Variability in population abundance and the classification of extinction risk

Wilson, Howard B., Kendall, Bruce E. and Possingham, Hugh P. (2011) Variability in population abundance and the classification of extinction risk. Conservation Biology, 25 4: 747-757. doi:10.1111/j.1523-1739.2011.01671.x

Author Wilson, Howard B.
Kendall, Bruce E.
Possingham, Hugh P.
Title Variability in population abundance and the classification of extinction risk
Journal name Conservation Biology   Check publisher's open access policy
ISSN 0888-8892
Publication date 2011-08
Sub-type Article (original research)
DOI 10.1111/j.1523-1739.2011.01671.x
Volume 25
Issue 4
Start page 747
End page 757
Total pages 11
Place of publication Hoboken, NJ, United States
Publisher Wiley-Blackwell Publishing
Collection year 2012
Language eng
Formatted abstract
Classifying species according to their risk of extinction is a common practice and underpins much conservation activity. The reliability of such classifications rests on the accuracy of threat categorizations, but very little is known about the magnitude and types of errors that might be expected. The process of risk classification involves combining information from many sources, and understanding the quality of each source is critical to evaluating the overall status of the species. One common criterion used to classify extinction risk is a decline in abundance. Because abundance is a direct measure of conservation status, counts of individuals are generally the preferred method of evaluating whether populations are declining. Using the thresholds from criterion A of the International Union for Conservation of Nature (IUCN) Red List (critically endangered, decline in abundance of >80% over 10 years or 3 generations; endangered, decline in abundance of 50-80%; vulnerable, decline in abundance of 30-50%; least concern or near threatened, decline in abundance of 0-30%), we assessed 3 methods used to detect declines solely from estimates of abundance: use of just 2 estimates of abundance; use of linear regression on a time series of abundance; and use of state-space models on a time series of abundance. We generated simulation data from empirical estimates of the typical variability in abundance and assessed the 3 methods for classification errors. The estimates of the proportion of falsely detected declines for linear regression and the state-space models were low (maximum 3-14%), but 33-75% of small declines (30-50% over 15 years) were not detected. Ignoring uncertainty in estimates of abundance (with just 2 estimates of abundance) allowed more power to detect small declines (95%), but there was a high percentage (50%) of false detections. For all 3 methods, the proportion of declines estimated to be >80% was higher than the true proportion. Use of abundance data to detect species at risk of extinction may either fail to detect initial declines in abundance or have a high error rate.
Keyword IUCN
Population decline
Red list
State-space model
Time series
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes "Contributed paper"

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2012 Collection
Ecology Centre Publications
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Citation counts: TR Web of Science Citation Count  Cited 26 times in Thomson Reuters Web of Science Article | Citations
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