Plant Distributions in the Southwestern United States: A Scenario Assessment of the Modern-Day and Future Distribution Ranges of 166 Species By Kathryn A. Thomas, Patricia P. Guertin, and Leila Gass Open-File Report 2012–1020 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Thomas, K.A., Guertin, P.P., and Gass, L., 2012, Plant distributions in the southwestern United States; a scenario assessment of the modern-day and future distribution ranges of 166 species: U.S. Geological Survey Open-File Report 2012–1020, 83 p. and 166-page appendix, available at http://pubs.usgs.gov/of/2012/1020/. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Contents Abstract ....................................................................................................................................................................... 1 Introduction ................................................................................................................................................................. 1 Purpose and Scope of Study ................................................................................................................................... 1 Background Information .......................................................................................................................................... 2 The Study Area ....................................................................................................................................................... 3 Methods ...................................................................................................................................................................... 3 Modeling Environment ............................................................................................................................................. 3 Model Input Data Sources and Initial Processing .................................................................................................... 3 Plant Species and their Occurrence Locations .................................................................................................... 3 Modern-day Climate Data .................................................................................................................................... 6 Future Climate Scenarios .................................................................................................................................... 6 Model Development................................................................................................................................................. 7 Suitable Habitats: Modern-day and Future scenarios ............................................................................................ 10 Model Agreement for Suitability Classes ............................................................................................................... 10 Species’ Vulnerability, Potential, and Risk Categories .......................................................................................... 10 Results ...................................................................................................................................................................... 11 Model Performance Metrics ................................................................................................................................... 11 Suitable Habitats—Modern-day and Future Scenarios .......................................................................................... 12 Species’ Vulnerability, Potential, and Risk Categories .......................................................................................... 16 Species Vulnerability to Loss of Modern-day Suitable Habitat ........................................................................... 16 Species Potential to Gain Suitable Habitat ........................................................................................................ 18 Relative Risk ...................................................................................................................................................... 19 Summary and Discussion ......................................................................................................................................... 24 Factors in Interpreting Results ........................................................................................................................... 25 Next Steps ......................................................................................................................................................... 26 Acknowledgments ..................................................................................................................................................... 27 References Cited ...................................................................................................................................................... 27 Contents of the Appendixes ...................................................................................................................................... 29 Appendix A Assessment results for the 166 plant species: Summary tables ........................................................ 29 Appendix B Assessment results for the 166 plant species: Spatial models ....................................................... 29 Appendix A Assessment Results for the 166 Plant Species: Summary Tables ..................................................... 34 Appendix B Assessment Results for the 166 Plant Species: Spatial Models Figures 1 to 166. ................................ 83 Figures 1. Map showing Southwest study area and ecoregions. .......................................................................................... 4 2. Example of map results reported for each species in appendix B. .................................................................... 15 iii Tables 1. Field studies supplying species’ location data. ..................................................................................................... 5 2. 2007 Intergovernmental Panel on Climate Change scenarios represented by Climate Wizard climate grids and used to predict future suitable habitat. ........................................................................................................... 7 3. General circulation models incorporated into Climate Wizard climate grids used to predict future suitable habitat. .................................................................................................................................................................. 8 4. Climate scenarios used to predict suitable habitat for modern-day and future conditions. ................................... 9 5. Future suitable habitat (SH) suitability classes and their relations to modern-day and future model suitability predictions. ........................................................................................................................................................ 10 6. Species were assigned to one of nine risk categories that represented three levels of vulnerability to loss of modern-day habitat and three levels of potential to gain of new habitat. ............................................................ 12 7. An illustrative subsection of summary data presented in appendix A, table 1. .................................................. 13 8. An illustrative subsection of summary data presented in appendix A, table 2. .................................................. 14 9. The average percentage and standard deviation for tree, shrub, and grass species of the total area predicted for each suitability class by all three model results concurrently to the total areas predicted by all three combined. ................................................................................................................................................. 16 10. An illustrative subsection of summary data presented in appendix A, Model agreement for future suitable habitat . .............................................................................................................................................................. 17 11. An illustrative subsection of summary data presented in appendix A, table 4 for the suitable habitat (SH) vulnerability and potential scores for a species. ................................................................................................ 18 12. Assignment of tree species to risk categories. ................................................................................................... 20 13. Assignment of shrub species to risk categories. ...............................................................................................