Corridors as the solution to maintaining urban biodiversity

Urban areas, often seen in the past as ecological deserts, are increasingly recognized as ecosystems in and of their own right.  With more attention being directed toward urban ecosystems for both research and conservation purposes, it’s time to take a step back and look at some of what we’ve learned.  To do so, Beninde et al., in their new publication in Ecology Letters, looked at 87 publications with study sites in cities across the globe and compared urban biodiversity within cities.  They then ran a meta-analysis that summarizes the effect of single factors on biodiversity levels between cities.

They found two factors were most important in determining biodiversity in cities: patch size and corridors.  Higher diversity was associated with larger patch sizes, a result that supports the validity of the species-area relationship in urban landscapes.  Corridors also came out as highly effective in supporting urban biodiversity, despite a small sample size.  This suggests that corridors may be more effective in promoting species richness than stepping stones, which decrease the distance between patches but without providing a functional corridor. Interestingly, they also found that fragmentation and edge effects were not consistently negative in impact of urban biodiversity, which is often assumed in studies.  Beyond patch size and corridors, the most prominent significant effects on biodiversity included water cover, management intensity, and biotic factors in general.

A few caveats emphasize the current state of knowledge in urban ecology.  Most of the studies were conducted in North America and Europe, although urban growth is projected to be greatest in Asia and Africa.  In addition, almost half of the data available focused on birds, with several other taxa woefully underrepresented.  The review highlights the need for additional work in both a wider range of urban settings and with a wider range of taxa.  The authors suggest that based on their results, the most important strategy in maintaining urban biodiversity is to increase the area of habitat patches and ensure a strong network of corridors.