Oli Davey, Co-Founder + Principal Design Engineer
The body of evidence in support of the many positive attributes of street trees is now significant and has indeed enabled the monetisation of these benefits, so that direct comparisons can be made with alternative forms of investment in our streets. I can readily find out, for example, that a single mature tree can absorb carbon at a rate of 21.6kg per year; and that a tree-lined street can lower particulate levels by 60%; and that a mature tree can capture 11,375 litres of rainwater a year; and that street trees can increase property prices by as much as 15%. In fact, it is estimated that, for every £1 spent on tree planting, £7 of expenditure is saved in other areas (for further information about the benefits of street trees I’ve found the following link a useful resource https://www.greenblue.com/gb/green-infrastructure/benefits-urban-trees/).
Whilst all of this data can be very helpful for those making the case for more street trees, especially at a time when capital budgets are tight – and maintenance budgets are even tighter, it can all start to sound a little too clinical. Don’t get me wrong: all of this empirical information is invaluable when it’s time to push back against a spot of value-engineering. However, Vienna proved to be a very welcome reminder of the simple yet joyful pleasure that a few street trees can engender.
With some rather austere architecture, an abundance of on-street parking and some functional catenary street lighting, many of Vienna’s residential streets can start to feel a little drab; even bleak. Add in the thirty-degree heat that we experienced on our trip, and many of the canyon-like streets can be pretty oppressive places to move through and spend time in.
However, throw in a few mature trees and suddenly otherwise identical, nondescript streets become elegant, welcoming avenues. I don’t doubt that they can also justify some fantastic cost-benefit ratios but, at a purely qualitative level, they simply result in attractive places to be. The reason that this was so striking to me in Vienna was the seemingly random selection of streets (and their residents) that get to enjoy these trees, or which miss-out.
Streets with otherwise identical cross-sections, often just one block apart, made for a stark reminder of the transformational effect that trees can have. And it is for this reason that I alone, amongst all my colleagues, have been allowed to show two photos (even if one is just inset).
So, thank you Vienna for providing a very welcome reminder of the everyday value of street trees that can sometimes get lost in all the number-crunching.