Spill-over of pest control and pollination services into arable crops

In order to make agriculture more sustainable it is important to enhance the natural processes supporting crop production, including pollination and pest control. The distance over which these services are delivered into the crop (referred to as spill-over) sets limitations on biodiversity mediated agriculture sustainability. We assess how pest control of aphids on wheat (Rhopalosiphum padi) and pollinator linked yield gain in oilseed rape decline with distance from the crop edge. For natural pest control we also assess how field margin floristic diversity (simple grass vs. species-rich wildflower) affects pest control. We do not consider the impact of field margins on oilseed rape pollination as perennial dominated field margins are not in flower at the time of oilseed rape seed set and so do not act to attract pollinators. Aphid colonies exposed to invertebrate natural enemies went extinct at a faster rate than colonies where they were excluded. The rate of decline in per capita growth rates of aphid colonies was greatest when exposed to natural predators, with this effect being detected up to 50 m into the crop where species-rich field margins were present. While oilseed rape yield gains were correlated with pollinator (bees and flies) visitation rates, there was no evidence that yield gain declined with distance from the crop edge. Possibly this was due to honeybees showing no evidence of declining visitation rates with distance into the crop (over 200 m). This contrast with bumblebees, solitary bees and flies which showed evidence of declining visitation rates with distance from the crop edge. Our results suggests that for a typical arable field (c. 12 ha) surrounded by species rich field margins, 50 % of the total area could benefit from enhanced pest control services. Increased yields of oilseed rape due to insect pollinators of c. 0.4 tonnes ha-1 were identified, but there was no evidence that field size would limit the spatial distribution of yields. Our results have implications for integrated crop management world-wide through the use of variable dose rate applications technologies that could be used to target pesticides to field centres and so help support biodiversity mediated ecosystem services

Effects of hedgerow management and restoration on biodiversity

Hedgerows can provide key semi-natural habitat within intensively farmed landscapes, and can deliver habitat and resources for a range of important wildlife, in addition to supporting ecosystem services. The value of hedgerows in supporting wildlife varies, depending on the management applied. Hedgerow management options have high uptake within agri-environment schemes (AES), both historically in Environmental Stewardship (ES) and in the current Countryside Stewardship (CS) scheme, including the Hedgerow and Boundaries grant. Previous studies on hedgerow management have shown substantial potential effects of hedgerow management regimes on the provision of resources for overwintering wildlife (Sparks and Croxton, 2007), and some indication of benefits for wildlife (Maudsley et al. 2000), but have not been quantified or rigorously tested. Here, results from three large-scale manipulative field experiments are presented, to assess different hedgerow management and rejuvenation methods in relation to the provision of resources for wildlife, and the response of invertebrates. The aims of this study were: 1) To examine the effects of simple hedgerow cutting regimes promoted by CS and ES, and the potential for cutting to allow incremental growth, on the quality and quantity of wildlife habitat, and food resources in hedgerows. 2) To identify, develop and test low-cost, practical options for hedgerow restoration and rejuvenation applicable at the large-scale under both CS and ES. Methods Two experiments were conducted to assess hedgerow cutting treatments. Experiment 1 consisted of replicated cutting frequency (every year vs. every two years vs. every three years) and timing (autumn vs. late winter) treatments, applied to replicate sections of hawthorn-dominated hedgerow at a single site in Cambridgeshire. Experiment 1 pre-dated this research project, and so it provided initial findings on these cutting regimes early in the project, which informed the revision of ES hedgerow options in 2012. Experiment 2 was run at five sites in lowland England over seven years (2010 – 2016), on hedgerows dominated by hawthorn (two sites), blackthorn (one site) or a mixture of woody species (two sites). In addition to testing the same cutting treatments as Experiment 1 on a wider range of hedgerow types and locations, Experiment 2 was designed to test the effect of cutting intensity, in order to assess a new hedgerow management option that might be included in future AES. A second multi-site experiment was conducted at five separate lowland sites in England, to compare traditional forms of hedgerow rejuvenation (Midlands style hedge-laying, coppicing) with alternative methods (conservation hedging, wildlife hedging, reshaping with a circular saw). Woody species composition varied between rejuvenation sites, further details below (Section 2.2). Rejuvenation methods were applied to replicate sections of hedgerows, and assessed immediately following implementation in terms of their cost and the time to apply each method. In addition, ongoing management (cut twice in five years as per current ES guidance) was applied to half of each rejuvenated plot, in a split-plot design. The other half was left unmanaged following the rejuvenation. Regrowth, hedgerow structure and berry provision were assessed over three years following the hedgerow rejuvenation. Key findings Hedgerow management (frequency, timing and intensity of cutting) • Cutting once every three years (a current AES hedgerow option) had clear benefits, compared with cutting once every year, which is the current standard practice for hedgerows outside AES schemes. Hedgerow plots cut once every three years had more flowers from two woody hedgerow species (hawthorn and blackthorn), which were shown to be linked to enhanced utilisation of these floral resources by pollinating invertebrates. • More berries were available for overwintering wildlife from four woody species (hawthorn, blackthorn, bramble and dog-rose) on plots cut once every three years. At some sites the increase in hawthorn and blackthorn berries were limited to plots cut in winter. • More Lepidoptera (butterfly and moth) caterpillars and pupae were present on plots cut once every three years, and there was a greater species richness on these plots. More eggs of brown hairstreak butterfly, a conservation priority species, were found on plots cut once every three years in autumn. • There was weaker evidence for the benefits of cutting once every two years. Plots cut once every two years had more hawthorn flowers at some sites and in some years, but flowers were not increased across multiple woody species. More berries were available over winter from four woody species (at some sites) on those plots cut once every two years in winter, but not on plots cut every two years in autumn. • Cutting to allow incremental growth (retaining around 10 cm recent growth when a hedge is cut, so the height and width gradually increases) forms part of the management advice for the current CS hedgerow option, but is not included as a compulsory management prescription. Results from this project provide strong support for the inclusion of this reduced, incremental trimming intensity in future AES hedgerow management prescriptions. • Cutting at a reduced intensity to allow incremental growth resulted in substantially more hawthorn and blackthorn flowers and berries, leading to increased utilisation of these plots by pollinating invertebrates. Lepidoptera diversity was also increased under this reduced intensity cutting treatment, as were the number of brown hairstreak butterfly eggs. Regrowth following incremental cutting was reduced for both blackthorn and field maple, compared to standard cutting intensity. • The benefits of an incremental cutting intensity were not dependent on the timing of cutting, unlike some benefits of the reduced cutting frequency treatments. On land where access for hedge cutting is limited to some times of year (e.g. on land too wet to access with a tractor and flail in late winter), this reduced intensity cutting will provide a range of benefits for wildlife. • The timing of cutting affected the Lepidoptera community using the hedgerows. Plots cut in winter had a greater overall abundance of larvae and pupae than those cut in early autumn, but fewer brown hairstreak butterfly eggs, a priority species for conservation. Timing of cutting should be tailored to the requirements of species present at particular sites. To achieve this, AES hedgerow option prescriptions should include some flexibility about the timing of cutting. Current hedgerow options within ES and CS do contain this flexibility. • Visitation rates of pollinating invertebrates to woody hedgerow flowers were strongly linked to floral abundance, within each species. Pollinating invertebrates made relatively more visits to blackthorn and bramble than hawthorn, perhaps because alternative floral resources are scarcer when blackthorn and bramble are flowering. • There was no evidence to support the assertion that cutting frequency can alter the woody structure of hedgerows, over the six years of this experiment. There was some weak evidence that maximum gap size in the base of hedgerows may be slightly smaller under an incremental trimming intensity, compared with plots cut back to a standard height and width. • Regrowth of hawthorn was largely unaffected by the timing and intensity of cutting. This suggests that the effort required for cutting hawthorn hedges under regimes that differ in timing and intensity should be about equal. In contrast, regrowth of blackthorn and field maple was reduced under the incremental cutting intensity treatment. Hedgerow rejuvenation methods • Of the three layed rejuvenation methods (Midlands hedge-laying, conservation hedging and wildlife hedging; see Section 2.2 for details), wildlife hedging was far quicker to apply than the other two methods (on average less than 1 minute vs. 12 and 33 minutes). However, it cost 62% of the price of conservation hedging and 33% that of Midlands hedge-laying. Wildlife hedging requires three people and heavy machinery, which may be why the time it took was reduced more than price. • Differences between the three layed rejuvenation methods in regrowth and berry provision were greatest in the two years immediately following rejuvenation. Berry provision was not reduced immediately following rejuvenation for wildlife and conservation hedging, but was for Midlands hedge-laying. However, by the third year there was no difference. Canopy regrowth in the second growth season following rejuvenation was less vigorous following wildlife hedging, though this difference was no longer apparent by the third season. • Regrowth from basal stools also differed between layed treatments, as wildlife hedging resulted in taller shoots and fewer basal stems with shoots. There were differences in the basal hedge structure between these three methods, as the wildlife hedging plots had a greater woody area and smaller maximum gaps than the other two layed treatments. • The conservation hedging was twice as quick to apply and about half the cost of Midlands hedge-laying. The conservation hedging plots had slightly lower rates of canopy regrowth in 2012 and a heavier berry weight in 2010-2012, but by 2013 did not differ from plots rejuvenated using Midlands hedge-laying in terms of regrowth, structure or berry provision. Conservation hedging has similar medium-term benefits as more traditional hedge-laying styles, and thus could provide a cost-effective rejuvenation alternative under AES such as Higher Level Stewardship, or the Higher Tier of the current CS scheme. • Coppicing was the second cheapest rejuvenation method tested if fencing was not required, and showed the most vigorous basal regrowth following rejuvenation. Coppice affected hedges over a longer time-scale than the other methods tested, shown by differences in regrowth, structure and berry provision that were still apparent three to four years later. Coppiced hedgerow sections had the most vigorous basal regrowth following rejuvenation. • Reshaping with a circular saw was the cheapest rejuvenation method tested, and had longer term effects on canopy regrowth and berry provision than the three layed methods. Circular saw plots continued to produce greater canopy regrowth compared with the unmanaged control plots three years after rejuvenation, and still had reduced berry weights four years later. The structure of circular saw plots was more similar to that of control plots than the other rejuvenation methods, as the density of woody material in the hedge base was not increased. • Reshaping with a circular saw and coppicing have benefits as cost-effective methods by which to encourage canopy and basal regrowth respectively. Both methods reduced berry provision even four winters following rejuvenation, compared to unmanaged plots. In addition, reshaping with a circular saw did not increase the density of hedge bases, and immediately following rejuvenation coppiced plots also had little basal woody material. Both methods may provide less shelter for mammals and invertebrates than the three layed rejuvenation methods, over the four year timescale tested in this project, and potentially longer. Summary The findings of this project provide support for some existing AES hedgerow management options, within both the ES and CS schemes, in terms of the provision of resources for wildlife and the invertebrate communities that utilise hedgerows. New management techniques have been shown by this project to have potentially more substantial and consistent benefits; reduced intensity cutting to allow incremental growth; and conservation hedging as an alternative to traditional hedge-laying. Early results from this project were used to inform the revision of hedgerow AES options in 2012, and through peer-reviewed papers, knowledge transfer events and resources, the findings of this project have been and continue to be widely communicated

Does agri-environmental management enhance biodiversity and multiple ecosystem services?:A farm-scale experiment

Agri-environmental management has been promoted as an approach to enhance delivery of multiple ecosystem services. Most agri-environment agreements include several actions that the farmer agrees to put in place. But, most studies have only considered how individual agri-environmental actions affect particular ecosystem services. Thus, there is little understanding of how the range of agri-environmental actions available to a farmer might be deployed on any individual farm to enhance multiple services. To address this knowledge gap, we carried out an experimental study in which we deployed a set of agri-environmental actions on a commercial farm in southern England. Agri-environmental actions comprised wildflower margins and fallow areas in arable fields, creating and enhancing grassland with wildflowers, and digging ponds. Alongside biodiversity responses, we measured effects on a number of ecosystem services: pollination, pest control, crop and forage yield, water quality, climate regulation and cultural services. Wildflower margins enhanced invertebrates, pest control and crop yield, and aesthetic appeal. A greater number of pollinators was linked to enhanced oilseed rape yield. But these margins and the fallows did not prevent run-off of nutrients and sediment into waterways, and showed limited carbon sequestration or reduction of greenhouse gas emissions. Newly-dug ponds captured large amounts of sediment and provided aesthetic appeal. Grasslands had higher soil carbon content and microbial biomass, lower N20 emissions, and net sequestration of carbon compared to arable land. Enhancement of grassland plant diversity increased forage quality and aesthetic appeal. Visitors and residents valued a range of agri-environmental features and biodiversity across the farm. Our findings suggest one cannot necessarily expect any particular agri-environmental action will enhance all of a hoped-for set of ecosystem services in any particular setting. A bet-hedging strategy would be for farmers to apply a suite of options to deliver a range of ecosystem service benefits, rather than assuming that one or two options will work as catch-all solutions. © 202