Road Verges Research Articles

Connectivity modelling with automatic determination of landscape resistance values. A new approach tested on butterflies and burnet moths

Abstract Our study presents a connectivity modelling approach to addressing issues relating to the decline in biodiversity in the landscape of Southern Moravia, one of the most productive agricultural areas in the Czech Republic, markedly changed in the post-war period of collectivization. A modified Hanski-based method was applied in modelling, with the use of least-cost distance evaluation. We propose a new concept of landscape resistance determination, based on occurrence data of species rather than expert opinion. This species-specific approach enables us not only to evaluate overall raster connectivity of landscape, but also to accurately identify locations where management intervention could support the targeted species, and where it would be ineffective. The approach is demonstrated using model groups of butterflies and burnets in the cadastral area of Sardice and its surroundings. Only day-active Lepidoptera associated with semi-natural grassland (43 species) were selected for connectivity modelling. Except for remnants of dry to mesic semi-natural grassland and transitional mosaic of grassland-forest habitat, the most preferable areas for the study and the model group are those of meadows and vineyards. Among the best routes for butterflies and burnets are the grassy verges of roads and railways. Closed forest, bushes, built-up areas and sports grounds are landscape segments of high resistance. The results suggest that, for organisms associated with open habitat, the existing platform for landscape protection is insufficient and, in some cases, even counterproductive.

An assessment of road-verge grass as a feedstock for farm-fed anaerobic digestion plants

Cuttings from road-verge grass could provide biomass for energy generation, but currently this potential is not exploited. This research assessed the technical, practical and financial feasibility of using grass harvested from road verges as a feedstock in farm-fed anaerobic digestion (AD) plants. The methane potential (191 mL CH4 gDM−1) and digestion characteristics of verge grass were similar to those of current farm feedstocks; indicating suitability for AD. Ensiling had no significant impact on the biomethane generated. Testing co-digestions of verge grass with current farm feedstocks showed enhanced methane yields, suggesting that verge grass could be a valuable addition to AD feedstock mixes. In a case study of the UK county of Lincolnshire, potential volumes and locations of verge grass biomass were estimated, with capacities and locations of existing AD plants, to assess the potential to supply practical grass volumes. Grass harvesting costs were modelled and compared with other feedstock costs. Finally, the attitudes of AD operators to using verge grass were investigated to understand whether a market for verge grass exists. In a small survey all operators were willing to use it as a feedstock and most were prepared to pay over the estimated harvesting cost. If verge grass was legally recognised as a waste product it could be attractive to AD operators especially where financial incentives to use waste feedstocks are in place. In rural areas, verge grass could be harvested and co-digested by existing farm-fed AD plants, potentially reducing the cost of road verge maintenance and increasing biodiversity.

Roadside diversity in relation to age and surrounding source habitat: evidence for long time lags in valuable green infrastructure

Abstract1. The severe and ongoing decline in semi‐natural grassland habitat during the past two centuries means that it is important to consider how other, marginal grassland habitat elements can contribute to landscape‐level biodiversity, and under what circumstances.2. To examine how habitat age and the amount of core grassland habitat in the surrounding landscape affect diversity in green infrastructure, we carried out inventories of 36 rural road verges that were either historical (pre‐1901) or modern (established post‐1901 and before 1975), and were surrounded by relatively high (>15%) or low (<5%) levels of grassland habitat. We recorded the number of plant species, grassland specialists, grassland conservation species and the fraction of the landscape's species and specialists found in the road verge.3. Road verge communities were characterised by high levels of grassland specialist species (35% of the 161 species recorded), with road verge sites supporting 15–20% of the specialist species found in the surrounding 25 km2 landscape.4. Richness of species and specialists were more closely related to road age than to the amount of surrounding habitat. Higher diversity in historical roads, despite the majority of modern roads being at least 60 years old, suggests a long time lag in the establishment of grassland communities in marginal grassland habitats. We identified no effect of historical surrounding land use on present day diversity in road verges.5. Road verge richness was not affected by the amount of surrounding grassland. This could be due to the relatively low amounts of grassland remaining in all landscapes, together with dispersal limitation commonly found in grassland plant communities contributing to a potential time lag.6. We identified road verges as potentially very important habitats for grassland communities. Because of the high levels of grassland specialists present, these and other marginal grasslands and grassland green infrastructure should be explicitly considered in landscape‐scale conservation management. Practitioners looking to identify the most species‐rich road verges should aim to find the oldest possible, while long time lags in community assembly suggests that seed sowing could be appropriate to enhance roadside diversity, even in decades‐old road verges.

Plant diversity in hedgerows and road verges across Europe

Abstract Linear landscape elements such as hedgerows and road verges have the potential to mitigate the adverse effects of habitat fragmentation and climate change on species, for instance, by serving as a refuge habitat or by improving functional connectivity across the landscape. However, so far this hypothesis has not been evaluated at large spatial scales, preventing us from making generalized conclusions about their efficacy and implementation in conservation policies. Here, we assessed plant diversity patterns in 336 vegetation plots distributed along hedgerows and road verges, spanning a macro‐environmental gradient across temperate Europe. We compared herb‐layer species richness and composition in these linear elements with the respective seed‐source (core) habitats, that is, semi‐natural forests and grasslands. Next, we assessed how these differences related to several environmental drivers acting either locally, at the landscape level or along the studied macro‐ecological gradient. Across all regions, about 55% of the plant species were shared between forests and hedgerows, and 52% between grasslands and road verges. Habitat‐specialist richness was 11% lower in the linear habitats than in the core habitats, while generalist richness was 14% higher. The difference in floristic composition between both habitat types was mainly due to species turnover, and not nestedness. Most notably, forest‐specialist richness in hedgerows responded positively to tree cover, tree height and the proportion of forests in the surrounding landscape, while generalist richness was negatively affected by tree height and buffering effect of trees on subcanopy temperatures. Grassland and road verge diversity was mainly influenced by soil properties, with positive effects of basic cation levels on the number of specialists and those of bioavailable soil phosphorus on generalist diversity. Synthesis and applications. We demonstrate that linear landscape elements provide a potential habitat for plant species across Europe, including slow‐colonizing specialists. Additionally, our results stress the possibility for land managers to modify local habitat features (e.g. canopy structure, subcanopy microclimate, soil properties, mowing regime) through management practices to enhance the colonization success of specialists in these linear habitats. These findings underpin the management needed to better conserving the biodiversity of agricultural landscapes across broad geographical scales.

Of mowers and growers: Perceived social norms strongly influence verge gardening, a distinctive civic greening practice

Road verge gardening is a civic greening practice undertaken by residents, which can contribute to the quantity, diversity and structural complexity of the greenery within the road easement. By understanding the social drivers of verge gardening, we can potentially increase biodiversity, ecosystem function and human amenity. We surveyed residents of single occupancy dwellings in Melbourne, Australia, and recorded demographic data and beliefs regarding road verge gardening. We used structural equation modelling to test causal models of cognitive constructs underlying verge gardening. We identified cultural background, gardening enthusiasm and level of education as significant factors differentiating respondents who planted verge understorey, planted street trees or did not verge garden. Normative beliefs were the main cognitive construct affecting resident behaviour, with those who did not verge garden more likely to think that others – and in particular municipal authorities – would disapprove of them verge gardening compared to residents who did verge garden. Sense of community, beliefs regarding the benefits of verge gardening, and feelings for nature had significant, but less direct, effects. Changing normative beliefs is a significant pathway to promoting verge gardening. Municipal authorities could reorient policy to encourage verge gardening and increase plantings in the verges they maintain. Planners and urban designers may wish to develop policy to better incorporate verge gardening into urban greening strategies.

Carbon and Metal(loid)s in Parkland and Road Verge Surface Soils in the City of Liverpool, UK

Urban soils are at the interface between land and people and provide a wide variety of important ecosystem services to highly populous areas. The aims of this soil survey were (1) to measure the bulk density, carbon (C) storage and pH of surface soils (0–15 cm depth) from public spaces (parks and road verges) in the city of Liverpool, UK, and (2) to determine the likely impact of these master variables on heavy metal concentrations (As, Cd, Cu, Pb and Zn). The bulk densities and organic matter contents varied considerably in the predominantly sandy textured soils within the city boundary, resulting in diverse C densities from 1–10 kg C m2. Organic carbon formed the majority of the labile, water-soluble and extractable C pool in these soils, a fact not easily elucidated from their organic matter or C content alone. The copper and lead concentrations in the sampled soils were correlated with organic matter and organic carbon in water-extracts. Cadmium and zinc appeared to be dependent only on soil pH, whilst arsenic was related positively to organic matter, but negatively to pH. Interrelationships, and hence synonymous distributions, of all metal(loid)s existed, but were strongest between Cu and As, and Cu and Pb. These results suggest that the diverse bulk densities, and hence carbon storage, of the urban soils surveyed influenced the dispersal of metals and arsenic.

Predicting Microhabitat Suitability for an Endangered Small Mammal Using Sentinel-2 Data

Accurate mapping is a main challenge for endangered small-sized terrestrial species. Freely available spatio-temporal data at high resolution from multispectral satellite offer excellent opportunities for improving predictive distribution models of such species based on fine-scale habitat features, thus making it easier to achieve comprehensive biodiversity conservation goals. However, there are still few examples showing the utility of remote-sensing-based products in mapping microhabitat suitability for small species of conservation concern. Here, we address this issue using Sentinel-2 sensor-derived habitat variables, used in combination with more commonly used explanatory variables (e.g., topography), to predict the distribution of the endangered Cabrera vole (Microtus cabrerae) in agrosilvopastorial systems. Based on vole surveys conducted in two different seasons over a ~176,000 ha landscape in Southern Portugal, we assessed the significance of each predictor in explaining Cabrera vole occurrence using the Boruta algorithm, a novel Random forest variant for dealing with high dimensionality of explanatory variables. Overall, results showed a strong contribution of Sentinel-2-derived variables for predicting microhabitat suitability of Cabrera voles. In particular, we found that photosynthetic activity (NDI45), specific spectral signal (SWIR1), and landscape heterogeneity (Rao’s Q) were good proxies of Cabrera voles’ microhabitat, mostly during temporally greener and wetter conditions. In addition to remote-sensing-based variables, the presence of road verges was also an important driver of voles’ distribution, highlighting their potential role as refuges and/or corridors. Overall, our study supports the use of remote-sensing data to predict microhabitat suitability for endangered small-sized species in marginal areas that potentially hold most of the biodiversity found in human-dominated landscapes. We believe our approach can be widely applied to other species, for which detailed habitat mapping over large spatial extents is difficult to obtain using traditional descriptors. This would certainly contribute to improving conservation planning, thereby contributing to global conservation efforts in landscapes that are managed for multiple purposes.

Ultrasonic device effectiveness in keeping rodents off the road

Finding achievable ways to reduce roads’ impacts on wildlife is a conservation priority. Road verges may be important refuges for small fauna, making them good hunting sites for predators. These make both prey and predators vulnerable to vehicle collisions. Thus, actions aiming to dissuade these animals from approaching roads are needed. Here we tested the effectiveness of ultrasonic devices to keep rodents away from the road verges. We hypothesised that exposing rodents to ultrasounds will cause them to stay away from the device and, consequently, from the road. We sampled rodents before and after the devices were switched on. Our results showed a reduction in animal activity after 10 days with the devices on. The next step is to analyse if this behaviour translates in a reduction of wildlife-vehicle collisions of rodents and their predators.

Ecosystem service provision by road verges

Abstract Roads form a vast, rapidly growing global network that has diverse, detrimental ecological impacts. However, the habitats that border roads (‘road verges’) form a parallel network that might help mitigate these impacts and provide additional benefits (ecosystem services; ES). We evaluate the capacity of road verges to provide ES by reviewing existing research and considering their relevant characteristics: area, connectivity, shape, and contextual ES supply and demand. We consider the present situation, and how this is likely to change based on future projections for growth in road extent, traffic densities and urban populations. Road verges not only provide a wide range of ES, 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) but also displace other habitats and provide ecosystem disservices (e.g. plant allergens and damage to infrastructure). Globally, road verges may currently cover 270,000 km2 and store 0.015 Gt C/year, which will further increase with 70% projected growth in the global road network. Road verges are well placed to mitigate traffic pollution and address demand for ES in surrounding ES‐impoverished landscapes, thereby improving human health and well‐being in urban areas, and improving agricultural production and sustainability in farmland. Demand for ES provided by road verges will likely increase due to projected growth in traffic densities and urban populations, though traffic pollution will be reduced by technological advances (e.g. electric vehicles). Road verges form a highly connected network, which may enhance ES provision but facilitate the dispersal of invasive species and increase vehicle–wildlife collisions. Synthesis and applications. Road verges offer a significant opportunity to mitigate the negative ecological effects of roads and to address demand for ecosystem services (ES) in urban and agricultural landscapes. Their capacity to provide ES might be enhanced considerably if they were strategically designed and managed for environmental outcomes, namely by optimizing the selection, position and management of plant species and habitats. Specific opportunities include reducing mowing frequencies and planting trees in large verges. Road verge management for ES must consider safety guidelines, financial costs and ecosystem disservices, but is likely to provide long‐term financial returns if environmental benefits are considered.

Road verges provide connectivity for small mammals: A case study with wood mice (Apodemus sylvaticus) in an agro-silvo pastoral system

Roads disrupt landscape connectivity for many terrestrial mammals. These infrastructures can be barriers to movement thereby threatening population persistence. Nonetheless, small mammals may use road verges as habitat or corridor, thus increasing migration across intensively managed landscapes. However, in well-preserved habitats where road verges show a similar vegetation structure to surrounding areas, their role is still unknown. Road verges would have an important role as fine-scale connectivity providers for small mammals in a well-preserved habitat depending on land management on road surroundings. We aimed to quantify the effects of road verges and paved lanes on the fine-scale landscape connectivity for the wood mouse (Apodemus sylvaticus) in a well-preserved Mediterranean woodland. Additionally, we assessed the impact on connectivity of vegetation cutting on verges and of management in surrounding areas (i.e. firebreaks, grazing, ploughing and cork stripping). We quantified connectivity using graph theory based on two years of capture-recapture data. We compared a set of connectivity metrics (derived from the probability of connectivity index) in a road area and in a virtual roadless scenario. We found that the presence of the road reduced overall fine-scale landscape connectivity, acting as a partial barrier for wood mice movement. However, verges had a key role in promoting movement on road surroundings. Vegetation cutting on verges, and land ploughing in the surrounding landscape were the only management activities compromising connectivity. Our study supports the already known role of road verges as habitat corridors for small mammals. However, it goes beyond existing knowledge by quantifying the connectivity enhancement provided by road verges and demonstrating that this role is highly relevant even in well-preserved landscapes. Therefore, our findings emphasize the critical role of road verges and suggest important management options to enhance landscape connectivity for small mammals.

Displacing and translocating hazel dormice (Muscardinus avellanarius) as road development mitigation measures

Road development can remove valuable wildlife habitat and reduce habitat connectivity. Where such works impact on European Protected Species in the UK, such as hazel dormice (Muscardinus avellanarius), mitigation is required to satisfy the relevant Statutory Nature Conservation Organisation licensing process. The study described here concerns the removal of dense road verge landscape planting occupied by hazel dormice prior to the construction of a new road junction and slip roads on a dual carriageway in Wales. Pre-construction monitoring started in May 2007, followed by vegetation clearance between August and September. Dormice were displaced into retained habitat through maximum daily vegetation clearance of 30 m lengths (varying widths), in parallel with translocation. This process resulted in the discovery of 48 natural (i.e. not within a nest box) dormouse nests, and the capture of 29 dormice for translocation; 90% were successfully released. Whilst within soft-release cages prior to release, dormice preferred a diet of blackberries (Rubus fruticosus agg.) and freshly picked hazel (Corylus avellana) nuts, prompting a recommendation for early Autumn (mid-August – September) as the ideal translocation season. Other recommendations for displacing and translocating dormice are provided, albeit limited in the absence of comprehensive pre-construction, and post-translocation monitoring.

Effects of road ditches on the vegetation composition in a saline environment

The construction of transportation corridors (such as roads) frequently disturbs and alters the natural disturbance regimes of ecosystems in many areas worldwide. In this study, by comparing the species richness, diversity, composition and soil among four ecotypes (non-road disturbance areas, road systems without ditches, road systems with large and small ditches), we tested the hypothesis that the presence of road ditches could facilitate the preservation of species and increase species richness in the Yellow River Delta, China. Both positive and negative effects of road ditches on the plant community were detected. The species richness in road systems (> 14) was significantly greater than that in the non-road disturbance areas (6). In the road systems without ditches, the refuges (relatively low soil salinity: 1.12 ± 0.15 mg/g) for non-halophytes were limited to road verges (0 m from a road verge). In the road systems that included a ditch, however, the refuge area expanded from road verges to 30 m from the verges. The width and structure affected ditch function. Both large ditches and small ditches effectively reduced the salinity of the soil, but the influence mechanisms differed, resulting in differences in the distribution of species diversity. The proportion of non-halophytes was significantly greater (37%) in the road systems with large ditches than in the road systems with small ditches (45.0%). In addition, the proper structure of large ditches with slopes increased the species diversity (the species richness was 26); in contrast, some structures of small ditches reduced the species diversity (the species richness was 14). The results of our study suggest that large ditches (width > 5 m) can be constructed 10 m from road verges to increase local species richness. Moreover, it is necessary to create buffer zones alongside roads (30 m from road verge), which can prevent the movement of invasive species into internal natural areas.

Vegetative propagation of Solidago canadensis – do fragment size and burial depth matter?

SummaryClonal species may benefit from human disturbance because their vegetative fragments may be distributed via soil. Solidago canadensis is an invasive rhizomatous perennial frequently found in ruderal environments. When creating new infrastructure, digging and cutting are two main factors that may influence the spread of S. canadensis into new areas. To have a better understanding of the invasive potential of S. canadensis, we investigated whether S. canadensis was able to survive and grow from stem cuttings as well as from rhizomes. Rhizomes and cuttings were collected from three populations in Eastern Norway. The rhizomes and cuttings were planted in a pot experiment to assess their vegetative ability to propagate. Rhizome fragments (5 and 10 cm long) were buried at 0.5, 10 and 30 cm depths. The cuttings were planted as 15 cm stems, with the bottom 5 cm pushed into the soil. The results showed that rhizome length did not have an effect on survival. Although some sprouting occurred at all burial depths, increasing depth had a negative effect on rhizome survival. In general, development of the cuttings was good, but there were differences between population performance and survival. These results imply that care must be taken when (i) constructing new sites, because digging and transport of soil masses may spread S. canadensis into new areas by rhizomes or cuttings, and (ii) mowing road verges and other ruderal areas to prevent the spread of stem cuttings from one area to another.

How grassland management methods affect spider diversity

Abstract The main objective of this paper is to report the effect of shrub removal, mowing, and grazing as grassland management methods on spider diversity. Sampling was conducted in the Mátra Mountains and four disturbed main road verges in Hungary. Shrub removal and mowing positively affected diversity. Moderate grazing caused increasing diversity, but intensive grazing reduced spider diversity. The intensity of mowing maintenance had various effects on diversity depending on the landscape impact. It is worth reducing the intensity of the application of mosaic treatments and considering the long-term maintenance of edge habitats in these areas.

Habitat islands outside nature reserves – Threatened biodiversity hotspots of grassland specialist plant and arthropod species

In transformed landscapes, many populations of grassland specialist plant and animal species live outside the few protected areas and are often preserved on 'small natural features' (SNFs) such as road verges, field margins and rocky outcrops. In the steppe and forest steppe zones of Eurasia ancient burial mounds (kurgans) are widespread SNFs providing refuge for grassland species. Based on a large-scale botanical and zoological survey of 138 kurgans in Hungary, we compared the management regimes, the presence of threatening factors and the conservation potential of kurgans embedded in non-protected transformed landscapes and in protected areas. We found that kurgans extend the borders of the protected areas by maintaining populations of grassland specialist plants and arthropods (ants, orthopterans, true bugs and rove beetles) even in transformed landscapes. We revealed that the lack of proper management, the presence of anthropogenic disturbances and encroachment of woody species are the most considerable threats to the long-term maintenance of biodiversity on kurgans located outside the protected areas. For their effective conservation a new approach is needed, which can cope with the small area and dispersed localities of the kurgans and can integrate them into the network of other SNFs on a landscape-level. As the ecological importance of kurgans is disproportionate to their size conservation actions focusing on their protection offers a greater rate of return of the efforts than can be expected in case of larger continuous sites.

Invasive occurrence and abundance changes of Armadillidium vulgare (Latreille, 1804) in Hungarian roadside verges

Background and purpose: The impact of invasive species in ecosystems is an important problem worldwide and the spreading of invader species are affected exceedingly by linear infrastructure. Primarily the aim of our investigation was to studied how the invasion of the species impacts the isopod diversity of roadside verges. Secondly, we determined what attributes of linear infrastructure affect on mass occurrence by the species. Materials and methods: Double-glass pitfall traps were established a total of 37 localities along highways and mainroads in Hungary between 2011 and 2015. To studied what attributes of roads affect the abundance of A. vulgare we considered seasons, adjacent areas, road edge proximity, leaf-litter depth, highway age, vegetation and mowing. Results: We collected a total of 18 isopod species. The A. vulgare was the most abundant and frequently encountered species in both road types, which represented 89% of the total isopod catches. The high abundance of the species negatively correlated with isopod diversity. The invasive nature of this species is promoted by summer conditions, proximity of arable fields, intermediate distance from the road, leaf-litter at a depth of 3 cm and the youthfullness of the sampling sites. On mainroad verges the highest abundance was in the non-mown sections of the arid grassland sites. Conclusions: Our results suggest that this species is likely to adversely impact ecosystem function of roadside verges in Hungary. Different land use, water supply, surrounding landscapes, habitat structure, vegetation, biogeographical context and human activities along road verges influence the invasiveness of A. vulgare.

Road verges are important secondary habitats for grassland arthropods

Semi-natural linear landscape elements such as road verges, hedgerows and field margins are important in maintaining the connectivity between habitat fragments of highly modified landscapes. Preservation of habitat specialist fauna requires conservation of the remaining natural habitat patches and connectivity of fragments. Our study focuses on the spider, ant and true bug fauna and functional diversity (FD) of fragmented forest steppe patches, moderately grazed pastures and road verges embedded in a matrix of forest plantations in Hungary, Central Europe. We established total 30 sampling sites, 10 in each, the grassland component of forest-steppes (F), pastures (P) and road verges (R) near pine forests. We collected arthropods with pitfall and sweep-net techniques. We calculated FD and species composition of arthropods using linear mixed models. We observed higher species richness in road verges for spiders and ants. We also found higher FD values for spiders and different trait composition for all taxa in road verges when compared with forest steppes and pastures. Species composition suggests that road verges do not serve as habitat for several forest-steppe and grassland species, in spite of the fact that numerous specialist species were found in the road verges. We show that forest steppes have higher species richness of spiders than pastures, and there are differences in species assemblage composition of the two habitat types for all taxa. Our results indicate that road verges should be considered as an important refuge for grassland specialist arthropods, as road verges provide secondary linear habitats for many arthropod species, and we would suggest the maintenance of these grassy strips in order to preserve arthropod biodiversity.

Springtails (Collembola) in meadows, pastures and road verges in Central Finland

Understanding of species distribution, abundance and habitat affinities is crucial for red-list assessment, conservation and habitat management. In Central Finland, we studied Collembola in three habitat types, namely non-grazedmeadows, pastures and road verges using pitfall traps. Altogether, 9,630 Collembola individuals were recorded. These belonged to 12 families, 34 genera and 60 species. The number of specimens was clearly higher in meadows than in pastures or road verges. The number of species, however, was higher in meadows and road verges (40 and 39 species, respectively) than in pastures (33 species). The overall species number is comparable to other large-scale sampling schemes in similar habitats. We recorded a few abundant species (Spatulosminthurus flaviceps, Sminthurus viridis and Sminthurus nigromaculatus) that have been previously recorded from very different biotopes. In conclusion, biodiversity inventories of soil fauna, as well as other biota, should also include marginal habitats, which often host peculiar communities.

Road verges support pollinators in agricultural landscapes, but are diminished by heavy traffic and summer cutting

Abstract 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.

Footpaths, tree cut-outs and social contagion drive citizen greening in the road verge

Verge gardening is a citizen-led form of public urban greening where residents plant and maintain understorey and trees in the road easement, and it has the potential to significantly increase the diversity and complexity of street greenery which is, most commonly, mown grass and monocultures of street trees. In Melbourne, Australia, two forms of verge gardening – understorey planted by residents and street trees planted by residents– were investigated. The distribution of verge gardens was tested for correlation with a range of urban form and social factors that included the proportion of garden in residential parcels, the proportion of the street set aside as road verge, age of street development, the presence of footpaths, tree cut-outs (tree pits) and social disadvantage. By better understanding the factors associated with verge gardening, we hope planners, urban designers and land managers will be able to better incorporate verge gardening into urban greening strategies and so maximise the biodiversity, ecosystem function and human amenity benefits associated with this significant public activity. We found that verge gardening was common, occurring in almost a quarter (22.1%) of verges and was strongly associated with verges without footpaths, tree cut-outs rather than continuous verges, and verges on local roads rather than collector roads. Neighbourhoods with proportionally more garden had more verge gardening. With the exception of the oldest streets in our study, streets that were newer had more verge gardening than those that were older. The presence of street trees planted by local government was associated with less verge gardening. Verge gardening was less common in neighbourhoods with greater social disadvantage, and spatial contagion increased the likelihood of neighbours having verge gardens. Local government can facilitate verge gardening through engagement, education, adopting alternative street types, using tree cut-outs to better strategic advantage, and targeting areas of social disadvantage.