CHAPTER OUTLINE
37.1 Conservation Biology and Biodiversity
Conservation biology is an interdisciplinary science with the explicit goal of protecting
biodiversity and the Earth’s natural resources. Conservation biology embodies the ethical
principles that biodiversity is desirable for the biosphere and therefore for humans, humaninduced extinctions are undesirable, complex interactions are desirable because they support
biodiversity and biodiversity generated by evolutionary change has intrinsic value.
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. Ecologists and conservation biologists describe biodiversity at three levels of
biological organization: genetic diversity, ecosystem diversity, and landscape
diversity.
37.2 Value of Biodiversity
Biodiversity is a resource of immense value.
Direct Value
Various individual species perform services for humans, contributing to the value we
place on biodiversity.
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 to be high producers.
Consumptive Use Value
Most freshwater and marine harvests depend on wild animals. The environment
provides other products that are sold in the marketplace worldwide.
Indirect Value
Ecosystems perform many services for modern humans that are said to be indirect
because they are pervasive and it is not easy to associate a direct dollar value to them.
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 to
inorganic nutrients that are used by the producers within ecosystems.
Provision of Fresh Water
The water cycle continually supplies fresh water to terrestrial ecosystems.
There is no substitute for fresh water.
Flood Prevention
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
Many people prefer to vacation in natural areas. Providing guided tours of natural
ecosystems is often more profitable than destroying them.
37.3 Threats to Biodiversity
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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
Habitat loss has occurred in all ecosystems, and human disruption of natural habitats is
the most influential factor in biodiversity loss.
Exotic Species
Exotic species are nonnative members of a community. Introduction of exotic species
can disrupt the balance of species that have evolved in an area by changing the
interactions between species in a food web. Exotics are the second most important reason
for biodiversity loss. 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 because they have unique assemblages of native
species that are closely adapted to one another and cannot compete well again
exotics.
Pollution
Pollution is any environmental change that adversely affects the lives and health of
living organisms. Pollution has been identified as the third main cause of extinction.
Biodiversity is particularly threatened by the following types of environmental pollution:
Acid deposition
Acid deposition decimates forests and lakes.
Eutrophication
Lakes are under stress due to overenrichment, receiving excess nutrients due to runoff,
which results in algae growth.
Ozone depletion
The ozone shield protects Earth from harmful ultraviolet radiation, its depletion has led to
dramatic increases in skin cancer.
Organic chemicals
Endocrine-disruptors affect the endocrine system and reproductive potential of animals,
including humans.
Climate change
The term climate change refers to recent changes in the Earth’s climate. The major
contributor to climate change is the phenomenon of global warming, an increase in
Earth’s temperature due to the increase of greenhouse gases. Climate change 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.
Disease
Wildlife is subject to emerging diseases just as humans are.
37.4 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
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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
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.
37.5 Working Toward a Sustainable Society
Human society in its current form is not sustainable. A sustainable society should be able to
provide the same goods and services for future generations that it provides for the current one and
at the same time, biodiversity would be conserved.
Energy
Most of the world’s energy supply comes from nuclear power (6%) and fossil fuels
(81%), finite, nonrenewable sources. Increasing our reliance on renewable energy
resources is a major step toward becoming a sustainable society.
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 clean and safe drinking
water. Most fresh water is utilized by industry and agriculture. 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 salttolerant crops, have been suggested. Reusing water and adopting conservation
measures could help the world’s industries cut their water demands by more than
half.
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 redirection
of grain to feed livestock. In addition, modern farming methods are environmentally
destructive in several ways.
Urban Growth
More and more people are moving to cities and growth of cities increases pollution via many
sources.
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