Background: The dunes sagebrush lizard (Sceloporus arenicolus) is an imperiled species that is restricted to shinnery oak (Quercus havardii) sand dune habitats in southeastern New Mexico and West Texas, USA. This region is also a hotspot of oil and gas development that is a major threat to the species. Methods: Here we use well data and a natural experiment to test the effectiveness of voluntary conservation agreements for slowing or stopping oil and gas well approval in the lizard’s habitat in New Mexico and Texas. Results: We show that the Candidate Conservation Agreement (CCA) and CCA with Assurances in New Mexico, both of which contain strong avoidance mechanisms, are associated with a steep decline in oil and gas well approval in the New Mexico portion of the lizard’s range, but not outside the lizard’s range. By contrast, the Texas Conservation Plan (TCP), which does not include mandatory avoidance, is not associated with any decline of oil and gas well approval in the lizard’s Texas range relative to the broader landscape. Conclusions: These results indicate that the TCP is insufficient to conserve the lizard in Texas, thereby jeopardizing genetic and geographic representation across the range of the species.