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CHAPTER 36: CONSERVATION BIOLOGY
36.1 Conservation Biology and Biodiversity
Conservation biology is an interdisciplinary field with the explicit goal of
protecting biodiversity and Earth’s natural resources.
Biodiversity
At its simplest level, biodiversity is the variety of life on Earth. To
develop a meaningful understanding of life on Earth, we need to know
more about species than their total number.
Conservation biologists describe biodiversity at three levels of
biological organization: genetic diversity, ecosystem diversity, and
landscape diversity.
36.2 Value of Biodiversity
Biodiversity is a resource of immense value.
Direct Value
Various individual species perform services for human beings.
Medicinal Value
Most of the prescription drugs used in the United States were
originally derived
from living organisms.
Agricultural Value
Crops such as wheat, corn, and rice are derived from wild
plants that have been
modified.
Consumptive Use Value
Most freshwater and marine harvests depend on wild animals.
Indirect Value
These services are said to be indirect because they are pervasive and
not easily discernible.
Biogeochemical Cycles
The biodiversity within ecosystems contributes to the workings
of the various
biogeochemical cycles.
Waste Disposal
Decomposers break down dead organic matter and other types
of wastes.
Provision of Fresh Water
The water cycle continually supplies fresh water to terrestrial
ecosystems.
Forests and other natural ecosystems soak
up water and then release it at a
regular rate.
Flood Prevention
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Forests and other natural ecosystems exert a “sponge effect,”
thereby reducing
flooding.
Prevention of Soil Erosion
Intact ecosystems naturally retain soil and prevent soil erosion.
Regulation of Climate
Globally, forests ameliorate the climate because they take up
carbon dioxide and
release oxygen.
Ecotourism
In the United States nearly 100 million people enjoy
vacationing in a natural
setting.
36.3 Threats to Biodiversity
We are presently in a biodiversity crisis—the number of extinctions
expected to occur in the near future is unparalleled in Earth’s history.
Habitat Loss
Human occupation of the coastline, semiarid lands, tropical rain
forests, and other areas are the most important cause of the loss of
biodiversity.
Exotic Species
Exotic species are nonnative members of an ecosystem. Humans have
introduced exotic species by the following means:
Colonization
Europeans, in particular, brought various familiar species with
them
when they colonized new places.
Horticulture and Agriculture
Some exotics now taking over vast tracts of land have escaped
from
cultivated areas.
Accidental Transport
Global trade and travel accidentally bring many new species
from one
country to another.
Exotics on Islands
Islands are particularly susceptible to environmental
discord caused by the introduction of exotic species.
Pollution
Pollution brings about environmental changes that adversely affect the
lives and health of living things.
Acid Deposition
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Acid deposition decimates forests and lakes.
Eutrophication
Lakes are under stress due to over-enrichment.
Ozone Depletion
The ozone shield protects Earth from harmful ultraviolet
radiation.
and
Organic Chemicals
Endocrine-disrupting contaminants affect the endocrine system
reproductive potential of animals.
Global Warming
Global warming is expected to have many detrimental effects.
Overexploitation
Overexploitation occurs when the number of individuals taken from a
wild population is so great that the population becomes severely reduced in
numbers. For example, a marine ecosystem can be disrupted by over fishing.
Disease
Wildlife is subject to emerging diseases just as humans are.
36.4 Habitat Conservation and Restoration
Habitat Conservation
Because habitat loss is the leading cause of species’ extinctions,
conservation of habitat is of primary concern. Some regions of the
world are called biodiversity hotspots because they contain unusually
large concentrations of species. We can also focus our efforts on
conserving habitat for “keystone species,” or those whose loss would
result in a great number of secondary extinctions.
Landscape Conservation and Reserve Design
Conservation often has to occur at the landscape level because
sufficient habitat may not be available in a single place to sustain a
viable population of a particular species.
Edge Effects
An edge reduces the amount of habitat typical of an ecosystem
because the edges around a patch have a habitat slightly
different from the interior of the patch.
Reserve Design
Conservation reserves are those areas that are set aside with the
primary goal of protecting biodiversity within them.
Habitat Restoration
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In cases where habitat has already been modified in an area to the
extent that conservation and reserve formation may not be viable, or
to reverse existing damage, habitat restoration is an alternative.
The Everglades
Because of the huge disruptions to natural water flows, the
Everglades are now
dying.
Restoration Plan
A restoration plan has been developed that will sustain the
Everglades ecosystem while maintaining the services society
requires.
36.5 Working Toward a Sustainable Society
A sustainable society would be able to provide the same goods and services
for future generations of human beings as it does now and biodiversity
would be conserved. Today’s society has several characteristics that indicate
it is not sustainable.
Energy
Approximately 81% of the world’s energy supply comes from
nonrenewable sources.
Renewable Energy Sources
Renewable types of energy include hydropower, geothermal
energy, wind power, and solar energy.
Water
In some areas of the world, people do not have ready access to
drinking water, and if they do, the water may be impure. Although the
needs of the human population overall do not exceed the renewable
supply of water, this is not the case in certain regions of the United
States and the world.
Conservation of Water
Solutions for expanding water supplies, such as planting
drought- and salt-tolerant crops, have been suggested.
Agriculture
Today, current agricultural practices provide enough food to provide
everyone on Earth a healthy diet consisting of 2,500 calories per day.
However, over 1 billion people are currently considered malnourished
due to lack of proper distribution and the fact that much of the grain
that is produced in MDCs is used to feed livestock rather than
humans. In addition, modern farming methods are environmentally
destructive in several ways.
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Urban Growth
More and more people are moving to cities and growth of cities
increases pollution via many sources.
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