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How sensitive are elasticities of long-run stochastic growth to how environmental variability is modelled?

How sensitive are elasticities of long-run stochastic growth to how environmental variability is modelled?
How sensitive are elasticities of long-run stochastic growth to how environmental variability is modelled?
A variable environment leaves a signature in a population's dynamics. Deriving statistical and mathematical models of how environmental variability affects population projections has – in the wake of reports of substantial climatic fluctuations – received much recent attention. If the model changes, then so too does the population projection. This is because a different model of environmental variability changes estimates of long-run stochastic growth, which is a function of demographic rates and their temporal sequence. Decomposing elasticities of long-run stochastic growth into constituent parts can assess the relative influence of different components. Here, we investigate the consequences of changing the environmental state definition, and therefore altering the shape of demographic rate distributions and their temporal sequence, by using age-structured matrix models to project vertebrate populations into the future under a range of environmental scenarios. The identity of the most influential demographic rate was consistent among all approaches that perturbed only the mean, but was not when only the variance was perturbed. Furthermore, the influence of each demographic rate fluctuated among projections by up to factors of six and two for changes to the variance and mean, respectively. These changes in influence depend in part upon how environmental variability – in particular, the color of environmental noise – is incorporated. In the light of predictions of increasing climatic variability in the future, these results suggest caution when drawing quantitative conclusions from stochastic population projections.
environmental noise, great tit, markov chain, ovis aries, parus major, matrix, perturbation analysis, soay sheep
0304-3800
191-200
Ezard, Thomas H.G.
a143a893-07d0-4673-a2dd-cea2cd7e1374
Coulson, Tim
65301555-92dd-4f85-a66f-cf07cf1aee98
Ezard, Thomas H.G.
a143a893-07d0-4673-a2dd-cea2cd7e1374
Coulson, Tim
65301555-92dd-4f85-a66f-cf07cf1aee98

Ezard, Thomas H.G. and Coulson, Tim (2010) How sensitive are elasticities of long-run stochastic growth to how environmental variability is modelled? Ecological Modelling, 221 (2), 191-200. (doi:10.1016/j.ecolmodel.2009.09.017).

Record type: Article

Abstract

A variable environment leaves a signature in a population's dynamics. Deriving statistical and mathematical models of how environmental variability affects population projections has – in the wake of reports of substantial climatic fluctuations – received much recent attention. If the model changes, then so too does the population projection. This is because a different model of environmental variability changes estimates of long-run stochastic growth, which is a function of demographic rates and their temporal sequence. Decomposing elasticities of long-run stochastic growth into constituent parts can assess the relative influence of different components. Here, we investigate the consequences of changing the environmental state definition, and therefore altering the shape of demographic rate distributions and their temporal sequence, by using age-structured matrix models to project vertebrate populations into the future under a range of environmental scenarios. The identity of the most influential demographic rate was consistent among all approaches that perturbed only the mean, but was not when only the variance was perturbed. Furthermore, the influence of each demographic rate fluctuated among projections by up to factors of six and two for changes to the variance and mean, respectively. These changes in influence depend in part upon how environmental variability – in particular, the color of environmental noise – is incorporated. In the light of predictions of increasing climatic variability in the future, these results suggest caution when drawing quantitative conclusions from stochastic population projections.

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More information

Published date: 24 January 2010
Keywords: environmental noise, great tit, markov chain, ovis aries, parus major, matrix, perturbation analysis, soay sheep
Organisations: Environmental

Identifiers

Local EPrints ID: 344727
URI: http://eprints.soton.ac.uk/id/eprint/344727
ISSN: 0304-3800
PURE UUID: e4e85c54-9492-4f6e-b12e-1182e8c9f8ca
ORCID for Thomas H.G. Ezard: ORCID iD orcid.org/0000-0001-8305-6605

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Date deposited: 31 Oct 2012 15:25
Last modified: 22 Jun 2024 01:46

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Contributors

Author: Thomas H.G. Ezard ORCID iD
Author: Tim Coulson

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