A Tale of Two Cities: a case study in contradictory approaches to urban greening

Recently, via the wonders of social media, I have become aware of what appears to be an example of two initiatives taking place within the same city which seem entirely at odds with each other when it comes to environmental sustainability.  The city is Sheffield in the north of England, where on the one hand there has been widespread acclaim for a recently delivered urban greening project, and on the other widespread despair at the removal of thousands of mature street trees.  What makes this even more noteworthy is that both of these schemes have been lead by the local authority, Sheffield City Council.  This blog post will explore the two approaches and how one appears to undermine the aspirations of the other.

Grey to Green Project

Let’s start with the positive.  The Grey to Green project is a multi-million pound scheme with the aim of transforming redundant roads in the Sheffield Riverside Business District into attractive new public spaces.  Phase 1 of the scheme was completed in Spring 2016 and included plantings of wildflowers, trees and shrubs, but the aspect which has won it such high praise has been the incorporation of a Sustainable Urban Drainage System (SUDS), the largest ever retro-fitted in the UK.

The principle of SUDS is that excess rainwater is managed in-situ rather than being channelled into the public sewerage system which can be overwhelmed during periods of heavy rainfall.  Flash flooding has already been a problem in this area of Sheffield, and with global warming increasing the risk of severe weather events a key ambition of the Grey to Green project is to “improve the city’s resilience to climate change”.  The SUDS in this case takes the form of a ‘rain garden’ whereby rainwater run-off is diverted into shallow drainage areas known as ‘swales’ which are then populated with plants that are able to tolerate both long dry spells and shorter periods of water-logging.  The planting can improve the rate at which excess water is absorbed, have a purification effect, and creates an attractive landscaping feature. There is much to recommend this approach both for public realm projects and in a domestic setting where rainwater from guttering may be diverted to a pond or swale in order to reduce the risk of flood damage to private properties while enhancing garden spaces.

Section of Grey to Green project planting (taken from Sheffield University website)

The Grey to Green project, which was delivered by Sheffield City Council in collaboration with the Department of Landscape at Sheffield University and contractors Amey plc (of which more later) and Robert Bray Associates, has been recognised with a number of regional and national awards, including three CEEQUAL Outstanding Achievement Awards for civil engineering where judges described the scheme as “a landmark in urban landscape development”.  Something of a triumph then, and an excellent example of public policy responding to sustainability issues.  But then again …

Streets Ahead

Meanwhile in the same city, the same local authority entered into the ‘Streets Ahead’ highways renewal contract with the very same contractor, Amey plc, for the management of street trees, i.e. those which are situated alongside public highways.  The contract was signed in 2012 for a period of 25 years and falls under the Private Finance Initiative (PFI) which provides a vehicle for public infrastructure projects and services to be funded and delivered through private capital.

The costs and benefits of outsourcing projects and services to private contractors has been a matter of debate for some time (see the recent Labour Party Conference), but the particular issue in the case of the Streets Ahead contract relates to the removal of mature street trees.  The Sheffield City Council website states that there are 36,000 street trees in the city and that it was estimated that 6,000 of these would require removal in the first 5 years.  The reasons for removing a mature street tree include damage, disease, and/or threats to the health and safety of local residents, and these are all accepted as valid aspects of street planting maintenance.

However, the contention of local activists represented by Sheffield Tree Action Groups is that perfectly healthy specimens have also been removed.  This particularly relates to those instances where tree roots are deemed to be causing damage to pavements and kerbs.  Activists note that alternative engineering solutions should be explored before a healthy tree is removed on these grounds and claim that Amey deliberately over-estimate the costs of such solutions in order to justify the easier and cheaper option of tree removal.  Of course this is denied and in fairness to Sheffield City Council it will, like all local authorities in the UK, be operating within the restrictions of recent funding cuts, so cost is not an insignificant issue.

The Council also notes that removed trees are being replaced on a one-to-one basis with newly planted trees.  While this is welcome it does not compensate for the loss of mature trees in the short to medium term.  The benefits of street trees include:

  • the effective absorption of Carbon Dioxide (significant to climate change)
  • reduction in the impact of flooding as tree roots take up water
  • reduction in the heat island effect found in cities
  • the creation of a habitat for wildlife
  • improvement to air quality as toxic particulates are absorbed
  • the creation of more attractive public spaces

Inevitably, trees which have been removed are replaced by smaller, younger specimens (as depicted above, ref: Sheffield Action Tree Groups) which simply do not provide the benefits listed above to the same extent as larger, mature specimens.  Given that trees may take anywhere between 10 and 50 years to reach full size, the short-fall created by removing thousands of mature trees in a relatively short period of time cannot be underestimated.  Furthermore activists claim that where trees have been replanted there are deficiencies in the way that this has been carried out such that trees may either struggle to establish or may end causing the same damage to pavements which caused their predecessor’s removal.


So there we have it: one city with two contrasting approaches to the development and management of urban landscapes.  Having committed significant funds to the award winning Grey to Green project with the aim of “improving the city’s resilience to climate change” it does seem counter productive to remove so many mature trees which play such a significant role in addressing that exact aspiration.  Clearly there are short term cost implications of maintaining street trees, but one wonders whether the longer term costs, both financial and environmental, of removing rather than seeking to retain healthy specimens wherever feasible, may be greater.

Perhaps a lesson to take away from this is that, whether in the context of public policy or domestic gardening, it is important to take a holistic approach when considering issues of environmental sustainability.  The introduction of one feature which is designed to attract wildlife or improve environmental conditions (e.g. creating a wildflower meadow) can easily be undermined by taking contradictory decisions which may have damaging consequences (e.g. using peat-based compost), and we should all be mindful of the sum of our actions.

5 thoughts on “A Tale of Two Cities: a case study in contradictory approaches to urban greening

  1. jkaybay October 12, 2017 / 1:20 am

    The before and after pictures make me sad 😦


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