The effect of fauna passages and landscape characteristics on barrier mitigation success
(English)Manuscript (preprint) (Other academic)
Transport infrastructure can impose significant barriers to movements to many, if not most terrestrial animals. Barrier effects can lead to increased isolation of wildlife populations, which in turn might have demographic effects and even increase genetic differentiation between neighbouring populations. This study attempted to clarify the role of fauna passages and generic landscape patterns for connectivity in fragmented landscapes, and to improve the theoretical basis for future experimental approaches to evaluate the effectiveness of barrier mitigation strategies. Specifically, the issue of whether it would be more effective to construct a single large rather than several small crossing structures (SLOSS) was addressed by this study. Three hypotheses were formulated on the relationship between habitat connectivity, as a prerequisite for genetic exchange, and habitat aggregation and contrast between habitat types. Random landscapes with different combinations of aggregation, contrast and number and size of fauna passages were created in a GIS. Connectivity was then quantified as a function of movement resistance using circuit theory and related methods, and measurements from the random landscapes were statistically analysed. The results indicate that in any landscape, it would be more effective to construct several small fauna passages instead of a single large one to mitigate the effect of a barrier. The level of aggregation appeared to have no influence per se on connectivity, and increasing the level of contrast increased the variance in the results. Results indicate that the effectiveness of a fauna passage will to a large extent rely on the location of a fauna passage relative to how the mitigation target species perceive the landscape in terms of contrast between different habitat types. A predefined interval between fauna passages could therefore result in highly ineffective mitigation, in a situation where a fauna passage would be located in habitat perceived as of high resistance. It is recommended that barrier effect mitigation strategies focus on the location and design of several small fauna passages rather than a single large one. Future research should focus on the development of dispersal and movement models for a set focal species that perceive a minimum degree of contrast between habitat types.
Fauna passages, Barrier effects, Mitigation, SLOSS, Transport Infrastructure
Research subject Land and Water Resources Engineering
IdentifiersURN: urn:nbn:se:kth:diva-176395OAI: oai:DiVA.org:kth-176395DiVA: diva2:866662
FunderSwedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 242-2009-1285