A Biodiversity and Conservation Assessment of the Edwards Plateau Ecoregion June 2004 © The Nature Conservancy This document may be cited as follows: The Nature Conservancy. 2004. A Biodiversity and Conservation Assessment of the Edwards Plateau Ecoregion. Edwards Plateau Ecoregional Planning Team, The Nature Conservancy, San Antonio, TX, USA. Acknowledgements Jasper, Dean Keddy-Hector, Jean Krejca, Clifton Ladd, Glen Longley, Dorothy Mattiza, Terry The results presented in this report would not have Maxwell, Pat McNeal, Bob O'Kennon, George been possible without the encouragement and Ozuna, Jackie Poole, Paula Power, Andy Price, assistance of many individuals and organizations. James Reddell, David Riskind, Chuck Sexton, Cliff Most of the day-to-day work in completing this Shackelford, Geary Shindel, Alisa Shull, Jason assessment was done by Jim Bergan, Bill Carr, David Singhurst, Jack Stanford, Sue Tracy, Paul Turner, O. Certain, Amalie Couvillion, Lee Elliott, Aliya William Van Auken, George Veni, and David Wolfe. Ercelawn, Mark Gallyoun, Steve Gilbert, Russell We apologize for any inadvertent omissions. McDowell, Wayne Ostlie, and Ryan Smith. Finally, essential external funding for this work This project also benefited significantly from the came from the Department of Defense and the U. S. involvement of several current and former Nature Army Corps of Engineers through the Legacy Grant Conservancy staff including: Craig Groves, Greg program. Without this financial support, many of the Lowe, Robert Potts, and Jim Sulentich. Thanks for critical steps in the planning process might not have the push and encouragement. Our understanding of ever been completed. Thank you. the conservation issues important to the Edwards Plateau was greatly improved through the knowledge and experiences shared by many Conservancy staff including Angela Anders, Gary Amaon, Paul Barwick, Paul Cavanagh, Dave Mehlman, Laura Sanchez, Dan Snodgrass, Steve Jester, Bea Harrison, Jim Harrison, and Nurani Hogue. A large number of scientific professionals from academia, government agencies, and non- governmental organizations in a variety of fields were integral to developing the database upon which these portfolios are based. We’d like to thank each of © Lynn McBride/ The Nature Conservancy the following individuals for the effort expended and the patience exhibited in working to complete this important task: John Abbott, Nathan Allan, Bill Armstrong, Keith Arnold, John Baccus, David Bezanson, Keith Blair, Timothy Bonner, David Bowles, Kathy Boydston, Joe Chapa, John Cornelius, Krishna Costello, David Diamond, Robert Dowler, Barbara Dugelby, Robert Edwards, William Elliot, Craig Farquhar, Gary Garrett, Fran Gelwick, Joe Grzybowski, Tim Hayden, David Hillis, Susan Hovorka, Robert Howells, Clark Hubbs, Sharon Edwards Plateau Biodiversity Assessment I Executive Summary capture examples of the biodiversity associated with those explicitly represented. Our approach Ecoregional biodiversity assessment is a global emphasizes the identification of large landscapes that objective of The Nature Conservancy. With these are more likely to be able to maintain the critical assessments we are developing a global “blueprint” ecological processes important to ecosystem for successfully implementing our conservation function. vision: To conserve portfolios of functional The resultant portfolio of areas includes 102 conservation areas within and across ecoregions. terrestrial areas of biodiversity significance and 62 Through this portfolio approach, we will work with aquatic areas and stream/river segments. Each area partners to conserve the full array of ecological represents one or more examples of a species, systems and viable native communities and species. community, or ecosystem of conservation concern. The Edwards Plateau of central Texas includes a Conservation goals in terms of both abundance variety of well-known Texas features. The terrestrial and distribution have been met for 29 of 275 (11%) and aquatic environments found here are home to a species, communities or ecosystems of conservation rich diversity of plants and animals, many of which concern. Data and research gaps were identified for occur in this ecoregion and nowhere else on the several taxonomic groups and individual targets. We planet. The Edwards Plateau is truly a unique place, also identified some key and widespread threats to even from a global perspective. biodiversity in these areas. The most prominent The Edwards Plateau is also one of the fastest threats include overgrazing, excessive herbivory, developing regions in the United States. The altered fire regime, residential/urban development, Conservancy recognizes the complexity of this region and fragmentation. Finally, we assessed the current not only in a biological context but also in a status of biodiversity conservation in the Edwards socioeconomic setting. Just as there are unique Plateau by comparing our portfolio to a set of known species of plants and animals within the region, so areas under varying degrees of conservation too are there unique population, economic, cultural, management. Our results suggest that approximately and social attributes. To meet our mission we must 4% of the identified terrestrial portfolio and 2% of frame our conservation action within the acceptable the aquatic portfolio are already being managed for limits of each community in which we work. If the the conservation of biodiversity. Conservancy is to be successful within the Edwards Areas of biodiversity significance in the Plateau, we must facilitate the means by which portfolios represent places whose collective humans can live productively and sustainably while conservation would help insure that the biological conserving biological diversity. diversity of the Edwards Plateau ecoregion will For this assessment, we used a coarse filter - fine persist over the long term. The Nature Conservancy, filter approach to identify areas of biodiversity acting alone and through diverse partnerships, will significance within the ecoregion. Our goal was to focus its foreseeable future conservation efforts in capture representative examples of a subset of these areas. These are not areas of land acquisition species, communities, and ecosystems, with the priorities. Protection of these areas will necessitate a underlying assumption that in doing so we will also Edwards Plateau Biodiversity Assessment II broad array of conservation actions implemented by private landowners, public natural resource agencies and private conservation organizations. We hope that this assessment will serve as an important resource to guide those cooperative ventures. Note: Most of the data used to develop this assessment and accompanying report can be obtained © Lynn McBride/ The Nature Conservancy by contacting The Nature Conservancy, P.O. Box 1440, San Antonio, Texas 78295 or by calling (210) 224-8774. Edwards Plateau Biodiversity Assessment III TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................................................................ I EXECUTIVE SUMMARY ........................................................................................................................................II I. INTRODUCTION AND ECOLOGICAL SETTING ...........................................................................................1 ECOREGIONS AND THE EDWARDS PLATEAU ...............................................................................................................1 Ecological Setting..................................................................................................................................................1 FOCUSING ON FUNCTIONAL LANDSCAPES ..................................................................................................................3 THE CHANGING LANDSCAPE ......................................................................................................................................4 II. SETTING PRIORITIES........................................................................................................................................6 IDENTIFYING CONSERVATION TARGETS.....................................................................................................................6 CONSERVATION TARGET OCCURRENCES ...................................................................................................................9 Distribution and Scale of Conservation Targets....................................................................................................9 Occurrence Mapping...........................................................................................................................................10 Mapping Aquatic Systems................................................................................................................................................. 11 Conservation Target Screening ...........................................................................................................................12 CONSERVATION GOALS............................................................................................................................................14 Stratification Units ..............................................................................................................................................14 Goal Values .........................................................................................................................................................14