The impact of impervious surface and neighborhood wealth on arthropod biodiversity and ecosystem services in community gardens

As the number of humans living in cities has grown, interest in the value of community gardens to provide agricultural products has increased. However, neighborhoods with different land cover patterns and socioeconomic characteristics often differ in their ecological attributes, leading to potential differences in biodiversity-mediated ecosystem services (e.g., pollination and pest control). Here we ask, how do impervious surface and socioeconomic features of the urban matrix around community gardens impact arthropod biodiversity and pollination and pest control services? We collected arthropods (insects, arachnids, myriapods, and isopods) across community gardens in Boulder Co., CO, and used experimental jalapeño pepper plants as a sentinel crop to measure herbivory damage and pollination services. We categorized arthropods into functional guilds to see how impervious surface and neighborhood wealth in the urban matrix surrounding a site impacts the abundance of three focal groups – pollinators, herbivorous pests, and predators. We also looked at how bee Hill-Simpson diversity responded to these variables. Through structural equation modeling, we found that fruit size increased as bee biodiversity increased, and bee biodiversity and overall pollinator abundance were negatively related to neighborhood wealth. Additionally, pollinator abundance was lower in gardens surrounded by more impervious surfaces. Neighborhood wealth and impervious surfaces were positively correlated with herbivore and predator abundances, but these abundances had no relationship with herbivory damage in our plants. This research shows that reducing the amounts of impervious surface in the urban matrix can help increase bee biodiversity and abundance and improve pollination services in urban community gardens.