Global patterns of bird richness and abundance along urbanization gradients and green areas

T MATTHEWS; MARIA I. BELLOCQ; LM LEVEAU; A RUGGIERO

Cartagena

Congreso; 28 TH INTERNATIONAL CONGRESS FOR CONSERVATION BIOLOGY (ICCB); 2017

Society for Conservation Biology

Urbanization is expanding continuously over natural and seminatural areas, it is essential to analyze its impact on biodiversity. The density- diversity paradox hypothesis proposes that urbanization favors the presence of bird communities characterized by higher densities than nonurban areas and with the presence of fewer species. On the other hand, although green patch size is a primary factor in determining bird species richness in urban areas, the worldwide consistency in the species- urban green area relationship (SRAu) remains unexplored. The objectives of this study were: 1) to explore global patterns of bird richness and abundance along urbanization gradients; 2) to assess the best model explaining the SARu; and 3) to analyze the global heterogeneity of SARu parameters, such as the fit and slope of the power model. We performed meta-analysis to analyze global effects of urbanization on bird richness and abundance and the presence of significant heterogeneity in results. We found a significant positive relationship between urbanization and bird abundance, and a significant negative relationship between urbanization and bird richness, supporting the density-diversity paradox hypothesis. Study grain, latitude and the number of exotic species in each study affected significantly the relationship between bird richness and urbanization. Continent affected the relationship between bird abundance and urbanization. Regarding the SARu, the linear model was found to be the best model for explaining the SARu; however, this model was affected by the number of patches in each study. The power function showed a consistent positive effect of area size on bird richness (slope = 0.20). Overall, our results showed that the impact of urbanization on bird richness and abundance is dependent on biological, methodological and socioeconomic factors. Furthermore, management actions that promote large green urban environments will have positive effects on bird richness worldwide