Two paradigms for conservation biology

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Two paradigms for conservation biology
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What is the best way to understand (and correct)
species declines?

• Caughley 1994
• Small population paradigm
• Declining population paradigm

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The small population paradigm

• population consequences of rareness and smallness
• population genetics and population dynamics
  problems of small populations
• responsible for much of the theoretical insights
  into conservation biology

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Tools of the small population paradigm

• Demographic and environmental stochasticity
• Heterozygosity and fitness
• Genetic drift
• Inbreeding depression
• metapopulations
• MVP, MDA
• effective population size, Ne
• PVA
• captive breeding
• reserve design

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Declining population paradigm

• focused on detecting, diagnosing, and halting
  causes of population decline
• present size of population not much concern
• external pressures are considered
• little or no theoretical basis (case by case)

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Tools of the declining population paradigm

• The evil quartet causes of extinction
• overkill
• habitat destruction and fragmentation
• introduced species
• chains of extinction
• Measurements of potential causes in pristine and
  impacted areas

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Management strategies for the small population
paradigm
vague practices with limited real world
applicability
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Successes and failures of the SPP

• MVP no known use
• PVA some success, many examples of misuse
• reintroductions a few successes
• Arabian Oryx EIW in 1972 reintroduced from
  populations in Phoenix zoo
• genetics few examples of important insights
  (authors doubt much of work on Cheetahs)

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Use of the DPP

• Use surveys and experiments to determine agents
  of decline
• Remove or reduce agents of decline
• Release small probe group
• Restock as quickly as possible
• Monitor

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The Lord Howe Wood Hen
Key Good science
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Another view from Krebs (2002)

• Two approaches to understanding population
  fluctuations
• density paradigm (density dependence)
• mechanistic paradigm (like DPP)

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Density paradigm

• works sometimes, but not always
• not very useful for solving management problems
• does not provide insight into why populations
  change size

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Density paradigm
Mechanistic paradigm
growth rate
growth rate
Population size
food
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Managing salmon populations with Ricker curves
Why might these curves differ?
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density relationships are variable over space
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Asquith (2001)
photo by R. Agha
The Javan Gibbon
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Two paradigms

• Which approach seems most effective to you?
• In what ways can implementation of only one
  paradigm lead to problems?
• How can these paradigms be combined?
• Compare the roles of theory and empirical data in
  conservation.