Determinants of local population size in patchy habitats

Fahrig, Lenore; Paloheimo, J. E.

doi:10.1016/0040-5809(88)90042-1

Cited by 121 publications

(73 citation statements)

References 32 publications

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“…Above the threshold the primary consequence of habitat removal is a decrease in the area of available habitat, and below the threshold the landscape is effectively disconnected into isolated patches of habitat ). This depends not only on the size of habitat patches and their degree of isolation (Dunning et al 1992;Andren 1994), but also on the dispersal characteristics of the species utilising the patches (Fahrig and Paloheimo 1988). During this study many sightings of koalas and their signs (pellets and tree scratches) were made in isolated trees and traversing cleared land and grasslands.…”

Section: Habitat Clearancementioning

confidence: 99%

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Sullivan¹,

Baxter²,

Lisle³

et al. 2004

Wildl. Res.

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Abstract. Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 ~30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.

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Section: Habitat Clearancementioning

confidence: 99%

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Sullivan¹,

Baxter²,

Lisle³

et al. 2004

Wildl. Res.

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“…Incorporating a wider range of habitats in the monitoring, the understanding about species' vegetation preferences will increase. As the ability to move is essential to population viability (Fahrig and Paloheimo, 1988), knowing which landscape features butterflies utilize, e.g. possible corridors, also outside semi-natural grasslands, will improve the ability for a landscapebased conservation effort (Dover and Settele 2009).…”

Section: Comparing Butterfly Distribution In Different Habitatsmentioning

confidence: 99%

Monitoring of butterflies within a landscape context in south-eastern Sweden

Jonason

Milberg

Bergman

2010

Journal for Nature Conservation

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SummaryMonitoring of butterflies is often directed only towards grassland fauna. Species associated with other habitats, as well as the impact of the surrounding landscape, are often neglected. The aim with this study was, in contrast, to perform and evaluate a landscape-based monitoring method for butterflies in diverse habitats and more specifically (i) to evaluate the impact of environmental variables on butterfly abundance, (ii) to compare the distribution of butterflies in different habitats, and (iii) to analyse data from the study with the aim of improving the method. Eight randomly placed study sites (750 m x 750 m) located in south-eastern Sweden were used. The vegetation composition (tree cover, percentage of coniferous and deciduous forest, shrubs, dry, mesic, damp and wet land) inside the squares was analysed using aerial photos and habitats along transects were categorized in the field. The butterfly composition varied depending on the landscape composition. Tree cover had the largest impact on butterfly abundance with a negative relationship between abundance and increasing tree cover. The most species-rich habitats were other grasslands (abandoned fields and fallows), clear-cuts, semi-natural grasslands, and bogs, each habitat also harbouring unique species. Clear-cut was the habitat harbouring the highest abundance and other grasslands the highest diversity of butterflies. Semi-natural grasslands, where the nationally-based monitoring of butterflies in Sweden currently is being performed, constitutes <1% of the total land area in Sweden, indicating a current bias in monitoring directed towards only a part of the species pool. The landscape-based kind of monitoring presented here can, if performed regularly, increase our knowledge of how 3 structural changes of landscape affect butterflies and thereby improve conservation efforts.

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“…This leaves the difficult situation of four processes potentially varying at once. However, simulation and empirical studies have shown that immigration increases the size of local populations (Connor et al 1983, Rey and Strong 1983, Fahrig and Merriam 1985, Fahrig and Paloheimo 1988, Venier and Fahrig 1996, and it is frequently suggested that immigration has important effects on population density in habitat fragments. Immigration is especially important for population density in shortterm experiments of the sort reviewed by Debinski and Holt (2000) because the effect of individuals dispersing from an experimentally created matrix into habitat patches is probably strongest during the few years following habitat removal.…”

Section: Introductionmentioning

confidence: 99%

Patch Size and Population Density: the Effect of Immigration Behavior

Bowman¹,

Cappuccino²,

Fahrig³

2002

Self Cite

138

123

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ABSTRACT. Many habitat fragmentation experiments make the prediction that animal population density will be positively related to fragment, or patch, size. The mechanism that is supposed to result in this prediction is unclear, but several recent reviews have demonstrated that population density often is negatively related to patch size. Immigration behavior is likely to have an important effect on population density for species that do not show strong edge effects, for species that have low emigration rates, and during short-term habitat fragmentation experiments. We consider the effect that different kinds of immigration behaviors will have on population density and we demonstrate that only a minority of possible scenarios produce positive density vs. patch size relationships. More commonly, these relationships are expected to be negative. Our results demonstrate the importance of considering autecological mechanisms, such as immigration behavior, when developing the predictions that we test in habitat fragmentation or other experiments.

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Determinants of local population size in patchy habitats

Cited by 121 publications

References 32 publications

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Low-density koala (Phascolarctos cinereus) populations in the mulgalands of south-west Queensland. IV. Abundance and conservation status

Monitoring of butterflies within a landscape context in south-eastern Sweden

Patch Size and Population Density: the Effect of Immigration Behavior

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