Bees and pollinators have always been a part of the city landscape. Parks, private and community gardens, and green roofs all contribute to habitat for a diverse pollinator fauna in cities. Indeed, there is some evidence that cities might be refugia for some bee species.
But with increasing interest in urban-based conservation, agriculture and gardens, their presence has become more noticeable—and more important. Furthermore, bee and pollinator conservation is a key concern outside of cities, with habitat loss, indiscriminant insecticide use and other issues threatening bee species and pollinators generally.
What role can cities play in bee and conservation, perhaps through policy encouraging green space with appropriate plantings and a reduction in the use of pesticides?
How can this role be supported, by both public and private actors?
And how can story of urban pollinators be better told to propel the conversation about urban pollinator conservation and their critical services?
Land use change from natural habitats to human-managed landscapes is generally perceived as having a negative impact on wildlife. Yet recent research indicates that towns and cities can provide suitable habitat for at least some groups of insect pollinators, particularly bees.
Compared to agricultural landscapes, urban areas are smaller in size (e.g. approximately 70 percent of U.K. land is managed for agriculture, whereas 7 percent is classified as ‘urban’); therefore, conserving pollinators requires action by both rural and urban land managers. Yet urban areas are home to over half of the global human population and, with urbanisation predicted to increase to accommodate an increasing global population, cities are likely to be increasingly important locations for wildlife conservation.
Several recent studies have shown that towns and cities can contain high pollinator diversity, and that bee diversity can be as high as, or even greater than, in nearby rural areas. This suggests that urban areas can provide suitable food and nesting resources for at least some native bee species. Gardens comprise approximately 25 percent of the urban landscape in the U.K. and gardening is a popular activity, so gardens are likely to provide important floral resources throughout the year in towns and cities. It is important to remember, though, that bee species vary in their habitat requirements and urban living may not suit them all. There are more than 270 bee species in the U.K. and approximately 20,000 species worldwide. Bees vary in their nesting habits, floral preferences and the time of year at which they are active, all of which are likely to affect their survival in urban habitats. Generalist species, including many of the bumble bees, can forage on a wide range of plant species and may be more suited to urban areas. Indeed, research has shown that bumblebee colony growth rate and nest density in suburban gardens can exceed that found in the countryside. In contrast, several studies have found floral specialists to be rare in cities.
What about the other pollinators? In temperate northern Europe, other pollinator groups include beetles, wasps, butterflies, moths and flies. These insects vary in their efficacy as pollinators, though recent research shows that non-bee insects are globally important crop pollinators. To support a population of a particular species, all of the species’ resources (e.g. larval food plant, nesting substrate, overwintering sites) must be available.
So can cities save pollinators? Research has shown that at least some species are able to use urban habitats. The bottom line, though, is that there is still much we don’t know about the habitat requirements for many pollinator groups and we need a lot more research to find out which pollinators use urban habitats worldwide.
Despite the knowledge gaps we need to address, there are steps we can take to ensure that urban habitats provide for pollinators and thus aid in their conservation. All pollinators feed on flowers, so increasing the numbers of flowers that provide good sources of nectar and pollen is essential. We need to plant a variety of flowers (different pollinators feed on different plants), to make sure nectar and pollen are available throughout the year and also to consider location. Creating corridors of favourable habitat will enable movement and dispersal of pollinators both within urban landscapes and between urban and adjacent rural habitats, thus increasing habitat connectivity and helping to maintain healthy pollinator populations at regional and national levels. Projects such as the Buglife-led B-Lines are seeking to create large-scale habitat corridors to achieve just this. It’s not just about the flowers, though: efforts to maintain and create pollinator habitat must consider other resource needs, including nesting sites.
How do we make this happen? The number of people and organisations involved in managing urban habitats is both a challenge and an opportunity. Local authorities must be on board to ensure that public land is favourably managed, but essentially anyone with access to land can do their bit, as well as encouraging neighbours, employers, local businesses and schools to take action. Recognition by and support from governments in the form of national pollinator strategies or action plans, as is the case in England, Ireland and the U.S., among others, is important in uniting stakeholders in both rural and urban areas to achieve shared goals.
Cities, and the people in them, can play an important role in helping pollinators. Managing our urban areas better for wildlife as a whole is part of the solution, but we must also ensure that we conserve natural habitats wherever possible.
Since becoming a beekeeper a decade ago, I have been on a journey that has opened my eyes to what cities can offer bees in terms of forage and habitat, and how that could be vastly improved by transforming flower beds in our parks and gardens with nectar and pollen-rich varieties (instead of colourful but sterile annual displays), planting up roof tops with trees and shrubs that supply year-round bee forage, and leaving areas undisturbed where wild bees can safely nest.
I now see cities in a completely different light. A tree-lined street has become an aisle in a bee supermarket, fully stocked for a short time during the year, and completely empty at others; a park is like a larder full of bee-friendly free ingredients; and the grey expanse of roofs that cover our cities are deserts where no food grows.
In London alone, we are currently paving or decking over gardens and losing the equivalent of two and a half Hyde Parks every year which, in addition to wiping out potential bee forage, exacerbates problems such as flooding, air pollution and rising temperatures caused by the heat island effect. If we ditch the decking and turn our cities into a vast bed and breakfast for bees, we not only feed and house bees, we also make cities more resilient for us to live in, too. Trees, as well as often providing the most abundant source of food for bees in cities and habitat for myriad species, soak up rainwater, store carbon, remove pollution and provide cooling canopy cover for us.
This week, I’m helping to plant new trees in a local inner London square. The trees have been chosen by myself in conjunction with the local council’s arboricultural officer to extend the foraging season for bees: a white cherry for early nectar and a Japanese pagoda for forage in late summer.
But the event will do much more than feed bees. It will bring the community together, making us all feel good for helping bees, making the square so much more attractive at different times of the year—from the blossom in spring to the leaves’ autumnal colour—and allow us urbanites to reconnect with nature and one another; in summary, it will increase our sense of wellbeing.
For this reason, it’s become clear to me that what we need to ask is not what cities can do for bees, but what bees can do for cities to make them better, more resilient places for all of us?
By pollinating plants, from the fruit trees in our backyards to the vegetables on our allotments, bees are increasing the yield of fresh, locally produced food we can eat in towns and cities. And their pollination services are providing much-needed fruits and berries for the wildlife we share our cities with, from songbirds to small mammals, as well as allowing flowers and plants to propagate in even the most barren looking wastelands.
In addition to the hugely important role bees play in promoting biodiversity in our urban eco-system, they also play a much undervalued role in reconnecting city dwellers with nature and, in so doing, improve our mental state. Most of us live in cities and, by 2050, 75 percent of the human population will live in urban centers. Nature deficit disorder—a term coined to describe the negative impact of a disconnect with the natural environment—can exacerbate behavioural problems in children and add to stress levels in adults. Research shows that nature has restorative and therapeutic powers. But if we sit in offices all day, oblivious to the changing seasons and natural world around us, how do we benefit from this eco-healing?
Bees, that’s how. By having a hive and learning about how honeybees work, or planting bee-friendly flowers in a window box, or making a DIY bee hotel where cavity-nesting solitary bees can check in to lay their eggs, people—from school children to alienated young people and even busy adults—in cities are learning about the nature on their doorstep. What’s more, they are getting to know work colleagues or neighbours in the process and breaking down the social isolation that blights urban existence.
So by making cities more bee-friendly, we are actually making them much more human-friendly places for us to live and work.
Eight years ago, I began developing a project called the Pollinator Pathway. The project is both a vision for an international system of design to connect cities, farms and wilderness, and a living essay on nature in the age of humanity. The project has ignited global conversation and is considered a massive cultural success, attracting scientists, curators, planners, architects and designers alike. Through this project, I’m investing what will ultimately be ten years into exploring history, botany, urbanism, social systems, environmental thought and systems of real estate—all with the question of how we might best build new systems and paradigms in the coming hundreds of years.
We are in the midst of a global transformation of landscape, from wild and biologically diverse to agrarian and urban dotted by fragmented green spaces, and with it, an increasingly globalizing ecology. We are essentially designing landscapes of cosmopolitan species—those species and ecosystems that can thrive globally, often in the systems we create (and the honeybee is one such species).
I think to answer any of these questions about cities, we need to think a great deal more about relationships between systems, and a great deal less about certain species or even several species. In fact, I think we should eliminate the entire concept of saving species. Therefore, I have a counter question: how can cities be better participants in a global ecology?
I think some of the most logical ways that cities can contribute to the ecology of the planet—to become active participants in the biosphere, so to speak—is through (at minimum) only using underused space in ecology projects, very definitely not adding more honeybees to our landscapes, connecting landscapes—and, above everything, developing policy and funding mechanisms that pair the development within cities with support for the connectivity of landscape outside cities.
Then—however rudimentary a level it may be—we’re beginning to make a real system of exchange, and thinking more like an ecosystem.
While urban habitats will never be a panacea for pollinator conservation, there are two important reasons why insect pollinator ecologists are increasingly turning their attention to towns and cities. First, urban habitats could be acting as refugia from some of the threats facing wild pollinators in agricultural landscapes. The rather limited data we have on pollinators (which is based on haphazardly collected records rather than systematic monitoring programmes), suggests that most pollinator species are in decline. The causes for bee declines appear to be multi-faceted and include parasites, pesticides and a lack of flowers. Although urbanisation is an important cause of habitat loss globally, the majority of these threats to pollinators appear to be primarily occurring in non-urban land. Second, and especially in the developed global north, the majority of people live in cities. Pollinators, especially bees and butterflies, are charismatic and apparent emblems of biodiversity that people enjoy sharing their parks and gardens with. If we lose pollinators from cities, we don’t just lose a pollination service, we also lose the psychological benefits that we gain from urban biodiversity.
Although research on urban pollinators has been increasing, most of the studies to date have been relatively small in scale, often focusing on a few urban habitats in a single city. However, a notable exception was a recent nationwide study that asked ‘Where is the U.K.’s pollinator biodiversity?’ By systematically surveying pollinators in 12 urban areas and comparing these urban pollinator communities with those of nearby farmland and nature reserves, Katherine Baldock and colleagues on the Urban Pollinators Project were able to show that towns and cities were just about as good for pollinators as farms and nature reserves. Moreover, when just looking at the bee species, urban areas were significantly more species-rich than farmland.
So, taken as a whole, it appears that cities can compare favourably to other habitats. But urban environments are notoriously heterogeneous, ranging from car parks and industrial estates to gardens and nature reserves. The second part of the Urban Pollinators Project sought to discover the urban pollinator ‘hot spots’ by comparing pollinator communities in nine different urban habitats across four U.K. cities. This work was followed up by a U.K.-wide experiment to investigate how best to enhance urban green spaces for pollinators. In partnership with local councils, schools and seed companies, members of the Project created 60 flower meadows across the U.K., including perennial meadows with only native species, and annual meadows containing mostly non-native species.
As the results emerge from the Urban Pollinators Project, we will certainly learn more about the value of towns and cities for pollinating insects and what we can do to make them better. But there is still a great deal more research required. By surveying insects visiting flowers, the Urban Pollinators Project was able to produce plant-pollinator networks for urban areas, but food (nectar and pollen) is not all that pollinators need to survive. Pollinators could also be nest-site limited in cities, and the popularity of ‘insect hotels’ (at least for cavity-nesting solitary bees) suggests that, for some wild pollinators, this is a real possibility. We also don’t know much about pesticide use in urban areas and its impact on pollinators, while other urban hazards such as pollution (e.g. diesel fumes) and vehicle collisions may well be having detrimental effects on urban pollinators. If cities are really to make a meaningful contribution to pollinator conservation, then an interesting question is whether they might act as a source habitat from which pollinators ‘spill over’ into surrounding non-urban land. There is some limited evidence that urban-rural spill-over can happen, but not enough to draw any firm conclusions.
Well publicised pollinator declines have stimulated policymakers in the British Isles, with national pollinator plans emerging in the last few years for Wales, then England and, most recently, Ireland. All of these strategies highlight the contribution required by urban land managers, and a recent policy note summarises the best available evidence for how to manage urban areas for insect pollinators. For instance, gardeners in the U.K. are being urged to plant both native and exotic plants to attract pollinators, whilst the creation of wildflower areas and relaxed mowing regimes can lead to increased pollinator abundance in amenity grassland. Urban landscaping to support pollinators is gradually becoming mainstream in the U.K., from the meadows of the London Olympic Park through to the River of Flowers in the road sides of Rotherham. At larger scales, initiatives are underway that seek to improve connectivity and facilitate dispersal between these pollinator-friendly habitat patches, e.g. the B-Line for London and Oslo’s Pollinator Passage.
At the heart of these various projects is the fact that people, at least on one level, ‘get’ urban pollinator conservation. Scientists have been broadly successful in communicating the message that pollinators are declining and people can readily understand the benefit of planting flowers in their own backyard or local park to do their bit to help the bees. But it’s not quite that simple. The majority of the public remains ignorant to the true diversity of wild pollinators. Many are only aware of bees and many of those think that bees are only one species—the domesticated honeybee. But of the thousands of insects sampled during the Urban Pollinators Project, bees comprised up to a third of records and honeybees just 7 percent. Most urban pollinators are flies, and most of the bees are bumblebees and solitary bees. Maybe it doesn’t matter that 93 percent of urban pollinators remain mysterious to many of us, but ask the schoolchild who’s just seen a live colony of bumblebees for the first time or the mother of the inner city child overwhelmed by an urban flower meadow and they will tell you a story of pollinator conservation that truly brings the city alive.
The city as a haven for bees
Research on insect pollinators is changing how we view the biological value and ecological importance of cities.
We know that insect pollinators are in decline globally due to a combination of human-caused and natural factors (habitat loss, intensification of agriculture, pesticides, disease, etc.) . This problem has been characterized as a “pollinator health crisis” where health refers to pollinator species diversity and abundance [2, 3].
In the midst of this problem, what has been surprising is that researchers are finding diverse species of bees in cities all over the world, such as Berlin, Germany ; Cardiff and London in the U.K. [5–7]; Melbourne, Australia ; Guanacaste Province, Costa Rica ; Vancouver, Canada ; Chicago, IL ; New York City, NY [12,13]; Phoenix, AZ ; and San Francisco, CA in the U.S. . In several cases, bee species diversity and abundance in cities is greater than in surrounding rural areas [6, 7, 12, 14].
A diversity of people in the world’s cities plant a diversity of flowering plants. Cultural norms, municipal codes, and aesthetic preferences shape the diversity of cultivated plants that provide forage for insect pollinators. Managed (and unmanaged) urban public and private greenspaces offer places to nest. Although the restoration and conservation of natural landscapes are important for insect pollinators, urban landscapes do play a role in species conservation.
Studies of insect pollinator health consistently show the primary driver of pollinator health is the presence and availability of flowers . The message is simple: planting more flowers in cities can have a positive impact on improving bee diversity and abundance. Further, when urban bee populations are healthy, a spill-over effect can occur where bees re-inhabit rural lands . This could be meaningful while governing organizations (e.g., in the U.S., the Environmental Protection Agency) investigate agricultural and horticultural chemicals. Until these fundamental questions about land-management practices are satisfactorily addressed in rural areas, cities could serve as a haven for insect pollinators.
Residential lawns, community greenspaces, and commercial properties can provide valuable habitat for urban bees. The small size and range of bees enables individuals who manage these lands to serve essential roles. For example, for smaller bee species that forage and nest within 500 meters, a few neighboring homeowners planting high-nectar flowers can contribute significantly to the quality of these bees’ habitat. Individuals with relatively small spaces can design these spaces to support the functional needs of bees.
It is true that urban development and sprawl is responsible for habitat loss and the extinction of many species . However, urban ecology research on bee species diversity and abundance reveals that humans can inhabit urban landscapes in a manner that does not always degrade habitat and can actually support the conservation of insect pollinators. Considering the amount of bee-pollinated foods in the human diet, this is of vital importance. In an urbanizing world riddled by seemingly insurmountable human and environmental problems, the “pollinator health crisis” is one problem that an individual urban dweller can truly do something about.
This post stems from a collaboration with Dr. Gerardo Camilo (Biology) supported by Saint Louis University’s Presidents’ Research Fellowship and Beaumont Development Awards.
- Potts SG, Biesmeijer JC, Kremen C, Neumann P, Schweiger O, Junin WE. 2010. Global pollinator declines: trends, impacts and drivers. Trends in Ecology & Evolution 25(6):345–353.
- White House, Office of the Press Secretary. 2014. Presidential memorandum-creating a Federal Strategy to promote the health of honey bees and other pollinators [Press release]. Available from: https://www.whitehouse.gov/the-press-office/2014/06/20/presidential-memorandum-creating-federal-strategy-promote-health-honey-b
- Goulson D, Nicholls E, Botias C, Rotheray EL. 2015. Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science 347(6229). doi: 10.1126/science.1255957.
- Saure C, Burger F, Dathe HH. 1998. Die bienenarten von Brandenburg und Berlin (Hym. Apidae). Entomologische Nachrichten und Berichte 42(3):155–166.
- Goulson D, Lye GC, Darvill B. 2008. Decline and conservation of bumble bees. Annual Review of Entomology 53:191–208.
- Baldock KCR, Goddard MA, Hicks DM, Kunin WE, Mitschunas N, Osgathorpe LM, et al. 2015. Where is the UK’s pollinator biodiversity? The importance of urban areas for flower-visiting insects. Proceedings of the Royal Society of London B: Biological Sciences 282(1803). doi:10.1098/rspb.2014.2849.
- Sirohi M, Jackson JI, Edwards M, Ollerton J. 2015. Diversity and abundance of solitary and primitively eusocial bee in an urban centre: a case study from Northampton, U.K. Journal of Insect Conservation 19:487–500.
- Threlfall CG, Walker K, Williams NSG, Hahs AK, Mata I, Stork N, et al. 2015. The conservation value of urban green space habitats for Australian native bee communities. Biological Conservation 187:240–248.
- Frankie GW, Vinson SB, Rizzardi MA, Griswold TL, Coville RE, Grayum MH, et al. 2013. Relationships of bees to host ornamental and weedy flowers in urban 226 northwestern Guanacaste Province, Costa Rica. Journal of Kansas Entomological Society 84(4): 325–351.
- Tommasi D, Miro A, Higo HA, Winston ML. 2004. Bee diversity and abundance in an urban setting. The Canadian Entomologist 136(06):851–869.
- Tonietto R, Fant J, Ascher J, Ellis K, Larkin D. 2011. A comparison of bee communities of Chicago green roofs, parks and prairies. Landscape and Urban Planning 103(1):102–108.
- Matteson KC, Ascher JS, Langellotto GA. 2008. Bee richness and abundance in New York city urban gardens. Annals of the Entomological Society of America 101(1):140–150.
Cities often support high local diversities of pollinators, particularly bees. At the same time, cities support a subset of the pollinator species in a surrounding region. Do these urban pollinator communities contribute to the total diversity of pollinators in a region? Is it possible—or practical—to increase a city’s contribution to regional pollinator diversity by restoring species that are currently missing from the urban pollinator community? The answers depend on characteristics of the species themselves.
Pollinators that are successful in cities are often very common in other habitats in the surrounding region. These species may provide great value within the city by pollinating urban crops, for example. It is possible that supporting regional abundance of common species has unappreciated long-term importance for regional biodiversity. However, when weighed against the immediate needs of uncommon, vulnerable species, conserving habitats that support mostly common species does not help regional pollinator diversity.
On the other hand, cities can support regionally rare pollinators. Some pollinators may be dependent on urban habitat because habitats outside cities are degraded, destroyed or otherwise unavailable. In my own collections, I have found some native bee species almost exclusively in towns and small cities, and rarely in nearby agriculture and forest habitat. Why? Habitats outside the towns are certainly altered from a “natural” state, but still support florishing communities of other native bees. Without knowing their specific habitat needs, all I can say is that urban habitats appear to be important in keeping these native bees abundant in the regional species pool.
Of the pollinator species that are missing from an urban area, I imagine two groups that are practical to restore. The first group includes species that are able to thrive in cities, but are generally uncommon and unlikely to be detected at sites with low numbers of individuals. These species can be restored by adding commonly limiting resources like flowers, which raise overall abundance of pollinators at a site. The second group may also thrive in cities, but commonly lacks one or two key resources. An example may be a habitat generalist/flower specialist like Peponapis pruinosa, which appears on squash and cucumber blossoms in community gardens in New York City. We can encourage these species to colonize urban habitats simply by adding the specific missing resource. Restoring either uncommon or specialist species in urban habitat is likely helpful for conserving regional diversity.
Many other pollinators are sensitive to a complex of environmental changes associated with urbanization that cannot be redressed by adding flowers. These include many habitat specialist pollinators that are consistently missing from urban pollinator surveys, such as spring Andrena bees associated with mature forest. Habitat specialists are priority species for conserving regional diversity, and mostly benefit from conservation efforts outside of the city. Nevertheless, we can support some of these species by protecting fragments of natural habitat within cities. And in some cases, it may be practical to widely integrate natural habitat into urban land use without loss of value to humans. For example, in the southwestern U.S., xeric backyard gardens that replicate native desert habitat appear to support much of the native desert bee community. If habitats outside of cities are extremely degraded, for example by intensive agriculture, then conserving regional pollinator diversity will require using these strategies to maximize the proportion of regional species that can survive within urban boundaries.
I suspect that natural and agricultural habitats still support the lion’s share of regional pollinator diversity. With respect to this important conservation goal, the benefits of urban pollinator conservation are probably outweighed by opportunity costs to conservation efforts outside the city. But since pollinator conservation within cities serves other goals, making it count towards regional diversity conservation should be pursued as a positive bonus.
Socioeconomic factors and mainstreaming urban bee conservation
Cities can help bees, but like many things—it depends. For instance, studies have shown which flowers to plant and where, how big gardens need to be and that proximity to larger ‘green space’ matters for bee conservation. Even novel—and really cool—artificial habitat, such as bee hotels, appear to encourage bees and simultaneously to send a message to citizens that there are ‘more than just honey bees’ that need our help. Since the majority of people live in cities, most of our experiences with wildlife occur in an urban context, so promoting these practices will help urban bees directly, and encourage care and concern for bees beyond our cities.
In terms of how urban habitats can be made to serve pollinator conservation, I’m interested in considering how city and neighbourhood age, development history, and diverse cultural perspectives might add new ways to propel local (and global) action. Cities and neighbourhoods can be further defined by a myriad of socioeconomic factors not commonly considered in analyses of urban bee diversity, including educational levels, lifestyle and social status, and other economic differences. Socioeconomic factors and their influence on patterns in urban bees have been entirely neglected in the literature, but could partially explain some of the emerging contrasting patterns seen in global urban bee diversity.
Cities expand in multiple ways and even neighbourhoods in the same city might expand differently and in different directions. Human population density similarly expands in non-linear ways. Growing cities bring together people of diverse cultures and socioecological values. Acknowledging these assets could add synergy to the who, what, when, where, why and how of urban bee conservation. In Toronto, a ‘city of neighbourhoods,’ with one of the most culturally diverse populations in the world, my colleagues and I recently completed a checklist of the bees of the city and the surrounding region and recorded 364 species! Linking cultural diversity and socioeconomic factors to bee conservation and pollination services could provide new ways to mainstream action on urban bee conservation by conveying their needs to the public through connection to everyday life factors not normally considered in promotion and management.
In my own study, from 2011 to 2013, I surveyed 200 community and home gardens, urban parks, and green roofs in Toronto using bee hotels and a large citizen science collective. Among many interesting findings, bee species richness increased with household income, and bee abundance increased with certain landscape factors, including the amount of open (e.g. non-forested) urban green space. Other studies have recorded an increase in plant diversity with household income, and coined this as the ‘luxury effect.’ Human preference for certain landscape conditions can remove resources for some species but increase them for others. Where finances permit, people can increase or decrease plant diversity through specific gardening techniques that would support bees, but these effects are generally unlikely to be conscious. The link between income and homeowner participation in activities to enhance native bees is not well researched, and participation is likely driven more by lifestyle choices, social status, and other forms of identity. More studies are needed to elucidate how standard (and freely available) socioeconomic and demographic data might impact patterns in pollinator diversity and the important services they provide.
The potential consequences of pollinator decline on the preservation of biodiversity and stability of food crop yields should guide the policies of pollinator conservation.
Even though urbanisation has a negative effect on insect fauna, wild bees are found in urban environments. Urban bees are those that lived in an area prior to urbanization and were able to adapt to anthropogenic alterations to the environment besides the exotic species that have become naturalized in there.
Natural areas are shrinking worldwide due to human interventions in the environment and it has been observed that urban areas have been progressively occupied by populations of non-domesticated species, thus turning into havens for wildlife. So, we find native bees living spontaneously in natural areas but also in urban areas where they exploit existing open spaces (gardens, orchards, squares, parks, sports fields, clubs, vacant lots, etc …) with flowering plants including ruderal plants, ornamental, fruit trees, vegetables, weeds and other species of varying sizes and habits.
Urban plants are usually intensively managed: watering, pruning and replanting produces floral resources that are more consistently available to pollinators, even in times of drought. In urban environments, the temperature is a little higher than outside the city and pesticides are of restricted use. Botanical species with different flowering periods are usually used in gardening in cities, which favors the ornamentation factor and, consequently, the supply of resources for pollinators is maintained throughout the seasons.
Thus, it becomes relevant, in urban areas, to have bee plants for maintaining the diversity of bees. The goal of offering more floral resources for bees in urban areas can be achieved by encouraging the growing of ornamental bee plants, in line with a gardening, landscaping and sustainability sensibility.
Plants defined as ornamental by the attractive shapes and colors of their leaves or flowers are part of numerous groups of cultivated and wild plants, including representatives of various plant families, and are often cosmopolitan, originating from different countries. They are aesthetically pleasing, suitable for gardening and landscaping, and can be used, in urban areas, as a draw and food resource for wild bees. We think such ornamental plants make it possible for ecologists, farmers, plant enthusiasts and gardeners to enhance the urban environment as a biological corridor, using them to connect nearby forest fragments. Ornamental bee plants can also be used as bee pasture species in urban beekeeping.
Ornamental plants are not often thought of as bee plants because they do not always offer conspicuous pollen or nectar resources. Moreover, frequent attributes of ornamental plants, such as double petals and a lack of stamens, nectar guides, and strong scents, among others characteristics, drive off bees. However, many of them are suitable for bees that visit them.
Bees and pollinators have always been a part of the city landscape, but outside cities modern agriculture has caused, and continues to cause, the destruction of bee habitat and the resulting declines in bumblebees, solitary bees, hoverflies, moths and butterflies. Cities have provided a relative sanctuary from the chemical and physical destruction of flower-rich meadows and indiscriminate insecticide use. Now there is increasing interest in urban-based conservation and wildlife gardening, so the presence of city bees amongst us has become more noticeable as well as more important.
Urban habitats can provide a fantastic range of varied pollinator resources. Existing wildflower sites, sometimes grasslands or railway banks and very often brownfield sites such as quarries or old mining spoil, can be protected and managed for their wildlife habitats. Roadside verges, playing fields, gardens, flat roofs, parks, even hanging baskets and green walls can be adapted to become flower rich bee havens.
The choice of pollen and nectar sources is important, tailoring planting to key local pollinator species and assemblages will increase the functionality of the habitats. While many pollinators are generalists, others visit only certain types of flower or are dependent on the flowers of just one plant. For instance ivy, speedwells, yellow loosestrife, white bryony, ragwort and scabious flowers all have specialist bees in Britain. Fostering flowers that support specialist bee species has the potential to ensure that cities not only maintain boosted populations of the widespread and generalist pollinators, but are also a refuge to a wide variety of bee species.
More pollen and nectar is the primary objective for bee habitat improvements, but nesting sites are also limiting factor for several species. Bumblebees will benefit from areas with long vegetation and banks where mice and voles can create the burrows that the bees so often occupy. Solitary bees have very varied nesting requirements. Solitary bee nest boxes are effective for a number of groups of solitary bees, and the retention of deadwood provides a more natural source of holes and cavities in which the bees can nest. We can also create banks and bare ground in which burrowing solitary bees can nest. For instance, Buglife’s ‘Get Glasgow Buzzing’ project installed large patches of sand in municipal parks so that sand nesting solitary bees could construct nests.
One of my favourite stories of urban bee conservation relates to the Long-fringed mini-miner bee (Andrena nivealis). It is a rare bee found in very few localities in southern Britain where it specialises on brassica, cabbage family, flowers. In Bees of Surrey (2008) David Baldock relates that the bee was found in abundance on a small holding in Ewell, feeding on purple sprouting broccoli. A woman living in an adjacent house had noticed the bees and spent hours observing them foraging and nesting in bare ground. When the small holding stopped growing brassicas the woman used her garden to grow a variety of flowering brassicas so that the little bees would have a chance of survival.
Engaging local people is key to delivering successful bee habitats. Passing on knowledge will enable them to manage flower rich bee friendly areas into the future, and they will learn for themselves that bee habitats have much wider benefits; delivering ecotherapy and the health and wellbeing benefits that come with nature engagement. Bee habitats, foraging and nesting, provides benefits to other pollinators and wildlife, giving the potential for people to access and to experience a wide range of invertebrate, plant, bird and mammal life close to where they live.
There is much still to learn about conserving bees in cities. The Buglife project ‘Get Plymouth Buzzing’ worked with Plymouth Council to develop wildflower meadows on municipal grassland. A subsequent study found that the wildflower meadows had more than twice as many bees as areas that were still standard municipal grassland. Buglife’s current ‘Urban Buzz’ project will be turning eight cities across the UK into bee wonderlands. But the project will also attempt to get a better understanding of how we can provide the greatest benefit to our bee fauna, by, for instance, experimenting and researching innovative aerial homes for solitary bees.
Working with Local Authorities brings the potential to develop a strategic network of pollinator sites. Existing wildflower areas can be expanded and linked together and the targeting of action can improve the landscape connectivity for bees—promoting corridors of bee friendly open spaces, roofs, gardens and walls—as is being planned with the London B-Line.
Pesticides are a big issue for bees and other pollinators. Neonicotinoids attack the nervous system of wild bees, preventing them from foraging successfully, finding their nests and producing queens or the next generation, other insecticides such as pyrethroids are also toxic to bees, and herbicides impact bee health as well, either directly or through the destruction of flowering plants. The non-agricultural use of pesticides is usually cosmetic and unnecessary.
France is leading the way, Paris has been pesticide free for over a decade and there are over 900 villes sans pesticides. In 2014 Minister of Ecology and Energy, Ségolène Royal, called on mayors to stop using pesticides ”Pesticides are a health risk and today there are products that enable us to stop using pesticides and win back biodiversity, namely species such as butterflies that have at times completely vanished from certain communes.” Seattle, Copenhagen and Tokyo are among other cities that have kicked the pesticide habit.
Cites alone will not save all the bees. If we want to have a healthy and sustainable agricultural system with adequate pollination services then we will have to restore pollinators across the countryside, defining wide corridors and sprinkling them with fields of flowers, as set out in the B-Lines scheme, is probably the most cost effective way of achieving this. There are also many bees that have fussy habitat requirements, conditions only found on heathlands, sand dunes or chalk grassland for instance. These bees will not be adequately catered for by the amount of habitat in urban areas, and therefore need targeted conservation management.
While cities may not be the panacea for bee conservation, they can make a hugely important contribution to conserving many species of bee, and urban bee conservation work also enables people to learn about and love bees: knowledge and passion that will provide the ground swell of support for the conservation of all bee species.
Can cities save bees and assist in pollinator conservation more broadly? This is an interesting question, where it’s likely the answer will be country- and city-specific. Bees in urban areas have been most extensively studied in the United States, Europe and the United Kingdom. In Australia, we know much less about how many species of bees occur in our cities and what types of habitats are important to their conservation. We know that bees need food, nesting sites and water, and that these three key things often occur in urban areas. However, exactly how important Australian cities are for bee conservation is yet to be determined.
Australia is one of the world’s most urbanised countries, and it is predicted that 90 percent of Australians will live in a city by 2050. This high density of Australia’s population in cities poses an obvious threat to biodiversity, including our native bees. But, it could also present enormous opportunities for targeted research, citizen science, evidence-based conservation policy and genuine science-practice partnerships. Cities could form an excellent platform to set out to achieve these things. However, there are currently some challenges to this goal.
There are over 1,500 species of bees in Australia, with records of over 150 species in some of our capital cities. Despite this diversity, there is only one published paper examining habitat for bees in an Australian city. We do not yet know how many types of bees occur in our cities, what habitat they need or how to manage that habitat to serve pollinator conservation. My colleagues and I at The University of Melbourne and The University of Sydney have been collecting data to remedy this situation, and we have a good inkling that our cities harbour a large proportion of the countries bee biodiversity, but until more work is done, we just don’t know for sure.
Our second major stumbling block is that most of our 1,500 species are small and solitary. Australian bees, albeit charismatic, are not as well recognised as bumblebees are in other countries, and are commonly mistaken for flies by the general public. However, many municipal authorities are working very hard on fantastic community engagement programs to remedy this apparent underappreciation for urban invertebrates, including The City of Melbourne’s Urban BioBlitz—where hundreds of participants gathered in the city’s parks and gardens to survey the urban pollinator community, providing data for their upcoming urban biodiversity policy—Or the Ku-ring-gai Council’s native bee hive program, which is so popular they have residents on waiting lists eager to take home their very own native bee hive. However, these types of programs are by no means common practice, and many more programs like this are needed before the urban public can empathise with the plight of our urban bees.
Our last stumbling block to realising the potential of cities as avenues for pollinator conservation is the lack of urban biodiversity policy that currently mentions bees (or any invertebrate, for that matter). Current policy often focusses on the threatened or rare, and much of the habitat that our native bees would happily utilise—such as gardens, vacant lots and brownfields—are not traditionally viewed as valuable for biodiversity, and subsequently do not feature in urban biodiversity policy.
So how can cities save bees and assist in pollinator conservation? I think cities require new approaches to conservation, including genuine, long-term collaborative partnerships between scientists, practitioners and policy makers. These partnerships need to operate at multiple scales, from local municipalities through to national scales. And these partnerships need to act in concert so that research informs policy and policy needs inform research, with a focus on providing opportunities and stories to engage citizens along the way. We are well on our way to forging these paths in Australia; however, the jury is still out on exactly what role cities will play in the conservation of our unique bee fauna into the future.