Bee on a hand

Greening city rooftops

Greening city rooftops

Garden on a roof

A rooftop garden

We are still trying to find a permanent home for our office hives and, while we have a few good options in the works, it has highlighted the challenges presented by legacy building designs. Up until quite recently, the roof space of city buildings was essentially dead space – something to keep the rain off, and maybe support an antenna or two.

This is rapidly changing, and the exteriors of buildings are increasingly important for everything from solar panels through to rooftop gardens. These uses of hidden spaces are not just about the roof, they can significantly improve building performance. 

In March 2015, France introduced regulations requiring 30 percent of all roof space be dedicated to either gardens or solar panels. The Canadian city of Toronto has mandated this since 2009, and there are numerous similar proposals worldwide. It has been driven at least as much by the benefits to public infrastructure as to improve the energy performance of buildings. The combination of shading, moist soil and respiration by the plants means that buildings with a green roof require significantly less cooling. In addition, the capture of water to irrigate the rooftop gardens reduces the demand on storm water infrastructure, particularly important during peak flows. 

It has a function too, with several major hotel chains making rooftop apiaries a standard feature, providing ultra-local honey for their restaurants.

This push to make roof spaces more functional presents a challenge to designers. In our case, we cannot put our hives on the roof due to a lack of safe access. The only access to the rooftop is via a two storey vertical ladder with no fall arrest. In addition to the need to provide safe access, provision needs to be made for the additional weight of water and soil, as well as a safe enclosure so that people can enjoy the gardens they create. A challenge, but in reality a small one given the lasting benefits for aesthetic and functional use of buildings.

Nectar and pollen analysis

The sustainable design focus doesn’t stop at the buildings; it also applies to the landscapes within our cities. One of the most beautiful features of Canberra is the urban forest, an integral part of the original design by Marion Mahoney Griffin and Walter Burley Griffin.

During the latter half of 2015, Cormac Farrell conducted an analysis of nectar and pollen resources from the Canberra urban forest, presenting the results to the Beekeepers Association of the ACT and local government representatives. 

Provided with access to a database covering over 260 000 trees in the urban forest by the Department of Territories and Municipal Services, Cormac’s analysis included all trees listed as providing significant pollen or nectar resources, and had some particularly interesting results.

There was a significant difference in the number of flowering trees within different parts of Canberra, ranging from just over 2 000 in the Weston Creek district to over 21 000 nectar-producing trees in the northern suburbs of Belconnen. The flowering periods of the trees also varied widely, with some areas having an intense burst in spring, whereas others had a more gradual build-up. This can be really important information for beekeepers and wildlife managers, as the available resources will affect breeding and honey production. The presentation was well received, and some of the beekeepers asked for specific analysis for their apiaries, such as the Realm Hotel hives shown below.

It is a good example of how big data can assist in unexpected ways – when this dataset was originally created, it was intended to manage maintenance cycles for the urban forest. It now has the potential to influence the species composition, providing a more consistent level of nectar and pollen, making the city more attractive to bees and native wildlife.

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