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The effects of landscape modifications on the long-term persistence of animal populations.

Nabe-Nielsen J, Sibly RM, Forchhammer MC, Forbes VE, Topping CJ - PLoS ONE (2010)

Bottom Line: Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain.Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance.A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.

View Article: PubMed Central - PubMed

Affiliation: Department of Arctic Environment, National Environmental Research Institute, University of Aarhus, Roskilde, Denmark. nabe@dmu.dk

ABSTRACT

Background: The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition.

Methodology/principal findings: Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place.

Significance: Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.

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Related in: MedlinePlus

Population growth in the original 10×10-km landscape after 95% reductions in population size.Perturbations occurred every 17 years, and points have different colors depending on how many times perturbations had occurred. Weather years (i.e. the year that the weather data originated from) are indicated with different symbols. Curves were fitted using a three-parameter logistic model (four-parameter for skylark).
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pone-0008932-g002: Population growth in the original 10×10-km landscape after 95% reductions in population size.Perturbations occurred every 17 years, and points have different colors depending on how many times perturbations had occurred. Weather years (i.e. the year that the weather data originated from) are indicated with different symbols. Curves were fitted using a three-parameter logistic model (four-parameter for skylark).

Mentions: Yearly population number increased logistically with time following disturbances for beetle, vole, skylark and spider (Fig. 2). Except for the vole, the number (1–10) of times a population was consecutively perturbed by removing a large part of the population had no effect on asymptotic population sizes (K). The logistic growth fluctuated among years with different weather conditions so that K varied between years, especially in the beetle and spider populations. Mean values of K varied among landscapes of different complexity (Fig. 3). Across landscapes low K was associated with long return time φ for the short-dispersing species (r = −0.92 for beetle; r = −0.87 for vole; P<0.01 for both species) whereas the correlation was non-significant for skylark and spider. Increasing disturbance intensities (i.e. removing a larger part of the population) caused large increases in φ, especially for the relatively slow-reproducing vole and skylark.


The effects of landscape modifications on the long-term persistence of animal populations.

Nabe-Nielsen J, Sibly RM, Forchhammer MC, Forbes VE, Topping CJ - PLoS ONE (2010)

Population growth in the original 10×10-km landscape after 95% reductions in population size.Perturbations occurred every 17 years, and points have different colors depending on how many times perturbations had occurred. Weather years (i.e. the year that the weather data originated from) are indicated with different symbols. Curves were fitted using a three-parameter logistic model (four-parameter for skylark).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2812489&req=5

pone-0008932-g002: Population growth in the original 10×10-km landscape after 95% reductions in population size.Perturbations occurred every 17 years, and points have different colors depending on how many times perturbations had occurred. Weather years (i.e. the year that the weather data originated from) are indicated with different symbols. Curves were fitted using a three-parameter logistic model (four-parameter for skylark).
Mentions: Yearly population number increased logistically with time following disturbances for beetle, vole, skylark and spider (Fig. 2). Except for the vole, the number (1–10) of times a population was consecutively perturbed by removing a large part of the population had no effect on asymptotic population sizes (K). The logistic growth fluctuated among years with different weather conditions so that K varied between years, especially in the beetle and spider populations. Mean values of K varied among landscapes of different complexity (Fig. 3). Across landscapes low K was associated with long return time φ for the short-dispersing species (r = −0.92 for beetle; r = −0.87 for vole; P<0.01 for both species) whereas the correlation was non-significant for skylark and spider. Increasing disturbance intensities (i.e. removing a larger part of the population) caused large increases in φ, especially for the relatively slow-reproducing vole and skylark.

Bottom Line: Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain.Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance.A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.

View Article: PubMed Central - PubMed

Affiliation: Department of Arctic Environment, National Environmental Research Institute, University of Aarhus, Roskilde, Denmark. nabe@dmu.dk

ABSTRACT

Background: The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition.

Methodology/principal findings: Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place.

Significance: Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.

Show MeSH
Related in: MedlinePlus