## Facts

- The Mexican spotted owl was listed as a threatened species under the Endangered Species Act (ESA).
- The U.S. Fish and Wildlife Service (FWS) designated about 8.6 million acres of federal land in several states as critical habitat for the owl.
- FWS identified three primary constituent elements (PCEs) for the owl’s critical habitat: forest structure, adequate prey base, and canyon habitat.
- The PCE descriptions combined qualitative terms (e.g., “adequate,” “high volumes,” “wide range”) with some quantitative measures (e.g., canopy coverage; minimum percentages of trees meeting diameter thresholds).
- The Arizona Cattle Growers’ Association (ACGA) challenged the designation, arguing that the PCEs lacked sufficient specificity, that FWS improperly treated certain areas as “occupied,” that the rule was not based on the best scientific data available, and that the economic analysis was legally deficient.
- The case proceeded on cross-motions for summary judgment by ACGA, FWS/Secretary of the Interior, and an intervenor conservation organization.

## Issues

1. Whether the ESA required FWS to define PCEs with greater precision than the rule’s mixed qualitative and quantitative descriptions.
2. Whether FWS reasonably interpreted and applied “occupied” habitat to include areas with intermittent or infrequent owl use.
3. Whether the designation was based on the best scientific data available and was not arbitrary or capricious under the Administrative Procedure Act (APA).
4. Whether FWS’s economic analysis satisfied the ESA and APA, including disputes over methodology for measuring impacts.

## Decision

- The court denied ACGA’s motion for summary judgment and granted summary judgment to FWS/Secretary of the Interior and the intervenor.
- The court upheld the critical habitat designation.
- The court held that the PCE descriptions were sufficiently specific under the ESA when read as a whole, including qualitative terms supported by more detailed parameters.
- The court deferred to FWS’s interpretation of “occupied” to include intermittent use and dispersal-related habitat.
- The court concluded FWS relied on the best scientific data available and made permissible methodological choices despite data limitations.
- The court found the economic analysis adequate and within the agency’s permissible interpretive discretion.

## Legal Principles

- The ESA’s critical habitat requirement allows PCE descriptions that use a combination of qualitative ecological descriptors and quantitative measures, so long as the features essential to conservation are identified in a coherent, scientifically grounded way.
- “Occupied” critical habitat may reasonably include areas used intermittently or for dispersal, not only areas of continuous residency, if the agency’s interpretation is reasonable.
- The ESA’s “best scientific data available” standard does not require scientific certainty; an agency may proceed using the best data actually available and exercise expert judgment in addressing uncertainty.
- Under APA review, courts generally uphold FWS scientific and methodological determinations where the agency explains its reasoning and the decision is not arbitrary or capricious.
- The ESA does not require a single mapping or boundary-description technique for critical habitat, provided the designated areas are reasonably ascertainable.

## Conclusion

The court upheld FWS’s Mexican spotted owl critical habitat designation, ruling that the ESA and APA permitted FWS’s use of mixed qualitative and quantitative PCE descriptions, a reasonable reading of “occupied” habitat that includes intermittent use, and the agency’s chosen scientific and economic methodologies.


Arizona Cattle Growers' Ass'n v. Kempthorne, 534 F. Supp. 2d 1013 (D. Ariz. 2008)