BIO320 CHAPTER 11

1. 11-1
ENVIRONMENTAL
SCIENCE
A Study of Interrelationships
15th Edition
Biodiversity Issues
Chapter 11
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or further distribution permitted without the prior written consent of McGraw-Hill Education.

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Outline
11.1 Biodiversity Loss and Extinction
11.2 The Value of Biodiversity
11.3 Threats to Biodiversity
11.4 What Is Being Done to Preserve Biodiversity?

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11.1 Biodiversity Loss and
Extinction (1 of 2)
Biodiversity is a broad term used to describe the diversity
of genes, species, and ecosystems in a region.
Extinction is the elimination of all the individuals of a
particular species.
• Extinction is a natural and common event in the history of biological
evolution.
• It, and the resulting loss of biodiversity, is also a major consequence
of human domination of the Earth.

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11.1 Biodiversity Loss and
Extinction (2 of 2)
Over the past few hundred years, humans are estimated to
have increased the extinction rate by a factor of 1,000 to
10,000 times above background rates typical over the
planet’s history.
• 1/8 of bird species, 1/4 of mammal species, 1/3 of amphibian
species, and 1/2 of turtle species are threatened.
• 10% of the world’s coral reefs have been lost.
• Mangrove forests are reduced by over 1% a year.
• 25% of global land is used to raise crops.

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Kinds of Organisms Prone to Extinction
(1 of 2)
Local extinctions, although relatively common, indicate the
future of a species is not encouraging.
As population is reduced in size, some of the genetic
diversity is likely to be lost.
Certain kinds of species are more likely to go extinct than
others:
• Species with small, dispersed populations
• Successful breeding is difficult.

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Kinds of Organisms Prone to Extinction
(2 of 2)
Table 11.1 Probability of Becoming Extinct
Most Likely to Become Extinct Least Likely to Become Extinct
Low population density High population density
Found in small area Found over large area
Specialized niche Generalized niche
Low reproductive rates High reproductive rates

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Extinction as a Result of Human
Activity
As human populations grew, and their tools became more
advanced, the impact a single human could have on
surroundings increased.
Environmental modifications allowed larger, dense human
populations to survive, but at the expense of previously
existing ecosystems.
Nearly all the Earth’s surface has been affected in some
way by human activity.

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Genetic Diversity (1 of 4)
Genetic diversity is a term used to describe the number
of kinds of genes present in a population.
• High genetic diversity indicates many different kinds of genes
present in individuals of a population.
• Low genetic diversity indicates nearly all individuals share the
same genes and therefore the same characteristics.

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Genetic Diversity (2 of 4)
Several things influence a population’s genetic diversity:
• Mutations introduce new genetic information into a population by
modifying current genes.
• Migration allows movement of genes from one population to
another.
• Sexual reproduction generates new genetic combinations.

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Genetic Diversity (3 of 4)
Population size is an important factor: The smaller the
population, the less genetic diversity it can contain.
• There are fewer variations for each characteristic.
• Random events can significantly alter the genetic diversity in small
populations.
Selective breeding can affect diversity because
undesirable characteristics are eliminated.
• Many domesticated plants and animals could not survive without
human help.

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Genetic Diversity (4 of 4)
Source: Lynn Betts, USDA Natural Resources Conservation Service

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Species Diversity (1 of 3)
Species diversity is a measure of the number of different
species present in an area.
• Species richness refers to the number of different kinds of species
in an area.
• Taxonomic richness takes into account the number of different
taxonomic categories of the species present.

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Species Diversity (2 of 3)
Several factors are known to influence the species
diversity of a particular location:
• Migration
• Size of the area
• Geologic and evolutionary history
• Human activity

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Species Diversity (3 of 3)

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Ecosystem Diversity (1 of 2)
Ecosystem diversity is a measure of the number of kinds
of ecosystems present in an area.
Many regions of the world appear to be quite uniform in
terms of the kinds of ecosystems present.
• For example, many parts of the world are deserts:
• While there are general similarities, each is different and has specific
organisms typical to the region.
• Local topographic conditions create unique patches of landscape.

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Ecosystem Diversity (2 of 2)

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11.2 The Value of Biodiversity
Biological and Ecosystem Services Values
Humans are totally dependent on the diversity of
organisms on Earth.
• Symbiotic nitrogen-fixing bacteria live in the roots of certain plants.
• Spoil-building organisms live on the dead organic matter provided
by plants and animals.
• It is impossible for organisms to function optimally unless it has its
supporting cast of players that are part of the ecosystem.

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Biological and Ecosystem Services Values
(1 of 5)
Nutrient cycling
• Carbon, nitrogen, phosphorus, and other chemical elements are
cycled through ecosystems.
Cultural Uses
• Enjoyment of landscapes, individual organisms, scientific study,
educational activities, and the spiritual significance of places.
Water regulation and supply
• Intact soil and vegetation slow water flow, allowing it to penetrate the
soil and recharge aquifers.
• Water is available for agriculture, industry, and domestic use.

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Biological and Ecosystem Services Values
(2 of 5)
Disturbance regulation and erosion control
• Land can be disturbed by fire, flood, windstorms, landslides, or
human actions.
• Colonization of these sites by plants and animals heals the scars
and prevents continued damage.
Waste Treatment
• Decomposer organisms remove excess nutrients and pollutants
from air, water, and soil.
Food and Raw Materials
• Many people harvest wild plants and animals as food and
medicine. Plants feed livestock, provide building materials, and
firewood.

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Biological and Ecosystem Services Values
(3 of 5)
Atmospheric and Climate Services
• Many atmospheric gases are cycled between organisms and the
atmosphere.
• Removal of carbon dioxide in photosynthesis helps control the warming
of the planet.
• Nitrogen and sulfur are modified by organisms.
• Ozone provides protection from UV light.
Recreation
• Natural areas provide recreational opportunities.
Biological Control Services
• All organisms have complex interrelationships. Some help remove
pests.

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Biological and Ecosystem Services Values
(4 of 5)
Pollination Services
• Many insects are pollinators. Careless use of insecticides can
negatively affect agricultural production.
Habitat/Refuges
• Refuges protect species, serve as nursery sites, and provide
temporary stopping places for migratory species.

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Biological and Ecosystem Services Values
(5 of 5)
Genetic Resources
• If an organism goes extinct, we have lost the ability to use it for our
own needs.
• Wild ancestors of our food grains are thought to be extinct.
• 50% of our common drugs come from plants and animals.
Soil Formation
• Weathering of rock, aided by bacteria, fungi, tiny animals, and
plants roots build soil.
• Our food supply depends on the protection and management of soil.

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Direct Economic Values (1 of 2)
Choices between competing uses for ecosystems are often
determined by economic values.
• Value can be assigned to services provided by intact, functioning
ecosystems.
• Some resources are difficult to assign specific monetary value:
• Wildlife (consumed by those who harvest it)
• Medicinal plants

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Assigning Value to Ecosystem Services
A case can be made
that all species have
an intrinsic value and
a fundamental right to
exist.
• Extinction is not
necessarily bad, but
human-initiated
extinction is.
• Experiencing natural
landscapes and
processes is an
important human right
Table 11.3 Estimates of Various Ecosystem Services
Ecosystem services Values (trillion US $)
Soil formation 17.1
Recreation 3.5
Nutrient cycling 2.3
Water regulation and supply 2.3
Climate regulation (temperature and precipitiation) 2.0
Habitat 1.4
Flood and storm protection 1.5
Food and raw materials production 0.8
Genetic resources 0.8
Atmospheric gas balance 0.7
Pollination 0.4
All other services 1.6
Total value of ecosystem services 34.4

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Direct Economic Values (2 of 2)
The values held by a
person are typically
shaped by experience.
• As the shift from rural to
urban continues, there is
continual erosion of natural
experiences that can shape
the values of people.
• These values are important
in determining how society
will approach threats to
biodiversity.

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Ethical Values
Many would argue that a case can be made that all species
have an intrinsic value and a fundamental right to exist
without being needlessly eliminated by the unthinking
activity of the human species.
This is an ethical position that is unrelated to social or
economic considerations.
The ethical positions held by a person are typically shaped
by experience.

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Five major human activities threaten to reduce
biodiversity:
• Habitat loss
• Overexploitation
• Introduction of exotic species
• Predator and pest control activities
• Climate change
11.3 Threats to Biodiversity (1 of 2)

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Habitat Loss
The International Union for Conservation of Nature and
Natural Resources (IUCN) estimates that 80% to 90% of
threatened species are under threat as a result of habitat
loss or fragmentation.
Habitat loss and fragmentation are thought to be a major
cause of past extinctions.

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Conversion to Agriculture
About 40% of the world’s land surface has been converted
to cropland and permanent pasture.
Typically, the most productive natural ecosystems (forests
and grasslands) are the first to be modified by humans.
Pressures to modify the environment are greatest in areas
with high population density.

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Forestry Practices (1 of 2)
Originally, half of the U.S., three-fourths of Canada, and
almost all of Europe, and significant portions of the rest of
the world were forested.
Deforestation is the process of destroying a forest, often
for the purposes of fuel, building materials, or to clear land
for farming.

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Forestry Practices (2 of 2)
Modern forest management practices involve a
compromise that allows economic exploitation while
maintaining some environmental values of the forest.
• Forested areas effectively:
• Reduce erosion.
• Reduce runoff.
• Modify the climate.
• Provide recreational opportunities.

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Environmental Implications of Various
Forest Harvesting Methods
Clear cutting is the removal of all trees in an area. It is
economical but increases erosion, especially on steep
slopes.
Patchwork clear cutting is clear cutting in small,
unconnected patches; preserves biodiversity.
Selective harvesting is single species tree harvesting. It is
not as economical, but reduces ecosystem damage.

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Special Concerns About Tropical
Deforestation (1 of 2)
Tropical forests have greater species diversity than any
other ecosystem.
They are not as likely as temperate forests to regenerate
after logging due to poor soil characteristics.
Currently, few tropical forests are being managed for long-
term productivity.

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Special Concerns About Tropical
Deforestation (2 of 2)
Several concerns are raised by tropical deforestation:
• It significantly reduces species diversity in the world.
• It impacts the climate via lowered transpiration.
• Deforested lands are easily eroded.
• Without the forests to trap CO2, there may be increased global
warming.
• Human population pressure is greatest in tropics, and still
increasing.

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Plantation Forestry
Many lumber companies maintain forest plantations as
crops and manage them in the same way farmers manage
crops.
• Plant single species, even-aged forests of fast growing hybrid trees.
• Competing species are controlled by fire, and insects controlled by
spraying.
• Trees mature to harvestable size in as low as 20 years (vs. 100).
• Quality of lumber reduced.
• Low species diversity and wildlife value.

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Forest Plantation

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Rangeland and Grazing Practices
(1 of 2)
Rangelands are lands too dry to support crops, but receive
enough precipitation to support grasses and drought-
resistant shrubs.
They are often used to raise low-density populations of
domesticated or semi-domesticated animals.
Wildlife are usually introduced species not native to the
region.

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Use of Rangelands
Source: Library of Congress Prints and
Photographs Division

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Rangeland and Grazing Practices
(2 of 2)
The conversion of rangelands to grazing by domesticated
animals has major impacts on biodiversity.
• Selective eating habits of livestock tend to reduce certain species of
native plants and encourage others.
• Important to regulate number of livestock on rangelands, especially
in dry areas.
• Overgrazing is a severe problem where human population pressures are
great.
• Desertification is the process of converting arid or semiarid land to
desert because of improper human use.

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Desertification
Source: U.S. Department of Agriculture.

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Habitat Loss in Aquatic
Ecosystems (1 of 2)
In marine ecosystems, much of the harvest is restricted to
shallow parts of the ocean where bottom-dwelling fish can
be easily harvested.
Trawls are nets dragged along the bottom.
• They disturb the seafloor and cause habitat damage.
About 25% of catch is undesirable, and thus discarded, but
they are usually dead, and their removal further alters the
ecological nature of the seafloor.

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Habitat Loss in Aquatic
Ecosystems (2 of 2)
Freshwater systems are often modified for navigation,
irrigation, flood control, or power production.
All of these processes may alter natural ecosystems and
change numbers or kinds of aquatic organisms present.
• River Channelization
• Dams
• Pollution
• Exotic Species
• Overexploitation
• Water Withdrawal
• Siltation

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Conversion to Urban and Industrial
Uses
About 4.3% of U.S. land is developed as urban centers,
industrial sites, and transportation infrastructure.
• Many areas are covered with impermeable surfaces that prevent
plant growth and divert rainfall.
• The trend is toward greater urbanization.

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Overexploitation
According to the IUCN, overexploitation is responsible for
over 30% of endangered animal species and 8% of
endangered plant species.
• Overexploitation occurs when humans harvest organisms faster than
the organisms are able to reproduce, threatening some, and causing
extinction in others.

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Overfishing of Marine Fisheries
U.N. estimates 70% of world’s marine fisheries are
overexploited or are fully exploited and in danger of being
overexploited.
• Amount of fish caught has remained relatively constant, while the
amount produced by fish farming has increased.
• The commercial fishing industry has been attempting to market
species previously regarded as unacceptable.

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Aquaculture (1 of 2)
Fish farming (aquaculture) is becoming increasingly
important as a source of fish production.
Currently, about 60% of all aquaculture production is from
freshwater systems.
The environmental impacts are similar to those of marine
systems:
• Nutrient overloads
• Escape into natural waters
• Land conversion

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Aquaculture (2 of 2)

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Unsustainable Harvest of Wildlife and Plants
(1 of 2)
Meat from wild animals is often referred to as bush meat.
The Wildlife Conservation Society estimates 70% of wildlife
species in Asia and Africa and about 40% of species in
Latin America are being hunted unsustainably.
• Hunting of wildlife is a part of all subsistence cultures.
• Many kinds of wildlife are considered delicacies and are highly
prized for the home and restaurant trade.

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Unsustainable Harvest of Wildlife and Plants
(2 of 2)
Harvest of living animals for the pet and aquarium trade is
a significant problem.
• The method of capture is often problematic.
• Destruction of bird nests.
• Toxins used to stun fish.
Wildlife are also hunted because parts of the animal may
have particular value.
• Ivory and animal skins
• Traditional medicines

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Traditional Medicine

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Introduction of Exotic Species (1 of 2)
Some introductions of exotic species are purposeful, while
others are accidental.
Globalization is responsible for spreading thousands of
invasive alien species around the world.
The IUCN estimates about 30% of birds and 15% of plants
are threatened because they are unable to successfully
compete against invasive exotic species.

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Introduction of Exotic Species ( 2 of 2)
Introduction of disease has had considerable impact on
American forests.
• Chestnut blight
• Dutch elm disease
Various insects have had an effect on ecosystem structure.
• Asian long horned beetle
Freshwater ecosystems have been greatly affected.
• Zebra mussel

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Invasive Species (1 of 2)

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Invasive Species (2 of 2)

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11.3 Threats to Biodiversity (2 of 2)
Systematic killing of certain organisms that interfere with
human activities also results in reduced biodiversity.
• Large predators have been locally exterminated because they
preyed on domestic animals.
• Passenger pigeons became extinct primarily because of increased
conversion of forested land.

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Control of Predator and Pest
Organisms
Predator and competitor
control activities have been
largely eliminated in North
America.
• It is generally not considered
to be cost-effective in most
cases.
• Hunting and trapping of
wolves in Alaska and
Canada is an exception.
• Control of cowbird
populations has been used to
enhance breeding success of
Kirtland’s warblers.

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Climate Change
The role of climate change on the survival of species has
become an issue.
• Many species live near the limit of their physiological tolerance. A
slight change in the temperature may push them over the brink.
• Amphibians, corals, and arctic species are greatly affected by climate
change.
• Planet warming may have caused a fungal disease in frogs.
• Melting sea ice is changing migration patterns and food availability.

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Climate Change Affects Arctic Animals

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11.4 What Is Being Done to Preserve
Biodiversity? (1 of 2)
The World Conservation Union (IUCN) lists over 21,000
species as threatened with extinction.
• IUCN classifies species in danger of extinction into four categories:
• Endangered
• Vulnerable
• Rare
• Indeterminate

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11.4 What Is Being Done to Preserve
Biodiversity? (2 of 2)
According to the IUCN Red List of Threatened Species, in a recent study
of 25,000 vertebrates:
• 41 percent of amphibians are threatened, as are
• 25 percent of mammals
• 22 percent of reptiles
• 13 percent of birds
• 33 percent of cartilaginous fish such as sharks, and
• 15 percent of bony fish such as southern bluefin tuna
While vertebrates make up just 3 percent of all species, they are vital to
the food chain and the overall ecosystem, and much more data are
available for them. Ecologist Edward O. Wilson has described vertebrates
as the “backbone” of diversity.

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Legal Protection (1 of 3)
Awareness and concern about loss of biodiversity are high in
many developed countries.
Most vulnerable species in these areas have already been
eliminated.
Loss of biodiversity is not a high priority for the general public
in developing countries.
They are more concerned with immediate needs of food and
shelter than long-range issues such as species extinction.

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Legal Protection (2 of 3)
In the U.S., the primary action related to the preservation of
biodiversity involved the passage of the Endangered Species
Act (1973).
This legislation designates species as endangered or
threatened and gives the U.S. government jurisdiction over
those species.
• Directs that no activity by a government agency should lead to the
extinction of an endangered species.
• Directs government agencies to use whatever means necessary to
preserve the species in question.

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Legal Protection (3 of 3)
Endangered species are those that have such small
numbers that they are in immediate danger of becoming
extinct.
Threatened species could become extinct if a critical
environmental factor is changed.
• The preservation question ultimately becomes one of assigning value
to the species.
• Amendments to ESA have weakened ability of U.S. government to add
new species to the list.

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Endangered Species
Source: U.S. Fish and Wildlife
Service/Patrick Kobernus
Source: U.S. Fish and
Wildlife Service/Mike Boylan
Source: U.S. Fish and Wildlife
Service/George Gentry
Source: U.S. Fish and
Wildlife Service/Tom smylie

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Sustainable Management of Wildlife
Populations
Habitat Analysis and Management
• Managing a particular species requires an understanding of the
habitat needs of that species.
• An animal’s habitat must provide food, water, and cover.
• Cover conceals or protects animals from the elements or enemies.
• Modifications made to enhance the success of a species are known
as habitat management.

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Population Assessment and
Management (1 of 2)
Game species are often managed so they do not exceed
carrying capacity of their habitat.
Wildlife managers use population censuses to check if
populations are within appropriate levels.
With suitable habitat and protection, most wild animals can
maintain a sizeable population.
High reproductive capacities and heavy protection have
caused very large populations to arise from once-rare
animals.

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Population Assessment and
Management (2 of 2)
Wildlife management often involves harvesting for sport and
meat.
• Regulating hunting activity is an important population management
technique.
• Seasons usually occur in the fall so surplus animals are taken before
the challenges of winter.
When populations get too small, artificial introductions can be
implemented.
• Native species can be reintroduced to areas where they had been
extinct.
• Non-native species are introduced for empty niches.

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Managing a Wildlife Population
Source: Data from Taber, R.D. and Dasmann, R.F “The Dynamics of Three
Natural Populations of the Deer Odocoileus hemionus columbianus,” Ecology
38, no. 2, 1957, pp. 233–46.

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Special Issues with Migratory
Animals
Migratory birds can travel thousands of kilometers.
• They travel north in spring to reproduce.
• They travel south in fall to escape cold temperatures.
International agreements may be necessary to maintain
appropriate habitat.

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Migration Routes for North American
Waterfowl

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Sustainable Management of Fish
Populations (1 of 2)
Coastal regions are most productive regions of the oceans.
• Sunlight penetration of shallow water makes it warm.
• Nutrient deposition from land makes this region fertile.
• Wind/wave action stirs nutrients.
Fishing pressure is concentrated here.
One of the major problems associated with the management
of marine fisheries is achieving agreement on harvest limits.

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Sustainable Management of Fish
Populations (2 of 2)
Humans have easy access to
freshwater ecosystems, so
management of these systems is
much more intense.
They are typically easier to
regulate because of containment
within a smaller political region.
Many North American freshwater
fisheries are primarily managed
for sport fishery.
Fisheries’ biologists pay special
attention to water quality.

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Summary (1 of 3)
Loss of biodiversity has become a major concern.
Ecosystems involve the interactions of organisms and their
physical environment.
Functioning ecosystems and their component organisms
provide many valuable services that are often overlooked
because they are not easily measured in economic terms.

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Summary (2 of 3)
Many people also consider the loss of biodiversity to be an
ethical problem.
The primary causes of habitat loss are by:
• Humans converting ecosystems to agriculture and grazing.
• Overexploitation by harvesting species at unsustainable levels.
• Introduction of exotic species that disrupt ecosystems and compete
or prey on native organisms.
• Purposeful killing of pest organisms such as large predators.

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Summary (3 of 3)
Protection of biodiversity typically involves legal protections
by national laws and international agreements, and
management of the use of species and ecosystems at
sustainable levels.