The Okanogan Valley of Washington State As a Case Study
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LINKING HABITAT FOR LARGE CARNIVORES BETWEEN THE CASCADES AND THE ROCKY MOUNTAINS: THE OKANOGAN VALLEY OF WASHINGTON STATE AS A CASE STUDY By Paris H McClusky A Thesis Submitted in partial fulfillment of the requirements for the degree Master of Environmental Studies The Evergreen State College June, 2019 i 2019 by Paris H McClusky. All rights reserved. ii This Thesis for the Master of Environmental Studies Degree By Paris H McClusky has been approved for The Evergreen State College by ________________________ Tyrus Smith, PhD Member of Faculty ________________________ Date iii ABSTRACT Linking Habitat for Large Carnivores Between the Cascades and the Rocky Mountains: the Okanogan Valley of Washington State as a Case Study Paris McClusky The Okanogan-Kettle subregion represents a transborder, physiographic ecoregion between the Cascades and the Rocky Mountains in northeast Washington State and southern British Columbia. Canada lynx (Lynx canadensis), wolverines (Gulo gulo), grizzly bears (Ursus arctos) and gray wolves (Canus lupis) currently occupy the east Cascades and the Okanogan Highlands in small, geographically isolated subpopulations. It is important to ensure that viable and connective habitat exists across the region in order to: A) facilitate gene flow between subpopulations, B) maintain sustainable population densities and C) provide long-term, generational demographic exchange between the Cascades and the Rocky Mountains across the Okanogan-Kettle subregion. Resource extraction like mining and clearcutting reduces and degrades existing, suitable habitat for wide-ranging large carnivores. Land conversion for development, infrastructure and to a lesser extent, ranching and agriculture isolates subpopulations, thus preventing gene flow across landscapes. All of these compounding factors result in disconnected and shrinking patches of habitat separated by increasing matrices of human activity. The case study area of interest for this thesis study examines known fracture zone, the Okanogan River Valley and US Highway 97 in Washington State. Infrastructure and development cut off a lateral dispersal opportunity for large carnivores as well as ungulates between the North Cascades and the Kettle Mountains, east of the Okanogan Valley. By constructing fine-grained, small-scale, least-cost corridor models for focal large carnivores: Canada lynx, grizzly bears and gray wolves, this thesis study provides solutions to fragmentation within the fracture zone. Additionally, private lands receive permeability rankings based on levels of residential housing density. This methodology provides a snapshot of the current permeability of private lands for wide- ranging large carnivores and statistical tools to assess the impacts of development on landscape permeability for these focal species over time. iv Table of Contents List of Figures ..................................................................................................................... vi List of Tables .................................................................................................................... viii Acknowledgements ............................................................................................................. ix INTRODUCTION .............................................................................................................. 1 Regional Context ......................................................................................................................... 8 Local context: case study area of interest .................................................................................. 11 LITERATURE REVIEW ................................................................................................. 17 Introduction ............................................................................................................................... 17 Habitat Fragmentation and Climate change .............................................................................. 19 Umbrella Species and Habitat Connectivity .............................................................................. 23 Conservation on the ground: from recommendations to implementation ................................. 35 Conclusion ................................................................................................................................. 42 METHODS ....................................................................................................................... 45 Determining the area of interest for a case study ...................................................................... 45 Analysis of variables within the AOI ........................................................................................ 55 Least-cost distance mapping for focal species across AOI ....................................................... 57 Using census data to determine permeability and conservation potential of private lands ....... 70 RESULTS & DISCUSSION............................................................................................. 75 Priority Habitat and Species areas, focal species occurrence data and climatic ........................ 75 factors ........................................................................................................................................ 75 Focal species least-cost distance maps ...................................................................................... 86 Gray Wolves ........................................................................................................................................ 86 Canada lynx ......................................................................................................................................... 91 Grizzly bear ......................................................................................................................................... 96 Permeability of private property across the AOI ..................................................................... 103 RECOMMENDATIONS FOR MANAGEMENT ......................................................... 114 FUTURE RESEARCH ................................................................................................... 123 CONCLUSION ............................................................................................................... 127 REFERENCES ............................................................................................................... 130 APPENDIX A ................................................................................................................. 139 Models and maps using Euclidean distance as a proxy for development ................................ 139 v List of Figures Figure 1. Ecosystem functions/ecosystem services ............................................................ 5 Figure 2. Three subregions of the transboundary area between the Cascades and the Rocky Mountains .............................................................................................................. 10 Figure 3. Columbia Plateau bottleneck at the Okanogan Valley ...................................... 24 Figure 4. Habitat corridor “naturalness” vs. constructed corridors .................................. 29 Figure 5. Public and private land ownership between the Cascades and the Kettles ....... 46 Figure 6. Linking wildlife across the Okanogan Valley fracture zone ............................. 47 Figure 7. Mean temperature and climate gradient corridors for the transboundary area between Washington State and BC, Canada .................................................................... 50 Figure 8. Wolverine least-cost corridors linking habitat concentration areas. ................. 53 Figure 9. 3D, Digital Elevation Map of western extent of the AOI ................................. 59 Figure 10. 3D, Digital Elevation Map of eastern extent of the AOI ................................. 59 Figure 11. Land cover/land use map of the AOI .............................................................. 60 Figure 12. Land cover types within AOI with associated raster cell values ..................... 61 Figure 13. Two part, habitat suitability and corridor model ............................................. 69 Figure 14. Map of known gray wolf packs within Washington State. ............................. 77 Figure 15. Grizzly bear confirmed occurrences and survey stations in WA and southern BC, Canada. ...................................................................................................................... 78 Figure 16. Focal species ocurrence data and PHS within Okanogan county ................... 79 Figure 17. Focal species occurrence data, protected areas and unprotected areas designated as critical for Priority Habitat and Speceis. .................................................... 80 Figure 18. Fire data and lynx habitat retention within the OLMZ between 2000-2015 ... 81 Figure 19. Canada lynx range contractions/expansion projections within the transboundary area between WA and BC, Canada ........................................................... 82 Figure 20. Wolverine range expansion/contraction projections across the transboundary area between WA and BC, Canada ................................................................................... 84 Figure 21. April 1 snowpack projections for the north east Cascades, the Okanogan Valley and the Kettle River Range ..................................................................................