Solitary bees do not organize themselves into hives. They do not have a queen, nor do they produce honey. They do not share their labor with other bees and each female builds her nest with several cells, either in the stems of plants, wood or even the ground. Like domestic bees (Apis mellifera), wild bees also feed on pollen and, thanks to their silent work, contribute to the germination of fruits and seeds. These small insects live alongside humans and city pavements are a refuge for species that nest in the pavement. An analysis carried out on the streets of Berlin, Germany, reveals that different wild bees and wasps usually prefer pavements to lay their eggs exposed to the sun.
Claudia Weber, a researcher at the Free University of Berlin, and her colleagues surveyed 12 locations (200 meters in total) in the German capital. The scientists detected 6,301 nests on the streets and discovered that of the 66 species recorded – including Apoidae, Vespidae, Ichneumonidae, Diptera and Formicidae—, at least 28 corresponded to wild bees and 22 to solitary wasps. Although it is a pilot study, the results of the work published in the journal Urban Ecosystems suggest that the proximity of streets to flower-filled gardens and parks may harbor surprisingly rich biodiversity in some cases.
Bees are able to build their nests by digging into sandy soils such as cobblestones or clay, and can develop real engineering feats underground. The insects use their mandibles and support their abdomens to flatten the ground. They build short or long tunnels an inch deep, and thousands of them can congregate in a single area. “Bees tend to cope with urbanization better than most other insects, which doesn’t mean it isn’t a big threat to them,” explains Sophie Lokatis, co-author of the article, by email. The findings indicate that most of the cell entrances were found near gardens. This is due to a greater availability of food sources and possible nesting sites, according to the scientists.
Cities, Lokatis says, are “mosaics.” Urban spaces have pieces, such as gardens, parks and cemeteries, that provide highly diverse environments. “Species that nest in urban pavement are pre-adapted to this habitat,” he adds. Berlin’s sidewalks range from cobblestones to tiles, where insects can burrow. However, the scientists observed fewer nests on streets completely sealed with concrete.
Pablo Vargas, a researcher at the Royal Botanical Gardens, points out that although Berlin has “very good green areas”, it shares a problem with hundreds of European cities: it has almost no parks. “It is good that there is soil and not asphalt, but it is important to diversify the type of plants,” says the biologist, who did not participate in the research. Although it is common to see bees fluttering among plants, near what we are eating or hidden among the petals of flowers, in general they do not like cities.
Ecologist Ignasi Bartomeus, a researcher at the Doñana Biological Station, maintains that urban environments “are hostile” to these insects. “Some bees can live in them, especially if there are enough green areas. We will not find rare and vulnerable species in cities,” stresses the expert, who was not part of the study. For Bartomeus, urban environments are still of a lower quality than natural ones, but they are not as bad as previously thought. Another investigation carried out by Spanish scientistsexplains that this behavior could be due to the size of the brain, which is related to a greater capacity of bees to reside in urban areas when their heads are larger.
“Any action that benefits biodiversity is positive, but it cannot be a substitute for conservation measures,” adds Bartomeus. Vargas, on the other hand, warns that caution must be exercised with the word adaptation Because bees, which have been on Earth for millions of years, are still adjusting to cities that are only 10,000 years old.
The researcher at the Botanical Garden emphasises the concept of biodiversification, a key step in thinking about the future of the old towns of a thousand cities in Europe that lack green areas. “Solitary bees seek diversity,” he says. In 2016, researchers in England examined 183 types of plants in the city of Sheffield. Three years later, in Bonthoux (France), other experts found more than 300 types of plants and in 2020, 57 species of plants were recorded between the cobblestones of the old town of Dubrovnik, in Croatia, but in general, there is little research on insects that nest in the pavement.
Sophie Lokatis acknowledges that to halt and reverse biodiversity loss, “man-made sites such as cities, industrial areas and agricultural lands need to be rethought on a massive scale.”
#Solitary #bees #refuge #city #sidewalks