Chapter 12 Biodiversity: The
Species Approach
What are the three types of species extinction?
The three levels of species extinction are local, ecological, and biological.
1.
Local extinction occurs when a species disappears from an area in which it once
inhabited, but is found elsewhere in the world.
2.
Ecological extinction occurs when the number of members of a particular species
is so low that they cannot fulfill their ecological roles in their biological
communities.
3.
Biological extinction occurs when a species has disappeared from the earth.
How do we classify Organisms headed for extinction?
Endangered species are so few in number that the species could soon become extinct over
all or part of its natural range.
Threatened/vulnerable species are still abundant in their natural range but, because of loss
in numbers, is likely to become endangered in the near future.
(E.O. Wilson states) “The first species to go tend to be the big, slow, and tasty and whose
valuable parts can be sold.”
The passenger pigeon represents lost natural capital, primarily because of overhunting and
habitat destruction directly attributable to man.
A survey in 2000 (Natural Conservancy) found that about one-third of 21,000 animal
and plant species in the U.S. are vulnerable to premature extinction.
Determining Extinction
Estimates of the current rate of species extinction are based on information about
habitat destruction and species-area relationship, use of models such as:
(1) population viability analysis (PVA), estimates of (2) minimum viable
population (MVP), estimates of (3) minimum dynamic area (MDA), and
differing assumptions about the earth's total number of species, their
distribution, and the rates of tropical deforestation.
Characteristics of species that are prone to extinction
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Low reproductive rate (K-strategist)- Blue whale, giant panda, rhinoceros
Specialized niche– Blue whale, giant panda, Everglades kite
Narrow distribution – many island species, elephant seal, desert pupfish
Feeds at a high trophic level- Bengal tiger, bald eagle, grizzly bear
Fixed migratory patterns- Blue whales, whooping cranes, sea turtles
Rare- Many island species, African violet, some orchids
Commercially valuable- Snow leopard, tiger, elephant, rhinoceros, rare plants
and birds
Large territories- California condors, grizzly bears, Florida panthers
What is the impact of human activities on extinction?
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Currently, the rate of extinction is estimated to be 1,000–10,000 times the
rate before mankind existed.
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Using estimated extinction rates, 20% of the world’s present plant and
animal species will be gone by 2030; 50% would vanish by 2099.
Factors influencing greater extinction rates
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Species loss and biodiversity loss will likely increase because of exponential
population growth.
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Biologically diverse areas’ (hot spots) rate of extinction may be as high as 25–
50%. The extinction rate in these “hot spots” deserves special attention.
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Possible colonization sites for new species are being eliminated, degraded,
and simplified by human activities so that new species cannot arise. By
reducing this rate of speciation, we are creating a speciation crisis.
Solution? - A precautionary strategy to prevent a significant decrease in the
genetic, species, ecological, and functional diversity of the earth is necessary.
Why should we preserve wild species?
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Wild species have value—economic and ecological—which are important to
the earth.
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We are destroying species biodiversity more quickly than new species can
evolve. It will take 5 million years for speciation to rebuild the animals and
plants we will destroy in 100 years. We should preserve species for their
instrumental value.
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Instrumental value- usefulness of a species to us in the form of economic or
ecological services
Examples:
Mountain Gorillas
Thailand Species Trade
Sharks
What are some of the economic and ecological
benefits?
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Medicinal properties are found in many plants and some animals.
Genetic information in species helps them adapt and produce new species. This
information can be used to develop food and medicines for people. Wild species
provide a bank of genetic information.
Recreational value is provided by plants and animals.
Eco-tourism generates money to help poor countries; preserving plants and
animals is much more economically wise than destroying them.
– A male lion skin is worth $1,000; a male lion living for 7 years produces
$515,000 in tourist dollars.
– Bats, often targeted for destruction by man, feed on crop-damaging insects,
pollinate flowers, as well as distribute plants by excreting undigested seeds.
Bats are keystone species in the tropics.
Some of the economic and ecological benefits of present species have not even been
identified; we are destroying our chance for a a future.
Secondary factors leading to premature extinction
HIPPO – Habitat destructions and fragmentation, Invasive
(alien) species, Population growth, Pollution and
Overharvesting
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Habitat destruction and fragmentation
Species are more vulnerable to extinction when their habitats are
divided and in to smaller more isolated patches
Invasive Species
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Deliberate or accidental
introduction of nonnative
species can trigger
ecological disruptions that
lead to premature
extinction of native
species. Once a nonnative
species gets established in
an ecosystem, its
wholesale removal is
virtually impossible. The
best strategy is to prevent
nonnative species from
being introduced and
becoming established.
Solution:
Prevention is the best way to reduce the threats from nonnative species because
once they have arrived it is difficult and expensive to slow their spread.
Invasive Species
Kudzu
Figure 12-10 Kudzu taking over a house and a truck. This
vine can grow 5 centimeters (2 inches) per hour and is now
found from east Texas to Florida and as far north as
southeastern Pennsylvania and Illinois. Kudzu was
deliberately introduced into the United States for erosion
control, but it cannot be stopped by being dug up or burned.
Grazing by goats and repeated doses of herbicides can
destroy it, but goats and herbicides also destroy other plants,
and herbicides can contaminate water supplies. Recently,
scientists have found a common fungus (Myrotheciurn
verrucaria) that can kill kudzu within a few hours, apparently
without harming other plants.
Fire Ants
Figure 12-11 Natural capital degradation:
expansion of the Argentina fire ant in southern states,
1918-2000. This invader is also found in Puerto Rico,
New Mexico, and California, (Data from U.S.
Department of Agriculture)
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Impact of Population Growth
Deer populations have exploded in the suburbs due to invasion of their habitats
by humans.
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Deer are edge species; they live in the woods and feed in more open
areas.
Deer kill more people in the U.S. than any other wild species due to
collisions between deer and vehicles.
No easy answers are available for reducing the deer population; each
proposed remedy is generally expensive and time consuming.
Researchers are experimenting with various possible methods of birth
control to decrease the population.
Poaching and Hunting
At least one-fourth of the international
trade in wild plants and animals
involves the illegal sale of endangered
or threatened species or their parts.
Most demand for illegal wildlife comes
from wealthy consumers, but illegal
hunting for bushmeat as a source of
protein for local people and for
restaurants in many parts of the world
is a growing problem.
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Planet in Peril Video Clip
To poachers, a live mountain gorilla is worth $150,000, a panda pelt $100,000 (only
about 1,500 pandas are left in the wild), a chimpanzee $50,000, and an Imperial
Amazon macaw $30,000. A rhinoceros horn is worth as much as $28,600 per
kilogram ($13,000 per pound) because of its use in dagger handles in the Middle
East and as a fever reducer and alleged aphrodisiac in China—the world's largest
consumer of wildlife—and other parts of Asia.
Protecting Wild Species- Legal Approach
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The 1975 Convention on International Trade in Endangered Species
(CITES) has helped to reduce international trade in many threatened
animals. The Convention on Biological Diversity (CBD) binds signatory
governments to reversing the decline in biodiversity, but it has not been
ratified by the United States and some other key governments.
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In the United States, The Lacey Act of 1900 prohibits the transport of live or
dead animals or their parts across state lines without a permit. The
Endangered Species Act of 1973 (ESA) prohibits the import or trading of
products made from an endangered or threatened species.
ESA Controversy
There is controversy over whether the government should compensate
private property owners who suffer financial losses when it restricts how
they can use their land because of the presence of threatened or
endangered species.
Congress has amended the Endangered Species Act to help landowners
protect endangered species on their land. Safe-harbor agreements and
voluntary candidate conservation agreements
U.S. Biological hot spots and recovery plans
Examples of successful recovery plans include those for the American alligator, the
gray wolf, the bald eagle, and the peregrine falcon. Bad news. About half of current
recovery plans exist only on paper, mostly because of political opposition and
limited funds.
Protecting Wild Species: The Sanctuary Approach
The sanctuary approach is being used to protect wild species.
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542 federal refuges protect wildlife, but the habitats are deteriorating due to
invasive species, pollutants, and little operational or maintenance funding.
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About one-fifth of U.S. endangered and threatened species have habitats in the
refuge system.
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Human overuse by hunters, fishermen, and off-road vehicle traffic has hurt the
refuges.
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Gene banks, botanical gardens, and farms can be used to raise threatened species
and help protect species from extinction, but funding is inadequate.
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Raising some threatened or endangered species on farms can take some of the
pressure off them and perhaps offer some for commercial sale.
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Zoos and aquariums can help protect some endangered animal species as well,
but they are both notoriously underfunded.
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More than three-fourths of the refuges are concentrated along major bird migration
corridors.
Major Migratory Flyways
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Reconciliation Ecology
• Reconciliation Ecology – the science of inventing,
establishing and maintaining new habitats to conserve
species diversity in place where people live, work or play.
• Michael L. Rosenzweig (Win-Win Ecology: How Earth’s
Species Can Survive in the Midst of Human Enterprise)
identifies the real challenge for biodiversity: to sustain
wild species in the human-dominated portion of nature.
• Rosenzweig advocates that we implement reconciliation
ecology: learn to share the spaces we dominate with other
species. It is the science of inventing, establishing, and
maintaining new habitats to conserve species diversity
where people live out their lives.
Reconciliation Ecology
There are several ways to implement reconciliation ecology.
1. Maintain diverse yards using native plants, which attract
certain species.
2. Share responsibility for supporting bio-diverse yards and
gardens.
3. Apply reconciliation ecology to local plant and animal life (for
example, bluebirds project).
4. Planting rooftop gardens can support a variety of species,
provide insulation, reduce evapotranspiration, conserve water,
and cool cities.
5. Golden Gate Park in San Francisco is a good example of
reconciliation ecology; it was transformed from sand dunes to
park by humans.
6. Government land, college campuses, and schools could be used
for reconciliation ecology laboratories.