Transcript Ch57_Lecture Conserv Bio

57
Conservation
Biology
57 Conservation Biology
• 57.1 What Is Conservation Biology?
• 57.2 How Do Biologists Predict Changes in
Biodiversity?
• 57.3 What Factors Threaten Species
Survival?
• 57.4 What Strategies Do Conservation
Biologists Use?
57.1 What Is Conservation Biology?
Conservation biology is an applied
science, devoted to preserving the
diversity of life.
Conservation biology is integrated with
other disciplines
genetics, evolution, population
ecology, biogeography, wildlife
management, economics, and
sociology
Photo 57.3 Pine cones open after fire.
Photo 57.4 Cones of ponderosa pine will not germinate until
opened by fire.
57.1 What Is Conservation Biology?
Conservation biologists are
motivated by the belief that
loss of biodiversity is negative.
Photo 57.7 Madagascar periwinkle (Catharanthus roseus),
source of antileukemia drugs.
Conservation biology is guided by the following three principles:
• Evolution is the process that unites all of
biology.
• The ecological world is dynamic.
• Humans are part of ecosystems.
Photo 57.10 Arabian oryx, saved from extinction by captives
being reintroduced into the wild.
Photo 57.14 Northern spotted owl (Strix occidentalis caurina) is
dependent on old-growth forest.
Human beings have caused
extinctions of other species for
thousands of years.
• 1st humans in N.
America 20,000 ya
• probably caused the
extinction of large
mammals
• similar extinction in
Australia 40,000 ya
Figure 57.1 Extinct Australian Megafauna
When Polynesian people settled Hawaii 2,000 years ago…
exterminated at least 39 endemic
species of birds (species found nowhere
else in the world)
But the current extinction situation is unique…how?
For the first time, all major
environmental changes on
Earth are human induced,
and we are aware of what
we are doing.
Why do we value biodiversity?
• We depend on other species for food,
fiber, and medicines.
• Species are necessary for the functioning
of ecosystems which provide us with so
many goods and services.
• We derive enormous aesthetic pleasure
from watching and interacting with other
species.
Photo 57.8 Bark of Pacific yew (Taxus brevifolia); chemicals
extracted from bark treat cancer.
Figure 57.2 Back from Extinction?
In 2004, the ivory-billed woodpecker
was believed to have been glimpsed
in Arkansas after 60 years without a
siting.
Estimating rates of extinction
species–area relationship: As area
decreases, number of species
decreases.
~ 90% loss in habitat  ~ 50% loss of species
57.2 How Do Biologists Predict Changes in Biodiversity?
The current rate of loss of tropical
evergreen forest (the most species-rich
biome) is about 2 percent per year.
If this rate of loss continues, at
least 1 million species will be
lost from this biome in this
century.
Figure 57.3 Deforestation Rates are High in Tropical Forests
57.3 What Human Activities Threaten Species Survival?
• Habitat destruction
• Introduction of exotic species
• Overexploitation
• Climate change
Figure 57.4 Proportions of U.S. Species Extinct or Threatened
HABITAT LOSS
• most important
cause of
endangerment
in U.S.,
especially in
freshwater
• habitat is
increasingly
fragmented
Figure 57.5 Edge Effects
Small patches can support only
small populations (greater risk of
extinction).
Figure 57.6 Species Losses Have Been Studied in Brazilian Forest Fragments
ANIMATION
Photo 57.20 Clear cuts on private timber land, Coos Bay, OR.
Photo 57.23 Satellite image of Rondonia State, Brazil
1975
1986
1992
Photo 57.19 Remains of southern beech forests burned to create
cattle pasture; southern Chile.
Figure 57.7 Habitat Corridors Facilitate Movement (Part 1)
Figure 57.7 Habitat Corridors Facilitate Movement (Part 2)
Until recently, humans caused extinctions mainly by overhunting.
Some species are still threatened today.
Elephants and rhinoceroses are killed for
their tusks and horns.
Powdered rhinoceros horn is used in
traditional Chinese medicine. An attempt
to replace it with saiga antelope horn
worked so well that it is now
endangered.
Figure 57.8 Endangered by Medical Practices
Intentional & Accidental Invasive Species
They spread widely and become
extremely abundant, often at a cost to
native species.
57.3 What Factors Threaten Species Survival?
• rabbits, intro. to Australia for sport
hunting.
Many small marsupials  competition
with rabbits; predation by introduced
cats, dogs, and foxes
• brown tree snake, Guam 1940s
very high densities now
caused the extinction of 15 bird
species, including three endemics
Figure 57.9 Agent of Extinction
More Examples
Chestnut blight
Dutch elm disease of trees
Avian malaria
Photo 57.9 Tree with Dutch elm disease; Great Falls, MT.
Climate Change  Change in Species Distributions
Global warming will increase average
temperatures by 2°C–5°C by the end
of this century.
Some habitats, such as alpine tundra,
may be completely eliminated.
Increasing sea surface temperatures…problem?
threatening corals
High temperatures cause them to expel
their photosynthetic endosymbiotic
dinoflagellates—called bleaching. Death
can result.
Forty percent of coral reefs worldwide are
likely to be killed off by 2010.
Figure 57.10 Global Warming Threatens Corals
Photo 57.21 Urbanization of a former estuary south of San Francisco, CA.