Quantifying nectar production by flowering plants in urban and rural landscapes

Abstract

Floral resources (nectar and pollen) provide food for insect pollinators but have declined in the countryside due to land use change. Given widespread pollinator loss, it is important that we quantify their food supply to help develop conservation actions. While nectar resources have been measured in rural landscapes, equivalent data are lacking for urban areas, an important knowledge gap as towns and cities often host diverse pollinator populations. We quantified the nectar supply of urban areas, farmland and nature reserves in the UK by combining floral abundance and nectar sugar production data for 536 flowering plant taxa, allowing us to compare landscape types and assess the spatial distribution of nectar sugar among land uses within cities. The magnitude of nectar sugar production did not differ significantly among the three landscapes. In urban areas the nectar supply was more diverse in origin and predominantly delivered by non‐native flowering plants. Within cities, urban land uses varied greatly in nectar sugar production. Gardens provided the most nectar sugar per unit area and 85% of all nectar at a city scale, while gardens and allotments produced the most diverse supplies of nectar sugar. Floral abundance, commonly used as a proxy for pollinators’ food supply, correlated strongly with nectar resources, but left a substantial proportion of the variation in nectar supply unexplained. Synthesis. We show that urban areas are hotspots of floral resource diversity rather than quantity and their nectar supply is underpinned by the contribution of residential gardens. Individual gardeners have an important role to play in pollinator conservation as ornamental plants, usually non‐native in origin, are a key source of nectar in towns and cities.

Challenging the sustainability of urban beekeeping using evidence from Swiss cities

“…see ref. 13 ) and estimate them across types of UGS in different cities as in 14 , which could be combined with high resolution landcover maps such as 11 . Second, we could not incorporate the responses (e.g.…”

Dwarf White Clover Supports Pollinators, Augments Nitrogen in Clover–Turfgrass Lawns, and Suppresses Root-Feeding Grubs in Monoculture but Not in Mixed Swards

“…That mindset seems to be changing, however, as the public becomes more aware of the threats to honey bee health [30], as well as steep declines in the populations of wild bees and other pollinators [31][32][33][34]. A reduction in floral resources (nectar and pollen) due to urbanization and other land-use changes is thought to be a major factor contributing to wild pollinator decline, especially in North America and Europe [32,35,36]. Urban ecologists are increasingly encouraging the conversion of traditional monoculture turfgrass lawns to more diverse habitats (e.g., [2,37]).…”

“…Trifolium repens produces copious amounts of pollen and nectar [36,44,45], and is highly attractive to wild bees and honey bees that forage in urban landscapes [21][22][23][46][47][48][49]. It is the most important nectar source in Britain [45], providing the highest portion of total nectar production by flowering plants in parks, cemeteries, and road verges, and more than half of the total nectar resources in lawns and other mowed amenity grasslands [36]. Due to its prolonged bloom period, T. repens can help to sustain pollinators during seasonal gaps in floral resource availability from other plants [46,49,50].…”

Urban Bees Benefit from a Native Forest Species Grown in a City Environment–A Case Study of Geranium Phaeum L.

“…As shown by Salisbury et al (2015), urban gardens can be enhanced as a pollinator habitat by planting a variety of flowering plants biased towards native and near-native species. The usefulness of plants for pollinators requires detailed studies on their blooming biology (Fisogni et al, 2020) and pollen/nectar availabil-Urban bees benefit from native species G. phaeum ity and quality (Garbuzov & Ratnieks, 2014;Tew et al, 2021). Knowledge of these traits is crucial for designing a "bee-friendly" urban greenspace (Stange et al, 2017).…”