Abstract
Most pollination ecosystem services studies have focussed on wild pollinators and their dependence on natural floral resources adjacent to crop fields. However, managed pollinators depend on a mixture of floral resources that are spatially separated from the crop field. Here, we consider the supporting role these resources play as an ecosystem services provider to quantify the use and availability of floral resources, and to estimate their relative contribution to support pollination services of managed honeybees. Beekeepers supplying pollination services to the Western Cape deciduous fruit industry were interviewed to obtain information on their use of floral resources. For 120 apiary sites, we also analysed floral resources within a two km radius of each site based on geographic data. The relative availability of floral resources at sites was compared to regional availability. The relative contribution of floral resources-types to sustain managed honeybees was estimated. Beekeepers showed a strong preference for eucalypts and canola. Beekeepers selectively placed more hives at sites with eucalypt and canola and less with natural vegetation. However, at the landscape-scale, eucalypt was the least available resource, whereas natural vegetation was most common. Based on analysis of apiary sites, we estimated that 700,818 ha of natural vegetation, 73,910 ha of canola fields, and 10,485 ha of eucalypt are used to support the managed honeybee industry in the Western Cape. Whereas the Cape managed honeybee system uses a bee native to the region, alien plant species appear disproportionately important among the floral resources being exploited. We suggest that an integrated approach, including evidence from interview and landscape data, and fine-scale biological data is needed to study floral resources supporting managed honeybees.
Highlights
Managed honeybees are globally important for crop production (Potts et al, 2010; Klein et al, 2007) and several studies have assessed the landscape requirements of managed honeybees (Henry et al, 2012a; Henry et al, 2012b; Naug, 2009; Rogers & Staub, 2013; Gallant, Euliss & Browning, 2014; Härtel & Steffan-Dewenter, 2014; Sponsler & Johnson, 2015)
This study focused on three general floral resource-types because they are considered most important by commercial beekeepers (Melin et al, 2014; Johannsmeier, 2001) and spatial data were available for these resource-types
When the availability of different floral resources was adjusted according to the number of hives at an apiary site, eucalypt was found to be of primary importance (Fig. 3C)
Summary
Managed honeybees are globally important for crop production (Potts et al, 2010; Klein et al, 2007) and several studies have assessed the landscape requirements of managed honeybees (Henry et al, 2012a; Henry et al, 2012b; Naug, 2009; Rogers & Staub, 2013; Gallant, Euliss & Browning, 2014; Härtel & Steffan-Dewenter, 2014; Sponsler & Johnson, 2015). A critical component that has not been accounted for in these studies is the putative ecosystem services provided by natural and human-modified landscapes that support managed pollinators (Millennium Ecosystem Assessment, 2003; Costanza et al, 1997), especially if they are not contiguous with the crop field where pollination services are delivered. Such an assessment is essential if an integrated management approach to pollination services is to be adopted, considering both wild and managed pollinators (Garibaldi et al, 2013; Melin et al, 2014). We examine the relative importance of natural and human-modified landscapes for supporting managed honeybees over spatial scales that extend well beyond the farm level (Fig. 1)
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