To tackle pollinator declines, there is a major need to increase the quantity of flower-rich habitats. Road verges offer one such opportunity but are exposed to diverse forms of pollution from roads and road traffic. We carried out a broad initial assessment to establish if and how pollution affects the quality of road verges as pollinator foraging environments. We assessed the spatial distribution of pollution, flowers and pollinators in road verges, then used field experiments to simulate and measure the impacts of four ubiquitous and little studied forms of road pollution (noise, turbulence, dust and metals) on pollinator densities and foraging behaviour. We found that pollinators in road verges were exposed to noise, turbulence, dust and metal pollution, which decreased with distance from the road edge but, with the exception of turbulence, extended more than 8 m into road verges. Pollinator densities were lower closer to the road edge—particularly within first 2 m (55% lower than at 7–9 m)—where pollution is greatest. This was despite a similar density and species richness of flowers. Simulated turbulence deterred pollinators by causing intermittent disturbance (reducing visit duration by up to 54%), and some pollinator taxa preferentially avoided concentrations of metals that were more frequently found in flowers within 2 m of roads (resulting in up to 75% fewer visits), while noise and dust had no apparent effect. Synthesis and applications. Pollinators in road verges are exposed to many forms of pollution, and we found impacts of roadside-realistic levels of turbulence and metals on pollinator densities and foraging behaviour. Although the findings suggest that road verges are largely suitable for pollinator conservation, management enhancements should prioritise areas more than 2 m from the road edge, and verges along roads with relatively lower traffic densities.

Abstract
. Artificial light at night (ALAN) and its associated biological impacts have regularly been characterized as predominantly urban issues. Although far from trivial, this would imply that these impacts only affect ecosystems that are already heavily modified by humans and are relatively limited in their spatial extent, at least as compared with some key anthropogenic pressures on the environment that attract much more scientific and public attention, such as climate change or plastic pollution. However, there are a number of reasons to believe that ALAN and its impacts are more pervasive, and therefore need to be viewed from a broader geographic perspective rather than an essentially urban one. Here we address, in turn, 11 key issues when considering the degree of spatial pervasiveness of the biological impacts of ALAN. First, the global extent of ALAN is likely itself commonly underestimated, as a consequence of limitations of available remote sensing data sources and how these are processed. Second and third, more isolated (rural) and mobile (e.g. vehicle headlight) sources of ALAN may have both very widespread and important biological influences. Fourth and fifth, the occurrence and impacts of ALAN in marine systems and other remote settings, need much greater consideration. Sixth, seventh, and eighth, there is growing evidence for important biological impacts of ALAN at low light levels, from skyglow, and over long distances (because of the altitudes from which it may be viewed by some organisms), all of which would increase the areas over which impacts are occurring. Ninth and tenth, ALAN may exert indirect biological effects that may further expand these areas, because it has a landscape ecology (modifying movement and dispersal and so hence with effects beyond the direct extent of ALAN), and because ALAN interacts with other anthropogenic pressures on the environment. Finally, ALAN is not stable, but increasing rapidly in global extent, and shifting toward wavelengths of light that often have greater biological impacts.

Roads form vast and pervasive networks across the earth, with diverse and often profound negative environmental impacts. However, these roads are bordered by a parallel network of habitats in the form of road verges. In this thesis, I propose that roads present a nearly ubiquitous environmental pressure, but that their verges offer an equally widespread opportunity to benefit nature, the environment and, as a result, people.

I begin by using spatial mapping and modelling to estimate the extent of road pollution, in various forms, across Great Britain. This reveals that half of land is less than 216 m from a road, and that roads have a zone of influence that extends across > 70% of the land area. Whilst high levels of road pollution are estimated to be relatively localised, low levels are pervasive.

Second, I synthesise the literature to determine the global potential of road verges for mitigating such pollution, for supporting nature and for providing further environmental and social benefits via ecosystem services. I estimate that road verges may currently cover 270,000 km2 globally, and that they provide a wide range of benefits, including biodiversity provision, regulating services (e.g. air and water filtration) and cultural services (e.g. health and aesthetic benefits by providing access to nature). However, verges also displace other habitats and provide ecosystem disservices (e.g. plant allergens and damage to infrastructure).

Third, I use satellite and ground-level imagery to estimate the extent of road verges across Great Britain and to explore their potential to benefit nature, the environment and people. I estimate that there are 2579 km2 (2149-3010 km2) of road verges in Great Britain, equivalent to 1.2% of land area, of which 707 km2 (27.5%) is short, frequently-mown grassland, 1062 km2 (40.9%) is regular grassland, 480 km2 (18.7%) is woodland, and 272 km2 (10.7%) is scrub. Only 27% of frequently-mown grassland verges contain trees, indicating potential for planting trees and shrubs to provide environmental and social benefits.

Fourth, I take insect pollinators as a case study and, using a combination of roadside surveys, field experiments, a literature review, and meta-analyses, determine the suitability of road verges for pollinator conservation, and how they could be enhanced for this purpose. The findings demonstrate that road verges can be hotspots of flowers and pollinators in human-dominated landscapes, but that traffic and road pollution can cause mortality and other negative impacts on pollinators. Surveys in Cornwall, UK, show that pollinator densities are lower closer to the road edge – particularly within the first 2 m (55% lower than at 7-9 m) – where pollution is greatest. Field experiments reveal that these trends can be explained by pollinators being deterred by turbulence, and avoiding concentrations of metals that are more frequently found in flowers within 2 m of roads. Overall, evidence suggests that the benefits of road verges for pollinators outweigh the negative impacts of road pollution and pollinator-vehicle collisions.

The research shows clearly that road verges already provide many environmental and social benefits, but that these could be enhanced considerably through strategic design and management. Several reoccurring management recommendations are reducing mowing frequencies to no more than twice per year, leaving some areas uncut on rotation, and planting trees in urban verges and in low quality verge habitats. I finish by reflecting on the project and its outcomes, and on the remaining barriers to managing road verges for nature, the environment and people. This reveals the most important directions for future research, namely, the importance of overcoming social barriers to change that inhibit uptake of environmental management recommendations.

Nature conservation often depends on the behaviour of individuals, which can be driven by socio-psychological factors such as a person's attitude, knowledge and identity. Despite extensive ecological research about pollinator declines, there has been almost no social research assessing the drivers of people's engagement in pollinator conservation. To address this gap, we used a large-scale, online questionnaire in the United Kingdom, broadly framed around the Theory of Planned Behaviour. We received a total of 1,275 responses from a wide range of ages, incomes and education levels, despite a selection bias towards people with a pre-existing interest in pollinators. A range of socio-psychological factors predicted people's pollinator conservation actions and explained 45% of the variation. Respondents’ diversity of nature interactions and perceived behavioural control (feeling able to help pollinators) were consistently important predictors of people's pollinator conservation actions, whilst the importance of other socio-psychological factors depended on the particular action. Notably, knowledge was far less important overall than people's perceptions and other socio-psychological factors, highlighting a knowledge-action gap. Further unexplained variation in people's behaviour could partly be due by structural and contextual factors, particularly regarding social norms around tidiness. From a practical perspective, our findings reveal three main insights. First, several simple, low-cost pollinator conservation actions (reduced mowing, leaving areas unmown and creating patches of bare ground for ground-nesting bees) are currently under-utilised so should be priorities for pollinator conservation programmes. Second, strategies are needed to overcome reported practical barriers, for example by providing free resources (e.g. seeds of pollen- and nectar-rich plants) and communicating simple beneficial actions that can be carried out with limited time, space and money. Third, knowledge is just one (relatively less important) factor that predicts pollinator conservation behaviour—other socio-psychological factors provide potential pathways for increasing uptake, and structural and contextual limitations also need to be considered. In practice, this could be achieved by engaging, inspiring and empowering the public to help pollinators and to take responsibility for their local environment, for example through environmental education and community programmes facilitating public interest and involvement in the management of greenspace. A free Plain Language Summary can be found within the Supporting Information of this article.

The importance of wild bees for crop pollination is well established, but less is known about which species contribute to service delivery to inform agricultural management, monitoring and conservation. Using sites in Great Britain as a case study, we use a novel qualitative approach combining ecological information and field survey data to establish a national list of crop pollinating bees for four economically important crops (apple, field bean, oilseed rape and strawberry). A traits data base was used to establish potential pollinators, and combined with field data to identify both dominant crop flower visiting bee species and other species that could be important crop pollinators, but which are not presently sampled in large numbers on crops flowers. Whilst we found evidence that a small number of common, generalist species make a disproportionate contribution to flower visits, many more species were identified as potential pollinators, including rare and specialist species. Furthermore, we found evidence of substantial variation in the bee communities of different crops. Establishing a national list of crop pollinators is important for practitioners and policy makers, allowing targeted management approaches for improved ecosystem services, conservation and species monitoring. Data can be used to make recommendations about how pollinator diversity could be promoted in agricultural landscapes. Our results suggest agri-environment schemes need to support a higher diversity of species than at present, notably of solitary bees. Management would also benefit from targeting specific species to enhance crop pollination services to particular crops. Whilst our study is focused upon Great Britain, our methodology can easily be applied to other countries, crops and groups of pollinating insects.

Context: Maximising insect pollination of mass-flowering crops is a widely-discussed approach to sustainable agriculture. Management actions can target landscape-scale semi-natural habitat, cropping patterns or field-scale features, but little is known about their relative effectiveness. Objective: to test how landscape composition (area of mass-flowering crops and semi-natural habitat) and field-scale habitat (margins and hedges) affect pollinator species richness, abundance, and pollen deposition within crop fields. Methods: We surveyed all flower visitors (Diptera, Coleoptera and Hymenoptera) in oilseed rape fields and related them to landscape composition and field features. Flower visitors were classified as bees, non-bee pollinators and brassica specialists. Total pollen deposition by individual taxa was estimated using single visit pollen deposition on stigmas combined with insect abundance. Results: the area of mass-flowering crop had a negative effect on the species richness and abundance of bees in fields, but not other flower visitors. The area of semi-natural habitat in the surrounding landscape had a positive effect on bees, but was not as important as the area of mass-flowering crop. Taxonomic richness and abundance varied significantly between years for non-bee pollinators. Greater cover of mass-flowering crops surrounding fields had a negative effect on pollen deposition, but only when non-bee pollinator numbers were reduced. Conclusions: Management choices that result in landscape homogenisation, such as large areas of mass-flowering crops, may reduce pollination services by reducing the numbers of bees visiting fields. Non-bee insect pollinators may buffer these landscape effects on pollen deposition, and management to support their populations should be considered.

Supporting pollinators in agricultural landscapes is important for reversing their global decline. Road verges and hedges are used by pollinators for feeding and reproduction, but few studies consider entire pollinator communities, and it remains unclear how they are distributed across adjacent verges, hedges and fields, or how they are affected by traffic and verge cutting. We surveyed flowers and pollinators, using transect counts and pan traps, to explore the role of road verges and their associated hedges in supporting pollinators in an agricultural landscape in southwest England, and the impacts of traffic and verge cutting. At 19 sites, we surveyed the road verge (verge edge and verge centre), the verge hedge (both sides), a field hedge and the field interior. Road verges and hedges had a much greater flower abundance, flower species richness and pollinator abundance than field interiors. Verge hedges had far less woody cover than field hedges, but greater flower species richness. There were fewer pollinators along verge edges (next to roads) than along verge centres (2–11 m from roads) and fewer pollinators in road verges next to busier roads. Road verges were generally cut once (in summer), and cuttings were never removed. There were substantially fewer flowers and pollinators in road verges that had been cut, even though surveys often took place many weeks after cutting. Synthesis and applications. Road verges and their associated hedges can provide hotspots of resources for pollinators in agricultural landscapes, but their capacity to do so is reduced by heavy traffic and summer verge cutting. We recommend that beneficial management for pollinators should prioritize wider road verges (at least 2 m wide), roads with less traffic, and areas away from the immediate vicinity of the road. Where possible, verge cutting should not be carried out during peak flowering times.