricultural Uses
• Most of the crops produced around the
world originated from a few areas of high
biodiversity.
• Most new crop varieties are hybrids, or
crops developed by combining genetic
material from other populations.
• History has shown that depending on too
few plants for food is risky. Famines have
resulted when an important crop was wiped
out by disease. But some crops have been
saved by crossbreeding them with wild plant
relatives.
Agricultural Uses
Ethics, Aesthetics, and Recreation
• Some people believe that we should preserve
biodiversity for ethical reasons. They believe
that species and ecosystems have a right to
exist whether or not they have any other
value.
• People also value biodiversity for aesthetic or
personal enjoyment such as keeping pets,
camping, picking flowers, or watching wildlife.
• Ecotourism is a form of tourism that supports
the conservation and sustainable development
of ecologically unique areas.
Biodiversity at Risk
• The extinction of many species in a
relatively short period of time is called
a mass extinction
• Earth has experienced several mass
extinctions, each probably caused by a
global change in climate.
• It takes millions of years for
biodiversity to rebound after a mass
extinction.
Biodiversity at Risk
Current Extinctions
• Scientists are warning that we are in the
midst of another mass extinction.
• The rate of extinctions is estimated to
have increased by a multiple of 50 since
1800, with up to 25 percent of all species
on Earth becoming extinct between 1800
and 2100.
• The current mass extinction is different
from those of the past because humans
are the primary cause of the extinctions.
Species Prone to Extinction
• Large populations that adapt easily to
many habitats are not likely to become
extinct.
• However, small populations in limited
areas can easily become extinct.
• Species that are especially at risk of
extinction are those that migrate, those
that need large or special habitats, and
those that are exploited by humans.
Species Prone to Extinction
• An endangered species is a species that
has been identified to be in danger of
extinction throughout all or a significant
part of its range, and that is thus under
protection by regulations or
conservation measures.
• A threatened species is a species that
has been identified to be likely to
become endangered in the foreseeable
future.
How Do Humans Cause Extinctions?
• In the past 2 centuries, human population
growth has accelerated and so has the
rate of extinctions.
• The numbers of worldwide species known
to be threatened, endangered, or recently
extinct are listed on the next slide.
• The major causes of extinction today are
the destruction of habitats, the
introduction of nonnative species, pollution,
and the overharvesting of species.
How Do Humans Cause
Extinctions?
Habitat Destruction and
Fragmentation
• As human populations grow, we use more
land to build homes and harvest
resources.
• In the process, we destroy and
fragment the habitats of other species.
• It is estimated that habitat loss causes
almost 75 percent of the extinctions
now occurring.
Habitat Destruction and
Fragmentation
• For example, cougars, including the
Florida Panther, require expansive
ranges of forest and large amount of
prey.
• Today, much of the cougars’ habitat has
been destroyed or broken up by roads,
canals, and fences.
• In 2001, fewer than 80 Florida panthers
made up the only remaining wild cougar
population east of the Mississippi River.
Invasive Exotic Species
• An exotic species is a species that is
not native to a particular region.
• Even familiar organisms such as cats and
rats are considered to be exotic species
when they are brought to regions where
they never lived before.
• Exotic species can threaten native
species that have no natural defenses
against them.
Harvesting, Hunting, and
Poaching
• Excessive hunting can also lead to
extinction as seen in the 1800s and
1900s when 2 billion passenger pigeons
were hunted to extinction.
• Thousands of rare species worldwide
are harvested and sold for use as pets,
houseplants, wood, food, or herbal
medicine.
• Poaching is is the illegal harvesting of
fish, game, or other species.
Pollution
• Pesticides, cleaning agents, drugs, and
other chemicals used by humans are
making their way into food webs around
the globe.
• The long term effects of chemicals may
not be clear until after many years.
• The bald eagle was endangered because
of a pesticide known as DDT. Although
DDT is now illegal to use in the United
States, it is still manufactured here and
used around the world.
Areas of Critical Biodiversity
• An important feature of areas of the
world that contain greater diversity of
species is that they have a large portion of
endemic species.
• An endemic species is a species that is
native to a particular place and that is
found only there.
• Ecologists often use the numbers of
endemic species of plants as an indicator
of overall biodiversity because plants form
the basis of ecosystems on land.
Tropical Rain Forests
• Biologist estimate that over half of the
world’s species live in these forests even
though they cover only 7 percent of the
Earth’s land surface.
• Most of the species have never been
described. Unknown numbers of these
species are disappearing as tropical
forests are cleared for farming or cattle
grazing.
• Tropical forests are also among the few
places where some native people maintain
traditional lifestyles.
Coral Reefs and Coastal Ecosystem
• Reefs provide millions of people with food,
tourism revenue, coastal protection, and
sources of new chemicals, but are poorly
studied and not as well protected by laws as
terrestrial areas are.
• Nearly 60 percent of Earth’s coral reefs are
threatened by human activities, such as
pollution, development along waterways, and
overfishing.
• Similar threats affect coastal ecosystems,
such as swamps, marshes, shores, and kelp
beds.
Islands
• When an island rises from the sea, it is
colonized by a limited number of species
from the mainland. These colonizing
species may then evolve into several new
species.
• Thus, islands often hold a very distinct
but limited set of species.
• Many island species, such as the
Hawaiian honeycreeper, are endangered
because of invasive exotic species.
Biodiversity Hotspots
• The most threatened areas of high species
diversity on Earth have been labeled
biodiversity hotspots and include mostly
tropical rainforests, coastal areas, and
islands.
• The hotspot label was developed by an
ecologist in the late 1980s to identify areas
that have high numbers of endemic species
but that are also threatened by human
activities.
• Most of these hotspots have lost at least 70
percent of their original natural vegetation.
Biodiversity Hotspots
Biodiversity in the United States
• The United States includes a wide variety
of unique ecosystems, including the Florida
Everglades, the California coastal region,
Hawaii, the Midwestern prairies, and the
forests of the Pacific Northwest.
• The United States holds unusually high
numbers of species of freshwater fishes,
mussels, snails, and crayfish. Diversity is
also high among groups of the land plants
such as pine trees and sunflowers.
Biodiversity in the United States
• The California Floristic Province, a
biodiversity hotspot, is home to 3,488
native plant species.
• Of these species, 2,124 are endemic and
565 are threatened or endangered.
• The threats to this area include the use
of land for agriculture and housing, dam
construction, overuse of water,
destructive recreation, and mining. All
of which stem from local human
population growth.
Saving Species One at a Time
• When a species is clearly on the verge
of extinction, concerned people
sometimes make extraordinary efforts
to save the last few individuals.
• These people hope that a stable
population may be restored someday.
• Methods to preserve individual species
often involve keeping and breeding the
species in captivity.
Captive-Breeding Programs
• Wildlife experts may attempt to restore
the population of a species through
captive-breeding programs.
• These programs involve breeding species in
captivity, with the hopes of reintroducing
populations to their natural habitats.
• This type of program has been used
successfully with the Californian condor,
for example. But the question remains
whether or not these restored populations
will ever reproduce in the wild.
Preserving Genetic Material
• One way to save the essence of a
species is by preserving its genetic
material.
• Germ plasm is hereditary material
(chromosomes and genes) that is usually
contained in the protoplasm of germ
cells and may be stored as seeds, sperm,
eggs, or pure DNA.
• Germ-plasm banks store germ plasm in
controlled environments for future use
in research or species-recovery efforts.
Zoos, Aquariums, Parks, & Gardens
• In some cases, zoos now house the few
remaining members of a species and are
perhaps the species’ last hope for
survival.
• Zoos, wildlife parks, aquariums, and
botanical gardens, are living museums of
the world’s biodiversity.
• But, these kinds of facilities rarely have
enough resources or knowledge to
preserve more than a fraction of the
world’s rare and threatened species.
More Study Needed
• Ultimately, saving a few individuals does
little to preserve a species as captive
species may not reproduce or survive
again in the wild.
• Also, small populations are vulnerable to
infectious diseases and genetic
disorders caused by inbreeding.
• Conservationists hope that these
strategies are a last resort to save
species.
Preserving Habitats and Ecosystems
• The most effective way to save species is
to protect their habitats.
• Small plots of land for a single population
is usually not enough because a species
confined to a small area could be wiped out
by a single natural disaster. While other
species require a large range to find
adequate food.
• Therefore, protecting the habitats of
endangered and threatened species often
means preserving or managing large areas.
Conservation Strategies
• Most conservationists now give priority
to protecting entire ecosystems rather
than individual species.
• By doing this, we may be able to save
most of the species in an ecosystem
instead of only the ones that have been
identified as endangered.
• The general public has now begun to
understand that Earth’s biosphere
depends on all its connected
ecosystems.
Conservation Strategies
• While conservationists focus on the
hotspots discussed earlier to protect
biodiversity worldwide, they also
support additional strategies.
• One strategy is to identify areas of
native habitat that can be preserved,
restored, and linked into large networks.
• Another promising strategy is to
promote products that have been
harvested with sustainable practices.
More Study Needed
• Conservationists emphasize the urgent need
for more serious study of the workings of
species and ecosystems.
• Only in recent decades has there been
research into basic questions as, How much
fragmentation can a particular ecosystem
tolerate?
• The answers to questions asked now may be
years or decades away, but decisions
affecting biodiversity continue to be made
based on available information.
Legal Protection for Species
• Many nations have laws and regulations
designed to prevent the extinction of
species, and those in the United States
are among the strongest.
• For example, in 1973, the U.S. Congress
pass the Endangered Species Act.
• The Endangered Species Act is
designed to protect any plant or animal
species in danger of extinction.
U.S. Laws
• Under the first provision of the Endangered
Species Act, the U.S. Fish and Wildlife
Service (USFWS) must compile a list of all
endangered and threatened species in the
United States. As of 2002, 983 species of
plants and animals were listed.
• The second main provision of the act protects
listed species from human harm.
• The third provision prevents the federal
government from carrying out any project
that jeopardizes a listed species.
U.S. Laws
Recovery Plans
• Under the fourth main provision of the
Endangered Species Act, the USFWS must
prepare a species recovery plan for each
listed species. These plans often propose to
protect or restore habitat for each species.
• However, attempts to restrict human uses of
land can be controversial. Real-estate
developers may be prohibited from building in
certain areas, and people may lose income and
may object when their interests are placed
below those of another species.
Habitat Conservation Plans
• Battles between environmentalists and
developers are widely publicized, and in
most cases, compromises are eventually
worked out. One form of compromise is a
habitat conservation plan.
• A habitat conservation plan is a land-use
plan that attempts to protect threatened
or endangered species across a given area
by allowing some tradeoffs between harm
to the species and additional conservation
commitments among cooperating parties.
International Cooperation
• At the global level, the International Union
for the Conservation of Nature and
Natural Resources (IUCN) facilitates
efforts to protect species and habitats.
• The IUCN publishes Red Lists of species in
danger of extinction around the world,
advises governments on ways to manage
their natural resources, and works with
groups like the World Wildlife Fund to
sponsor projects such as attempting to
stop poaching in Uganda.
International Trade and Poaching
• One product of the IUCN has been an
international treaty called CITES (the
Convention on International Trade in
Endangered Species).
• The CITES treaty was the first effective
effort to stop the slaughter of African
elephants being killed by poachers who would
then sell the ivory tusks.
• In 1989, the members of CITES proposed a
total worldwide ban on all sales, imports, and
exports of ivory, hoping to put a stop the
problem.
International Trade and
Poaching
• Some people worried that making ivory
illegal might increase the rate of
poaching instead of decrease it.
• They argued that illegal ivory, like illegal
drugs, might sell for a higher price.
• But after the ban was enacted, the
price of ivory dropped, and elephant
poaching declined dramatically.
The Biodiversity Treaty
• One of the most ambitious efforts to
tackle environmental issues on a worldwide
scale was the United Nations Conference
on Environment and Development, also
known as the first Earth Summit. An
important result of the Earth Summit was
the Biodiversity Treaty.
• The Biodiversity Treaty is an international
agreement aimed at strengthening national
control and preservation of biological
resources.
The Biodiversity Treaty
• The treaty’s goal is to preserve biodiversity
and ensure the sustainable and fair use of
genetic resources in all countries.
• However, the treaty took several years to be
adopted into law by the U.S. government.
• Some political groups objected to the treaty,
especially to the suggestion that economic
and trade agreements should take into
account any impacts on biodiversity that
might result from the agreements.
Private Conservation Efforts
• Many private organizations work to protect
species worldwide, often more effectively
than government agencies.
• For example, the World Wildlife Fund
encourages the sustainable use of resources
and supports wildlife protection. The Nature
Conservancy has helped purchase millions of
hectares of habitat preserves in 29
countries. Conservation International helps
identify biodiversity hotspots. And,
Greenpeace International organizes direct
and sometimes confrontational actions.
Balancing Human Needs
• Attempts to protect species often come into
conflict with the interests of the world’s
human inhabitants.
• An endangered species might represent a
source of food or income. Or a given species
may not seem valuable to those who do not
understand the species’ role in an ecosystem.
• Many conservationists feel than an important
part of protecting species is making the
value of biodiversity understood by more
people.
Graphic Organizer
Food and Agriculture
Finz 2012
Land Use and Land Cover
• We use land for many purposes,
including farming, mining, building cities
and highways, and recreation.
• Land cover is what you find on a patch
of land, and it often depends on how the
land is used. For example, land cover
might be a forest, a field of grain, or a
parking lot.
• There are different types of land cover
and different human uses for each
Land Use and Land Cover
Land Use and Land Cover
• Urban describes an area that contains a
city, or an area that contains 2,500 or
more people and usually has a governing
body, such as a city council.
• Rural describes an area of open land
that is often used for farming, or any
population not classified as urban.
• Most land provides one or more
resources that humans consume. These
resources include wood in forests, crops
Where We Live
• Until about 1850, most people lived in
rural areas.
• Many of them were farmers, who grew
crops and raised livestock. Others
managed the forests, worked in local
mines or mills, or manufactured the
necessities of life for the town.
• The Industrial Revolution changed this
pattern as machinery made it possible
for fewer people to operate a farm or
Where We Live
• Thousands of rural jobs were
eliminated, and many people had to move
to cities to find jobs.
• As a result, urban areas grew rapidly
during the 20th century and spread
over more land.
• The movement of people from rural to
urban areas happened in developed
countries between about 1880 and 1950.
Now, this movement is occurring rapidly
Where We Live
• Today, most people throughout the
world live in urban areas.
The Urban-Rural Connection
• Whether people live in cities or in the
countryside, people are dependent on
resources produced in rural areas.
• These resources include clean drinking
water, fertile soil and land for crops,
trees for wood and paper, and much of
the oxygen we breath, which is
produced by plants.
• An ecosystem service is the role that
organisms play in creating a healthful
The Urban-Rural Connection
Supporting Urban Areas
• The area of rural land needed to
support one person depends on many
factors, such as the climate, the
standard of living, and how efficiently
resources are used.
• Each person in a developed country uses
the ecosystem services provided by
about 8 hectares of land. But, many
people in developing countries do not
have access to all the resources for a
Urbanization
• Urbanization is an increase in the ratio
or density of people living in urban areas
rather than in rural areas. People usually
leave rural areas for more plentiful and
better paying jobs in towns and cities.
• In developed countries, urbanization
slowed in the second half of the 20th
century.
• As urban populations have grown, many
small towns have grown together and
Urbanization
• Urban areas that have grown slowly are
often relatively pleasant places to live,
in part because roads and public
transportation have been built to handle
the growth allowing traffic to flow
freely.
• Buildings, roads, and parking lots are
mixed with green spaces that provide
these urban areas with much needed
ecosystem services such as moderation
The Urban Crisis
• A rapidly growing population, however,
can overwhelm the infrastructure,
leading to traffic jams, substandard
housing, and polluted air and water.
• Infrastructure is the basic facilities of
a country or region, such as roads,
bridges, sewers, and railroads.
• When more people live in a city than its
infrastructure can support, the living
conditions deteriorate. This growth
Urban Sprawl
• Urban sprawl is the rapid spread of a
city into adjoining suburbs and rural
areas.
• Much of this growth results in the
building of suburbs, or housing and
associated commercial buildings on the
boundary of a larger town.
• Many of these suburbs are built on land
that was previously used for food
production. In fact, each year suburbs
Development on Marginal
Lands
• Many cities were first built where there
was little room for expansion. As the
cities grew, suburbs were often built on
marginal land, or land that is poorly
suited for building.
• For example, Los Angeles was built in a
basin, and has expanded onto slopes
that are prone to landslides.
• Structures built on marginal land can
become difficult or impossible to repair
Other Impacts of
Urbanization
• Environmental conditions in the center
of a city are different from those of
the surrounding countryside, as cities
both generate and trap more heat.
• Heat island is an area in which the air
temperature is generally higher than
the temperature of surrounding rural
areas.
• Heat is generated by the infrastructure
that makes a city run. Roads and
Other Impacts of
Urbanization
• Scientists are beginning to see that
heat islands can affect local weather
patterns. Hot air rises over a city,
cooling as it rises, and eventually
produces rain clouds.
• In Atlanta, Georgia, and many other
cities, increased rainfall is a side effect
of the heat island effect.
• The heat-island effect may be
moderated by planting trees for shade
Urban Planning
• Land-use planning is a set of policies
and activities related to potential uses
of land that is put in place before an
area is developed.
• The federal government requires
developers to prepare detailed reports
assessing the environmental impact of
many projects, and the public has a
right to comment on these reports.
• Developers, city governments, local
Intelligent Design
• Land-use planners have sophisticated
methods and tools available to them
today.
• The most important technological tools
for land-use planning involve using the
geographic information system.
• A geographical information system
(GIS) is an automated system for
capturing, storing, retrieving, analyzing,
manipulating, and displaying geographic
Intelligent Design
• GIS software allows a user to enter
different types of data about an area,
such as the locations of sewer lines,
roads, and parks, and then create maps
with the data.
• Each image corresponds to a different
combination of information.
• The power of GIS is that it allows a
user to display layers of information
about an area and to overlay these
Transportation
• Most cities in the United States are
difficult to travel in without a car.
• Most cities in the United States were
constructed after the invention of the
automobile. In addition, availability of
land was not a limiting issue, so many
American cities sprawl over large areas.
• By contrast, most cities in Europe were
built before cars, and are compact with
narrow roads.
Transportation
• In many cities, mass transit systems
were constructed in order to get people
where they wanted to go. Mass transit
systems use buses and trains to move
many people at one time.
• Mass transit systems save energy, limit
the loss of land to roadways and parking
lots, reduce highway congestion, and
reduce air pollution.
• Where the construction of mass transit
Open Space
• Open space is land within urban areas
that is set aside for scenic and
recreational enjoyment. It also has
many environmental benefits and
provides valuable functions.
• Open spaces include parks, public
gardens, and bicycle and hiking trails.
• Open spaces left in their natural
conditions are often called greenbelts.
These greenbelts provide important
Open Space
• The plants in open spaces absorb carbon
dioxide, produce oxygen, filter out
pollutants from air and water, and help
keep a city cooler in the summer.
• Open spaces, especially those with
vegetation, also reduce drainage
problems by absorbing more of the
rainwater runoff from building roofs,
asphalt, and concrete resulting in less
flooding.
GIS Views of Seattle,
Washington
Land Management
• The main categories of rural land are
farmland, rangeland, forest land,
national and state parks, and wilderness.
• We have sometimes managed these
lands sustainably so that they will
provide resources indefinitely. We have
also sometimes reduced their
productivity by overusing or polluting
them.
• The condition of rural land is important
Farmlands
• Farmland is land that is used to grow
crops and fruit. The U.S. contains more
than 100 million hectares of prime
farmland.
• However, in some places, urban
development threatens some of the
most productive farmland.
• In 1996, the U.S. government
established a national Farmland
Protection Program to help state,
Rangelands
• Land that supports different vegetation
types like grasslands, shrublands, and
deserts and that is not used for farming
or timber production is called rangeland.
• Rangelands can be arid, like the
rangelands in the desert Southwest, or
relatively wet, like the rangelands of
Florida.
• The most common human use of
rangeland is for the grazing of
Rangelands
• Cattle, sheep, and goats are common
livestock on the rangeland, which are
valued for their meat, milk, wool, and
hides.
• Native wildlife also graze these lands.
• Like farmland, rangeland is essential for
maintaining the world’s food supply.
World population growth may require a
40 percent increase in the food
production of rangeland from 1977 to
Problems on the Range
• Overgrazing is the depletion of
vegetation due to the continuous
feeding of too many animals.
• Overgrazing often results in changes in
the plant community. Less desirable
plants may invade the area and replace
more-desirable plant species.
• In cases of severe overgrazing, all the
vegetation that covers the land is eaten.
Once the plants are gone, there is
Maintaining the Range
• Much of the rangeland in the U.S. is
public land managed by the federal
government, which leases the rangeland
to ranchers. However, much of the
rangeland in the U.S. is degraded.
• The Public Rangelands Improvement Act
of 1978 was enacted to reverse this
trend and improve land management
practices.
• Sustaining the productivity of rangeland
Maintaining the Range
• Improving rangeland that has been
degraded by overgrazing often includes
methods such as killing invasive plants,
planting native vegetation, and fencing
areas to let them recover to the state
they were in before they were
overgrazed.
• Ranchers also control grazing by digging
many small water holes so that the
vegetation around a single water hole is
Forest Lands
• Trees are harvested to provide
products we use everyday, such as
paper, furniture, and lumber and
plywood for our homes.
• In addition to wood and paper, we also
value forest products such as maple
syrup and turpentine.
• There are many ecosystem services
provided by forests. However, one of
the most important is the removal of
Harvesting Trees
• People use enormous amounts of wood.
• The worldwide average is 1,800 cm3 of
wood used per person each day.
• However, on average, each person in the
United states uses about 3.5 times this
amount.
• About 1.5 billion people in developing
countries depend on firewood as their
main source of fuel.
Harvesting Trees
• The timber industry classifies forest
lands into three categories:
• Virgin forests: forests that have never
been cut.
• Native forests: forests that are planted
and managed.
• Tree farms: areas where trees are planted
in rows and harvested like other crops.
• The two most widely used methods of
harvesting trees are clear-cutting and
selective cutting.
Harvesting Trees
• Clear-cutting is the process of removing
all of the trees from and area of land.
Clear-cutting large areas destroys
wildlife habitat and causes soil erosion.
• Selective cutting is the process of
cutting and removing only middle-aged
or mature trees. It is more expensive
than clear-cutting, but is usually much
less destructive. It is usually practiced
on smaller areas owned by individuals.
Harvesting Trees
Deforestation
• Deforestation is the process of
clearing forests.
• Most countries become severely
deforested as populations expand and
the demand for forest products
increases.
• Forests are cleared to convert the land
into farmland, and to make space for
roads, homes, factories, and office
buildings.
Deforestation
• For example, when forests are cleared
from hillsides, soil erosion usually
results if the area is not quickly planted
with a cover crop. Without tree roots to
hold the soil in place, it is easily washed
or blown away into the valley below.
• The rate of deforestation is especially
high in tropical rain forests, where the
soil is relatively thin. Farmers who clear
forests in these areas must always move
Reforestation
• Reforestation is the reestablishment
and development of trees in a forest
land.
• In some places, reforestation is
happening faster than trees are being
cut down.
• The price of deforestation, which
causes soil erosion, landslides, and
flooding, is sometimes too high, so in
some areas the forest has been allowed
Reforestation
• Some governments require
reforestation after timber has been
harvested from public land. However,
worldwide, more than 90 percent of all
timber comes from forests that are not
managed by an agency that monitors the
health of forest ecosystems.
• Many governments are currently
working to improve reforestation
efforts and to promote less destructive
Parks and Preserves
• In the 1870s, a group of explorers
approached Congress with news of a
magnificent expanse of land in Wyoming
and Montana they believed would be
damaged by the development that had
changed the northeastern United
States.
• Congress agreed to protect this land by
setting it aside for the public to use and
enjoy, and the first national park,
Parks and Preserves
Parks and Preserves
• Most public lands are not as protected
as the national parks are.
• Some public lands are leased to private
companies for logging, mining, and
ranching. Others are maintained for
hunting, fishing, wild-life refuges, or to
protect endangered species.
• International efforts include the
Biosphere Program that has set up
several hundred preserves, called
Parks and Preserves
Wilderness
• The U.S. Wilderness Act, passed in
1964, designated certain lands as
wilderness areas.
• Wilderness is a region that is not
cultivated and that is not inhabited by
humans.
• So far, 474 regions covering 32 million
acres have been designated as
wilderness in the United States. These
areas are open to hiking, fishing, and
Benefits of Protected Areas
• Protected areas often provide the only
place where unspoiled forests, deserts,
or prairies remain. Without these areas,
the plants and animals that can survive
only in these ecosystems would
disappear.
• Wilderness areas serve as outdoor
classrooms and research labs where
people can learn more about the natural
world.
Threats to Protects Areas
• Around the world, more people visit
national parks and wilderness areas each
year and leave their mark on the land.
Litter and traffic jams now plague many
of our national parks.
• Rangelands, mining and logging sites, oil
and gas operations, power plants, and
urban areas are often close enough to
affect the parks.
• In addition, preserved areas are
Threats to Protect Areas
• In attempts to protect wilderness from
damage, limits have been set in some
areas on the number of people
permitted in the area at any given time.
• Some areas are completely closed to
visitors to allow wild animals to breed.
• In addition, volunteer programs are now
active in many wilderness areas.
Volunteers help pick up trash, build
trails, control invading or exotic
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