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Wednesday, April 11 • 11:45am - 12:00pm
FOREST LANDSCAPE PROCESSES: Predicting Changes in Gopher Tortoise Habitat Connectivity in Georgia, USA

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AUTHORS: Jeffrey Hepinstall-Cymerman, Warnell School of Forestry and Natural Resources, University of Georgia; T. Prebyl, Warnell School of Forestry and Natural Resources, University of Georgia; B. Nuse, Georgia Cooperative Fish and Wildlife Research Unit, Warnell School of Forestry and Natural Resources, University of Georgia; C. Moore, U.S. Geological Survey and Georgia Cooperative Fish and Wildlife Research Unit, Warnell School of Forestry and Natural Resources, University of Georgia

ABSTRACT: Gopher tortoises require suitable soils and pine or mixed stands with open canopies where light penetrates to a ground layer of forbs and grasses maintained by prescribed fire or mechanical treatment.  Movement is known to be an important process in tortoise populations, although much uncertainty remains regarding general features of dispersal. Because the gopher tortoise is currently being considered for listing under the Endangered Species Act, however, there is immediate interest in predicting populations’ responses to future landscape changes and in identifying areas of habitat most conducive to population maintenance. Our objectives here were to determine the current and future extent and connectivity of habitat for gopher tortoises in Georgia. To map current habitat, we used SSURGO soil attributes, 2011 National Land Cover Data, Landsat-derived forest structure characteristics, and ecoregion layers and over 15,000 burrow locations to develop logistic regression models of burrow occurrence and ranked them with AIC.  Our top model contained variables from two spatial scales and included variables describing soil suitability, forest structure, land cover, and ecoregion.  From our model parameter estimates, we developed predictive maps of habitat suitability, which we then used the inverse of to estimate resistance to movement and quantified least cost paths and landscape connectivity with Linkage Mapper and Circuitscape. We compared connectivity of known populations against connectivity of large patches of predicted habitat to identify key areas to survey for gopher tortoises and key linkages between known and potential populations. We used predicted urbanization in 2050 to modify land cover and re-ran habitat and connectivity measures. While additional urbanization is not predicted to be extensive by 2050 in Georgia, some regions will likely experience increased isolation as urbanization creates barriers to dispersal and movement.

Wednesday April 11, 2018 11:45am - 12:00pm CDT
Spire Parlor