Connectivity in urbanizing landscapes: The importance of habitat configuration, urban area size, and dispersal

Abstract

Human activities affect both the amount and configuration of habitat. These changes have important ecological implications that can be measured as changes in landscape connectivity. I investigated how urbanization interacts with the initial amount and aggregation of habitat to change dispersal potential, restoration potential, and the risk of spatially extensive disturbances. I used a factorial set of simulated landscapes and subjected each landscape to habitat loss by overlaying 66 different US urban areas. I used a common connectivity metric, CONNECT, to assess the magnitude and direction of changes for a range of dispersal distances. My results show that the relationship between habitat loss and connectivity loss is non-linear and subject to interactions between the spatial patterns of habitat distribution, urban morphology, and dispersal capabilities. The implications of a given urban form vary widely as a function of habitat distribution and dispersal capabilities. This implies that impact assessments, restoration activities, and conservation planning should consider historical habitat distribution when evaluating observed changes in connectivity. While my results clearly show that more aggregated or continuous habitats are more vulnerable to connectivity loss, this approach can also be used to identify landscapes where restoring connectivity will be particularly effective, for example through placement of stepping stone habitats.

Spatial assessment of landscape ecological connectivity in different urban gradient

“…There are some statistical procedures proposed to select potential indicator species, including ordination and clustering methods (Dufrêne and Legendre 1997) and quantitative criteria such as the frequency of occurrence and habitat specialization (Carignan and Villard 2002). Third, this study utilized a circular shape for zonal classification, but using different geometric shapes or any other arbitrary shapes to describe urban forms would be possible (Snellen et al 2002;Bierwagen 2005Bierwagen , 2007. If asymmetric or irregular shapes can technically be applied to this type of analysis, it may capture more realistic urbanization density structure even though little difference would likely to be found for connectivity patterns.…”

Environment and Biodiversity

“…This effect may be exacerbated by the larger numbers of land parcels in areas of higher density. Crucially though, the ecological impact of changes in habitat patch sizes depends on whether habitat characteristics of patches also vary with their size, the minimum patch areas that particular species can tolerate, and the ability of species to disperse across the landscape to other patches (Watson et al, 2005;Bierwagen, 2007).…”

Balancing urban growth and ecological conservation: A challenge for planning and governance in China

“…Urban expansion and associated land changes can fragment or destroy habitats (McKinney 2002), thus adversely impacting native species dispersal (Bierwagen 2007). Urbanization may increase species richness, but it can also facilitate colonization by introduced species often at the cost of native species (McKinney 2002(McKinney , 2006.…”