BLOG: The Contribution of trees and GI (Green Infrastructure) to creating resilient cities

29 November 2018

Mike Harris, associate from Greengage, writes about the recent City of Trees seminar.

On the 21st November City of Trees hosted ‘The contribution of trees and GI (Green Infrastructure) to creating resilient cities’ seminar.

During the day nine excellent presentations were delivered.

The key messages were:

  • The contribution of trees and GI to creating resilient cities is huge
  • GI has to be a fundamental part of the design process
  • GI has to be considered on a strategic scale as well as a single development, local scale
  • It requires collaboration between multiple parties to maximise the benefits of GI
  • The benefits of GI need to be promoted more and in a way that showed tangible benefits.

To kick off the day, Pete Stringer of City of Trees discussed how the use of spatial data could inform where GI was delivered. He also presented evidence of how these benefits were being quantified, for example:

  • How a green barrier had reduced mean NO2 concentrations and PM10 by 9% and 21% respectively on the side away from the main road
  • How a new drainage system combined with specialist tree pits had resulted in an average delay of storm water peak flow of 68 minutes, amongst other benefits; and
  • How an experiment found that the presence of a tree over an asphalt plot was able to reduce air temperature by 11oC and the surface temperature of the asphalt by 8oC.

Caroline Simpson, Corporate Director of Place from Stockport Metropolitan Borough Council (SMBC) presented SMBC's innovative and forward-thinking proposal for the Stockport Interchange. The project will deliver an improved bus station with a two acre park on the roof. The park will provide space for walkers and cyclists as well as a link to new commercial activities. Rain gardens within the park will filter run-off from a section of the A6, cleaning the water before it is released in to the drainage system.

‘We don’t trim our bushes’ was the title of the next talk delivered by Adam Higgins of Capital&Centric. Adam explained why Capital&Centric think differently. They see the value of GI in creating places with function, places to meet and socialise. A result of this approach has been increased value and saleability of their product.

United Utilities discussed the importance of an integrated approach and the consideration of natural capital accounting in decision making. How looking at the risks holistically can ensure that the solutions brought forward provide multiple benefits. An example provided was how historical sludge lagoons can be transformed in to a nature reserve which provides environmental benefit through water filtering, biodiversity gain and water attenuation and social benefit through recreational space and health and wellbeing.

Pete Swift from Planit IE announced the ‘Reclaiming of Red Bank’, providing an insight in to the proposals for the Northern Gateway project. Pete outlined the proposals to ‘extend the valley’, ‘activate the Irk’ and to bring back life. The project will use the existing river valley and create new, strong green links in to the surrounding urban area to make this historical resource more accessible and open it up to the public.

Next up was Councillor Alex Ganotis who spoke about how Greater Manchester would meet their ambition of being one of Europe’s leading green cities. The stand out message from his presentation was on how Natural Capital benefits the City. £860m was the calculated total annual benefit. Health benefits from Natural Capital over the next 60 years alone was estimated at £11bn.

How strategic GI can manage air pollution for improved public health was discussed by James Levine. This was not about removing pollutants, which he noted should be the primary focus, but managing human’s exposure to them. He presented evidence that showed vegetative barriers could reduce concentrations of pollutants by up to 50% in the immediate area. But there was also a warning, the wrong GI in the wrong area can make the situation worse. As a result of this, a platform is being created that can identify the best GI option for a specific urban location.

The afternoon session began with John Alker of UKGBC discussing the key barriers to GI as raised by their members in a recent poll. Lack of financial mechanisms, insufficient national and local policy, a concern around long-term maintenance and trade-offs with other sustainable designs. All good reasons but reasons that hopefully the growing evidence base of the benefits of GI will change, with a little help (hopefully) from the new environmental bill as well.

The final talk of the day was from Tom Armour of Arup. Tom provided excellent examples of innovative GI around the world showing the benefits of GI and how it can be integrated in to the design stage. The stand out slide though, was a figure showing the land surface temperature in the west end of London and in Richmond Park. Whilst the West End was 31oC, Richmond Park was 23oC. 

Technically, there was a tenth presenting slot - resilience bingo, delivered expertly by Pete Stringer of City of Trees. It made many wonder whether he had been a bingo master in a previous life - and was so much more than  just a presentation! I look forward to playing again next year!

This blog has been written by Mike Harris from Greengage, who were one of the Event Sponsors of the event.