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• One-third of all plant
and vertebrate species
live on just 1.5% of
Earth’s land
• Every year, humans
destroy an area of
tropical rain forest
equal to the size of
West Virginia
Introduced Species
• Introduced species
– #2 cause of extinction and loss of
Earth’s biodiversity; border questions
• Kudzu, a Japanese plant
• Burning of fossil fuels is the most
likely cause of global warming
Impact on the Carbon Cycle
• The increased use of fossil fuels
– raises the level of CO2 in the atmosphere
Impact on the Nitrogen Cycle
• Sewage treatment facilities and fertilizers
– add large amounts of nitrogen and phosphates to
aquatic systems, causing heavy growth of algae
Impact on the Water Cycle
• Destruction of
tropical rain forest
– alters local and global
weather patterns
– the water cycle
Deforestation and Chemical Cycles: A Case Study
• The Hubbard Brook Experimental Forest is a
study site for nutrient cycling in a forest ecosystem
of tree cutting
The Release of Toxic Chemicals to Ecosystems
• Humans are adding new toxics to ecosystems and
they often cannot be degraded by microorganisms
• Biological
DDT concentration
increase of 10
million times
DDT in
25 ppm
DDT in large fish
2 ppm
DDT in
0.5 ppm
DDT in
0.04 ppm
DDT in water
0.000003 ppm
• It was once thought that the atmosphere
could absorb our gaseous waste products; smog
Depletion of Atmospheric Ozone
• The ozone layer
– absorbs UV radiation, preventing most of
it from striking organisms in the biosphere
• Our protective
ozone layer
(a) Ozone hole
(b) Thickness of ozone layer
– started thinning due to
the build up of CFCs
Monthly averages for October
• The consequences of ozone depletion
– are quite severe for all life on Earth
The Loss of Species
• The current mass extinction
– caused by human activity
– broader and faster than other past extinctions
• At the current rate of destruction over
one half of all plant and animal species
will be gone by the end of this century
The Three Main Causes of the Biodiversity Crisis
• 1. Human destruction of habitat
Introduced Species
• 2. Introduced species
• 3. Overexploitation of wildlife
Why Biodiversity Matters
• Humans rely on
biodiversity for
– food, clothing, shelter
– oxygen, soil fertility,
medicinal substances
• Conservation biology
– a goal-oriented science that seeks
to counter the loss of biodiversity
Biodiversity “Hot Spots”
• A biodiversity hot spot
– a relatively small area with an
exceptional concentration of species
Tropical forest hot spots
Chaparral hot spots
• Endemic species
– found nowhere else; common in hot spots
– highly sensitive to habitat degradation
Conservation at the Species Level
• Much of the discussion of the
biodiversity crisis centers on species
• The U.S. Endangered Species Act
– an endangered species is “in danger of extinction
throughout all or a significant portion of its range”
Conserving Species amid Conflicting Demands
• Conservation biology
– deals with relationships between biology and society
• Competing demands for habitat are always an issue
Sustainable Development
• Sustainable development
– balances human needs with
the health of the biosphere
• The goal of sustainable development
– the long-term prosperity of human societies
and the ecosystems that support them
Habitat Fragmentation
• Population fragmentation
– the splitting and
consequent isolation of
portions of populations
by habitat destruction
• A movement corridor
– a narrow strip or series of small clumps of quality
habitat connecting otherwise isolated populations
An artificial corridor
• Corridors
– promote dispersal and help sustain populations
– especially important to species that
migrate between different habitats
Zoned Reserves
• A zoned reserve
– an extensive region of land that includes
one or more areas undisturbed by humans
• The areas surrounding zoned reserves are buffer
zones that support both agriculture and tourism