The New York Times ran a story at the start of the week attributing dramatic changes to New York’s streetscapes over the course of the last 80 years or so to the planting of trees.
The Times includes a series of ‘before and after’ slides comparing bare streetscapes from the 20s and 30s with the same streets as they are today. They’re now “softened” with many more trees and look much greener and more welcoming. (1)
I discussed the benefits of planting trees in streets a couple of years ago and it’s worth revisiting that topic now in light of the Times story (Can’t we do more with trees in streets?).
Street trees provide many benefits, both to residents and the wider population. Depending on site-specific factors and design decisions, they can:
- Enhance the visual amenity of streets.
- Provide shade, shelter and points of interest for pedestrians.
- Reduce home cooling costs.
- Attenuate noise.
- Support bird life.
- Remove pollutants and carbon dioxide from the air. (2)
Urban designer Dan Burden reckons it costs between $250 and $600 in the US to establish a tree over three years, but the direct social benefits over its lifetime exceed $90,000 (excluding aesthetic benefits).
Some residents and local authorities, however, think trees are too much trouble. Detractors argue trees:
- Require costly attention to get started.
- Are vulnerable to vandalism in their early years.
- Roots can interfere with services and foundations.
- Branches snag power lines and have to be pruned regularly
- Leaves, bark and seeds clog residents’ gutters.
- Some species drop death-sized branches from time to time.
- Natives are preferred in many locations because of their drought tolerance, but they can block sunlight to houses in winter.
- Trees sometimes come at the expense of parking spaces.
There is a surprisingly large number of streets with trees in the established suburbs of cities like Melbourne, but there’re also quite a few that don’t have any. Bare streets seem to be mostly larger arterials or located in lower income suburbs.
In those case the existing trees are sometimes too small – presumably so they don’t interfere with power lines in older suburbs – and not planted closely enough to create a strong sense of an avenue or a canopy.
To my eye, some of the species also look scrappy with thin foliage. Whatever their merits as individual trees, they don’t contribute as effectively to the whole as alternative (native) species would.
I’d like to see a major national program to “green the streets of Australia”. The objective would be to improve the public realm through better design, especially (but not solely) by planting trees in streets.
Many local government authorities already have tree planting programs but I suspect they work best in higher income suburbs. I also think they’re often too uncoordinated and don’t produce an integrated or “designed” whole.
A national program would have to be led by the three tiers of government and it wouldn’t be easy. There’d be difficult issues like loss of parking, shifting/undergrounding services, funding, cost-sharing with residents, species selection, and maintenance.
Streets with different land uses would require a separate approach and there’d undoubtedly be people who simply don’t want trees in their street. It would need to be flexible enough to adapt to local circumstances, right down to the level of individual streets.
The proposal needs to be assessed carefully of course, but on the face of it, it’s hard to think of a more cost-effective way of improving the quality of urban streetscapes and the amenity of residents than planting street trees. And it’d be an opportunity to improve streets for cyclists and pedestrians.
Cars, of course, are another big change
There are claims that trees can also reduce the incidence of asthma and crime.