Selecting Effective Umbrella Species

Abstract

Even a well-designed shortcut can miss its destination. The role of umbrella species in conservation planning is a case in point. In the face of limited time and resources, umbrella species offer an appealing shortcut to land managers. But they do not shorten every road. The idea of umbrella species is straightforward: the conservation of some species is thought to provide a protective umbrella to numerous co-occurring species. It is often faster and less expensive to sample a few species than it is to survey the entire assemblage. Hence, umbrella species can reduce the investments in sampling that are necessary when prioritizing areas for competing land uses. However, there is little empirical evidence that this approach actually works. Furthermore, few researchers have offered guidance on identifying umbrella species and the contexts in which this approach work best. In theory, selection of umbrella species is prospective; in practice, it has almost always been retrospective. Species have been suggested as umbrellas not on the basis of occurrence patterns or ecological traits, but simply because they are imperiled and have statutory protection. The northern spotted owl (Strix occidentalis) and California gnatcatcher (Polioptila californica) are well known examples of species proposed as umbrellas subsequent to their listing under the U.S. Endangered Species Act. As a result, ecologists and managers have been restricted to asking—after the fact—whether other species will benefit from the conservation of these and other listed species. Using existing data sets for birds and butterflies, we found that umbrella species can be selected prospectively using objective ecological criteria. Here, we describe three key aspects of a species' distribution and ecology that should be considered when selecting umbrella species. Using these factors, we developed a numerical index to measure the potential of each species to serve as an umbrella for its regional species assemblage. Because few data support the notion that conservation of species in one taxonomic group effectively protects species in other groups, we focused on umbrellas within a taxonomic group.