Wild bees have found a surprising place to nest in cities

Urban pavements can prove unlikely havens for wild bees and other insects, a survey on the streets of Berlin suggests.

Sophie Lokatis at the Free University of Berlin and her colleagues explored 200-metre-long sections of pavement at 12 locations in the German city. They recorded insect nest locations and collected individuals found at the entrance to nests, crawling on the pavement or flying within a metre of the ground. They also analysed soil from nests using DNA sequencing techniques.

The team recorded 66 species using pavements as a habitat. Many of these were pollinators and other beneficial insects, including 28 species of wild bees and 22 species of solitary and parasitoid wasps.

They also found that there were significantly more nests, and a higher diversity of species, on pavements within 200 metres of insect-friendly flower gardens, created by initiatives bringing together conservation groups and housing associations in the city.

“Only a few years ago, insect-friendly gardens near apartments and extensive, rarely cut meadows in parks were almost unthinkable,” says Lokatis. “This has shifted dramatically: many people understand the urgency of the biodiversity crisis and seem to long for more nature and wildlife, including near their homes.”

Berlin’s pavements mainly consist of small cobble stones or tiles with a sand mixture between them, where insects can dig burrows. The benefits of this kind of paving can be an example to other cities, says Lokatis.

“Considering the highly negative effects that asphalt has on urban climate, it would be worthwhile looking at other options, that can then also allow herbs and insects to accumulate,” she says.

The findings disprove the idea that cities are biodiversity deserts, says Sarah Parsons at Western Carolina University in North Carolina, who wasn’t involved with the work.

“The effect of urbanisation on species can be quite complex and can, in some cases, result in a greater diversity of species than we may expect,” she says. “The study underlines the importance of flower gardens in urban spaces to promote bee and wasp diversity, and paves a path forward for how we can design future cities.”