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Title:
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Using scalar models for precautionary assessments of threatened species |
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Author:
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Bridges, Todd S; Akcakaya, H. Resit; Dunham, Amy E
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Abstract:
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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. |
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Citation:
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Bridges, Todd S, Akcakaya, H. Resit and Dunham, Amy E. (2006). "Using scalar models for precautionary assessments of threatened species." http://hdl.handle.net/1911/21695. |
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URI:
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http://hdl.handle.net/1911/21695 |
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Date:
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2006-10 |
