Modelling the negative effects of landscape fragmentation on habitat selection

- Habitat selection in fragmented landscapes deviates from optimal selection.
- With increasing fragmentation, more individuals have to select low-quality habitat.
- Constrained habitat selection results therefore in a lower reproductive output.
- These effects can generate source-sink dynamics in fragmented landscapes.

Landscape fragmentation constrains movement of animals between habitat patches. Fragmentation may, therefore, limit the possibilities to explore and select the best habitat patches, and some animals may have to cope with low-quality patches due to these movement constraints. If so, these individuals experience lower fitness than individuals in high-quality habitat. I explored this negative effect of fragmentation on habitat selection in a modelling study. Model landscapes were generated containing different amounts of habitat with differences in the degree of connectivity. In these landscapes, the behaviour of two model species was simulated with different dispersal ranges. I found that habitat selection of the species with limited dispersal range increasingly deviates from optimal selection when fragmentation increases. This effect of fragmentation on habitat selection largely limits the spatial distribution of species with limited dispersal range because constrained habitat selection is expected to result in lower mean reproductive output when more individuals occur in low-quality habitat. In addition to the often suggested causes for extinction in small, isolated patches, i.e. increased sensitivity to environmental and demographic stochasticity, constrained habitat selection may lead to an increase in extinction probability of populations when a large fraction of the individuals occur in low-quality habitat.

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