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Most of the global population are urban, with inhabitants exposed to raised levels of pollution. Pollutants negatively impact human wellbeing, and can alter the structure and diversity of ecosystems. Contrastingly, urban biodiversity can positively contribute to human wellbeing. We know little, however, about whether the negative impacts of pollution on wellbeing could be lessened for householders living on more biodiverse streets, as the complex interlinkages between pollution, biodiversity and wellbeing have rarely been examined. Here, we used structural equation modelling to simultaneously test whether biodiversity (actual and perceived) mediates the relationship between traffic-related pollution (noise, dB; nitrogen dioxide, NO2) or air pollution (PM2.5) and wellbeing (mental wellbeing, happiness). In summer 2019, we conducted questionnaires and biodiversity surveys, and collected noise and air pollution data, from households (n = 282) across the streetscapes of Leeds, UK. Biodiversity (actual or perceived) showed no mediating effects. However, increased flowering plant richness was positively associated with mental wellbeing. Traffic-related pollution negatively affected pollinator and flowering plant richness, but not wellbeing. This could be because householders are not exposed to high levels of noise or NO2 because they do not maintain front gardens on noisier streets. There was no measurable effect of air pollution on biodiversity or wellbeing. These findings shed light on the complex mechanisms through which biodiversity could improve human wellbeing. Enhancing the diversity of plant species in streetscapes would have a positive effect on wellbeing, further emphasising the important role that biodiverse urban streetscapes play in improving the liveability of cities.

Additional file 1: Supplementary Table 1. Proportion of missing values per variable. Supplementary Table 2. Complete case vs Imputed case analysis.

1. KEY POINTS\ud 1. The novelty of nature-based solutions (NbS) for cities lies in a focus on the cost-effective provision of multiple co-benefits for many urban residents.\ud 2. A participatory placemaking approach to equitable co-design, co-creation and co-management of NbS that include multiple stakeholders and beneficiaries has the potential to maintain or improve biodiversity while simultaneously addressing societal issues such as climate change and other socio environmental inequalities across both spatial and temporal scales.\ud 3. NbS harnesses blue and green infrastructure, such as sustainable drainage systems (SuDS), green roofs, rivers, urban trees and community green spaces, which support significantly higher levels of biodiversity than constructed ‘grey’ infrastructure. These features can also help urban areas adapt to increased and more extreme temperature and rainfall events associated with climate change whilst delivering important environmental, social and economic benefits.\ud 4. Due to the multidisciplinary nature of NbS, its implementation in cities is inherently complex and at odds with many siloed governance structures, largely due to knowledge and skills gaps and the lack of coordination across sectors or departments, particularly at local authority level.

This review assesses current knowledge about the interplay between landscape and pollinator communities. Our primary aim is to provide an evidence base, identify key gaps in knowledge and highlight initiatives that will help develop and improve strategies for pollinator conservation. Human-dominated landscapes (such as arable land and urban environments) can have detrimental impacts on pollinator communities but these negative effects can be ameliorated by proximity to semi-natural habitat and habitat corridors. There is also evidence to suggest that increased landscape heterogeneity and landscape configuration can play an important role in the maintenance of diverse pollinator communities. Landscape characteristics have direct impacts on pollinator communities, but can also influence abundance and richness through interaction with other drivers such as changing climate or increased chemical inputs in land management. The majority of existing literature focuses on specific hymenopteran groups, but there is a lack of information on the impact of landscape changes on non-bee taxa. Research is also needed on the effectiveness of management interventions for pollinators and multiple year observations are required for both urban and rural initiatives. Current policies and monitoring schemes could contribute data that will plug gaps in knowledge, thus enabling greater understanding of relationships between landscapes and pollinator populations. This would in turn help design mitigation and adaptation strategies for pollinator conservation. A lay summary is available for this article.

Slides from the presentation at the Urban Biodiversity and Design, URBIO 2012, conference in Mumbai in October 2012.

Pollen beetles (Nitidulidae, Meligethinae) are among the most abundant flower-visiting insects in Europe. While some species damage millions of hectares of crops annually, the biology of many species is little known. We assessed the utility of a 797 base pair fragment of the cytochrome oxidase 1 gene to resolve Molecular Operational Taxonomic Units in 750 adult pollen beetles sampled from flowers of 63 plant species sampled across the UK and continental Europe. We used the same locus to analyse region-scale patterns in population structure and demography in an economically important pest, Brassicogethes aeneus. We identified 44 Meligethinae at ca. 2% divergence, 35 of which contained published sequences. A few specimens could not be identified because the MOTUs containing them included published sequences for multiple Linnaean species, suggesting either retention of ancestral haplotype polymorphism or identification errors in published sequences. Over 90% of UK specimens were identifiable as Brassicogethes aeneus. Plant associations of adult B. aeneus were found to be far wider taxonomically than for their larvae. UK Brassicogethes aeneus populations showed contrasting affiliations between the north (most similar to Scandinavia and the Baltic) and south (most similar to western continental Europe), with strong signatures of population growth in the south.

Planted meadows are increasingly used to improve the biodiversity and aesthetic amenity value of urban areas. Although many ‘pollinator-friendly’ seed mixes are available, the floral resources these provide to flower-visiting insects, and how these change through time, are largely unknown. Such data are necessary to compare the resources provided by alternative meadow seed mixes to each other and to other flowering habitats. We used quantitative surveys of over 2 million flowers to estimate the nectar and pollen resources offered by two exemplar commercial seed mixes (one annual, one perennial) and associated weeds grown as 300m2 meadows across four UK cities, sampled at six time points between May and September 2013. Nectar sugar and pollen rewards per flower varied widely across 65 species surveyed, with native British weed species (including dandelion, Taraxacum agg.) contributing the top five nectar producers and two of the top ten pollen producers. Seed mix species yielding the highest rewards per flower included Leontodon hispidus, Centaurea cyanus and C. nigra for nectar, and Papaver rhoeas, Eschscholzia californica and Malva moschata for pollen. Perennial meadows produced up to 20x more nectar and up to 6x more pollen than annual meadows, which in turn produced far more than amenity grassland controls. Perennial meadows produced resources earlier in the year than annual meadows, but both seed mixes delivered very low resource levels early in the year and these were provided almost entirely by native weeds. Pollen volume per flower is well predicted statistically by floral morphology, and nectar sugar mass and pollen volume per unit area are correlated with flower counts, raising the possibility that resource levels can be estimated for species or habitats where they cannot be measured directly. Our approach does not incorporate resource quality information (for example, pollen protein or essential amino acid content), but can easily do so when suitable data exist. Our approach should inform the design of new seed mixes to ensure continuity in floral resource availability throughout the year, and to identify suitable species to fill resource gaps in established mixes.