Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8268
Title: Temporal correlations in population trends:Conservation implications from time-series analysis of diverse animal taxa
Author: David M. Keith, H. Resit Akcakaya, Stuart H.M. Butchart, Ben Collen, Nicholas K. Dulvy, E. E. Holmes, J. A. Hutchings, Doug Keinath, Michael K. Schwartz, Andrew O. Shelton, Robin S. Waples
Publication Year: 2015
Journal: Biological Conservation
Keywords: endangered species,decline,population growth rates,simulation model,time series

Population trends play a large role in species risk assessments and conservation planning, and species are often considered threatened if their recent rate of decline meets certain thresholds, regardless how large the population is.  But how reliable an indicator of extinction risk is a single estimate of population trend?  Given the integral role this decline-based approach has played in setting conservation priorities, it is surprising that it has undergone little empirical scrutiny.  We compile an extensive global dataset of time series of abundance data for over 1300 vertebrate populations to provide the first major test of the predictability of population growth rates in nature.  We divided each time series into assessment and response periods and examined the correlation between growth rates in the two time periods.  In birds, population declines tended to be followed by further declines, but mammals, salmon, and other bony fishes showed the opposite pattern:  past declines were associated with subsequent population increases, and vice versa.  Furthermore, subsequent growth rates were higher when initial declines were more severe.  These patterns agreed with those in data simulated under a null model for a dynamically stable population experiencing density dependence.  However, this type of result could also occur if conservation actions positively affected the population following initial declines—a scenario that our data were too limited to rigorously evaluate.  This ambiguity emphasizes the importance of understanding the underlying causes of population trajectories in drawing inferences about rates of decline in abundance.

Theme: Recovery and rebuilding of marine and coastal species
Official Citation:

Keith, D.M., H.R. Akcakaya, S.H.M. Butchart, B. Collen, N. K. Dulvy, E. E. Holmes, J. A. Hutchings, D. Keinath, M. K. Schwartz, A. O. Shelton, and R. S. Waples.  2015.  Temporal correlations in population trends:  Conservation implications from time-series analysis of diverse animal taxa.  Biological Conservation 192:247-257.