Access the full text.
Sign up today, get DeepDyve free for 14 days.
J. Rotenberry, J. Wiens (1985)
Statistical Power Analysis and Community-Wide PatternsThe American Naturalist, 125
N. Andrew, B. Mapstone (1987)
Sampling and the description of spatial pattern in marine ecologyOceanography and Marine Biology, 25
T. Gerrodette (1991)
Models for Power of Detecting Trends: A Reply to Link and HatfieldEcology, 72
R. Lamberson, R. McKelvey, B. Noon, C. Voss (1992)
A Dynamic Analysis of Northern Spotted Owl Viability in a Fragmented Forest LandscapeConservation Biology, 6
J. Skalski, D. McKenzie (1982)
Design for aquatic monitoring programs, 14
W. Hinds (1984)
Towards Monitoring of Long-term Trends in Terrestrial EcosystemsEnvironmental Conservation, 11
A. Solow, J. Steele (1990)
On sample size, statistical power, and the detection of density dependence.Journal of Animal Ecology, 59
M. Belsky (1984)
Environmental Policy Law in the 1980's: Shifting Back the Burden of ProofEcology Law Quarterly, 12
(1984)
On the power of catch per unit effort series to detect declines in WMe stocks . Report of the International Whaling Commission
P. Holgate, H. Caswell (1990)
Matrix Population Models.Biometrics, 46
J. Barlow, Luis Fleischer, K. Forney, Octavio Maravilla-Chavez. (1993)
AN EXPERIMENTAL AERIAL SURVEY FOR VAQUITA (PHOCOENA SINUS) IN THE NORTHERN GULF OF CALIFORNIA, MEXICOMarine Mammal Science, 9
T. Gerrodette (1987)
A POWER ANALYSIS FOR DETECTING TRENDSEcology, 68
C. Howson, P. Urbach (1989)
Scientific Reasoning: The Bayesian Approach
Timothy Halverson, J. Teare (1989)
Carfentanil and Overwinter Survival in Bison: The Alternative Hypothesis, 25
J. Quinn, A. Dunham (1983)
On Hypothesis Testing in Ecology and EvolutionThe American Naturalist, 122
S. Buckland, K. Burnham, David Anderson, J. Lake (1981)
Wildlife Monographs: Estimation of Density from Line Transect Sampling of Biological PopulationsJournal of Animal Ecology, 50
R. Peterman (1990)
Statistical Power Analysis can Improve Fisheries Research and ManagementCanadian Journal of Fisheries and Aquatic Sciences, 47
C. Toft, Pat Shea (1983)
Detecting Community-Wide Patterns: Estimating Power Strengthens Statistical InferenceThe American Naturalist, 122
R. Peterman (1990)
The Importance of Reporting Statistical Power: The Forest Decline and Acidic Deposition ExampleEcology, 71
A. Franklin, J. Ward, R. Gutiérrez, Gordon Gould (1990)
Density of northern spotted owls in northwest CaliforniaJournal of Wildlife Management, 54
R. Holt, T. Gerrodette, J. Cologne (1987)
RESEARCH VESSEL SURVEY DESIGN FOR MONITORING DOLPHIN ABUNDANCE IN THE EASTERN TROPICAL PACIFIC
D. Parkhurst (1990)
Statistical Hypothesis Tests and Statistical Power in Pure and Applied Science
(1970)
The natural control of a population of T a ~ n y Owls ( S & u ~ w )
J. Berger (1988)
Statistical Decision Theory and Bayesian Analysis
Roger Green (1989)
Power analysis and practical strategies for environmental monitoring.Environmental research, 50 1
(1990)
Population biology and exploitation of the vaquita , Pbocoenu sinus Working paper SU 4 uSM 24
L. Eberhardt, J. Thomas (1991)
Designing Environmental Field StudiesEcological Monographs, 61
P. Green, B. Winer, Donald Brown, K. Michels (1963)
Statistical Principles in Experimental Design
H. Cyr, J. Downing, S. Lalonde, S. Baines, M. Pace (1992)
Sampling Larval Fish Populations: Choice of Sample Number and SizeTransactions of The American Fisheries Society, 121
B. Noon, C. Biles (1990)
Mathematical demography of spotted owls in the Pacific northwestJournal of Wildlife Management, 54
J. Hayes (1987)
The positive approach to negative results in toxicology studies.Ecotoxicology and environmental safety, 14 1
R. Peterman, M. Bradford (1987)
Statistical Power of Trends in Fish AbundanceCanadian Journal of Fisheries and Aquatic Sciences, 44
(1988)
Factors atfecring the recovery of P h o c o m sinus , the vaquita or Gulf of California harbor porpoise
The consequences of accepting a false null hypothesis can be acute in conservation biology because endangered populations leave little margin for recovery from incorrect management decisions. The concept of statistical power provides a method of estimating the probability of accepting a false null hypothesis. We illustrate how to calculate and interpret statistical power in a conservation context with two examples based on the vaquita (Phocoena sinus), an endangered porpoise, and the Northern Spotted Owl (Strix occidentalis caurina). The vaquita example shows how to estimate power to detect negative trends in abundance. Power to detect a decline in abundance decreases as populations become smaller, and, for the vaquita, is unacceptably low witin the range of estimated population sizes. Consequently, detection of a decline should not be a necessary criterion for enacting conservation measures for rare species. For the Northern Spotted Owl, estimates of power allow a reinterpretation of results of a previous demographic analysis that concluded the population was stable. We find that even if the owl population had been declining at 4% per year, the probability of detecting the decline was at most 0.64, and probably closer to 0.13; hence, concluding that the population was stable was not justified. Finally, we show how calculations of power can be used to compare different methods of monitoring changes in the size of small populations. The optimal method of monitoring Northern Spotted Owl populations may depend both on the size of the study area in relation to the effort expended and on the density of animals. At low densities, a demographic approach can be more powerful than direct estimation of population size through surveys. At higher densities the demographic approach may be more powerful for small populations, but surveys are more powerful for populations larger than about 100 owls. The tradeoff point depends on density but apparently not on rate of decline. Power decreases at low population sizes for both methods because of demographic stochasticity.
Conservation Biology – Wiley
Published: Sep 1, 1993
Read and print from thousands of top scholarly journals.
Already have an account? Log in
Bookmark this article. You can see your Bookmarks on your DeepDyve Library.
To save an article, log in first, or sign up for a DeepDyve account if you don’t already have one.
Copy and paste the desired citation format or use the link below to download a file formatted for EndNote
Access the full text.
Sign up today, get DeepDyve free for 14 days.
All DeepDyve websites use cookies to improve your online experience. They were placed on your computer when you launched this website. You can change your cookie settings through your browser.