‘City of Trees’ launched in Manchester

The ‘City of Trees’ project is campaigning for a greener Manchester and aims to plant millions of trees around the Greater Manchester area over the next few decades. It has so far planted 94,380 trees around Greater Manchester since it’s launch in late 2015. Director Tony Hothersall explains after its primary aim of planting 3 million trees, which is “a tree for every man woman and child [in Manchester]”, they are also “very much focused on bringing existing woodland into management because there is no point in planting new woodland if you can’t manage what you’ve got.”

Mr Hothersall also emphasises the project’s goal to educate the public about the multiple benefits of trees and woodland. Aside from being aesthetically pleasing, there have been myriad studies that show the presence of trees and greenery in urban environments can aid mental wellbeing, as well as having cooling properties and the ability to reduce air pollution. Research here at the university, alongside the City of Trees project, United Utilities, and the Environment Agency, is also looking into the use of trees in reducing surface water flooding.

Lead researcher, Dr James Rothwell explains: “Traditionally water off roads and pavements is taken straight down into the sewer system. It’s treated, and there are costs associated with that, especially such a big cities like Manchester. It can become overloaded so you get a water ponding on streets and then flooding.” Dr Rothwell’s research explores how trees mitigate against flooding in the urban environment, using nature as a helping hand.

This research is the first of its kind in the UK. “It’s really novel, so what we’ve got is effectively a very large tree treat trench, with three large trees on the street in Salford. We’ve connected from road to sewer but interrupting that using the trees to help us to effectively slow the flow of water, reduce the volumes of water and the speed of water.”

Initial data from the study is promising, which shows that water flow into the sewer is slowed by up to two hours and the volume reduced by 60 per cent. Dr Rothwell is excited by the prospect of this research, saying that the slow advancements in urban greenery in the UK could be due to lack of hard evidence. This not only has environmental implications but also financial ones. A household’s water bill includes the service of taking surface water off the property into sewers, so reducing the volume of water could reduce bills and be a way of providing incentives to developers to get on board with the scheme.

This research and the ‘City of Trees’ project has gained a lot of interest of late, including from the Secretary of State for Environment, Andrea Leadsom, whom Dr Rothwell showed round the study’s site just recently. He hopes this study provides a demonstration of yet another benefit of trees in the urban environment and it becomes “business as usual” to include trees into the infrastructure of new city developments.