Branching out: how can we help our urban trees?

 Katie Bishop – s4100159 – AD5600

   Our urban trees bring an endless list of benefits. Whilst providing habitat and stable ecology, there is a strong correlation with urban trees to improved mental health, lower temperatures and reduced noise pollution (Wolf, et al., 2020). Certain large street trees can prevent the overwhelming of sewage systems by each absorbing up to 2000 litres of stormwater daily, with an annual saving of $34 (The Mersey Forest, 2014).

Figure 1: Daily Mail, 2018

 Each of the most common street trees – Plane, Sycamore, Silver Birch, Horse Chestnut (Begum, 2022) – are hardy, low maintenance, and reach maturity after 20-50 years. Often, however, these mature trees will be felled and replaced with younger ones, which significantly reduces their environmental, economic and social benefits (Woodland Trust, 2022).

   Over 150,000 trees nationwide were felled by UK councils between 2010 and 2017, equivalent to 58 per day. Council justifications included soil erosion, dead or dying specimens, and nearly 9% were felled because they were causing “structural damage” (Kirby, 2017).  This will likely have been caused by the roots lifting to the surface due to a lack of water, soil, or air. It seems reasonable to assume that the ultimate downfall of these trees is that they were destined to fail – having been planted without the necessary means to survive.

Figure 2: Author, 2022

The Stockholm system is one innovative drive to fix this issue and create healthy trees which will thrive into maturity. These are a cheaper, plastic free and ecologically favourable alternative to the crate systems which many trees are currently grown in (Stockholm Tree Pits, 2022).

Figure 3: Stockholm Tree Pits, 2022

This system uses structural soil, a stone-based medium, which leaves sizable space for water permeability, air diffusion and root growth. Any type of paving, including impermeable tarmac, can be laid on top of the system. Rainwater collected from roads and roofs is diverted into the pits, combatting water stress and contributing to Sustainable drainage efforts (Stockholm Tree Pits, 2022).

   So, there is a method to create healthy new trees, but what can be done to help the existing ones? Retrofitting tree pits may be the answer to giving them another chance.  It is recommended tree pits are fitted where 6ft of pavement will be left for pedestrian traffic, which is achievable on many urban main roads. A tree pit as small as 8ft long can allow considerably more air and water to penetrate the ground and reach the roots. Options for penetrable surface materials include woodchip, herbaceous planting, stone, or gravel, which additionally can improve the appearance of the space. The process to retrofit a tree pit is quick and easy, as the existing pavement can be cut through and then removed with hand tools to prevent damage to the roots. This should allow the tree to experience immediate improvements (Staehli, 2018). This could be a majorly efficient method to improve public experience of urban roads, as not only would existing trees see a large boost in health, but excess stormwater could be prevented from pooling and causing floods.

   As awareness of the need for sustainable materials increases, more products are becoming available to contribute to the issue. For example, Addaflex-R, a resin-bound material made of aggregates and recycled rubber, can be laid on tree pits. It is flexible, porous, and able to withstand foot weight (Addagrip, 2022). Products such as this can make a huge difference to our urbanscapes and allow us to enjoy all the benefits of our street trees. It is clear that the drive to create and maintain healthy trees within cities is gaining traction. Whilst new innovations are making a big step to resolve the issue, there is still a matter of raising public awareness on the value of urban trees and increasing the effort to protect such a vital asset to towns and cities.

Figure 4: Addagrip, 2022

Bibliography

Addagrip. (2022). ADDAFLEX-R. Retrieved from Addagrip: https://addagrip.co.uk/systems/resin-bound-porous-surfacing/addaflex-r/

Begum, T. (2022, November 09). UK tree identification: five common urban trees. Retrieved from National History Museum: https://www.nhm.ac.uk/discover/uk-tree-identification.html

Kirby, D. (2017, March 31). Revealed: The trees on our streets are being felled at a rate of 58 a day. INews, p. 1.

Redwood, F. (2018, December 8). Put down roots: Why having a tree in your garden can add value to your property - and even slash heating bills. Retrieved from Mail Online: https://www.dailymail.co.uk/property/article-6471749/Put-roots-Tree-lined-streets-enduring-appeal-good-soul-too.html

Staehli, P. (2018, February 5). Tree Pits Are the “Pits” But We Can Make Them Better. Retrieved from DeepRoot: https://www.deeproot.com/blog/blog-entries/tree-pits-are-the-pits-but-we-can-make-them-better/

Stockholm Tree Pits. (2022). TREE PITS WITH STRUCTURAL SOILS. Retrieved from https://stockholmtreepits.co.uk/assets/downloads/tree-pits-with-structural-soils-practice-note-V1-4.pdf

The Mersey Forest. (2014). Urban Catchment Forestry prospectus.

Wolf, K., Lam, S., McKeen, J., Richardson, G., Bosch, M. v., & Bardekjian, A. (2020, June 18). Urban Trees and Human Health: A Scoping Review. PubMed Central, p. 1.

Woodland Trust. (2022). What urban trees do for us. Retrieved from Woodland Trust: https://www.woodlandtrust.org.uk/protecting-trees-and-woods/street-trees/benefits-of-urban-trees/

 

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