Taxonomic and functional homogenization in bird communities: the role of land-use changes

Abstract

Among driving forces of biotic homogenization, change in the physical environment that reduces habitat heterogeneity has been underlined as playing a key role to explain biodiversity changes in time. Yet this process has hardly been quantified on a large scale through simple indices, and the connection between land-use change and biotic homogenization has hardly been established. Here, we aimed at exploring the impacts of land-use change on bird taxonomic and functional diversities’ dynamics in Metropolitan France. Biodiversity measures were computed using a standardized breeding-bird monitoring scheme for a 10 year period. We applied the partitioning of Rao quadratic entropy to calculate α β and ϒ diversities for the taxonomic and functional facets of biodiversity. We also computed a measure of community specialization (CSI).Land-use change dynamics were evaluated with the national CORINE land-cover database. We proposed a relevant tool to quantify habitat diversity at the landscape level, accounting for ecological distances between habitat types. This index ( ) was sensitive to landscape homogenization and differentiation and to the intensity of those processes. We related the changes in multifaceted and scale-dependent diversity components to an integrative land-use change gradient ( ).Overall, we found that some components of taxonomic and functional diversity dynamics were negatively impacted by past land-use homogenization and differentiation. Land-use homogenization, reducing diversity and number of available niches, had a negative impact on diversity dynamics. Land-use differentiation was associated to landscape artificalization, decrease in mean patch size, and increase in edge effect. Therefore, it is likely that habitat differentiation would be perceived as habitat disturbance and/or fragmentation at the community level, having an adverse effect on biodiversity dynamics.To our knowledge, this is the first time such a gradient of landscape diversity dynamics was used to quantify land-use change impacts on biodiversity. We believe that a multifaceted and multi-scale approach of communities and landscapes diversity will increase our understanding of the consequences of land-use change on biodiversity. We expect this approach to reveal interesting patterns of biodiversity dynamics when applied to different taxa and to different diversity facets (e.g., phylogenetic diversity).