Influence of urbanization on the avian species-area relationship: insights from the breeding birds of Rome

Abstract

The species-area relationship (SAR) is one of the most investigated patterns in ecology and conservation biology, yet there is no study testing how different levels of urbanization influence its shape. Here we tested the impact of urbanization on avian SARs along a rural-urban gradient using the breeding birds of Rome (Central Italy). We divided the city into 360 cells of 1 km2. Each cell was classified as rural, suburban or urban using the proportion of impervious surface calculated from remote sensing data. For each of these three landscape categories, we constructed a SAR as a species accumulation curve (Gleason function) using bird species distribution data. SAR intercepts (i.e. the number of species per unit area) decreased from rural to urban areas, which indicates that urbanization depressed the number of species, reflecting the loss of specialized species strictly associated with natural habitats. The slope was highest for the rural curve, indicating that natural landscapes have the highest turnover due to their higher habitat heterogeneity. A higher slope for the urban cells, compared to the suburban ones, can be explained by the presence of green spaces embedded in the built-up matrix which host different avian communities. Previous studies that compared whole cities with natural areas failed to find differences in the respective SARs. Our study, which constructed SARs for different levels of urbanization, indicated significant changes in the SARs along the rural-urban gradient. Further analyses in other cities and taxa will be useful to test how general are our findings.

Urban landscapes are richer in bird species when compared to farming lands: evidence from Morocco (Northwest Africa)

“…Equally, the majority of breeding birds were not related to specific habitats. Contrary to recent findings from the Northern slope of the Mediterranean basin (Murgui 2009;Calegaro-Marques & Amato 2014;Di Pietro et al 2021), breeding birds were more abundant in rural than urban areas. The minority were concentrated in green spaces, followed by farmlands and rural ecosystems.…”

“…The minority were concentrated in green spaces, followed by farmlands and rural ecosystems. This is in contradiction with current results sited in the Northern slope of the Mediterranean basin (Murgui 2009;Calegaro-Marques & Amato 2014;Di Pietro et al 2021), in which breeding birds were abundant in rural areas more than cities.…”

“…In terms of habitat richness and similarity, rural areas were the most diverse habitats with birds, followed by farmlands and peri-urban zones, while the urban centres hosted only two birds. This confirms the hypothesis that rural zones are richer in species because of low population size and intact habitats (Sengupta et al 2014;Di Pietro et al 2021). On the other hand, breeding species have revealed variable affinities toward studied habitats.…”

Taxonomic, Phylogenetic and Functional Diversity of Bird Assemblages in Urban Green Spaces: Null Model Analyses, Temporal Variation and Ecological Drivers

“…Green spaces are a key element for biodiversity conservation in cities since they represent available habitat for a wide range of organisms (Cornelis and Hermy, 2004;MacGregor-Fors et al, 2016) and much of the research on diversity in urban green spaces has focused on birds (Magle et al, 2012;Beninde et al, 2015). Studies have mainly reported reductions in both the number of species and diversity indices together with compositional changes (Carvajal-Castro et al, 2019;Di Pietro et al, 2020 but see Benitez et al, 2021). Although species richness has been a widely-used measure of biodiversity to assess the effect of urbanization on bird communities (Rush et al, 2014;Canedoli et al, 2017;Matthies et al, 2017) the assumption of species being equivalent may not be ecologically precise (Chave, 2004).…”

Influence of Land Use on Avian Diversity in North African Urban Environments

“…The relationship between avian biodiversity and urbanization in the Mediterranean climate has been addressed by Di Pietro et al [75] and Vignoli et al [76], both investigating it in the metropolitan area of Rome. The first study, focusing on breeding birds, showed that the effects of urbanization are little investigated in other species-area relationship studies in urban ecology.…”