ELR Citation: ELR 20107
No(s). 07-16641 (9th Cir. May 18, 2009)

The Ninth Circuit reversed and remanded a lower court decision upholding the U.S. Department of the Interior's (DOI's) decision to remove the flat-tailed horned lizard from its proposed list of threatened species under the Endangered Species Act (ESA). The administrative record does not support DOI's finding that the lizard persists in a substantial portion of its range. DOI argued that it relied on population studies to conclude that the lizard is persisting in the vast majority of its range. Yet it previously reported that "[i]nformation concerning population dynamics of flat-tailed horned lizard populations is limited and inconclusive." If the science on population size and trends is underdeveloped and unclear, DOI cannot reasonably infer that the absence of evidence of population decline equates to evidence of persistence. Here, DOI relied on ambiguous studies as evidence of persistence (i.e., stable and viable populations). It then argued that this "evidence" of persistence proves that the lizard's lost range is insignificant for purposes of the ESA. This conclusion is unreasonable. On remand, DOI must again consider whether to withdraw the proposed listing of the lizard. However, DOI reasonably determined that one of the habitats at issue was not significant due to that population's relatively small size, isolation from other remaining lizard populations, and lack of importance for maintenance of genetic diversity. This is a reasonable approach to assessing the significance of threatened range.