Agri-Environment Schemes Targeting Farmland Bird Populations Also Provide Food for Pollinating Insects
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Agricultural and Forest Entomology (2018), DOI: 10.1111/afe.12289 Agri-environment schemes targeting farmland bird populations also provide food for pollinating insects Pierre Ouvrard and Anne-Laure Jacquemart Research Team ‘Genetics, Reproduction, Populations’, Earth and Life Institute – Agronomy, Université catholique de Louvain, Croix du Sud 2, Box L.7.05.14, 1348, Louvain-la-Neuve, Belgium Abstract 1 Farmland biodiversity has declined over the past few decades. European Common Agricultural Policy encourages farmers to set up agri-environment schemes (AES) that support biodiversity and associated ecosystem services such as pollination. Although few AES are specifically devoted to pollinating insects, many AES could provide resources for pollinators. In Belgium, AES designed to provide seed resources for wild birds (bird-strip AES) contain mixed-plant communities that may benefit insects, although their ability to support pollinators has not yet been evaluated. 2 The present study aimed to assess the ability of bird-strip AES to support pollinating insects. We identified and quantified floral resources, flower-visiting insects and insect–flower interaction networks over 2 years on four bird strips located in intensive agro-ecosystems in Belgium. 3 The bird strips contained plant species that were either purposely sown or established spontaneously. The spontaneous Cirsium species, with its high nectar production, offered floral resources that complemented those of the sown species Raphanus sativus and Phacelia tanacetifolia. Most of the flower-visiting insects considered as pollinators belonged to the orders Hymenoptera and Diptera. 4 In conclusion, bird-strip AES provided floral resources to pollinators, even in the absence of annual sowing. Keywords Bees, Cirsium, field strips, flower resources, seed strips, syrphids. Introduction In the European Union, the second pillar of the Common Agri- cultural Policy subsidizes agri-environment schemes (AES) in an Pollinator abundance and diversity are decreasing worldwide effort to combat landscape simplification and support farmland (Kells et al., 2001; Marshall & Moonen, 2002; Kluser & Peduzzi, biodiversity (European Commission, 2017; Wood et al., 2017). 2007; Burkle et al., 2013; Garibaldi et al., 2013; Morandin & However, AES still need to be optimized to increase the resulting Kremen, 2013). This decline is widely linked to changes in biodiversity gains (Merckx et al., 2009). Most AES have focused agricultural management during the last century (Kluser & on a single purpose (e.g. annual cornfield conservation, erosion Peduzzi, 2007; Potts et al., 2009; Kluser et al., 2010; Ollerton et al., 2014). Agricultural intensification, associated in particular limitation, beetle banks or skylark nesting plots in cereal fields); with the widespread use of pesticides (Robinson & Sutherland, however, a single scheme could serve several purposes because 2002; Goulson et al., 2015), increased field size, and removal improving habitat for one target species often improves the habi- of field margins and hedgerows, has contributed to landscape tat for a wider group of nontarget species (Mckenzie et al., 2013). simplification (MacDonald & Johnson, 2000). Simplified land- Flower-strips are common AES implemented in farmland areas scapes have fewer plant species (Kleijn & Raemakers, 2008; (Marshall et al., 2006; Haenke et al., 2009; Haaland & Gyllin, Scheper et al., 2014) and fewer semi-natural areas to provide 2010, 2011; Haaland et al., 2011; Feltham et al., 2015; Wood floral food resources and nesting habitats for insects (Kennedy et al., 2015; Campbell et al., 2017; Sutter et al., 2017). Such et al., 2013; Deguines et al., 2014; Bretagnolle & Gaba, 2015; schemes aim to provide food and a refuge area for wild fauna, Goulson et al., 2015). often birds or insects. In farmland areas, flower-strips are often implemented with the intention of supporting insects that then Correspondence: Pierre Ouvrard. Tel.: +32 10 47 89 34; e-mail: provide pollination or pest management services to the sur- [email protected] rounding fields (Balzan et al., 2014, 2016; Feltham et al., 2015; © 2018 The Royal Entomological Society 2 P. Ouvrard and A.-L. Jacquemart Table 1 The four studied bird-strip agri-environment schemes (AES) located in Hesbaye, Belgium Bird-strip AES Locality Location (Lat. Long.) Length (m) Width (m) Number of sections A Opprebais 50∘41′05′′N4∘47′09′′E 570 12 3 B Opprebais 50∘40′25′′N4∘48′41′′E 500 12 3 C Gembloux 50∘32′53′′N4∘38′08′′E 600 9 2 D Goesnes 50∘27′10′′N5∘11′53′′E 320 12 2 Tschumi et al., 2016; Campbell et al., 2017). When established feeding on bird-strip flowers; (iv) which flowering plant species in intensively managed farmland, flower-strips were found to are visited by insects; and (v) are floral resources resilient to be dominated by a limited number of common insect species annual changes? that visited only a portion of the flowering plant species present (Pywell et al., 2005; Carvell et al., 2007). Therefore, the attrac- tiveness and suitability of such flower-strips for insects are ques- Materials and methods tionable (Kovács-Hostyánszki et al., 2016). In Wallonia (Belgium), pollinator flower-strip AES are specif- To assess the diversity and quantity of available floral resources, ically designed to support flower-visiting insects, in particular we recorded floral diversity and density throughout the year pollinators (Terzo & Rasmont, 2007; Service public de Wallonie, and also estimated pollen and nectar quantity. To evaluate the 2012). The most effective and recognized pollinating insects attractiveness of bird-strip AES to pollinators, we recorded the are Hymenoptera, including mainly bees (Kevan & Baker, diversity and number of visiting insects and the plant species that 1983; Free, 1993; Willmer, 2011), Diptera, including mainly they visited. hoverflies (Ssymank et al., 2008; Inouye et al., 2015), and Lepidoptera (Crepet, 1984; Weiss, 1995; Willmer, 2011). Other categories of AES, such as Walloon AES that are designed Studied sites to provide seed resources (food) and shelter to grain-eating From April to September in 2015 and 2016, we studied four farmland wild birds during the winter (bird strips, Natagriwal, bird strips in Hesbaye, southern Belgium (50∘36′N, 4∘34′E, 2016), could also be important for insects (Carvell et al., 2007). 100–150 m a.s.l. (Table 1). This region is characterized by high Bird-strip AES may include entomophilous flowering plant soil fertility (Witte et al., 2009). The agricultural landscapes species (e.g. Helianthus annuus, Medicago sativa, Phacelia are classical open fields dominated by cereals (44%), sugar tanacetifolia, Raphanus sativus, etc.) (Carreck et al., 1999) beet (Beta vulgaris, 20%), potato (Solanum tuberosum,5%)and sown in a ‘feeding section’ that can provide floral resources to maize (Zea mays, 5%), which are interspersed with meadows insects. A further two components of bird strips include a tall (13%) (Witte et al., 2009). We chose bird-strip AES located in grass ‘refuge section’, which is left uncut for several consecutive open field land, situated at least 2 km away from other landscape years, and an optional harrowed section. The presence of stubble elements, such as apiaries, orchards, forests, hedges,or villages, and hollow-stem plants (Poaceae and Brassicaceae), as well as to minimize interactions with honeybee hives or semi-natural access to bare soil, provides potential nesting sites, especially habitats. All bird strips were 320–600 m long at least 3 km apart for solitary bees (Westrich, 1996; Cane, 1997; Falk, 2015) and to avoid pseudo-replication. other small animals (Kells & Goulson, 2003; Cole et al., 2015). Bird strips were organized into two or three longitudinal However, the potential of such AES to provide appropriate food sections: (i) a 2–3 m wide unmown grass refuge section, sown resources for pollinating insects has not yet been evaluated. in 2008 with a 20 kg/ha mix of Dactylis glomerata (50% To effectively support insect propagation and diversity, an seed weight), Schedonorus arundinaceus (49%) and Trigonella AES must provide uninterrupted dietary resources each year, sp. (1%); (ii) a 3–9 m wide feeding section, sown in 2015 in addition to nesting opportunities (Schellhorn et al., 2015; with a 40 kg/ha mix of the cereal Triticum aestivum (65% of Scheper, 2015; Holzschuh et al., 2016; Moquet et al., 2017). seed weight) and the three entomophilous species Fagopyrum Regarding the plant species present in AES, the species that are esculentum (25%), Phacelia tanacetifolia (3%) and Raphanus deliberately sown are likely to be dominant, as observed in other sativus (7%); and (iii) sn optional 2-m wide unsown and annually sown schemes, although the final plant community harrowed section, which was present in two bird strips (Table 1). will be a mix of both purposely sown and spontaneously In 2016, self-seeding was effective for the three entomophilous established native plant species (Fiedler et al., 2008). Therefore, species sown in 2015 (F. esculentum, P. tanacetifolia and R. it would be relevant to evaluate the relative contribution of sativus) on bird strip B, for P. tanacetifolia and R. sativus in bird insect floral resources by spontaneous and sown plant species in strip A, and for R. sativus only in bird strip C. None of these bird-strip AES. species were observed in bird strip D in 2016. In the present study, we investigated four bird-strip AES during 2015 and 2016 in southern Belgium to evaluate