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Two paradigms for conservation biology

Two paradigms for conservation biology. What is the best way to understand (and correct) species declines?. Caughley 1994 Small population paradigm Declining population paradigm. The small population paradigm. population consequences of rareness and smallness

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Two paradigms for conservation biology

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  1. Two paradigms for conservation biology

  2. What is the best way to understand (and correct) species declines? • Caughley 1994 • Small population paradigm • Declining population paradigm

  3. 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

  4. 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

  5. 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)

  6. 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

  7. Management strategies for the small population paradigm vague practices with limited “real world” applicability

  8. 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)

  9. 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

  10. The Lord Howe Wood Hen Key: Good science

  11. Another view from Krebs (2002) • Two approaches to understanding population fluctuations • density paradigm (density dependence) • mechanistic paradigm (like DPP)

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

  13. Density paradigm Mechanistic paradigm growth rate growth rate Population size food

  14. Managing salmon populations with Ricker curves Why might these curves differ?

  15. density relationships are variable over space

  16. Asquith (2001) photo by R. Agha The Javan Gibbon

  17. 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.

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