Biological Diversity Modeling
Impact model to capture the effects of land cover change on bird populations
The biological diversity component of this project focuses on understanding colonization and extinction of birds in an urbanizing landscape, and developing models of changes in bird species composition and relative abundance in response to forest loss. We can then generalize and test theory, and suggest general planning and management considerations for those interested in maintaining biological diversity in urbanizing landscapes. Our research on biological responses to land cover change has focused primarily on birds with some additional work on plants and small mammals. Our study sites included139 landscapes (each 1km squared): 115 single-family residential sites, 14 commercial/industrial sites, and 10 forested sites with minimal development.
To predict future patterns of richness and relative abundance of bird species, we developed a coupled model of land cover change and bird diversity by linking the land cover change model and a series of statistical models of birds’ responses to change in landscape composition and configuration. We used point-count date from the 139 study landscapes to create development-sensitive guilds. The study involved a land cover characterization of each 1 km2 bird study area based on land cover data from 2002 to calculate the percent forest, percent urban, and aggregation index of the forest, as well as the number of patches of forest, and the number and mean size of the urban patches. To better characterize the study sites, we used land use information derived from 2002 parcel data to calculate the percent patch density, and aggregation index of residential parcels, and the development age of all the parcels within each study area.
We developed two a priori models of species richness and relative abundance based on previous studies, on landscape measures relevant to urban planners, and on variables available as output from our land cover change mode. A first simple model (SM) included: 1) percentage of forest (in linear and quadratic form); 2) aggregation of residential land use; and 3) development age of parcels within a 1-km2 window. A more complex model added seven more variables: 1) percentage of grass and forest land cover; 2) forest aggregation index; 3) number of unique patches of forest land cover; 4) number of unique patches of urban land cover; 5) mean patch size of unique patches of urban land cover; 6) percent of residential land use; and 7) patch density of residential land use.
Applying the parameter estimates from models of species richness and relative abundance to the future landscapes generated by the land cover changes model, we can predict the total guild- and sub guild-specific species richness, and relative abundance for all species.
Hepinstall, J.A., J.M. Marzluff, M. Alberti. 2008a. Modeling the responses of birds to predicted changes in land cover in an urbanizing region. In J. Millspaugh and F. R. Thompson (editors). Models for Planning Wildlife Conservation in Large Landscapes. Elsevier Science, The Netherlands.
Hapinstall, J. A., Alberti, M., Marzluff, J. (2008), Predicting land cover change and avian community reponses in rapidly urbanizing environments, Landscape and Urban Planning, DOI 10.1007/s10980-008-9296-6.
Hepinstall, J.A., J.M., Marzluff, M. Alberti. 2008c. Predicting avian community responses to increasing urbanization. Studies in Avian Biology. (In Press).
Marzluff, J. M., Withey, J. C., Whittaker, K. A., Oleyar, M. D., Unfried, T. M., Rullman, S. and J. DeLap. 2007. Consequences of habitat utilization by nest predators and breeding songbirds across multiple scales in an urbanizing landscape. Condor 109:516-534.
Marzluff, J. M. and A. D. Rodewald. 2008. Conserving biodiversity in urbanizing areas: non-traditoinal views from a bird’s perspective. Cities and the Environment. In press.