Biodiversity Metrics in Urban Landscapes

Urban landscapes -- comprising 3% of global land area but housing > 55% of the world's population and expanding at
approximately 1.5% per year -- represent both the primary terrestrial habitat for most humans and a globally significant
biodiversity context where urban ecological communities are shaped by the unique stressors of heat island effects,
impervious surface cover, artificial light at night, noise, invasive species, and management intensity. Measuring,
monitoring, and improving urban biodiversity is increasingly central to urban planning, Nature-based Solutions policy, and
the EU Biodiversity Strategy 2030 green infrastructure targets, but standardised urban biodiversity metrics that integrate
across green space types, taxa, and the unique urban biodiversity patterns (biotic homogenisation, urban adapters vs.
avoiders, heat island range expansion) are lacking. This study developed and validated an Urban Biodiversity Index
(UBI) integrating species richness, functional diversity, native species proportion, and green space connectivity across 42
urban green space sites in Vienna (Austria; 2,840 species-site records; plants, arthropods, birds; 2021-2023). UBI
explained 68.4% of variance in urban ecosystem service provision (pollination, urban cooling, recreation quality,
stormwater retention; r = +0.84 with total ES value). High-UBI sites (> 0.70; n = 14) showed 2.84-fold higher total ES
value than low-UBI sites (< 0.40; n = 10). Impervious surface cover was the strongest negative predictor of UBI (r =
-0.84), while tree canopy cover (r = +0.74) and green space connectivity (r = +0.64) were the strongest positive predictors
-- providing evidence-based urban planning targets for Vienna's 2030 biodiversity and green infrastructure strategy.