Socio-economic status and non-native species drive bird ecosystem service provision in urban areas

Areas of higher socio-economic status within urban areas generally have
higher levels of taxonomic diversity than poorer areas, representing a
form of environmental injustice. This inequality may result in
lower-income areas experiencing both lower cultural (e.g., non-material
services provided by bird aesthetics) and regulating (e.g., pest control
by insectivorous birds) ecosystem service provision. Furthermore, urban
areas are hotspots for the introduction of non-native species, which can
potentially alter the functional space of invaded communities, and hence
their ecosystem service provision. However, the relationship between
socio-economic status and the ecosystem services that both native and
non-native urban biodiversity provide has yet to be fully addressed. We
tested whether functional diversity associated with avian cultural and
regulating ecosystem services varied along the socio-economic gradient of
functional urban areas (FUAs) in the Iberian Peninsula. We used bird
atlases from Spain and Portugal to characterise the bird communities of
all FUAs across each country, calculating both species richness and
functional dispersion of traits related to cultural and regulating
ecosystem services. We then applied generalized linear mixed models to
understand the relationships between these diversity metrics and the
socio-economic status of each community, measured as annual median
household income. Furthermore, we assessed whether the presence or absence
of non-native species moderated community responses along the
socio-economic gradient. Both cultural and regulating ecosystem services
were negatively affected by socio-economic status, while species richness
followed the opposite trend. However, invaded communities showed higher
species richness and cultural ecosystem services than non-invaded
communities. Our results suggest a negative relationship between
socio-economic status and ecosystem service provision, with non-native
species playing a major role in shaping this relationship. Our
counterintuitive findings highlight the need for targeted management
strategies that address both socio-economic and ecological inequalities in
urban planning, in addition to non-native species management.