PARENT SESSION
Oral Session # 67: Urban Ecology I: Dynamics, Values, and Systems.
Presiding: A Yeakley
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.

Changes in habitat connectivity resulting from different patterns of urban growth.

Bierwagen, Britta^*,1, ¹ University of California, Santa Barbara, Santa Barbara, CA

ABSTRACT- The conversion of habitat to other land-uses is one of the major drivers of global change. Many studies document the negative impacts of habitat loss and fragmentation on species persistence and community composition; however, the functional effects on ecological processes such as dispersal are less clear. This research develops a theoretical framework for understanding the impacts of urban growth on habitat connectivity over time. I evaluated the impacts of land-use change on butterflies with different dispersal abilities across a range of initial habitat configurations. I addressed the problem by applying a cellular automata-based land-use change model to simulate different urban growth patterns, varying relative emphasis on road-mediated, urban edge-mediated, or leap-frog type development. I generated initial landscape configurations using a neutral landscape model and varied the amount of habitat and its aggregation systematically. Image analysis techniques were used to calculate landscape metrics with a variable window size corresponding to different butterfly dispersal distances. This approach effectively scaled the view of each urbanizing landscape according to dispersal capabilities of different butterfly classes. Results suggest that urban growth spreading from one compact area has the highest habitat connectivity at first; however, as the urban area spreads, connectivity drops nearly exponentially for the shortest distance dispersers. Initial configurations with many small urban areas distributed across the landscape begin with up to 60% lower habitat connectivity compared to landscapes with a few urban centers. The growth of the many small urban areas results in a slower rate of decline in habitat connectivity. This work underscores the importance of understanding land-use changes as dynamic drivers of ecological systems.

Key words: butterfly dispersal, fragmentation, habitat connectivity, land-use change