The city of Utrecht made world news in 2019 by introducing bee-friendly green roofs on its bus shelters. High time to take stock. Erik Verhagen, a Global Sustainability Science student at Utrecht University, conducted research on the importance of the location of such a bus shelter. After all, how decisive is a green environment in attracting bees to green roofs?
Green roofs throughout the city
If you haven’t seen them yet, look up the next time you wait for the bus in Utrecht. A total of 316 bus shelters have been roofed with succulents. The green roofs provide cooling, capture particulate matter and retain water during torrential rain, all of which make life in the city just a little more pleasant. They also provide a whole host of nectar and pollen, which bees love to use. And this is much needed: bees often struggle in cities, where it can be difficult to gather the necessary nutrients and a place to build nests. This includes not only honey bees, but especially wild bees, many species of which are endangered. Therefore, it is important to know how bees make use of the "green bushes. Does the environment in which they are located matter, or do they come buzzing to the rooftops regardless of their location?
You might expect all this to be self-explanatory, but bees are also complicated: they are picky and take the route that will give them the most nectar and pollen in a short time. Therefore, how they make use of the green bushels is not yet certain.
The effect of urban green space
The study revealed a number of things. First, certainly not all parts of the city are equally green. Especially in the old city center, the proportion of green spaces is small. Second, the number of bees attracted to the green bus shelters also varied throughout the city. After combining these results, a pattern can be seen: it seems that more bees could be found on bus shelters surrounded by green spaces.
This means that green bus shelters are more effective when they are surrounded by greenery. Moreover, the study found that the connection is stronger if the greenery is as close as possible to the bus shelters. Bees prefer to go to green roofs that are next to a park or parkland rather than a few dozen meters away. So pollinators benefit when cities green up, and this makes smart solutions like green roofs more effective. However, it is still uncertain whether the type of green space matters in attracting bees. For example, it could be that parks attract more bees to the area than vegetable gardens, but more research is needed to find this out.
It is also important to help bees in other ways besides greening, such as by reducing pollution or implementing more nature-friendly mowing policies.
Every bit of green helps
Verhagen’s research has shown that the attractiveness of green roofs to bees depends on the amount of greenery in the environment. Hopefully in the future it will become clearer how we can best use green roofs to make bee-friendly cities the norm. For now, every bit of greenery helps, be it in a park of a few square miles or in your own backyard.