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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

Landscape from Bjerringbro, Denmark (10×10-km).Insets show increasingly simplified landscapes used in simulations: (A) magnified portion of the original landscape; (B) landscape with homogenized patch shapes, but with unaltered patch sizes and locations. (C) randomly interchanged patch locations, patch shapes as in B. On the landscape scale (but not in the insets) the relative cover of each patch type is unaltered in A–C; (D) randomized patch locations and sizes. Potential dispersal barriers (roads, houses, lakes etc.) were maintained as in the original landscape throughout.
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pone-0008932-g001: Landscape from Bjerringbro, Denmark (10×10-km).Insets show increasingly simplified landscapes used in simulations: (A) magnified portion of the original landscape; (B) landscape with homogenized patch shapes, but with unaltered patch sizes and locations. (C) randomly interchanged patch locations, patch shapes as in B. On the landscape scale (but not in the insets) the relative cover of each patch type is unaltered in A–C; (D) randomized patch locations and sizes. Potential dispersal barriers (roads, houses, lakes etc.) were maintained as in the original landscape throughout.

Mentions: The population simulations were carried out in four different landscapes (a small part of each is shown in Fig. 1A–D). Reference simulations were obtained using a real agricultural landscape (main map in Fig. 1; 1A). Thereafter we progressively reduced landscape complexity by removing the constraints on patch arrangement and sizes imposed by human activities, soil types etc., thereby obtaining decreasingly structured landscapes. First, potential corridors were removed by homogenizing patch shapes (B). Next, patch arrangement was randomized by interchanging homogenized patches of similar sizes (C). Steps B–C resulted in alterations of landscape configuration without changing landscape composition. As similar patches at the same time became more separated, it therefore resulted in increasing landscape fragmentation sensu Fahrig [5]. In the final step (D) patch arrangement was randomized by interchanging homogenized patches irrespective of their sizes. This changed the relative cover of the different patch types (see Fig. S1) and the landscape composition was consequently altered.


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)

Landscape from Bjerringbro, Denmark (10×10-km).Insets show increasingly simplified landscapes used in simulations: (A) magnified portion of the original landscape; (B) landscape with homogenized patch shapes, but with unaltered patch sizes and locations. (C) randomly interchanged patch locations, patch shapes as in B. On the landscape scale (but not in the insets) the relative cover of each patch type is unaltered in A–C; (D) randomized patch locations and sizes. Potential dispersal barriers (roads, houses, lakes etc.) were maintained as in the original landscape throughout.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0008932-g001: Landscape from Bjerringbro, Denmark (10×10-km).Insets show increasingly simplified landscapes used in simulations: (A) magnified portion of the original landscape; (B) landscape with homogenized patch shapes, but with unaltered patch sizes and locations. (C) randomly interchanged patch locations, patch shapes as in B. On the landscape scale (but not in the insets) the relative cover of each patch type is unaltered in A–C; (D) randomized patch locations and sizes. Potential dispersal barriers (roads, houses, lakes etc.) were maintained as in the original landscape throughout.
Mentions: The population simulations were carried out in four different landscapes (a small part of each is shown in Fig. 1A–D). Reference simulations were obtained using a real agricultural landscape (main map in Fig. 1; 1A). Thereafter we progressively reduced landscape complexity by removing the constraints on patch arrangement and sizes imposed by human activities, soil types etc., thereby obtaining decreasingly structured landscapes. First, potential corridors were removed by homogenizing patch shapes (B). Next, patch arrangement was randomized by interchanging homogenized patches of similar sizes (C). Steps B–C resulted in alterations of landscape configuration without changing landscape composition. As similar patches at the same time became more separated, it therefore resulted in increasing landscape fragmentation sensu Fahrig [5]. In the final step (D) patch arrangement was randomized by interchanging homogenized patches irrespective of their sizes. This changed the relative cover of the different patch types (see Fig. S1) and the landscape composition was consequently altered.

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