A New Approach for Monitoring Multiple Species

Article excerpt

The Sonoran Desert Conservation Plan (SDCP) is an innovative and comprehensive strategy to preserve the biological diversity and cultural heritage of Pima County, Arizona, in response to unprecedented human population growth and its associated impacts (see www.pima.gov/sdcp). Pima County is now implementing the SDCP through a host of conservation measures, including development set-asides, purchase and lease of open space, and habitat restoration. The Pima County Multi-species Conservation Plan (MSCP) is an important component of the SDCP. It will ensure that development-related activities comply with the Endangered Species Act (ESA) through issuance of a section 10 "incidental take" permit from the U.S. Fish and Wildlife Service. The Pima County MSCP currently includes coverage for 36 "Priority Vulnerable Species" (PVS): 4 species of plants, 8 mammals, 8 birds, 7 reptiles, 6 fishes, 2 amphibians, and 1 invertebrate. To complete the MSCP package, Pima County is developing a monitoring program.

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Monitoring for Conservation

Ecological monitoring is one of the most challenging endeavors in ecology and natural resource management. Single-species monitoring can be expensive, and the number and breadth of species covered under most MSCPs, like that being developed for Pima County, creates a financial burden if the goal is to effectively track populations over time. While some efficiency can be gained by monitoring multiple species using similar field methods and employing prudent sampling design elements (see Elzinga et al. 2001), costs can still remain prohibitive, particularly because many vertebrate species covered under MSCP plans are rare and secretive. This expense can lead to increased program costs because of the extra level of survey work needed to estimate population and/or occupancy for these rare species. In addition to cost, monitoring for dozens of species has been problematic from the perspective of adaptive management, in part because causes of observed population changes are often unknown or ambiguous or, in the case of migratory species, the result of conditions outside the control of a local manager. The high cost and management challenges posed by monitoring multiple species require a new approach for MSCP monitoring in Pima County.

A major focus of the approach being advocated for the Pima County MSCP involves monitoring a broad suite of biotic and abiotic indicators (environmental characteristics) that are known to influence biodiversity over large landscapes. …