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Chapter 55
Conservation Biology
Biodiversity Crisis
• Extinction is a common occurrence since life
began, it is the rate that is startling now
• Three Levels of Biodiversity
– Genetic diversity
– Species diversity
– Ecosystem diversity
Loss of Genetic Diversity
• Takes into consideration individual variation
within a population and variation between
populations associated with adaptations to
local conditions
Loss of Species Diversity
• Endangered species: a species in danger of
extinction throughout all or a significant
potion of its range
• Threatened species: a species likely to
become endangered in the foreseeable future
• 13% of all birds are threatened
• 30% of plants are threatened
• 20% of freshwater fish have become extinct
during recent times
Hundred Heartbeat Club
• These species have fewer than 100
individuals, and are close to extinction
Loss of Ecosystem Diversity
• Variety in the communities that make up an
ecosystem
• Tropical rain forests are about the size of the US,
and lose as much land as West Virginia each year
• “We must consider our planet to be on loan from
our children, instead of a gift from our ancestors”
– Chinese Proverb
Benefits of Biodiversity
• Aesthetic Value
• Moral and Ethical Value
• Crucial natural resource
– Crops
– Fibers
– Medicines
• 25% of prescriptions are derived from plants
• A periwinkle from Madagascar can help cure Hodgkin’s
lymphoma and childhood leukemia
Ecosystem Services
• By allowing the extinction of species and the
degradation of habitats to continue, we risk our
own species’ survival
• Ecosystem Services:
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Purification of air and water
Detoxification and decomposition of wastes
Pollination of crops and vegetation
Dispersal of seeds
Nutrient cycling
Protection from UV rays
Moderation of weather extremes
• All add up to about $33 trillion in services = more than all of
the world’s GDP
Threats to Biodiversity
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Habitat Destruction
Introduced species
Overexploitation
Food chain disruptions
Habitat Destruction
• Single greatest threat to biodiversity
• Account for 73% of extinctions since recorded
• 93% of coral reefs are damaged by human
activity
– About 1/3 of the fish use them as their habitat
• Many landscapes have been fragmented
Introduced Species
• Second in the cause of biodiversity decline
• Accounted for 40% of extinctions since they
have been recorded
• Can be intentional or accidental
– Kudzu
– European starling (because of Shakespeare)
– Caulerpa (from someone’s aquarium)
• In US, there are about 50,000 introduced
species, costing $130 billion a year to control
Overexploitation
• Human harvesting of wild plants or animals at
rates that exceed the ability of a population to
rebound
– Overhunting and overfishing
• Elephants, whales, rhinoceroses
• Great auk
– Feathers, meat and eggs
Overexploitation
• African Elephant:
– Take 10-11 years to reach sexual maturity
– Calf every 3-9 years
– Illegal ivory hunting
• North Atlantic Blue fin Tuna
– Used to be only used in cat food for a few cents a
pound
– Now is $100 per pound
Disruption of Food Chains
• Black-footed ferret
– Prey is prairie dogs
Small Population Approach
• Study the processes that can cause very small
populations to finally become extinct
– It’s the populations’ smallness that finally drives it
to extinction after factors such as habitat loss have
taken their toll on the population
• Extinction vortex: a downward spiral unique
to small populations
– Prone to positive feedback loops of inbreeding
– Loss of genetic variation for evolution
How Small is Too Small?
• Minimum Viable Population Size (MVP)
– Include how many individuals are likely to be killed
by a natural catastrophe
• Population viability analysis (PVA): makes a
reasonable prediction of a population’s
chances for survival over a particular time
• Effective population size: based on breeding
potential of the population
Case Study: The Greater Prairie
Chicken
• Habitat fragmented from agriculture
• Decline associated with the decrease in
hatching rate of eggs
• Genetic variation is too small
• Transplanted birds from different areas to
increase diversity
Declining Population Approach
• Focuses on threatened and endangered
populations even if they are far greater than
minimum viable size
• Emphasizes the environmental factors that
caused populations decline
Steps in Diagnosis and Treatment of
Declining Populations
1. Confirm the species is presently in decline or that it
was formerly more widely distributed or more
abundant
2. Study the species’ natural history to determine its
environmental requirements
3. Determine all possible causes of the decline
4. List the predictions of each hypothesis for the decline
5. Test the most likely hypothesis first, designing an
experiment to determine if this factor is the main
cause of the decline
6. Apply the results of this diagnosis to the management
of the species
Case Study: Red-Cockaded
Woodpecker
• Requires mature pine forests dominated by
longleaf pine
• Nest in living trees
• Understory of plants around the trunk must
be of low profile
• Used controlled fires to return some habitat to
the desired form for the woodpecker
Weighing Conflicting Demands
• Human needs vs animal needs
• Which ones to save because we can’t save all
of them
– Keystone species
Landscape Ecology
• Boundaries (edges) between ecosystems and
within are defining features of landscapes
• Edge has its own soil, topography, disturbance
features
– Some organisms thrive in edge communities
because they require resources from the two
adjacent areas
• Ex: White tailed deer
• Edge landscape is increasing
Landscape Ecology
• Movement corridor: a narrow strip or series
of small clumps of quality habitat connecting
otherwise isolated patches
• Can promote dispersal and reduce inbreeding
in declining populations
– Help species that migrate among populations
– Could help the spread of disease
Reserve Design
• Should the reserve be managed to minimize
the effect of different natural processes?
• Should it be left as natural as possible?
• 7% of the world’s land is in reserves
• Biodiversity hot spot: relatively small area
with exceptional concentration of endemic
species and a large number of threatened or
endangered animals
Reserve Design
• One large or several small?
• Zoned reserve: an extensive region of land
that includes one or more areas undisturbed
by humans surrounded by lands that have
been changed by humans for economic gain
– Serve as buffer zones against further intrusion into
the undisturbed areas
Restoration Ecology
• Applies ecological principle in an effort to
return degraded ecosystems to conditions as
similar as possible to their natural,
predegraded state
• Seeks to reverse population and community
declines
– Assume that the damage is irreversible
Bioremediation
• Use of living organisms, usually prokaryotes,
fungi, or plants, to detoxify polluted
ecosystems
• Some plants soak up heavy metals
• Some lichens eat uranium dust
• Clean up oil spills on beaches
Biological Augmentation
• Uses organisms to add essential materials to a
degraded ecosystem
• Requires determining what factors have been
removed and are limiting factors
• Certain plants can help speed up the
ecological succession rate
• Can replant natural plants to recolonize
natural animal populations
Adaptive Management
• Uses the experimental method in trying
several promising types of management to
find out what works best
• Must consider alternative ways of
accomplishing goals and to learn from
mistakes