The plans frequently fail to provide adequate conservation measures for such species, the article argues, and as a result, species that are present but not confirmed to be are placed in increased danger.

Habitat conservation plans are intended to allow development to occur that is compatible with conservation of species listed as endangered or threatened under the Endangered Species Act. Permit seekers often list multiple species in their plans, because if a species not covered by the plan is subsequently listed under the act, this could hinder the continued activities of the permittee.

The BioScience article, by Matthew E. Rahn of San Diego State University and two colleagues, analyzed 22 multispecies plans approved by the US Fish and Wildlife Service before 2005. On average 41 percent of the species covered in the plans had not been confirmed as present in the planning area, a result the authors describe as "alarming."

Furthermore, most of these unconfirmed species lacked any species-specific conservation measures. The authors point out that if a species is in fact present but not confirmed as such and therefore not studied, a multispecies habitat conservation plan could actually represent a threat.

Most multispecies conservation plans call for nonuniform land use, and such use represents a danger if it is not tailored to the species being protected. Rahn and colleagues argue that "assumptions of occurrence should be justified" in multispecies conservation plans.

They suggest that the US Fish and Wildlife Service has been inclined to issue permits for multispecies conservation plans in the absence of data, relying instead on professional judgment.

Rahn and colleagues term that a "dangerous practice" and suggest that it may help explain why species in multi-species habitat conservation plans fare poorly compared to species with dedicated plans.

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American Institute of Biological Sciences