Two new studies focus on how wildlife populations in southern California are affected by the expansion of both urban areas and the ‘exurban’ areas that surround them. The findings are relevant to other areas where natural vegetation is being rapidly converted to development. In the first issue of the new open-access journal Ecosphere, Burdett and colleagues built habitat models for puma from telemetry data and then, using a detailed projection of future development patterns, projected how the distribution of puma habitat would change over the coming decades. The authors found that if, as in many previous studies, low-density or ‘exurban’ development had not been distinguished from other types of land use, they would have underestimated the impact of development on puma populations. Although not all pumas in their study avoided exurban areas, those that used such areas had higher mortality risk.
In a complementary study to the north in the Los Angeles metro area, Delaney and colleagues, writing in the journal PLoS One, found that urbanization can lead to rapid genetic fragmentation even in populations of common and previously widely-distributed species. Populations of three species of lizard and a bird showed strong genetic structure that was correlated with the pattern and history of loss of natural vegetation in the region. It is well accepted that fragmentation can lead to genetic divergence and decreased genetic diversity through genetic drift and inbreeding, which may reduce viability of isolated populations. The Delaney et al. paper is significant because few previous studies have provided such detailed evidence of genetic changes associated with fragmentation at this scale.
