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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
HUMAN IMPACT
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• Introduced species
Introduced Species
– #2 cause of extinction and loss ofEarth’s biodiversity; cane toads
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HUMAN IMPACT ON ECOSYSTEMS
• Burning of fossil fuels is the mostlikely cause of global warming
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• The increased use of fossil fuels
Impact on the Carbon Cycle
– raises the level of CO2 in the atmosphere
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• Sewage treatment facilities and fertilizers
Impact on the Nitrogen Cycle
– add large amounts of nitrogen and phosphates to aquatic systems, causing heavy growth of algae
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• Destruction oftropical rain forest
Impact on the Water Cycle
– alters local and global weather patterns
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• The Hubbard Brook Experimental Forest is a study site for nutrient cycling in a forest ecosystem
Deforestation and Chemical Cycles: A Case Study
Completion of tree cutting
Altered
Control
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• Humans are adding new toxics to ecosystems and they often cannot be degraded by microorganisms
The Release of Toxic Chemicals to Ecosystems
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• Biological magnification
DDT concentration increase of 10 million times
DDT in fish-eating birds25 ppm
DDT in large fish2 ppm
DDT in small fish0.5 ppm
DDT in zooplankton0.04 ppm
DDT in water0.000003 ppm
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• It was once thought that the atmospherecould absorb our gaseous waste products; smog
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• The ozone layer
Depletion of Atmospheric Ozone
– absorbs UV radiation, preventing most of it from striking organisms in the biosphere
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• Our protectiveozone layer
– started thinning due to the build up of CFCs (chlorofluorocarbons)
(a) Ozone hole
(b) Thickness of ozone layer
Monthly averages for October
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• The consequences of ozone depletion
– are quite severe for all life on Earth
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• The current mass extinction
The Loss of Species
– 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 specieswill be gone by the end of this century
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• 1. Human destruction of habitat
The Three Main Causes of the Biodiversity Crisis
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• 2. Introduced species
Introduced Species
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• 3. Overexploitation of wildlife
Overexploitation
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• Humans rely on biodiversity for
Why Biodiversity Matters
– food, clothing, shelter
– oxygen, soil fertility, medicinal substances
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• Conservation biology
CONSERVATION BIOLOGY
– a goal-oriented science that seeksto counter the loss of biodiversity
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• A biodiversity hot spot
Biodiversity “Hot Spots”
– a relatively small area with anexceptional concentration of species
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Tropical forest hot spots
Chaparral hot spots
Equator
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• Endemic species
– found nowhere else; common in hot spots
– highly sensitive to habitat degradation
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• Much of the discussion of thebiodiversity crisis centers on species
Conservation at the Species Level
• The U.S. Endangered Species Act
– an endangered species is “in danger of extinction throughout all or a significant portion of its range”
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• Conservation biology
Conserving Species amid Conflicting Demands
– deals with relationships between biology and society
• Competing demands for habitat are always an issue
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• Sustainable development
Sustainable Development
– balances human needs withthe health of the biosphere
• The goal of sustainable development
– the long-term prosperity of human societiesand the ecosystems that support them
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Habitat Fragmentation
• Population fragmentation
– the splitting and consequent isolation of portions of populations by habitat destruction
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• A movement corridor
– a narrow strip or series of small clumps of quality habitat connecting otherwise isolated populations
An artificial corridor
Corridors
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• Corridors
– promote dispersal and help sustain populations
– especially important to species thatmigrate between different habitats
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• A zoned reserve
Zoned Reserves
– an extensive region of land that includesone or more areas undisturbed by humans
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• The areas surrounding zoned reserves are buffer zones that support both agriculture and tourism