Chapter 8.  Sustaining Biodiversity:  The Species Approach

• Types of extinction:
• Local extinction - species extinct in a community, but found in others.
• Ecological extinction - population size so low that species plays no significant ecological role.
• Biological extinction - gone for good.
• Estimating extinction rates
• Some problems:
• Extinction takes a long time and is difficult to document
• Only a fraction of the world's species have been described and studied:
• Total world biodiversity = 5-100 million
• Total decried species = 1.5 million
• Some approaches to estimation of extinction rates:
• Working with species/area curves.  Example.
• Monitoring rates of tropical habitat destruction (because most species are restricted to the tropics).
• What places a species at risk?  See Figure 8-4
• Low reproductive rate
• Narrow niche
• Fixed migratory patterns
• Large breeding territory
• Commercially valuable
• Why preserve species?
• The "goods and services" argument
• Economic goods
• Ecological services
• Ecotourism - what is a lion "worth"?
• The ethical argument
• Causes of extinction
• The fundamental causes are human activities, see the list on p. 168.
• Habitat loss, degradation and fragmentation.
• Introduction of alien species.
• Commercial hunting and poaching
• Overfishing
• Climate change and pollution
• Protecting species
• The legal approach
• Convention on Biological Diversity (an international treaty not ratified by the USA).
• Endangered Species Act (1973, 1982, 1988)
• The sanctuary approach
• Refuges
• Gene banks and botanical gardens
• Zoos and aquariums