Left: Distribution of Terrapene coahuila
in Coahuila, Mexico. Red dots = museum and literature occurrence records of native populations based on Iverson (1992) plus more recent and authors’ data; gray dot = extirpated population; olive shading = extirpated range; green shading = projected distribution based on GIS-defined hydrologic unit compartments (HUCs) constructed around verified localities and then adding HUCs that connect known point localities in the same watershed or physiographic region, and similar habitats and elevations as verified HUCs (Buhlmann et al. 2009), and adjusted based on authors’ data. Right: The Cuatro Ciénegas Basin (bold outline) and the current geographic range of T. coahuila
(grey polygon). Distribution is denoted by known sites of collection or sight records, 2002–07 (solid circles), and has been greatly reduced compared to the historic distribution, 1958–68 (Fig. 2 in Brown 1974). See Fig. 6 for photographic illustration of habitat loss from 1965–2002. Documented T. coahuila
wetland habitat loss has primarily occurred in the western and northern sections of the geographic range. The town of Cuatrociénegas de Carranza (diamond) is the human population center of the valley and supports irrigated agriculture.