The spread of invasive species creates serious environmental problems as well as economic hazards for residents and will hamper implementation of parts of the SDCP.

An assessment of the problems that are presented by non-native and introduced species in maintaining native species and natural systems. Divided into two major sections, the study covers representative ecosystems in Pima County as well as representative species that have a negative impact on native species.

A companion to the study issued on July 5, 2000 entitled 'Cactus Ferruginous Pygmy-Owl Investigations in Pima County.' The major objective was to determine whether pygmy-owls chose nest sites or perch trees with characteristics that differ from other available sites within a nesting territory.

Letter report of pollen study suggests the Colorado Plateau Pollen Chronology