Nigel Boatman

Historical nectar assessment reveals the fall and rise of floral resources in Britain

There is considerable concern over declines in insect pollinator communities and potential impacts on the pollination of crops and wildflowers. Among the multiple pressures facing pollinators, decreasing floral resources due to habitat loss and degradation has been suggested as a key contributing factor. However, a lack of quantitative data has hampered testing for historical changes in floral resources. Here we show that overall floral rewards can be estimated at a national scale by combining vegetation surveys and direct nectar measurements. We find evidence for substantial losses in nectar resources in England and Wales between the 1930s and 1970s; however, total nectar provision in Great Britain as a whole had stabilized by 1978, and increased from 1998 to 2007. These findings concur with trends in pollinator diversity, which declined in the mid-twentieth century but stabilized more recently. The diversity of nectar sources declined from 1978 to 1990 and thereafter in some habitats, with four plant species accounting for over 50% of national nectar provision in 2007. Calcareous grassland, broadleaved woodland and neutral grassland are the habitats that produce the greatest amount of nectar per unit area from the most diverse sources, whereas arable land is the poorest with respect to amount of nectar per unit area and diversity of nectar sources. Although agri-environment schemes add resources to arable landscapes, their national contribution is low. Owing to their large area, improved grasslands could add substantially to national nectar provision if they were managed to increase floral resource provision. This national-scale assessment of floral resource provision affords new insights into the links between plant and pollinator declines, and offers considerable opportunities for conservation.

Evidence for pollinator cost and farming benefits of neonicotinoid seed coatings on oilseed rape.

Chronic exposure to neonicotinoid insecticides has been linked to reduced survival of pollinating insects at both the individual and colony level, but so far only experimentally. Analyses of large-scale datasets to investigate the real-world links between the use of neonicotinoids and pollinator mortality are lacking. Moreover, the impacts of neonicotinoid seed coatings in reducing subsequent applications of foliar insecticide sprays and increasing crop yield are not known, despite the supposed benefits of this practice driving widespread use. Here, we combine large-scale pesticide usage and yield observations from oilseed rape with those detailing honey bee colony losses over an 11 year period, and reveal a correlation between honey bee colony losses and national-scale imidacloprid (a neonicotinoid) usage patterns across England and Wales. We also provide the first evidence that farmers who use neonicotinoid seed coatings reduce the number of subsequent applications of foliar insecticide sprays and may derive an economic return. Our results inform the societal discussion on the pollinator costs and farming benefits of prophylactic neonicotinoid usage on a mass flowering crop.

A Bayesian sensitivity analysis applied to an Agent-based model of bird population response to landscape change

Agricultural land management has important impacts on land use and vegetation that can rapidly induce ecosystem change. Birds are often used as indicators of such impacts of landscape change on ecosystems. However, predicting the response of birds to changes in their environment is an ongoing challenge. Agent-based models (ABMs) have the potential to provide useful insights but have not been widely used in such studies to date. This paper illustrates the use of agent-based modelling for policy decision-making, using the case study of the impacts of the removal of set-aside land on Skylark populations in Denmark.In order to address the importance of critical interpretation of ABMs, we introduce a novel methodology with which to analyze the sensitivity of an ABM, Bayesian Analysis of Computer Code Outputs (BACCO). BACCO constructs an emulator of the model in order to provide a rapid and thorough sensitivity analysis. This allows us to identify input parameters in the model that require more rigorous parameterization, as some parameters are highly sensitive and are found to produce spurious results when varied even a small amount. Highlights? We use an Agent-based model (ABM) to explore the impacts of set-aside removal on Skylarks in Denmark. ? Our novel BACCO sensitivity analysis of an ABM is both rapid and thorough. ? We identify an influential input parameter that requires more rigorous parameterization. ? We analyze and distill some of the complexity of an ABM.

Climate-driven spatial mismatches between British orchards and their pollinators: increased risks of pollination deficits

Understanding how climate change can affect crop-pollinator systems helps predict potential geographical mismatches between a crop and its pollinators, and therefore identify areas vulnerable to loss of pollination services. We examined the distribution of orchard species (apples, pears, plums and other top fruits) and their pollinators in Great Britain, for present and future climatic conditions projected for 2050 under the SRES A1B Emissions Scenario. We used a relative index of pollinator availability as a proxy for pollination service. At present, there is a large spatial overlap between orchards and their pollinators, but predictions for 2050 revealed that the most suitable areas for orchards corresponded to low pollinator availability. However, we found that pollinator availability may persist in areas currently used for fruit production, which are predicted to provide suboptimal environmental suitability for orchard species in the future. Our results may be used to identify mitigation options to safeguard orchard production against the risk of pollination failure in Great Britain over the next 50 years; for instance, choosing fruit tree varieties that are adapted to future climatic conditions, or boosting wild pollinators through improving landscape resources. Our approach can be readily applied to other regions and crop systems, and expanded to include different climatic scenarios.

Species Distribution Models for Crop Pollination: A Modelling Framework Applied to Great Britain

Insect pollination benefits over three quarters of the worlds major crops. There is growing concern that observed declines in pollinators may impact on production and revenues from animal pollinated crops. Knowing the distribution of pollinators is therefore crucial for estimating their availability to pollinate crops; however, in general, we have an incomplete knowledge of where these pollinators occur. We propose a method to predict geographical patterns of pollination service to crops, novel in two elements: the use of pollinator records rather than expert knowledge to predict pollinator occurrence, and the inclusion of the managed pollinator supply. We integrated a maximum entropy species distribution model (SDM) with an existing pollination service model (PSM) to derive the availability of pollinators for crop pollination. We used nation-wide records of wild and managed pollinators (honey bees) as well as agricultural data from Great Britain. We first calibrated the SDM on a representative sample of bee and hoverfly crop pollinator species, evaluating the effects of different settings on model performance and on its capacity to identify the most important predictors. The importance of the different predictors was better resolved by SDM derived from simpler functions, with consistent results for bees and hoverflies. We then used the species distributions from the calibrated model to predict pollination service of wild and managed pollinators, using field beans as a test case. The PSM allowed us to spatially characterize the contribution of wild and managed pollinators and also identify areas potentially vulnerable to low pollination service provision, which can help direct local scale interventions. This approach can be extended to investigate geographical mismatches between crop pollination demand and the availability of pollinators, resulting from environmental change or policy scenarios.

Chapter 1:Impacts of Agricultural Change on Farmland Biodiversity in the UK

Over the past 50 years, there has been a marked decline shown by many species closely associated with lowland farmland in the UK, which is widely considered to be a key issue in British nature conservation. Increased availability of survey data has meant it is now possible to quantify changes in bio...

Entry Level Stewardship may enhance bird numbers in boundary habitats

Capsule Hedgerows and margins managed under agri‐environment schemes appear to attract greater numbers of some farmland bird species. Aims To examine fine‐scale habitat associations of farmland birds to determine whether Entry Level Stewardship, the wider countryside agri‐environment scheme for England, provides a mechanism for affecting population changes. Methods Ninety‐seven 1‐km squares in East Anglia were surveyed to create two‐dimensional habitat maps showing the location of all habitat patches and associated stewardship management. Modified territory‐mapping techniques were used to produce relative estimates of bird numbers within each discrete habitat patch within each square. The effect of Entry Level Stewardship on species density was then analysed using glms. Results Boundaries managed under Entry Level Stewardship appeared to attract higher densities of Blue Tits, Dunnocks, Common Whitethroats and Yellowhammers. Margins managed under the scheme also had higher densities of Yellowhammers. Conclusions Existing boundary habitat management under Entry Level Stewardship may provide a mechanism for increasing the populations of some farmland bird species. Boundary management options should continue to be promoted, although rebalancing the scheme more towards in‐field options is likely to be more widely beneficial.

A method for the objective selection of landscape‐scale study regions and sites at the national level

1. Ecological processes operating on large spatio-temporal scales are difficult to disentangle with traditional empirical approaches. Alternatively, researchers can take advantage of ‘natural’ experiments, where experimental control is exercised by careful site selection. Recent advances in developing protocols for designing these ‘pseudo-experiments’ commonly do not consider the selection of the focal region and predictor variables are usually restricted to two. Here, we advance this type of site selection protocol to study the impact of multiple landscape scale factors on pollinator abundance and diversity across multiple regions. 2. Using datasets of geographic and ecological variables with national coverage, we applied a novel hierarchical computation approach to select study sites that contrast asmuch as possible in four key variables,while attempting tomaintain regional comparability and national representativeness. There were three main steps to the protocol: (i) selection of six 100 9 100 km2 regions that collectively provided land cover representative of the national land average, (ii) mapping of potential sites into a multivariate space with axes representing four key factors potentially influencing insect pollinator abundance, and (iii) applying a selection algorithm which maximized differences between the four key variables, while controlling for a set of external constraints. 3. Validation data for the site selection metrics were recorded alongside the collection of data on pollinator populations during two field campaigns. While the accuracy of the metric estimates varied, the site selection succeeded in objectively identifying field sites that differed significantly in values for each of the four key variables. Between-variable correlations were also reduced or eliminated, thus facilitating analysis of their separate effects. 4. This study has shown that national datasets can be used to select randomized and replicated field sites objectively within multiple regions and alongmultiple interacting gradients. Similar protocols could be used for studying a range of alternative research questions related to land use or other spatially explicit environmental variables, and to identify networks of field sites for other countries, regions, drivers and response taxa in a wide range of scenarios.