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Using scalar models for precautionary assessments of threatened species

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dc.contributor.author Bridges, Todd S
Akcakaya, H. Resit
Dunham, Amy E
dc.date.accessioned 2008-09-16T21:50:55Z
dc.date.available 2008-09-16T21:50:55Z
dc.date.issued 2006-10
dc.identifier.uri http://hdl.handle.net/1911/21695
dc.description.abstract Scalar population models, commonly referred to as count-based models, are based on time-series data of population sizes and may be useful for screening-level ecological risk assessments when data for more complex models are not available. Appropriate use of such models for management purposes, however, requires understanding inherent biases that may exist in these models. Through a series of simulations, which compared predictions of risk of decline of scalar and matrix-based models, we examined whether discrepancies may arise from different dynamics displayed due to age structure and generation time. We also examined scalar and matrix-based population models of 18 real populations for potential patterns of bias in population viability estimates. In the simulation study, precautionary bias (i.e., overestimating risks of decline) of scalar models increased as a function of generation time. Models of real populations showed poor fit between scalar and matrix-based models, with scalar models predicting significantly higher risks of decline on average. The strength of this bias was not correlated with generation time, suggesting that additional sources of bias may be masking this relationship. Scalar models can be useful for screening-level assessments, which should in general be precautionary, but the potential shortfalls of these models should be considered before using them as a basis for management decisions.
dc.description.sponsorship Hazard/Risk Focus Area of the Army’s Environmental Quality Technology research program NSF
dc.language.iso eng
dc.publisher Blackwell Publishing
dc.subject population viability analysis
threatened species
matrix models
extinction risk
count-based PVA
age structure
dc.title Using scalar models for precautionary assessments of threatened species
dc.type Journal article
dc.type.dcmi Text
dc.identifier.citation Bridges, Todd S, Akcakaya, H. Resit and Dunham, Amy E. (2006). "Using scalar models for precautionary assessments of threatened species."

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