Arable Field Margins Research Articles

Deterioration of bio-based polylactic acid plastic teabags under environmental conditions and their associated effects on earthworms

In response to the plastic waste crisis, teabag producers have substituted the petrochemical-plastic content of their products with bio-based, biodegradable polymers such as polylactic acid (PLA). Despite widespread use, the degradation rate of PLA/PLA-blended materials in natural soil and their effects on soil biota are poorly understood. This study examined the percentage mass deterioration of teabags with differing cellulose:PLA compositions following burial (−10 cm depth) in an arable field margin for 7-months, using a suite of analytical techniques, such as size exclusion chromatography, 1H nuclear magnetic resonance, dynamic scanning calorimetry, and scanning electron microscopy. The effect of 28-d exposure to teabag discs at environmentally relevant concentrations (0.02 %, 0.04 % and 0.07 % w/w) on the survival, growth and reproduction (OECD TG 222 protocol) of the key soil detritivore Eisenia fetida was assessed in laboratory trials. After 7-month burial, Tbag-A (2.4:1 blend) and Tbag-B (3.5:1 cellulose:PLA blend) lost 66 ± 5 % and 78 ± 4 % of their total mass, primarily attributed to degradation of cellulose as identified by FTIR spectroscopy and a reduction in the cellulose:PLA mass ratio, while Tbag-C (PLA) remained unchanged. There were clear treatment and dose-specific effects on the growth and reproductive output of E. fetida. At 0.07 % w/w of Tbag-A adult mortality marginally increased (15 %) and both the quantity of egg cocoons and the average mass of juveniles also increased, while at concentrations ≥0.04 % w/w of Tbag-C, the quantity of cocoons was suppressed. Adverse effects are comparable to those reported for non-biodegradable petrochemical-based plastic, demonstrating that bio-based PLA does not offer a more ‘environmentally friendly’ alternative. Our study emphasises the necessity to better understand the environmental fate and ecotoxicity of PLA/PLA-blends to ensure interventions developed through the UN Plastic Pollution Treaty to use alternatives and substitutes to conventional plastics do not result in unintended negative consequences.

Foraging preferences of bumble bee castes are weakly related to plant species cover on two arable agri-environment habitat types

Arable field margins provide important floral resources for insect foragers. This study assessed the significance of cultivated margins and floristically enhanced margins, both English agri-environment scheme (AES) options, to foraging bumble bees (Bombus species). We examined plant foraging preferences in each habitat according to species and caste. Additionally, detailed botanical surveys were carried out to determine vascular plant densities on the study margins. Overall, our results emphasised the importance of spontaneous (Asteraceae) species emerging from the seed bank in the provision of forage across Bombus species and castes, and highlighted that Bombus foraging preferences appeared to be only weakly related to floral species densities. Although found only occasionally in high densities, the popularity of these dicots was likely due to high nectar sugar mass. Bombus queens were recorded relatively infrequently, implying that these habitats are failing to provide the preferred floral resources of all Bombus spp. queens. Queens that were observed were found to favour earlier-flowering species (e.g. Anchusa arvensis) and species with longer corollas (e.g. Vicia sativa). Worker bees across Bombus spp. showed high overlap in plant preferences (e.g. Cirsium arvense, Ononis spinosa). However, some variability in preferences between castes within a species were noted, for example, only B. terrestris/lucorum drones were found to forage on Crepis vesicaria in cultivated margins. Additionally, bumble bee abundance was only found to increase as dicot cover increased. Overall, our findings highlight the importance of continuing to utilise multiple AES types in order to fully support Bombus and other pollinating insect populations on farmland.

Major field margin vegetation types in France and their relationships with climate, agricultural landscapes and management intensity

ABSTRACT Arable field margins are an important semi-natural habitat providing multiple functions in agroecosystems. Despite three decades of research, analyses of species assemblage and functional traits are lacking. Leveraging a national monitoring network in metropolitan France, we aim to provide a comprehensive taxonomic and functional synthesis of field margin flora, outline main field margin types and explore their associations with management practices, climate, and agricultural landscapes. We analysed data from 532 field margins surveyed between 2013 and 2017, using both uni- and multivariate analyses. Field margins exhibited great diversity with 711 distinct taxa (12% of all flora in mainland France) at the national scale and an average of 16 species per 10 m2 locally. While field margins contained few species of conservation value, they offered a refuge for many declining species as well as rare arable weed species. We identified seven main field margin types, each linked to distinct conditions of climate, soil, landscape and agricultural practices. Mediterranean field margins notably differed from all others. In the main cluster, vineyard margins also stood out as distinct from annual crop margins. Additionally, field margins in landscapes with a high proportion of grassland differed from those within intensively cultivated field crop plains in conventional agriculture. Overall, our study highlights the high botanical diversity of field margins and their interest for plant conservation in agricultural landscapes. Promoting the installation and/or maintenance of field margins through agri-environmental schemes should thus favour biodiversity conservation and associated ecosystem provision.

Floral enhancement of arable field margins increases moth abundance and diversity

Moth populations have declined across large parts of north-western Europe since the mid-20th century due, in part, to agricultural intensification. Agri-environment schemes (AES) are widely implemented across Europe to protect biodiversity in agricultural landscapes. Grass field margins enriched with wildflowers typically out-perform grass-only margins in terms of increasing insect abundance and diversity. However, the effect of wildflower enrichment on moths remains largely unstudied. Here, the relative importance of larval hostplants and nectar resources for adult moths within AES field margins are investigated. Two treatments and a control were compared: (i) a plain grass mix, the control, (ii) a grass mix enriched with only moth-pollinated flowers, and (iii) a grass mix enriched with 13 wildflower species. Abundance, species richness and Shannon diversity were up to 1.4, 1.8 and 3.5 times higher, respectively, in the wildflower treatment compared to plain grass. The difference in diversity between treatments became greater in the second year. There was no difference in total abundance, richness or diversity between the plain grass treatment and grass enriched with moth-pollinated flowers. The increase in abundance and diversity in the wildflower treatment was due primarily to the provision of larval hostplants, with nectar provision playing a smaller role. The relative abundance of species whose larval hostplants included sown wildflowers increased in the second year, suggesting colonisation of the new habitat.Implications for insect conservation.We show that, at the farm scale, moth diversity can be greatly enhanced and abundance moderately enhanced by sowing diverse wildflower margins, providing these insects with both larval hostplants and floral resources, compared to grass-only margins.

Evidence that agri-environmental measures in arable fields could be a conservation benefit to northern vipers Vipera berus and other reptiles

In Britain, some reptiles species have been formally recorded inhabiting arable field margins but previous reports on the incidence of northern vipers or adders Vipera berus in this situation have been anecdotal. In 2017, reptile monitoring was initiated in a field margin that had been created ten years earlier and was located near two chalk grassland nature reserves with established viper populations. In the first three years of recording, numbers of vipers in the field margin were low and limited to a few juveniles and adults. In the fourth year, there was a noticeable increase in number, which were now represented by all life stages. In the fifth year the population doubled again and then remained stable in the sixth year. A similar encounter trajectory was observed for grass snakes, while slow worms and common lizard encounters had different trajectories. There was some evidence of vipers moving between the nature reserves and field margin, even crossing a road to do so, but at least 75 % of vipers in the field margin were only ever detected there. The arable field was mostly used for cropping cereals and oilseeds but, exceptionally, in the three years from 2016 to 2018 it was put down to herbal leys of red clover and grass. In the USA and continental Europe, red clover is known to be a preferred dietary item of voles Microtus spp and has been associated with vole population increase. It is suggested that the increase in the viper population in the field margin may relate to a rise in the number of voles, which are an important component of the viper diet. Likewise, for grass snakes, small mammals may contribute 25 % or more of their diet. The use of herbal leys may present an important opportunity for the conservation of northern vipers in field margins and other adjacent habitats.

Discrepancies between the drivers of alpha and beta plant diversity in arable field margins.

Field margins are major habitats for biodiversity conservation and ecosystem functioning in agricultural landscapes, but biotic homogenization of plant communities threatens their ecological and agronomic functions. Our objective is to determine the drivers of plant diversity in field margins for conservation and restoration purposes. To do so, we assessed the effects of field margin structure and long-term management over 20 years (1995-2015) on the taxonomic and functional α- and β-diversity, and the functional composition of herbaceous plant communities. In 2015, we surveyed 302 field margins in bocage landscapes of Brittany, northwestern France. Results were very similar between taxonomic and functional diversity but revealed important discrepancies between the drivers of α- and β-diversity. Deep ditches, mowing and grazing increased α-diversity but did not affect β-diversity. Denser hedgerows had lower α-diversity than other field margins but strongly contributed to β-diversity by harbouring more unique sets of species or life strategies. Long-term herbicide spraying in field margins and cropping intensity in adjacent habitats did not affect α-diversity, but had more complex effects on β-diversity and selected for common weeds. All in all, preservation of dense hedgerows, abandonment of herbicide spraying, and protection against agrochemical drifts are key measures to prevent the establishment of common weeds and biotic homogenization of herbaceous plant communities in field margins. Above all, our study shows how important it is to go beyond α-diversity to make robust conservation and restoration decisions.

Neonicotinoid use on cereals and sugar beet is linked to continued low exposure risk in honeybees

Risks posed to bees from neonicotinoid seed treatments (clothianidin, thiamethoxam, imidacloprid) led in 2013 to the European Union instigating a moratorium for their use on mass-flowering crops, including oilseed rape in the UK. This restriction did allow for the continued use of these seed treatments, in particular clothianidin, on non-flowering crops like winter wheat. To determine the impacts of the moratorium, we assessed neonicotinoid concentrations pre- (2014) and post- (2015−17) moratorium in 347 honey samples collected across Great Britain. While the probability of detecting clothianidin declined immediately following the moratorium, detection rates remained constant over the following three years (mean = 0.10 ppb, maximum = 2.8 ppb). In contrast, after three years thiamethoxam residues entirely disappeared while detection of imidacloprid was infrequent but persistent over the whole period. For those hives where neonicotinoids were detected, there was no evidence that the concentrations in the honey declined over the three years following the ban. Using metabarcoding approaches, we identified plants foraged upon by honeybees during the production of honey. After the moratorium came into effect, the highest neonicotinoid residues were associated with honey produced by foraging on both oilseed rape and several wild plants found in arable field margins. Concerns about soil persistence and uptake by non-target flowering plants ultimately led to a full European Union ban in 2018. Our results suggest that before this full ban came into effect, the use of clothianidin on non-flowering crops maintained a low-level probability of encountering this neonicotinoid within honey. However, these concentrations were low and would have been unlikely to pose significant risks to honeybees.

Local Factors Rather than the Landscape Context Explain Species Richness and Functional Trait Diversity and Responses of Plant Assemblages of Mediterranean Cereal Field Margins

Arable field margins are valuable habitats providing a wide range of ecosystem services in rural landscapes. Agricultural intensification in recent decades has been a major cause of decline in plant diversity in these habitats. However, the concomitant effects on plant functional diversity are less documented, particularly in Mediterranean areas. In this paper, we analyzed the effect of margin width and surrounding landscape (cover and diversity of land use and field size), used as proxies for management intensity at local and landscape scales, on plant species richness, functional diversity and functional trait values in margins of winter cereal fields in southern Spain. Five functional traits were selected: life form, growth form, seed mass, seed dispersal mode and pollination type. RLQ and fourth-corner analyses were used to link functional traits and landscape variables. A total of 306 plant species were recorded. Species richness and functional diversity were positively related to margin width but showed no response to landscape variables. Functional trait values were affected neither by the local nor landscape variables. Our results suggest that increasing the margin width of conventionally managed cereal fields would enhance both taxonomic and functional diversity of margin plant assemblages, and thus the services they provide to the agro-ecosystem.

Topsoil translocation in extensively managed arable field margins promotes plant species richness and threatened arable plant species

Since the 1950s, agriculture has intensified drastically, which has led to a significant biodiversity decline on arable lands. This decline was especially dramatic for segetal plant species, the specialist species of cereal fields. Due to the low population density and poor dispersal abilities of many segetal species, the recovery of species-rich fields may fail even though the environmental conditions are suitable. Therefore, conservation efforts including active restoration measures aimed at recovering segetal vegetation are needed. To this purpose, we propose to alleviate dispersal limitation by means of topsoil translocation from a species-rich donor arable field. At two receiver sites, we tested this technique using two topsoil-spreading densities, i.e. 2.5Lsoil/m2 and 5Lsoil/m2 in experimental plots (3 m2). At one receiver site, we tested the impact of topsoil translocation from two different donor sites, while in the other receiver site one donor site was used. We compared plant species diversity and composition of treated plots with control plots as well as with the species composition of the donor sites (field survey) and their seed bank (greenhouse survey). Species richness was increased by topsoil spreading, including richness of threatened species. 33% and 71% of the threatened species were successfully translocated respectively at the two receiver sites. At one site, plant cover was also increased, including threatened species cover. Conversely, topsoil spreading did not promote pernicious species that could affect farmer acceptance negatively. Vegetation of translocated plots was more similar in terms of species composition to donor site seed banks than to donor site field survey. The higher spreading density led to increased species richness when seed bank in topsoil had lower density. Our results show that topsoil translocation can be a highly effective method for restoring threatened segetal plant communities in agricultural landscapes. Even when a full plant community was already present (Receiver 1) topsoil transfer led to a doubling in species richness. The seed bank surveys were a good indicator of plant community composition upon topsoil translocation in the field and are therefore advisable to implement in the project-planning phase to evaluate donor site potential. From our results, we recommend to spread soil at an overall rate of 500 seeds/m2 equivalent. Future studies need to assess the long-term fate of the translocated species as well as the impacts of soil harvests on the donor sites to establish sustainable use levels.

Use of field margins managed under an agri-environment scheme by foraging Barn Swallows Hirundo rustica

ABSTRACTCapsule: Barn Swallows Hirundo rustica were more likely to forage along arable field margins that were enhanced with wildflowers or legumes than control grass margins.Aims: To determine if foraging Barn Swallows displayed preferences for specific arable field boundary habitats (grass margins versus floristically enhanced margins) that were managed as part of an agri-environment scheme. We also aim to determine how Barn Swallow food abundance related to these habitats.Methods: Two foraging activity surveys took place on all grass and floristically enhanced margins (n = 56) present within the 600 m foraging range of seven Barn Swallow colonies during June and July 2016. Margin habitat use was measured by recording the presence/absence of foraging individuals during surveys, the total number of individuals and by calculating an index of foraging activity. Habitat information relating to adjacent boundary type, transect crop type and neighbouring crop type were also recorded.Results: Foraging Barn Swallows were significantly more likely to be recorded when survey transects included a floristically enhanced margin, but there was no significant impact of floristically enhanced margins on the total number of individuals recorded or on the index of foraging activity. Foraging activity was higher along grass verges and hedgerows when compared to treelines and was positively related to length weighted Diptera abundance (a measure of food biomass).Conclusion: Our results suggest that there may be a role for floristically enhanced margins in the conservation of Barn Swallows on arable farmland. More research, however, is needed to determine whether invertebrate-rich agri-environment scheme habitats can influence colony size or improve the breeding success of this species.

Assessing non-intended effects of farming practices on field margin vegetation with a functional approach

To assess the unwanted side effects of farming practices on non-target plants, we used a nationwide survey of the vegetation of arable field margin strips. The vegetation was surveyed during two years (2013, 2014) in 430 field margins distributed over all agricultural regions of France. We used two complementary multivariate, trait-based approaches to examine how ten plant traits were related to ten environmental variables describing abiotic conditions, landscape factors, field margin management and in-field practices. Generalized additive mixed models were also developed to assess how the same environmental variables correlated with species richness, functional diversity and relative richness of agrotolerant versus hemerophobic species. Traits responded primarily to an environmental gradient of landscape diversity and field margin management. For instance, narrow field margin strips, frequent management and presence of a ditch favoured annual plants, small size at maturity and perennial plants, respectively. The second environmental gradient affecting plant traits was related to field size and intensity of in-field farming practices. On this gradient, fertilizer drift appeared to have a much stronger effect on plant trait composition of field margin strips than herbicide drift. The relationship between species richness, or functional diversity, and environment was consistent with the trait-based approach: the two former variables were negatively correlated with agriculture intensification (e.g. field size). However, this analysis also highlighted new covariates, such as a negative relationship between frequency of herbicide use and species richness. Some of the observed patterns seemed to be driven by differential responses of agrotolerant versus hemerophobic species, with the latter being more species-rich under organic than under conventional farming. Despite efforts to reduce nitrogen inputs since the 2000s, our results shows that N-fertilization still has significant non-intended effects on field margin vegetation. More generally, increasing the width of field margin strips, keeping or restoring semi-natural elements (ditches, hedges) in the field boundary, and lowering the number of management events may promote grassland plant species more typical of semi-natural habitats.

Effects of Field-Relevant Concentrations of Clothianidin on Larval Development of the Butterfly Polyommatus icarus (Lepidoptera, Lycaenidae).

Arable field margins are often sown with wildflowers to encourage pollinators and other beneficial or desirable insects such as bees and butterflies. Concern has been raised that these margins may be contaminated with systemic pesticides such as neonicotinoids used on the adjacent crop, and that this may negatively impact beneficial insects. The use of neonicotinoids has been linked to butterfly declines, and species such as the common blue butterfly ( Polyommatus icarus) that feed upon legumes commonly sown in arable field margins, may be exposed to such toxins. Here, we demonstrate that the larval food plants of P. icarus growing in an arable field margin adjacent to a wheat crop treated with the neonicotinoid clothianidin not only contain the pesticide at concentrations comparable to and sometimes higher than those found in foliage of treated crops (range 0.2-48 ppb) but also remain detectable at these levels for up to 21 months after sowing of the crop. Overall, our study demonstrates that nontarget herbivorous organisms in arable field margins are likely to be chronically exposed to neonicotinoids. Under laboratory conditions, exposure to clothianidin at 15 ppb (a field-realistic dose) or above reduced larval growth for the first 9 days of the experiment. Although there was evidence of clothianidin inducing mortality in larvae, with highest survival in control groups, the dose-response relationship was unclear. Our study suggests that larvae of this butterfly exhibit some deleterious sublethal and sometimes lethal impacts of exposure to clothianidin, but many larvae survive to adulthood even when exposed to high doses.

Functional response of plant assemblages to management practices in road-field boundaries

Questions Management practices implemented on road verges are partly established to preserve biodiversity in agricultural landscapes. Their evaluation was primarily based on the analysis of the taxonomic structure and composition of communities. What is the relationship between management practices and the functional characteristics of road-field plants within elements? Location Western-central France. Methods We sampled the berm, the embankment and the field margin of 40 road-field boundaries located in Western-central France, an area where a delayed mowing of some berms has been practised since 2009 for biodiversity reasons. We characterised management practices implemented on the different elements, i.e. the frequency and timing of mowing (early summer or late summer), the frequency of herbicide treatment in field margins and the nitrogen input rate. We retrieved from databases seven functional traits and types known to be influenced by management practices. To identify relationships between traits and environmental variables we first performed partial RLQ analyses to remove any potential confounding effect of the landscape context studied. We then computed fourth-corner statistics to quantify relationships between traits, environmental variables and partial RLQ axes. Results Late mowing of the berm promoted nitrophilous species within berms and competitive rather than ruderal species within arable field margins. The frequency of herbicide treatment in field margins promoted broadleaf species within this element and, to a lesser extent, within embankments. Finally, the functional characteristics of communities of the three elements were not influenced by the level of nitrogen input in field margins. Conclusions In our environmental context, managing road verges affected the functional structure of plant assemblages both within them and within their adjacent arable field margins. We suggest a single early mowing of berms as a valuable practice for both conservation purposes and weed risk control in adjacent field margins. This article is protected by copyright. All rights reserved.

Enhancing the diversity of breeding invertebrates within field margins of intensively managed grassland: Effects of alternative management practices.

Severe declines in biodiversity have been well documented for many taxonomic groups due to intensification of agricultural practices. Establishment and appropriate management of arable field margins can improve the diversity and abundance of invertebrate groups; however, there is much less research on field margins within grassland systems. Three grassland field margin treatments (fencing off the existing vegetation “fenced”; fencing with rotavation and natural regeneration “rotavated” and; fencing with rotavation and seeding “seeded”) were compared to a grazed control in the adjacent intensively managed pasture. Invertebrates were sampled using emergence traps to investigate species breeding and overwintering within the margins. Using a manipulation experiment, we tested whether the removal of grazing pressure and nutrient inputs would increase the abundance and richness of breeding invertebrates within grassland field margins. We also tested whether field margin establishment treatments, with their different vegetation communities, would change the abundance and richness of breeding invertebrates in the field margins. Exclusion of grazing and nutrient inputs led to increased abundance and richness in nearly all invertebrate groups that we sampled. However, there were more complex effects of field margin establishment treatment on the abundance and richness of invertebrate taxa. Each of the three establishment treatments supported a distinct invertebrate community. The removal of grazing from grassland field margins provided a greater range of overwintering/breeding habitat for invertebrates. We demonstrate the capacity of field margin establishment to increase the abundance and richness in nearly all invertebrate groups in study plots that were located on previously more depauperate areas of intensively managed grassland. These results from grassland field margins provide evidence to support practical actions that can inform Greening (Pillar 1) and agri‐environment measures (Pillar 2) of the Common Agricultural Policy (CAP). Before implementing specific management regimes, the conservation aims of agri‐environment measures should be clarified by defining the target species or taxonomic groups.

Earthworm communities in arable fields and restored field margins, as related to management practices and surrounding landscape diversity

Abstract Agricultural intensification has negative impacts on biodiversity at spatial scales from field to landscape. Earthworms are important for soil functioning, so it is crucial to understand the responses of earthworm communities to agricultural management and land use. We aimed to: 1) investigate whether earthworm communities differed between relatively undisturbed field margins, and highly disturbed arable fields; and 2) quantify how earthworm communities of arable fields and field margins are affected by three environmental filters, i.e. soil properties, management practices, and composition of the surrounding landscape. Earthworms were sampled in 26 arable fields and 15 field margins, across a polder area in The Netherlands. While earthworm density, total biomass and species richness did not differ significantly among arable fields and field margins, rarefied earthworm species richness and community composition did. The three environmental filters affected earthworm communities of arable fields and field margins differently. In arable fields, earthworm communities were explained by arable management only (26%). In contrast, all three filters contributed significantly to the variation in earthworm communities of field margins, where management practices explained a larger part of the variation (18%) than the surrounding landscape (11%) and soil properties (10%). Our results suggest that soil properties and surrounding landscape can affect earthworm communities of field margins. However, in the arable fields, where more diverse lumbricid communities are desirable to improve soil functions, such influences are negated by the impact of management at field scale. We demonstrated that field margins enhance earthworm biodiversity in arable landscapes, but surrounding landscape and field margins had limited impact on earthworm communities in arable fields. Decision-making and research should focus on less intensive management options for arable fields to stimulate earthworms and earthworm-mediated soil functions.

Spatial targeting of habitat creation has the potential to improve agri‐environment scheme outcomes for macro‐moths

Summary Agri‐environment scheme (AES) interventions are a major avenue for habitat creation and restoration across Europe. To maximize benefits for biodiversity, AES interventions are sometimes spatially targeted relative to existing semi‐natural habitat (SNH). However, the evidence base for effective spatial targeting is deficient; studies until now have collated data across several taxa and regions, resulting in non‐specific advice that is only useful at the regional scale. We present a field study using macro‐moths (Lepidoptera) to test (i) the impact of creating grassland habitat on arable field margins, (ii) how the impact of this type of AES intervention varies according to species specialism and (iii) the potential impact of spatially targeting AES interventions for proximity to semi‐natural chalk grassland (CG). We surveyed macro‐moths on arable fields with and without AES interventions across a range of levels of connectivity to CG. We also surveyed macro‐moths on CG habitat. Macro‐moth abundance was highest on CG and lowest on arable field centres. The benefits of AES interventions were largest for grassland‐associated macro‐moths: abundance was ∼1·4 times higher on AES margins than on control margins for this group. Chalk grassland‐associated macro‐moths only benefited from AES interventions that were close (<1 km) to large areas (>10 ha) of CG habitat. We estimate that clustering AES interventions around CG could lead to a ∼17% increase in CG macro‐moth abundance on arable margins across our sampled region, leading to an overall increase of 2·6% within the sampled region. Synthesis and applications. We provide evidence that for conservation of species associated with a specific type of semi‐natural habitat (SNH), agri‐environment scheme (AES) interventions are most effectively positioned close to that habitat. Our study on macro‐moths in arable fields with and without AES interventions across a range of levels of connectivity to chalk grassland represents a template for the production of tailored spatial targeting advice. We show that optimal positioning of AES habitat creation depends on the extent of SNH in the surrounding landscape as well as the ecology and life history of species being conserved.

Nectar accessibility determines fitness, flower choice and abundance of hoverflies that provide natural pest control

Summary In modern agricultural landscapes, many organisms providing ecosystem services such as pollination and natural pest control are likely constrained by shortage of nectar and/or pollen required for adult nutrition. More and more flower‐rich field margin strips and other habitats are created to eliminate these constraints. For most target organisms, however, it is not well known which (types of) flowers are effective in providing suitable pollen and nectar. We studied the suitability of a wide range of flowers as a food source for zoophagous hoverflies (hoverflies with predatory larvae) at five different levels: nectar accessibility (based on flower morphology), realized adult fitness, flower choice (both based on cage experiments), flower visitation and hoverfly abundance in mixed vegetation (both based on field observations). Realized survival of Episyrphus balteatus is related to effective flower depth by a sigmoid function. The critical flower depth is 1·6 mm, which is less than the proboscis size of the hoverfly. For Asteraceae, the critical floret depth is even less than 1·0 mm, which – in contrast to common knowledge – rules out most species within this family. Both flower choice in the laboratory and flower visitation rates in the field are well correlated with nectar accessibility and realized adult survival. In mixed floral vegetation, the number of zoophagous hoverflies is highly correlated with the abundance of only those flowers that have accessible nectar for these hoverflies. Synthesis and applications. This comparative study demonstrates that nectar (and not pollen) accessibility is the main driver determining flower resource suitability, flower choice and abundance of zoophagous hoverflies in arable field margins. The study identifies the limited range of plant species that can effectively support these beneficial insects. Preserving the right flowers in and around agricultural fields could enhance local populations and the pest control and pollination services they provide.

Neonicotinoid Residues in Wildflowers, a Potential Route of Chronic Exposure for Bees.

In recent years, an intense debate about the environmental risks posed by neonicotinoids, a group of widely used, neurotoxic insecticides, has been joined. When these systemic compounds are applied to seeds, low concentrations are subsequently found in the nectar and pollen of the crop, which are then collected and consumed by bees. Here we demonstrate that the current focus on exposure to pesticides via the crop overlooks an important factor: throughout spring and summer, mixtures of neonicotinoids are also found in the pollen and nectar of wildflowers growing in arable field margins, at concentrations that are sometimes even higher than those found in the crop. Indeed, the large majority (97%) of neonicotinoids brought back in pollen to honey bee hives in arable landscapes was from wildflowers, not crops. Both previous and ongoing field studies have been based on the premise that exposure to neonicotinoids would occur only during the blooming period of flowering crops and that it may be diluted by bees also foraging on untreated wildflowers. Here, we show that exposure is likely to be higher and more prolonged than currently recognized because of widespread contamination of wild plants growing near treated crops.

Effects of breeding habitat and field margins on the reproductive performance of Skylarks (Alauda arvensis) on intensive farmland

Field margin management is a common measure employed in Europe to support farmland bird populations. In this study we found and analysed 237 nests of the Skylark Alauda arvensis in the Netherlands over a period of 6 years to determine the effects of arable field margins and breeding crop on nest-level reproductive success. Additionally, the effect of field margins on predation was investigated and food availability in crops and field margins was compared. Neither clutch size, nest survival nor nestling body weight were improved by field margin availability, irrespective of the breeding crop used. However, the choice of breeding crop had important effects. Nestling weight was significantly lower in cereals than in grassland and lucerne, corresponding with the low prey densities present in cereals. Nest survival was lowest in grassland due to frequent silage cutting. Predation rates were highest in cereals but were not affected by field margin proximity. The highest reproductive success was achieved in lucerne, which was mown twice a year and retained a suitable height for breeding throughout the breeding season. We conclude that field margins are not sufficient to maintain a Skylark population in this intensively farmed area. The presumably more subtle effects of increased food availability cannot compensate for the high nest failure rates resulting from agricultural operations and predation. In this and similar areas, the provisioning of safe nesting habitat throughout the breeding season is essential to improve breeding performance. Our research suggests that this can be achieved by reducing the frequency of silage cutting on grassland and by increasing the surface area of lucerne.

Influence of agri-environment scheme options on territory settlement by Yellowhammer (Emberiza citronella) and Corn Bunting (Emberiza calandra)

Conserving farmland birds is a key objective for agri-environment schemes (AES) across Europe, with a number of management options aimed at providing invertebrate food and nesting habitats. We analysed territory settlement by two widespread but declining farmland buntings with contrasting nesting requirements: the Yellowhammer Emberiza citrinella, a boundary-nesting species, and the Corn Bunting Emberiza calandra, a ground-nesting species. The study was conducted on farms participating in the English Higher Level Stewardship scheme to test whether territory settlement is influenced by the provision of key arable AES options. Both species settled preferentially in localities containing sown arable field margins, while Corn Bunting also settled in localities containing nectar flower mixtures. These preferences are likely to reflect foraging rather than nesting habitat requirements. Yellowhammer selected territories containing hedgerows under AES management, which are nesting rather than foraging habitat but may also provide food. Uptake by land owners of several AES options likely to provide limiting resources for farmland birds was very low, and because uptake at the landscape scale is also low, wider-scale population level benefits are likely to be constrained. However, this is one of few studies demonstrating selection of widely applied arable AES options by breeding farmland birds.