New research in the UK highlights the benefits of urban habitats for bees and other pollinators. Whilst the focus of this research from Bristol University was on ground level habitats for pollinators, there is great potential to increase the forage habitat available for pollinators at roof level.
Green roofs are already known to provide valuable space for pollinators, especially bees, in urban areas. Furthermore the type of habitat that can found on green roofs is often less likely to be encountered at ground level in cities - namely ‘dry’ grasslands associated with open mosaic habitats. These habitats are generally found on previously developed land known as brownfield land. In many cases these sites are some of the most important habitats for pollinators, especially rare bees, in the UK. In London, a majority of the green roofs that have been installed over the last 15 years have been designed with this kind of biodiversity provision in mind and many are on developments that were built on brownfields.
View of Green roof for Biodiversity on Media
Centre, London Olympics - credit Stuart Connop
The largest green roof installed at the Olympics to meet the Olympic Biodiversity Action Plan (OBAP) has already excelled in delivering biodiversity. The Media Centre is not only a green roof biodiversity, however, it is also combined with solar panels. An example of how renewable energy and biodiversity targets can be meet on one roof. A survey in 2014, undertaken by the University of East London (as yet unpulblished) shows that the species targeted by the action plan and the design have all managed to take up residence on the roof.
Toadflax Brocade on Purple Toadflax - credit Stuart Connop
With careful planting, the implementation of the green roof has been able to attract some rare and important species. Bombus humilisis one of our rarer solitary bees; several individuals were seen foraging on the green roof. Furthermore a rare moth Toadflax Brocade Calophasia lunula, another target species, was noted on the roof. Its larvae feed on Linaria species. Linaria purpurea is relatively abundant on the Media Centre roof and during the late summer attracted a surprisingly large number of Toadflax Brocade caterpillars that feed on this species along with Linaria vulgare.
Caterpillar on Toadflax credit
Ecologists and nature conservationists will acknowledge that the provision of good native wildflowers for pollinators is an important design consideration for green roofs. However, when it comes to designing green roofs with solar panels this can all too often be overlooked. Energy production can override consideration of how the green roof is designed.
Good ecosystem services design can ensure that renewable energy delivery can also achieve good habitat for pollinators in urban areas. The opportunites for improved populations of bees, butterflies and other pollinators in cities across Europe is huge. London is ensuring that green roofs are installed on new developments as well as having distinct renewable energy targets for new developments. Combining these targets on roofs is win win situation.
There are 175,000m2 of green roofs in Central London. Of these just over 5% are combined with solar panels. Whilst there has been increased interest within the solar industry in UK to place solar on roofs, this should not be at the expense of green roofs and biodiversity. We should be combining both technologies and refining designs to ensure the maximum benefit for pollinators.