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HUMAN IMPACT. 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.
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HUMAN IMPACT • 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 ofEarth’s biodiversity; border questions
HUMAN IMPACT ON ECOSYSTEMS • Burning of fossil fuels is the mostlikely 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 oftropical 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 Altered Completion of tree cutting Control
The Release of Toxic Chemicals to Ecosystems • Humans are adding new toxics to ecosystems and they often cannot be degraded by microorganisms
Biological magnification DDT concentration increase of 10 million times DDT in fish-eating birds 25 ppm DDT in large fish 2 ppm DDT in small fish 0.5 ppm DDT in zooplankton 0.04 ppm DDT in water 0.000003 ppm
It was once thought that the atmospherecould 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 • has nothing to do with global warming
Our protectiveozone layer (a) Ozone hole (b) Thickness of ozone layer • started thinning due to the build up of CFCs (chlorofluorocarbons) 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 • boom and echo? • At the current rate of destruction over one half of all plant and animal specieswill be gone by the end of this century
The Three Main Causes of the Biodiversity Crisis • 1. Human destruction of habitat; interaction?
Introduced Species • 2. Introduced species
Overexploitation • 3. Overexploitation of wildlife
Why Biodiversity Matters • Humans rely on biodiversity for • food, clothing, shelter • oxygen, soil fertility, medicinal substances
CONSERVATION BIOLOGY • Conservation biology • a goal-oriented science that seeksto counter the loss of biodiversity
Biodiversity “Hot Spots” • A biodiversity hot spot • a relatively small area with anexceptional concentration of species
Equator 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 thebiodiversity 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 withthe health of the biosphere • The goal of sustainable development • the long-term prosperity of human societiesand the ecosystems that support them
Habitat Fragmentation • Population fragmentation • the splitting and consequent isolation of portions of populations by habitat destruction
Corridors • 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 thatmigrate between different habitats
Zoned Reserves • A zoned reserve • an extensive region of land that includesone or more areas undisturbed by humans
The areas surrounding zoned reserves are buffer zones that support both agriculture and tourism