Arboriculturists reveal why the controversial removal and replacement programme is vital in the face of disease and a lack of diversity in species
Travel along Rivelin Valley or Montgomery Road as the lime leaves unfurl this spring and most of us would go with the popular ‘majestic tree-lined avenue’ description.
A modern arboriculturalist may well agree. But they’d also be thinking ‘monoculture,’ which is bad news for disease resistance, longevity and climate change mitigation. For the tree experts actually doing the work, this is the key to Sheffield’s now infamous tree removal and replacement programme.
“A healthy tree population for a city needs to be diverse in age and species, the trees need to be genetically different to build a resilient and healthy population in years to come,” says arboriculturist Brian Stocks. “And we’re trying to do that.”
He and his Sheffeld Council predecessors have been aware of the problem over many years of funding cutbacks. Early this century tree officers were warning that many if not most of the Victorian and Edwardian trees of Nether Edge and Broomhill were likely to be dead by 2050, while the second (post-war) waves of municipal planting were mainly genetically identical cultivars that are prone to disease and often varieties that would be avoided nowadays.
Most of our older cherry trees, says Brian, are infected with bleeding canker which tends to kill trees over a number of years and can also spread to other species.
Do we want to protect and preserve the stock now at all costs and just manage it? Or put our heads in the sand and leave it to the next generation?
“We want to mix up cultivars and species if we can,” says Brian.
“People often do like uniformity, but diversity is good, for wildlife and insects as well as trees.”
“The question is what do we do about it?” says Amey’s former arboricultural operations manager Jeremy Willis. “Do we want to protect and preserve the stock now at all costs and just manage it? Or put our heads in the sand and leave it to the next generation to decide, which in truth is what was done in the past? Or do we take the opportunity of this contract to try and address the problems that are facing us?”
So the plan under the Streets Ahead funding was to replace around 10-15 per cent of the city’s street trees over the initial five year period, and replace them with younger and more varied species, with particular consideration to trees suitable for a changing urban climate.
It’s worth keeping that in mind, Jeremy says, when reading about ecocide on the streets of Sheffield.
Less than 30 of Rivelin Valley Road’s 528 trees are to be replaced, for example.
“That’s 5 per cent,” he says. “That’s not decimating the street.”
Despite Streets Ahead being a road and pavement maintenance contract with only scope for ‘like for like’ replacements (and little input from tree experts at the time it was written), over its first few years the programme replaced several thousand older street trees in the north and east of the city with a younger, more diverse population of 42 different varieties, including gingko, maple, hornbeam, cedar and new varieties of cherry and lime.
Jeremy and Brian have both worked with trees for over 20 years, and take issue with several street tree factoids in circulation: our often derided ‘saplings’ take on lots of CO2 as they grow, for example, and while a mature tree does store CO2, it’s about as much in a year as a typical Sheffield car driver produces in a few days.
And yes, big trees do reduce heat on city streets, and can soak up some atmospheric pollutants, but in some cases their canopies can also trap pollution at pavement level.
And Brian notes that ‘engineering solutions’ to try and retain a mature street tree will often compromise its shallow roots.
For example, the council says the contract insists on kerbs to keep road pollution away from tree roots and reduce rainwater ingress under the pavements as well as to provide a neat road edge. If kerbs are a must, resulting root damage can easily lead to future disease.
So is it better to just take the tree out and replace it with a younger one?
Jeremy believes the two sides in the dispute have become entrenched with Amey stuck in the middle, and very much hopes to see “some further conversations in future, as long as it’s sensible.”
He adds: “What we’re doing will not affect Sheffield’s status as a green city with over four million trees.
“When we’ve finished the street tree population will be in a better state than when we started.
“Our aim is to give our highway trees the resilience to go on for generations and generations.”
Environmental campaigner Professor Ian Rotherham said diversity was just one of many factors to consider and the original 2007 consultant’s report suggested that a total of only 500 trees required removal.
He added: “Others required care and maintenance and this is where Amey seem to seek to save money - in cutting basic care and maintenance over the short- and longer-term.
“To be fair the city council has under-resourced this area for nearly thirty years and this is one reason for the current situation.
“However, neither the council nor (especially) Amey seem to have any joined-up strategy that links the street tree / urban forest management to things like pollution management, water / flood-risk reduction, climate change mitigation, green corridors, human health and wellbeing, pollinating insects, breeding birds, bats and insects (biodiversity), landscape quality, heritage (i.e. the ancient trees now in the urban area but originating in the countryside landscape).
“S o there is no real strategic thinking behind all this and the community had zero involvement in determining such a long-lasting and hugely significant strategy for the city.
“The council and Amey have really failed to carry the public with them or to effectively engage and answer concerns and worries, or to listen to positive suggestions and ideas.
“So this was really a fait accompli by the time local communities got to hear of it and furthermore, it knocks major holes in other existing conservation strategies and the like and is counter to almost all the green policies and promises that the council have made over thirty years or more.
“The proposals and work programmes take no account at all of public opinion - for or against.”
He added: “There are major underlying issues of long-term central government cuts to local services which are disproportionate for cities like Sheffield - so a loss of key skills and staff in countryside, woodlands, trees etc. W ithout these cuts then this situation would not have arisen.
“Huge issues of lack of transparency and of accountability - for ‘our’ money - due to the public-private deal - and consequently a public service paid for by the public being delivered badly (by any measure we care to apply), but in order to make a profit for a private sector partner.
“It is clearly work that is now not on target and not to an appropriate standard or even cost-effective in its delivery.
“Worse still the work is not in accord with agreed national strategies or standards - such as ‘Trees in Towns’ for example - and this is fairly basic stuff.
“Lots of tree experts have visited the city and have been appalled by what they have seen.
“One of my other big concerns is the inappropriate use of the security people and the police by Amey and SCC on its own people - who are actually the ones paying for the service in the first place.
“Instead of bringing calm, common sense, and unity the council seems to have been incredibly ham-fisted and divisive in all its handling of this.
“The behaviour applied to the situation by SCC and Amey has been a failure, has been prohibitively expensive, and overall, totally unacceptable.”