Forest and grassland habitats support pollinator diversity more than wildflowers and sunflower monoculture

Abstract

1. Intensively managed agricultural landscapes often lack suitable habitats to support diverse wildlife, particularly harming pollinator communities. Besides mass flowering crops, remnant patches of natural and semi-natural vegetation may play a key role in maintaining and conserving biodiversity. Yet, the effects of different natural habitats, including forests and grasslands, on different pollinator communities are poorly understood at the landscape scale.2. We examined the abundance, richness, and diversity of wild bees and hoverflies, two key pollinator groups, across a land-use gradient spanning forest edges, grassland, wildflower strips, and sunflower monoculture. We also examined the distribution of hoverfly larvae trophic guilds and wild bee nesting traits across the above-mentioned land-use gradient. Finally, we evaluated the impact of landscape structure (forest, grassland, and water cover in the surrounding landscape) on pollinator community composition.3. Our results indicate that forest and grassland habitats supported a higher abundance and greater richness of pollinators than wildflower strips and sunflower monocultures. Furthermore, hoverflies were more sensitive to habitat and floristic homogenization than wild bees. Sunflower and wildflower habitats also hosted a lower diversity of larvae trophic guilds and wild bee nesting guilds as compared to forests and grasslands. 4. Our study suggests that conserving and restoring forest and grassland habitats within agricultural mosaics may serve as the main 'refuge' for wild pollinators.

Dutch landscapes have lost insect‐pollinated plants over the past 87 years

“…Moreover, grassland and forest tend to differ substantially in plant diversity (Buscardo et al., 2008; Veldman et al., 2015) and pollinator availability (Ganuza et al., 2022; Vujanović et al., 2023). Consequently, we incorporated habitat types of grassland and forest as interaction terms to assess whether the diversity of plants with different pollination modes exhibits distinct trends in these habitats.…”

“…As we restricted our study to (semi‐)natural habitats, our ability to measure the effects of land‐use on plant diversity was limited. However, the transition of habitats from grassland to forest could potentially alter biodiversity (Buscardo et al., 2008; Veldman et al., 2015) and influence pollinator availability (Ganuza et al., 2022; Vujanović et al., 2023). Since the inception of phytosociology in the early 20th century (Becking, 1957), European vegetation surveys have adhered to standardised methodologies.…”

“…Moreover, grassland and forest tend to differ substantially in plant diversity (Buscardo et al, 2008;Veldman et al, 2015) and pollinator availability (Ganuza et al, 2022;Vujanović et al, 2023).…”

Limited function of road verges as habitat for species connecting plant–bee networks in remnant semi-natural grasslands

“…Because there is no comprehensive habitat map available for the area, we extracted land cover classes from an open access, area resource map (AR5 [29]); and combined this with detailed maps of semi-natural grasslands in the Trondheim municipality [22]. Habitats with vegetation dominated by grasses and herbs (hereafter called open green space) have been shown to provide resources for many bees [9,30,31]. In the measure of open green space, we therefore included the land cover classes semi-natural grasslands, areas with barren or scattered vegetation cover and pastures.…”