Cities could play a key role in conserving pollinators, new research shows. According to a study published in the journal “Nature Ecology and Evolution”, residential and community gardens in urban areas are pollinator ‘hotspots’. “Urbanization is increasing globally, and it is thus crucial to promote management strategies that support key ecosystem services provided by urban biodiversity, such as pollination,” the researchers write. “Furthermore, given the threats to pollinators present in farmland, urban areas provide an increasingly important opportunity for pollinator conservation.” The research, carried out by scientists at the Universities of Bristol, Edinburgh, Leeds and Reading in collaboration with Cardiff University and the National Socio-Environmental Synthesis Center, assessed all major urban land uses for pollinators, including cemeteries, gardens and man-made surfaces. While there have been a few small-scale studies on pollinators in some urban land uses, this is the first study which considered cities in their entirety, they said. “We present a large-scale, well-replicated study of floral resources and pollinators in 360 sites incorporating all major land uses in four British cities.”

The study found that residential gardens and allotments (community gardens) are particularly good for pollinators. The researcher write that lavender, borage, dandelions, thistles, brambles and buttercups are important plant species for pollinators in urban areas which they use as food sources. Gardens are pollinator hotspots due to their extensive area, and allotments due to their high pollinator diversity and leverage on city-scale plant-pollinator community robustness. Robustness is a measure of how a community responds to species loss, the University of Bristol explained in a press release. Robust communities can survive the disappearance of some species but species loss in fragile communities leads to a domino effect of other extinctions. “By understanding the impact of each urban land use on pollinators, whether it is gardens, allotments, road verges or parks, we can make cities better places for pollinators,” said Dr Katherine Baldock, lead researcher from the University of Bristol.

The authors designed a new measure of management success based on community robustness that considers the stability of whole communities of pollinators, and not just individual species. They recommend that public greenspaces should be managed in a way they benefit pollinators. “Parks, road verges and other public greenspaces make up around a third of cities but have fewer pollinator visits and resources for pollinators than other land uses,” they said. Their research showed that increasing the numbers of flowers, for example by mowing less often, can help urban pollinators. The scientists also call for a better garden management. Gardens make up a quarter to a third of the area of UK cities and better garden management in new developments and existing gardens is likely to benefit pollinator conservation. Furthermore, city planners and local councils should also increase the number of community gardens in towns and cities. “Allotments have a high floral abundance and diversity as they host many weeds, in addition to flowers grown for cutting, and flowering fruit and vegetables. Allotments are also recognized as beneficial for human health and wellbeing,” they wrote in the journal. “Thus, expanding areas cultivated for urban food growing confers multiple benefits and should be incorporated into city-level planning strategies for pollinators,” they concluded (ab)