Download Genetic Diversity

Biology 102 Week 11
Conservation Biology and
Restoration Ecology
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: The Biodiversity Crisis
• Conservation biology integrates these fields:
– Ecology
– Evolutionary biology
– Physiology
– Molecular biology
– Genetics
– Behavioral ecology
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• Restoration ecology applies ecological principles
to return degraded ecosystems to conditions as
similar as possible to their natural state
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• Tropical forests containing some of the greatest
concentrations of species are being destroyed at
an alarming rate
• Throughout the biosphere, human activities are
altering ecosystem processes on which we and
other species depend
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 55.1: Human activities threaten Earth’s
biodiversity
• Rates of species extinction are difficult to
determine under natural conditions
• The high rate of species extinction is largely a
result of ecosystem degradation by humans
• Humans are threatening Earth’s biodiversity
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The Three Levels of Biodiversity
• Biodiversity has three main components:
– Genetic diversity
– Species diversity
– Ecosystem diversity
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LE 55-2
Genetic diversity in a vole population
Species diversity in a coastal redwood ecosystem
Community and ecosystem diversity
across the landscape of an entire region
Genetic Diversity
• Genetic diversity comprises genetic variation
within a population and between populations
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Species Diversity
• Species diversity is the variety of species in an
ecosystem or throughout the biosphere
• An endangered species is in danger of becoming
extinct throughout its range
• A threatened species is likely to become
endangered in the future
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• Conservation biologists are concerned about
species loss because of alarming statistics
regarding extinction and biodiversity
• Researchers estimate that at current rates of
extinction more than half of current plant and
animal species will disappear in this century
• Harvard biologist E. O. Wilson has identified the
Hundred Heartbeat Club: species with fewer than
100 individuals
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LE 55-3
Philippine eagle
Chinese river
dolphin
Javan
rhinoceros
Ecosystem Diversity
• Human activity is reducing ecosystem diversity,
the variety of ecosystems in the biosphere
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Biodiversity and Human Welfare
• Human biophilia allows us to recognize the value
of biodiversity for its own sake
• Species diversity brings humans practical benefits
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Benefits of Species and Genetic Diversity
• Many pharmaceuticals contain substances
originally derived from plants
• For example, the rosy periwinkle contains
alkaloids that inhibit cancer growth
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The loss of species also means loss of genes and
genetic diversity
• The enormous genetic diversity of organisms has
potential for great human benefit
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Ecosystem Services
• Ecosystem services encompass all the processes
through which natural ecosystems and their
species help sustain human life
• Some examples of ecosystem services:
– Purification of air and water
– Detoxification and decomposition of wastes
– Cycling of nutrients
– Moderation of weather extremes
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Four Major Threats to Biodiversity
• Most species loss can be traced to four major
threats:
– Habitat destruction
– Introduced species
– Overexploitation
– Disruption of “interaction networks”
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Habitat Destruction
• Human alteration of habitat is the greatest threat
to biodiversity throughout the biosphere
• Many natural landscapes have been broken up,
fragmenting habitat into small patches
• In almost all cases, habitat fragmentation and
destruction lead to loss of biodiversity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Introduced Species
• Introduced species are those that humans move
from native locations to new geographic regions
• Introduced species that gain a foothold in a new
habitat usually disrupt their adopted community
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• Sometimes humans introduce species by
accident, as in case of the brown tree snake
arriving in Guam as a cargo ship “stowaway”
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LE 55-6
Brown tree
snake, introduced to Guam
in cargo.
Introduced kudzu thriving in South Carolina
• Humans have deliberately introduced some
species with good intentions but disastrous effects
• An example is the introduction of kudzu in the
southern United States
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Overexploitation
• Overexploitation is human harvesting of wild
plants or animals at rates exceeding the ability of
populations of those species to rebound
• For example, the fishing industry has greatly
reduced populations of some game fish, such as
bluefin tuna
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Disruption of Interaction Networks
• Extermination of keystone species by humans can
lead to major changes in community structure
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 55.2: Population conservation focuses on
population size, genetic diversity, and critical habitat
• Biologists focusing on conservation at the
population and species levels follow two main
approaches:
– The small-population approach
– The declining population approach
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Small-Population Approach
• The small-population approach studies processes
that can make small populations become extinct
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The Extinction Vortex
• A small population is prone to positive-feedback
loops that draw it down an extinction vortex
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 55-9
Small
population
Inbreeding
Genetic
drift
Lower
reproduction
Higher
mortality
Loss of
genetic
variability
Reduction in
individual
fitness and
population
adaptability
Smaller
population
• The key factor driving the extinction vortex is loss
of the genetic variation necessary to enable
evolutionary responses to environmental change
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Case Study: The Greater Prairie Chicken and the
Extinction Vortex
• Populations of the greater prairie chicken were
fragmented by agriculture and later found to
exhibit decreased fertility
• To test the extinction vortex hypothesis,
scientists imported genetic variation by
transplanting birds from larger populations
• The declining population rebounded,
confirming it had been on its way down an
extinction vortex
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 55-10
Number of male birds
200
150
100
50
0
1970
1975
1980
1985
Year
1990
1995
2000
Population dynamics
Eggs hatched (%)
100
90
80
70
60
50
40
30
1970–74 1975–79 1980–84 1985–89
Years
Hatching rate
1990
1993–97
Minimum Viable Population Size
• Minimum viable population (MVP) is the minimum
population size at which a species can survive
• The MVP factors into a population viability
analysis (PVA), which predicts a population’s
chances for survival over a particular time
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Effective Population Size
• A meaningful estimate of MVP requires
determining the effective population size, which is
based on the population’s breeding size
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Case Study: Analysis of Grizzly Bear Populations
• One of the first population viability analyses was
conducted as part of a long-term study of grizzly
bears in Yellowstone National Park
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• This study showed that the grizzly bear population
has grown substantially in the past 20 years
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LE 55-12
150
Females with cubs
Number of individuals
Cubs
100
50
0
1973
1982
1991
Year
2000
Declining-Population Approach
• The declining-population approach
– Focuses on threatened and endangered
populations that show a downward trend,
regardless of population size
– Emphasizes the environmental factors that
caused a population to decline
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Steps for Analysis and Intervention
• The declining-population approach
– Requires that declines in population be
evaluated on a case-by-case basis
– Involves a step-by-step proactive conservation
strategy
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Case Study: Decline of the Red-Cockaded
Woodpecker
• Red-cockaded woodpeckers had been forced
into decline by habitat destruction
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LE 55-13
A red-cockaded woodpecker perches at the
entrance to its nest site in a longleaf pine.
Forest that can
sustain redcockaded
woodpeckers has
low undergrowth.
Forest that cannot sustain red-cockaded
woodpeckers has high, dense undergrowth
that impacts the woodpeckers’ access to
feeding grounds.
• In a study where breeding cavities were
constructed, new breeding groups formed only in
these sites
• Based on this experiment, a combination of
habitat maintenance and excavation of breeding
cavities enabled this endangered species to
rebound
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Weighing Conflicting Demands
• Conserving species often requires resolving
conflicts between habitat needs of endangered
species and human demands
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Concept 55.3: Landscape and regional
conservation aim to sustain entire biotas
• Conservation biology has attempted to sustain the
biodiversity of entire communities, ecosystems,
and landscapes
• Ecosystem management is part of landscape
ecology, which seeks to make biodiversity
conservation part of land-use planning
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Landscape Structure and Biodiversity
• The structure of a landscape can strongly
influence biodiversity
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Fragmentation and Edges
• The boundaries, or edges, between ecosystems
are defining features of landscapes
• Some edges are natural, but some are created by
human activity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 55-14
Natural edges. Grasslands give way to forest
ecosystems in Yellowstone National Park.
Edges created by human activity. Pronounced edges
(roads) surround clear-cuts in this photograph of a
heavily logged rain forest in Malaysia.
• Biodiversity decreases as habitat fragmentation
increases and edges become more extensive
• Research led to discovery of two groups of
species, those that live in forest edge habitats and
those that live in the forest interior
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Corridors That Connect Habitat Fragments
• A movement corridor is a narrow strip of quality
habitat connecting otherwise isolated patches
• Movement corridors promote dispersal and help
sustain populations
• In areas of heavy human use, artificial corridors
are sometimes constructed
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Establishing Protected Areas
• Conservation biologists apply understanding of
ecological dynamics in establishing protected
areas to slow the loss of biodiversity
• Much of their focus has been on hot spots of
biological diversity
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Finding Biodiversity Hot Spots
• A biodiversity hot spot is a relatively small area
with a great concentration of endemic species and
many endangered and threatened species
• Biodiversity hot spots are good choices for nature
reserves, but identifying them is not always easy
Video: Coral Reef
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LE 55-17
Terrestrial
biodiversity
hot spots
Equator
Philosophy of Nature Reserves
• Nature reserves are biodiversity islands in a sea of
habitat degraded by human activity
• One argument for extensive reserves is that large,
far-ranging animals with low-density populations
require extensive habitats
• In some cases, reserves are smaller than the area
needed to sustain a population
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LE 55-18
0
50
100
Kilometers
43°
Montana
Wyoming
42°
Yellowstone
National
Park
Montana
Idaho
41°
Grand Teton
National Park
Wyoming
Idaho
40°
Zoned Reserves
• The zoned reserve model recognizes that
conservation often involves working in landscapes
that are largely human dominated
• Zoned reserves are often established as
“conservation areas”
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LE 55-19a
Nicaragua
CARIBBEAN SEA
Costa
Rica
National park land
Buffer zone
PACIFIC OCEAN
Boundaries of the zoned reserves are indicated by black outlines.
LE 55-19b
Local schoolchildren marvel at the diversity of life in one
of Costa Rica’s reserves.
• Some zoned reserves in the Fiji islands are closed
to fishing, which actually improves fishing success
in nearby areas
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 55.4: Restoration ecology attempts to
restore degraded ecosystems to a more natural state
• Given enough time, biological communities can
recover from many types of disturbances
• Recovery time depends more on the spatial scale
than on the type of disturbance
• Whether a disturbance is natural or caused by
humans seems to make little difference in this
size-time relationship
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 55-21
104
Natural disasters
Human-caused disasters
Natural OR humancaused disasters
1,000
Meteor
strike
Industrial
pollution
Groundwater
exploitation
Urbanization Salination
Modern
Volcanic Acid
eruption rain
Flood
agriculture
100
Slash
& burn
Forest Nuclear Tsunami
bomb
Oil fire
spill
Landslide
10
Tree
fall
Lightning
strike
1
10–3
10–2
10–1
1
10
Spatial scale (km2)
(log scale)
100
1,000
104
• A basic assumption of restoration ecology is that
most environmental damage is reversible
• Two key strategies are bioremediation and
augmentation of ecosystem processes
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Bioremediation
• Bioremediation is the use of living organisms to
detoxify ecosystems
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Biological Augmentation
• Biological augmentation uses organisms to add
essential materials to a degraded ecosystem
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Exploring Restoration
• The newness and complexity of restoration
ecology require considering alternative solutions
and adjusting approaches based on experience
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 55.5: Sustainable development seeks to improve
the human condition while conserving biodiversity
• Facing increasing loss and fragmentation of
habitats, how can we manage Earth’s resources?
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Sustainable Biosphere Initiative
• The goal of the Sustainable Biosphere Initiative is
to define and acquire basic ecological information
for responsible development, management, and
conservation of Earth’s resources
• Sustainable development is the long-term
prosperity of human societies and the ecosystems
that support them
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Case Study: Sustainable Development in Costa
Rica
• Costa Rica’s conservation of tropical
biodiversity involves partnerships between the
government, other organizations, and private
citizens
• Human living conditions in Costa Rica have
improved along with ecological conservation
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LE 55-23
200
80
Life expectancy
Infant mortality
70
150
60
100
50
50
40
0
30
1900
1950
Year
2000
Biophilia and the Future of the Biosphere
• Our lives differ greatly from early humans who
hunted and gathered and painted on cave walls
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LE 55-24
Detail of animals in a 36,000-year-old cave painting, Lascaux, France
Biologist Carlos Rivera Gonzales examining a tiny tree frog in Peru
• But our behavior reflects remnants of our
ancestral attachment to nature and the diversity of
life—the concept of biophilia
• Our sense of connection to nature may motivate
realignment of our environmental priorities
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings