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The effect of fauna passages and landscape characteristics on barrier mitigation success
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment)
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.ORCID iD: 0000-0002-1640-8946
(English)Manuscript (preprint) (Other academic)
Abstract [en]

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.

Keyword [en]
Fauna passages, Barrier effects, Mitigation, SLOSS, Transport Infrastructure
National Category
Ecology
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-176395OAI: oai:DiVA.org:kth-176395DiVA: diva2:866662
Projects
GESP
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 242-2009-1285
Available from: 2015-11-03 Created: 2015-11-03 Last updated: 2015-11-03Bibliographically approved
In thesis
1. Road Ecology for Environmental Assessment
Open this publication in new window or tab >>Road Ecology for Environmental Assessment
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transport infrastructure is closely linked to several politically relevant sustainability issues, and since 1985 a formalized environmental assessment process is linked to planning and construction of new roads and railways in the EU (EU directives 85/337/EEC and 2001/42). The aim of the environmental assessment process is to think in advance; to identify, predict and evaluate significant environmental changes resulting from a proposed activity, in order to adjust the proposed activity accordingly and to avoid unnecessary and unexpected consequences. Biodiversity is a component of sustainable development that is in many ways affected by road and railway construction, but which has been challenging to fully account for within the environmental assessment process. This thesis presents four studies on the role of biodiversity in environmental assessment of road and railway plans and projects. Paper I presents the state of the art of road and railway impacts on ecological patterns and processes sustaining biodiversity, and reviews the treatment of biodiversity in a selection of environmental assessment reports from Sweden and the UK. Paper II presents a quantitative assessment of the impact of the Swedish road network on birds and mammals, and how fragmentation and road disturbance might affect a selection of ecological profiles. Paper III demonstrates how scientific models, data and knowledge can be mobilized for the design and evaluation of railway corridors, and Paper IV analyses how habitat connectivity, as a prerequisite of genetic exchange, relates to landscape composition and size and number of fauna passages. The results from Paper I show that road and railway impacts on biodiversity need to be addressed at every level of planning; from corridor alignment in the landscape to utilization and maintenance. The review of environmental assessment reports shows that the treatment of biodiversity in environmental assessment has improved over the years, but that problems with habitat fragmentation, connectivity and the spatial delimitation of the impact assessment study area remain. The results from Paper II identify natural grasslands and southern broadleaved forest, prioritized habitat types important for biodiversity, to most likely be highly affected by road impacts, and suggest road disturbance to have a high impact on overall habitat availability. The results from Paper III demonstrate how the landscape specific distribution of ecological and geological resources can be accounted for in railway corridor design, and potentially lead to more resource efficient outcomes with less impact on ecological processes. The results from Paper IV indicate that the several small fauna passages would increase connectivity more across a barrier than the construction of a single large. Effective barrier mitigation will also depend on the selection of focal species and the understanding of how the focal species perceive the landscape in terms of resistance to movement. This thesis demonstrates how quantitative assessment can benefit biodiversity impact analysis and address issues such as habitat connectivity and fragmentation, which have been difficult to account for in environmental assessment. It is recommended that biodiversity impact analysis moves towards an increasing use of quantitative methods and tools for prediction, evaluation and sensitivity analysis. Future challenges include verification and calibration of relevant spatial ecological models, and further integration of road ecology knowledge into road and railway planning.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 51 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2015:06
Keyword
Roads, Railways, Biodiversity, Environmental Assessment, GIS, Decision Support
National Category
Environmental Sciences
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-176399 (URN)978-91-7595-746-3 (ISBN)
Public defence
2015-11-25, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Projects
GESP
Funder
Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, 242-2009-1285
Note

QC 20151103

Available from: 2015-11-03 Created: 2015-11-03 Last updated: 2015-11-03Bibliographically approved

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Mörtberg, Ulla

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