Proportion of native plants is a key predictor of pollinator richness in urban greenspaces

Thomas Lilkendey, Brittany M. Mason, Nadja Pernat, Marina Marquis, Jacob S Francis, Corey T Callaghan 

Pollinator declines are caused by a multitude of factors including pollution, global warming, disease, urbanization, deforestation, and habitat loss. Given the global increase in urbanization, identifying ways to support pollinators in cities has become an important conservation priority. Here, we investigate the effect of urbanization on pollinator richness. Using >100,000 iNaturalist observations collected between 2014 and 2024 across 129 urban greenspaces in Florida, U.S.A., we investigate how native and non-native angiosperm richness, along with greenspace-level characteristics, influence pollinator richness. Pollinator richness was positively associated with overall angiosperm richness, regardless of origin. However, a higher proportion of native angiosperm species was associated with increased pollinator richness, whereas a higher proportion of non-native species was associated with decreased pollinator richness. Among greenspace-level landscape characteristics, pollinator species richness had a significant positive relationship with percent of impervious surface cover (β = 0.0044, p = 0.010), percent tree cover (β = 0.0047, p = 0.001), and greenspace size (β = 0.0282, p = 0.037), but was not significantly associated with grass cover (β = 0.0020, p = 0.391) or percent water cover (β = -0.00005, p = 0.985). Our results suggest that greenspace managers should prioritize enhancing floral richness —especially of native species—to support greater pollinator richness. Increasing tree cover and maintaining large greenspaces within cities may also contribute positively to pollinator richness. Leveraging broad-scale participatory citizen science data provides an avenue to further monitor pollinator richness within urban greenspaces.