Subdivision design and stewardship affect bird and mammal use of conservation developments.

Abstract

Developing effective tools for conservation on private lands is increasingly important for global biodiversity conservation; private lands are located in more productive and biologically diverse areas, and they face accelerated rates of land conversion. One strategy is conservation development (CD) subdivisions, which cluster houses in a small portion of a property and preserve the remaining land as protected open space. Despite widespread use, the characteristics that make CD more or less effective at achieving biodiversity conservation are not well understood. We investigated CD's ability to successfully protect animal populations by examining bird and mammal occurrences in 14 CD subdivisions and four undeveloped areas (range: 14-432ha) in northern Colorado, USA. Using point count and camera trap data in an occupancy modeling framework, we evaluated the relative importance of nine subdivision design factors (e.g., housing density, proportion of CD protected) and 14 stewardship factors (e.g., presence of livestock, percent native vegetation cover) in influencing the overall community composition and the probability of use by 16 birds and six mammals. We found that habitat use by 75% of birds and 83% of mammals was associated with design characteristics that maximized the natural or undisturbed land area both within and near the development (e.g., proportion of CD protected, total area of protected open space, proportion of natural land cover in the surrounding landscape). These factors were also associated with an increasing dominance of human-sensitive bird species, larger-bodied mammals, and mammals with larger home ranges. Habitat use by birds was also influenced by local land use composition and quality, and use by several bird and mammal species decreased with increased localized disturbances. We found few differences in habitat use between sampling sites in undeveloped areas and in CD subdivisions. These similarities indicate that, if CDs are large enough or located within a matrix of undeveloped land, they can provide habitat that supports similar use patterns as protected areas without housing development. By incorporating characteristics that promote the persistence of sensitive birds and mammals on private lands, CDs have potential to preserve native biodiversity in areas threatened by expanding residential development.