Beyond Historic Baselines: Restoring Bolson Tortoises to Pleistocene Range

Abstract

Ecological restoration in North America traditionally has strived to return ecosystems to some semblance of the early historic (post-Columbian) condition. Emerging alternative paradigms recognize the large impacts exerted by pre-Columbian peoples, the ever-changing nature of ecosystems regardless of anthropogenic effects, and the possibility of using other benchmarks. Recently, the Turner Endangered Species Fund (TESF) initiated a project to restore the endangered bolson tortoise to an area in southern New Mexico within its late Pleistocene, but not historic, range. Justifications included the likelihood that prehistoric humans extirpated it from New Mexico, the presence of habitats similar to those in its current range in Mexico, and escalating threats to the species there. Thirty tortoises long kept captive outdoors in Arizona, another part of its prehistoric range, formed the basis for the restoration effort. The TESF and the Living Desert Zoo and Gardens State Park near Carlsbad, New Mexico, maintain the adults in outdoor enclosures, and incubate eggs and rear young in smaller facilities. The TESF is initiating studies to assess whether the species can persist in the wild in New Mexico. Restoring imperiled species to prehistoric ranges has some precedent in North America and, we believe, merits increasing consideration as historic ranges of some species offer increasingly less security.