《环境生态学Cha》.ppt

Chapter 7
Conserving BiologicalResources
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Chapter 7 Conserving BiologicalResources
Value of Wild Sumber of species that occur in an area
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The number of species is counted in a gradually enlarged area of sampling, the result is a curve. The number of species rises rapidly at first, but it slows as the area of sampling increases because the same species are encountered again and again.
The species-area curve:
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Figure Preserving 50% of total habitat area often leaves about 90% of the original species remaining alive
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Extinction
Species extinction:
Ecological extinction:
a species has become so rare that it has essentially no role or impact on its ecosystem
a species has died out in a local area
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Change physical environment:
disruption
Examples
Drain swamp, toxic pollution
Change biological environment:
new species
3. Overhunting
4. Secondary extinctions
New predator
Big-game hunting
Loss of food species
Table Four ways that humans cause population decline and species extinction
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One is that small populations may have breeding problems.
The second cause is that small populations are much more easily wiped out by random environmental fluctuations
Two basic causes for this extinction vortex
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The smallest population size needed to stay above the extinction vortex is often called the minimum viable population (MVP)
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Reasons for Decline of Biodiversity
Physical Alteration of Habitats
The Population Factor
Exotic Species
Overuse
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Adopt specific national biodiversity action plans and strategies
Establish a system of protected areas and ecosystems within the country
Establish policies that provide incentives to promote sus­tainable use of biological resources
Convention on Biological Diversity (1992 in Rio de Janeiro)
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Resto