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Maintaining Habitat Connectivity for Conservation by Bronwyn Rayfield

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Maintaining Habitat Connectivity for Conservation by Bronwyn Rayfield Maintaining Habitat Connectivity for Conservation by Bronwyn Rayfield A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto Copyright c 2009 by Bronwyn Rayfield Abstract Maintaining Habitat Connectivity for Conservation Bronwyn Rayfield Doctor of Philosophy Department of Ecology and Evolutionary Biology University of Toronto 2009 Conserving biodiversity in human-dominated landscapes requires protecting networks of ecological reserves and managing the intervening matrix to maintain the potential for species to move among them. This dissertation provides original insights towards (1) identifying areas for protection in reserves that are critical to maintain biodiversity and (2) assessing the potential for species' movements among habitat patches in a re- serve network. I develop and test methods that will facilitate conservation planning to promote viable, resilient populations through time. The first part of this dissertation tests and develops reserve selection strategies that protect either a single focal species in a dynamic landscape or multiple interact- ing species in a static landscape. Using a simulation model of boreal forest dynamics, I test the effectiveness of static and dynamic reserves to maintain spatial habitat re- quirements of a focal species, American marten (Martes americana). Dynamic reserves improved upon static reserves but re-locating reserves was constrained by fragmenta- tion of the matrix. Management of the spatial and temporal distribution of land-uses in the matrix will therefore be essential to retain options for re-locating reserves in the future. Additionally, to include essential consumer-resource interactions into reserve selection, a new algorithm is presented for American marten and its two primary prey species. The inclusion of their interaction had the benefit of producing spatially aggre- gated reserves based on functional species requirements. ii The second part of this dissertation evaluates and synthesizes the network-theoretic approach to quantify connectivity among habitat patches or reserves embedded within spatially heterogeneous landscapes. I conduct a sensitivity analysis of network-theoretic connectivity analyses that derive least-cost movement behavior from the underlying cost surface which describes the relative ecological costs of dispersing through different landcover types. Landscape structure is shown to affect how sensitive least-cost graph connectivity assessments are to the quality (relative cost values) of landcover types. I develop a conceptual framework to classify network connectivity statistics based on the component of habitat connectivity that they quantify and the level within the network to which they can be applied. Together, the combination of reserve design and network connectivity analyses provide complementary insights to inform spatial planning deci- sions for conservation. iii Acknowledgements My research on the protection of habitat networks would not have been possible with- out a very supportive social network of collaborators, friends, and family. I want to thank, first and foremost, my advisor and mentor Dr. Marie-Jos´eeFortin. Working with her has taught me so much about ecology, research, leadership, and life. I hope to be as good an advisor to my own students one day. I am also thankful to my com- mittee members, Dr. Don Jackson and Dr. Lisa Manne, for their thoughtful sugges- tions and ongoing encouragement. A special thank-you is reserved for my Aunt Jan, an inspirational wildlife biologist and naturalist, who showed me my first caribou and shared her passion for Canadian wilderness with me. This research benefited greatly from my collaborations with Dr. Andrew Fall, Dr. Atte Moilanen, and Dr. Dean Urban. Andrew and I shared many inspiring discussions about my research, particularly at the formative stages, and his sharp thinking helped to clarify and refine many ideas. Atte was a role model for efficiency in writing and he generously shared his insights into conservation planning and his conservation software - Zonation. Dean kindly hosted me at Duke University to share with me his enthusi- asm and ideas about the many conservation applications of graph and network models. Generous financial support for my work was provided by the Natural Sciences and Engineering Research Council of Canada through a Postgraduate Scholarship (PGS- A) and a Canada Graduate Scholarship (CGS) awarded to myself and a Discorvery Grant awarded to my advisor, Dr. Fortin. Additional funding was provided by The Department of Ecology and Evolutionary Biology at the University of Toronto. The Department of Ecology and Evolutionary Biology at the University of Toronto has been a wonderful place to do graduate work. The whole Information Technology Group, and Stephen Smith in particular, were invaluable. I am enormously grateful to all members of Spatial Ecology Lab (LE Lab), especially Patrick James, Aleksan- dra Polakowska, Stephanie Melles, Pilar Hernandez, Alistair MacKenzie, Josie Hughes, iv Jonathan Ruppert, and Allan Brand. It has been a pleasure to share the daily comings and goings of grad life along with major successes and challenges with these people. Many thanks to my lifelong friends - Emily, Melissa, Aleks, Ryan, and Colin - who never let me take myself too seriously. Lastly, thank you to my loved ones: Mom, Dad, Sarah, Marc, Monkey, and Jamie. No words can express what you each mean to me. v Chapter Acknowledgements This thesis is comprised of five co-authored manuscripts that are either published, in press, submitted, or in preparation for peer-reviewed journals (Chapters 1-5). Permis- sions to use published materials in this dissertation have been obtained from the pub- lishers. Experimental design, analyses, and manuscript preparation were all carried out by the principal author and PhD candidate. Co-authors of the chapters contributed conceptual discussions, expertise in computer programming, and editing of written ma- terials. Chapter 1 introduces and provides the motivation for the dissertation. Chapter 6 concludes the dissertation and provides a starting point for future research. 1. Rayfield, B., Fortin, M.-J., Urban, D. (in prep.) A network approach for conser- vation planning in dynamic landscape mosaics. (Chapter 1) 2. Rayfield, B., James, P., Fall, A., and Fortin, M.-J. (2008) Comparing static ver- sus dynamic protected areas in dynamic boreal ecosystems. Biological Conserva- tion 141:438-449. Reprinted with permission from Elsevier. (Chapter 2) 3. Rayfield, B., Moilanen, A., and Fortin, M.-J. (2009) Incorporating consumer- resource spatial interactions in reserve design. Ecological Modelling. 220, 725- 733. Reprinted with permission from Elsevier. (Chapter 3) 4. Rayfield, B., Fortin, M.-J., Fall, A. (accepted with minor revisions March 2009; LAND-08-1820 ) The sensitivity of least-cost habitat graphs to relative cost sur- face values. Landscape Ecology. (Chapter 4) 5. Rayfield, B., Fortin, M.-J., Fall, A. (in prep.) Connectivity for conservation: A framework to classify habitat network connectivity statistics. (Chapter 5) vi Contents 1 Network approach for conservation planning 1 1.1 Introduction . 1 1.1.1 Static and equilibrated landscapes: Island Biogeography Theory . 2 1.1.2 Network models and dynamic landscape mosaics . 4 1.2 Network-theoretical insights into conservation planning and reserve design 5 1.2.1 Assessing the resilience of reserve networks . 5 1.2.2 Network robustness and network structure . 8 1.2.3 Connectivity and resilience in reserve networks . 10 1.3 Conclusion . 11 1.4 Dissertation overview . 12 1.4.1 Chapter 2: Dynamic reserves in a dynamic boreal forest . 12 1.4.2 Chapter 3: Consumer-resource interactions in reserves . 13 1.4.3 Chapter 4: Sensitivity of habitat network connectivity assessments 13 1.4.4 Chapter 5: Quantifying connectivity of habitat networks . 14 1.4.5 Chapter 6: Conclusions and future directions . 14 2 Comparing static versus dynamic reserves 15 2.1 Abstract . 15 2.2 Introduction . 16 2.3 Methods . 20 vii 2.3.1 Study area . 20 2.3.2 Boreal forest landscape dynamics model . 21 2.3.3 Protected areas . 25 2.4 Results . 32 2.5 Discussion . 35 3 Consumer-resource interactions in reserves 41 3.1 Abstract . 41 3.2 Introduction . 42 3.3 Methods . 44 3.3.1 Summary of the Zonation reserve-selection algorithm . 44 3.3.2 Introducing novel spatial consumer-resource interactions into Zona- tion . 49 3.3.3 Case study: predator-prey interaction in the boreal forest of Qu´ebec (Canada) . 51 3.3.4 Reserve-selection scenario comparison with different combinations of species-specific and interaction connectivity layers . 52 3.4 Results . 53 3.5 Discussion . 56 3.6 Conclusion . 62 4 Sensitivity of least-cost habitat graphs 64 4.1 Abstract . 64 4.2 Introduction . 65 4.3 Methods . 71 4.3.1 Generation of artificial landscape spatial patterns . 71 4.3.2 Cost values to quantify resistance to movement . 74 viii 4.3.3 Graph-theoretic representations of habitat connectivity using least- cost links . 75 4.3.4 Measuring the sensitivity of graphs with least-cost links . 79 4.4 Results . 79 4.5 Discussion . 84 4.6 Conclusion . 88 5 Classification of network-connectivity statistics 90 5.1 Abstract . 90 5.2 Introduction . 91 5.3 Background . 93 5.4 Development of methods to construct habitat networks . 97 5.5 Quantifying connectivity in habitat networks . 101 5.6 Classification framework of habitat network connectivity statistics . 102 5.6.1 Network levels of analysis . 103 5.6.2 Components of habitat connectivity . 105 5.7 Missing habitat-network connectivity statistics . 110 5.8 Selecting network connectivity statistics . 113 5.9 Spatio-temporal connectivity in dynamic habitat networks . 113 5.10 Conclusions . 115 6 Conclusions 128 6.1 Thesis summary . 128 6.2 Future research directions . 133 Bibliography 136 ix List of Tables 2.1 Description of alternative protected area (PA) scenarios . 26 3.1 Focal species' habitat, home range, and dispersal parameter estimates . 46 3.2 Differences among reserve-selection scenarios . 54 4.1 Chronological and alphabetical presentation of connectivity studies using a cost surface to identify least-cost routes .
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