## Facts

- The U.S. Fish & Wildlife Service (FWS) issued a 2003 proposed rule and a 2004 final rule listing the central California population of the California tiger salamander (*Ambystoma californiense*) as “threatened” under the Endangered Species Act (ESA).
- FWS found the listing warranted under four ESA factors: habitat destruction/modification, disease or predation, inadequacy of existing regulatory mechanisms, and other natural or manmade factors; it did not rely on overutilization.
- The administrative record reflected some improved information between the 2003 proposal and the 2004 final rule, including reports of reduced threats and a more favorable outlook than earlier assessments.
- FWS nevertheless concluded the species remained at risk due to ongoing and cumulative threats, including development and habitat fragmentation, urbanization pressures, nonnative predators, contaminants, road mortality, hybridization, and insufficient local regulatory protections.
- Home Builders Association of Northern California and other building-industry plaintiffs sued under the Administrative Procedure Act (APA), alleging the threatened listing was arbitrary and capricious and contrary to the ESA’s requirement to rely on the best scientific and commercial data available.
- The case was decided on cross-motions for summary judgment.

## Issues

1. Whether FWS’s decision to list the salamander population as “threatened” was arbitrary, capricious, or otherwise unlawful under the APA.
2. Whether FWS complied with the ESA requirement to base listing decisions solely on the best scientific and commercial data available.
3. Whether FWS reasonably concluded the species was likely to become endangered within the “foreseeable future” despite evidence of some improved conditions.

## Decision

- The court upheld the 2004 final rule listing the salamander population as threatened.
- The court denied plaintiffs’ motion for summary judgment.
- The court granted the government’s cross-motion for summary judgment.
- Applying deferential APA review, the court declined to reweigh competing scientific views where the agency explained its reasoning and grounded it in the record and statutory factors.

## Legal Principles

- Under the APA, a court must uphold an agency action unless it is arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law; courts generally defer to agency scientific judgments when the agency considered relevant factors and explained its decision.
- ESA listing decisions must be based solely on the best scientific and commercial data available; this standard requires reasoned use of available information, not certainty or unanimity.
- FWS may list a species as threatened based on the cumulative effect of multiple threats, even if some indicators show improvement, so long as the agency reasonably explains why the species remains likely to become endangered within the foreseeable future.
- An agency may rationally rely on several statutory listing factors to support a threatened determination; failure to find support under one factor does not preclude listing when other factors justify the result.

## Conclusion

The court sustained FWS’s threatened listing for the central California tiger salamander population, holding that the agency reasonably relied on the administrative record and statutory listing factors and that plaintiffs’ disagreement with FWS’s predictive and scientific judgments did not show APA or ESA error.


Home Builders Ass'n of N. Cal. v. U.S. Fish & Wildlife Serv., 529 F. Supp. 2d 1110 (N.D. Cal. 2007)