Scientists have suggested that bees benefit a lot from urban ‘greening’ projects. The study shows us that if governing bodies seriously looked into this there could be lot more benefits both for us as well as birds, animals and insects that live alognside us in urban areas.
Ohio State University researchers studying ways to encourage biodiversity in vacant urban lots found that experimental plots surrounded by 15 or more connected acres of greenspace and flowering prairies containing native plants created conditions most conducive to the conservation of native bees and predatory wasps.
Bees are the best natural pollinators out there and are necessary for efficient crop productivity. While they are abundant in rural areas, there is a threat to their population in urban areas. Scientists say that optimizing bees’ city-living conditions could also help offset threats to their diversity and survival. Bee populations are challenged by a range of stressors – habitat loss, climate change, pesticides and invasive species – that “are huge issues that aren’t going away anytime soon.”
The researchers sought to assess urban “greening” strategies that could support multiple ecosystem services provided by plants and insects and the results suggest that while infrequently mowed turf grass used for many urban greening efforts can support insects, some other types of minimally managed greenspaces could offer even more benefits to important native pollinators.
The research is published online in the journal Conservation Biology.
This study of how greenspace quality, size and configuration affected bee and predatory wasp nesting was part of a long-term, large-scale project for which the team designed different vacant lot management styles in eight neighborhoods across Cleveland.
Among 40 of those lots, five greenspace designs were tested for effects on bee and wasp reproduction, with the existing weedy vegetation in lots mowed monthly serving as a control. Experimental treatments included a dense no-mow grass lawn, a flowering lawn of mixed grasses, a prairie of tall native grasses, and a native flowering prairie of grasses and plants.
The researchers assembled a bee and wasp trap nest composed of a series of cardboard straws at each site. Over the three-year study researchers X-rayed each straw to count the number of larvae inside, and confirmed those counts by observing the emergence of adult bees and wasps in the spring. Of the 17 species identified, 64% were bees.
The analysis showed that a higher abundance of native larvae was associated with the conservation plots surrounded by larger patches of additional urban greenspace – at least 15 connected acres was ideal – and more native bee larvae were observed in the flowering prairie.
In addition, native flowering prairies attracted a unique composition of bee and wasp species when compared to the control lots containing natural occurring weedy plants and turf grasses – a clue that greening urban spaces with native flowering plants could provide an important bee and wasp habitat.
The findings could prove useful to the world’s estimated 350 “legacy” cities – former industrial hubs whose landscapes have changed dramatically as a result of lost manufacturing industries and depopulation.