Socio-Economic Status and Non-Native Species Drive Bird Ecosystem Service Provision in Urban Areas

Abstract

Areas of higher socio-economic status within cities often support greater biodiversity than poorer areas, representing a form of environmental injustice. This inequality may result in lower income areas experiencing both lower cultural (e.g., bird aesthetics) and regulating (e.g., pest control) ecosystem service provision. Urban areas are also hotspots for non-native species, which can alter community functional structure and, consequently, ecosystem service provision. However, the influence of socio-economic status on services provided by both native and non-native urban biodiversity remains underexplored. We assessed how functional diversity related to avian cultural and regulating ecosystem services varied along the socio-economic gradient of functional urban areas (FUAs) in the Iberian Peninsula. Using breeding bird atlases from Spain and Portugal, we characterised bird communities in all FUAs, calculating species richness and functional dispersion based on traits linked to ecosystem services. We used generalised linear mixed models to examine relationships between diversity metrics and median household income. Additionally, we evaluated whether the presence of non-native species moderated community responses along the gradient. Both cultural and regulating ecosystem services were negatively associated with socio-economic status, while species richness increased with income. However, invaded communities supported higher species richness and cultural service provision than non-invaded ones. Our findings reveal a counterintuitive pattern in which ecosystem service provision is higher in lower-income areas, partly due to non-native species. These results underscore the need for urban management strategies that simultaneously address socio-economic and ecological inequalities, while considering the complex roles of non-native species in shaping urban biodiversity and its benefits.

Keywords: FUA; Iberian Peninsula; alien bird; functional diversity; luxury effect; wealth.

FIGURE 1

Map of the Iberian Peninsula (Portugal and Spain) and Balearic Islands with Functional Urban Areas (red polygons) and annual median household income per neighbourhood (from light grey to black). Median household income data was not available for white polygons. Cities of Lisbon and Madrid are labelled (capitals of Portugal and Spain respectively). Map lines delineate study areas and do not necessarily depict accepted national boundaries.

FIGURE 2

Response of Species richness (a) and CFD [i.e., SES values for corrected functional dispersion, quantification of both Cultural (b) and Regulating (c) ecosystem services provision] to the median income gradient (standardised) in FUAs of Iberian Peninsula. Dot size is proportional to community species richness. The density curves represent the distribution of CFD (both Cultural and Regulating) and species richness distribution. Brown represents the invaded communities (i.e., at least one non‐native species was found in the grid cell), and orange represents the non‐invaded communities (i.e., no non‐native species were in the grid cell). Underdispersed communities are represented by negative CFD values. Overdispersed communities are represented by positive CFD values.

FIGURE 3

Response of Species richness (a) and CFD [i.e., SES values for corrected functional dispersion, quantification of both Cultural (b) and Regulating (c) ecosystem services provision] to the median income gradient (standardised) in FUAs of Iberian Peninsula. Dot size is proportional to community species richness. The density curves represent the distribution of CFD (both Cultural and Regulating). Brown represents the invaded communities (i.e., at least one non‐native species was found in the grid cell), orange represents the non‐invaded communities (i.e., no non‐native species were in the grid cell), and black represent the invaded no alien communities (i.e., excluding non‐native species from the invaded communities). Underdispersed communities are represented by negative CFD values. Overdispersed communities are represented by positive CFD values.