Habitat loss and the habitat fragmentation threshold: An experimental evaluation of impacts on richness and total abundances using grassland invertebrates

M. Parker, R. Mac Nally

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68 Citations (Scopus)

Abstract

Based on empirical analyses and computer-based modelling, it has been suggested that the impact of habitat loss is essentially independent of habitat fragmentation when >10–30% of the original habitat is left and that habitat fragmentation is influential only when less that this amount remains. This is the threshold effect of habitat fragmentation. In many systems, effects of habitat loss cannot be distinguished from those of habitat fragmentation in a way needed to critically evaluate the existence of the threshold effect. Therefore, we used an experimental model system (EMS) that was constructed to produce multiple micro-landscapes in which the habitat-loss and habitat-fragmentation impacts were potentially distinguishable. We used responses of terrestrial invertebrates to measure the impacts. We did not find an interaction between habitat-loss and habitat-fragmentation effects in the predicted fashion, although it is possible the threshold of habitat loss we used for the experiments (90%) may have still been above a critical level for the invertebrates. The only significant components were a strong ‘edge–centre’ difference in both richness and abundance, and a temporal change in both variables. Thus, in this EMS, there was little support for the threshold phenomenon or for general effects of habitat loss and fragmentation although this conclusion needs to be tempered by the limited duration of the experiment.
Original languageEnglish
Pages (from-to)217-229
Number of pages13
JournalBiological Conservation
Volume105
Issue number2
DOIs
Publication statusPublished - 2002

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habitat loss
habitat fragmentation
habitat destruction
invertebrate
grasslands
grassland
invertebrates
evaluation
experiment
effect
duration
habitat
habitats
modeling

Cite this

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title = "Habitat loss and the habitat fragmentation threshold: An experimental evaluation of impacts on richness and total abundances using grassland invertebrates",
abstract = "Based on empirical analyses and computer-based modelling, it has been suggested that the impact of habitat loss is essentially independent of habitat fragmentation when >10–30{\%} of the original habitat is left and that habitat fragmentation is influential only when less that this amount remains. This is the threshold effect of habitat fragmentation. In many systems, effects of habitat loss cannot be distinguished from those of habitat fragmentation in a way needed to critically evaluate the existence of the threshold effect. Therefore, we used an experimental model system (EMS) that was constructed to produce multiple micro-landscapes in which the habitat-loss and habitat-fragmentation impacts were potentially distinguishable. We used responses of terrestrial invertebrates to measure the impacts. We did not find an interaction between habitat-loss and habitat-fragmentation effects in the predicted fashion, although it is possible the threshold of habitat loss we used for the experiments (90{\%}) may have still been above a critical level for the invertebrates. The only significant components were a strong ‘edge–centre’ difference in both richness and abundance, and a temporal change in both variables. Thus, in this EMS, there was little support for the threshold phenomenon or for general effects of habitat loss and fragmentation although this conclusion needs to be tempered by the limited duration of the experiment.",
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AB - Based on empirical analyses and computer-based modelling, it has been suggested that the impact of habitat loss is essentially independent of habitat fragmentation when >10–30% of the original habitat is left and that habitat fragmentation is influential only when less that this amount remains. This is the threshold effect of habitat fragmentation. In many systems, effects of habitat loss cannot be distinguished from those of habitat fragmentation in a way needed to critically evaluate the existence of the threshold effect. Therefore, we used an experimental model system (EMS) that was constructed to produce multiple micro-landscapes in which the habitat-loss and habitat-fragmentation impacts were potentially distinguishable. We used responses of terrestrial invertebrates to measure the impacts. We did not find an interaction between habitat-loss and habitat-fragmentation effects in the predicted fashion, although it is possible the threshold of habitat loss we used for the experiments (90%) may have still been above a critical level for the invertebrates. The only significant components were a strong ‘edge–centre’ difference in both richness and abundance, and a temporal change in both variables. Thus, in this EMS, there was little support for the threshold phenomenon or for general effects of habitat loss and fragmentation although this conclusion needs to be tempered by the limited duration of the experiment.

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