At what spatial scale do high‐quality habitats enhance the diversity of forbs and pollinators in intensively farmed landscapes?

Abstract

1.Over the last decades, biodiversity in agricultural landscapes has declined drastically. Initiatives to enhance biodiversity, such as agri-environment schemes, often have little effect, especially in intensively farmed landscapes. The effectiveness of conservation management may be improved by scheme implementation near high-quality habitats that can act as a source of species. We evaluated up to what distance high-quality habitats (nature reserves and artificially created flower-rich patches) affect the diversity of forbs and pollinators in intensively farmed landscapes of the Netherlands. 2. We surveyed forbs, inflorescences, bees and hover flies and estimated pollination services in transects along ditch banks extending 300 m from four nature reserves forming small islands in landscapes dominated by agriculture. 3. In a separate experiment, we surveyed inflorescences, bees and hover flies in 1500 m long transects on farmland adjacent to five newly introduced flower-rich patches and in five control transects. 4. Species density of forbs declined over the first 75 m and species density and abundance of hover flies declined over the first 125 m beyond the nature reserves. Beyond these distances, no further declines were observed. The effects of flower-rich patches were spatially limited. The species density and abundance of bees and hover flies were significantly enhanced in the flower-rich patch, but only the abundance of hover flies was enhanced up to 50 m beyond the patch. 5. Synthesis and applications. In intensively farmed areas, remnant high-quality habitats sustain more abundant and diverse pollinator and forb communities than the surrounding countryside. They do enhance biodiversity on nearby farmland but increases are spatially restricted (< 150 m) and relatively small. These habitats may therefore function only as dispersal sources for ecological restoration sites or agricultural fields under extensification schemes that are located in close proximity. Habitat restoration in intensively used farmland should therefore be implemented preferentially in the immediate vicinity of high-quality habitats. In the short term, newly created flower-rich habitats are no alternative to pre-existing seminatural habitats for the promotion of pollinators on nearby farmland.

Invertebrates in field margins: taxonomic group diversity and functional group abundance in relation to age

“…To our knowledge, this is the first time that such a pattern has been described for field margins for a broad range of invertebrates and over a considerable period of time. It is not surprising that there is a slow but steady increase in richness, because the small margins have to be colonised by small invertebrates moving through a hostile environment (Steffan-Dewenter and Tscharntke 1999; Ö ckinger and Smith 2007; Kohler et al 2008), and similar patterns of increasing diversity have been described for other habitats (Mook 1971;Judd and Mason 1995;Desender et al 2006;Cameron and Bayne 2009). Increasing functional diversity in species communities will lead to a greater variety of ecosystem processes (Naeem et al 1994;Tilman et al 1996;Heemsbergen et al 2004) and with time, therefore, margins left on their own may develop towards more natural ecosystems.…”

“…Frequently established semi-natural areas on arable lands are field margin habitats (e.g., De Snoo 1999;Marshall and Moonen 2002). These margins can be beneficial to biodiversity in several ways: they serve as refuge habitats for species unable to persist in intensively managed arable fields or in the declining acreage of natural habitat (Vickery et al 2002;Marshall et al 2006;Carvell et al 2007;Smith et al 2008a), provide overwintering sites for a variety of small animals (e.g., Thomas et al 1992;Dennis et al 1994) and may act as ecological corridors (e.g., Kohler et al 2008).…”

Consequences of Uncertainty in Global-Scale Land Cover Maps for Mapping Ecosystem Functions: An Analysis of Pollination Efficiency

“…Previous research indicates that the abundance and species richness of wild pollinators decreases with increasing distance from the closest edge of natural elements or decreases with a decreasing percentage of natural land cover in the landscape. This can be translated into a percentage yield loss relative to a situation with optimal pollination [31][32][33][34][35].…”

Quantifying Trade-Offs Among Ecosystem Services, Biodiversity, and Agricultural Returns in an Agriculturally Dominated Landscape Under Future Land‑Management Scenarios

“…Hedgerows have been associated with higher bird and moth diversity, provide movement corridors for fauna and host natural enemies that control agricultural pests (Swinton et al 2006). In addition, remnant areas close to agricultural areas improve pollination services with positive consequences for crop yields (Greenleaf and Kremen 2006;Morandin and Winston 2006;Kohler et al 2008;Ricketts et al 2008). …”