‘Bristol City Council needs to retain trees rather than fell them’

Another important tree is threatened with felling, and in response, the “Save the Ashley Down Oak” protest group has been formed. There is a platform in the tree and concerned residents are promising to occupy it for as long as needed.

The failure to consult over the management of urban trees has once again meant that Bristol City Council is like a rabbit in the headlights, unaware that local people care so much about trees.

Yet, all around the city, this is happening again and again as trees are being removed for a variety of reasons without any genuine consultation on options.

Only those who wish to see trees removed have a seat at the table. Bristol Tree Forum is not consulted.  This means that key arguments are often not explored, false claims not exposed and the range of alternative solutions not considered. Risks or costs need to be balanced by the benefits that the tree provides.

Professor John Adams argues that the failure to do this, results in what he terms “bottom loop bias” where decisions are made predominantly by considering risks.

We hear that an “independent expert” has recommended the felling of the tree and presumably is making similar decisions regarding other trees that are being felled around Bristol. But we do not know under what basis the “independent expert” makes these decisions because there is no underlying management plan for Bristol’s trees.

Now we are in the situation where a decision that has already been made is becoming open to scrutiny.  This puts council officers in an uncomfortable position, especially if the decision becomes increasingly difficult to defend as new information appears.

Far better to consult and get all the information on the table beforehand. It might be less work for hard-pressed council officers than dealing with massive controversies that can go on for months or years. So what are the key facts that need to be taken into account?

Bristol City Council have said that the felling of a historic tree in Ashley Down is “unavoidable”. Photo: Martin Booth

The first fact to consider is that local residents care about this tree and their councillors support them. They care enough to make banners and build a platform to occupy the tree. More than 1,600 people have signed a petition.

This alone is an important reason which was not apparent because the neighbours were not consulted when the decision was made.

A methodology known as Community Asset Valuation of Amenity Trees  values this tree at £160,000.  But the problem with things as they stand is that felling a tree represents a low cost option for the insurers and the council. Were the insurers to be charged the value of the tree, they would not be so keen and might find another solution such as underpinning.

Local new planting cannot replace this tree and Bristol City Council does not do itself justice by promoting this claim. Everybody states that they are planting more trees than they are felling (HS2 included), as if that makes it alright.

For a start, few of these new trees are being planted in the middle of this city on busy roads. Not one of the “almost 250 new trees” to be planted at Sefton Park Primary School is ever likely to become as large. They consist of hedging, a few fruit trees and some “trees” to be planted in pots. Worthy as that may be, they are never going to replace this important tree.

The Bristol Tree Forum carbon calculator determines that around 100 trees (that are six years old) would need to be planted to become carbon neutral by 2030.  They would need to be trees that could grow to a similar size.

Clearly, you cannot give with one hand while you take away with the other and ever expect to achieve the goal of doubling Bristol’s tree canopy cover.

The plans to replace the felled tree with smaller trees nearby. Image: Vassili Papastavrou

Where there is subsidence and a tree in the vicinity, a causal relationship needs to be determined. In Bishopston it turned out that there was no evidence that the street tree to be felled was causing the subsidence.  Many houses in the same road that are not near trees also suffer from subsidence because they all have inadequate foundations and are built on clay.

The London Tree Officers Association, together with major insurance companies, has determined a way of resolving these issues called the Joint Mitigation Protocol. The Bristol Tree Forum supports the Joint Mitigation Protocol – as well as defining an agreed format and timescale for investigations, it also requires greater proof for more important trees.

If a causal relationship is determined then there will be a variety of options.  The cheapest is usually to fell the tree (though this may create problems of heave afterwards). Another option would be strengthening the foundations of the house by underpinning.

Insurance companies are aware that the climate emergency is an existential threat to their future: many have developed glib policies that claim to address this issue. As a first step they need to use their expertise to retain trees rather than fell them. And Bristol City Council needs to do likewise.

Bristol City Council say that the felling of the holm oak in Ashley Down is “unavoidable” – photos: Martin Booth

EDITOR’S NOTE
This is the independent report that Bristol City Council commissioned about the holm oak on Ashley Down Road:

“The evidence reviewed… confirms, on the balance of probabilities, that [the tree] is a material cause of subsidence damage to… [an adjacent house]. The soil below foundations at the front is medium shrinkage potential clay, which contains oak roots. Soil investigations suggested that the soil was desiccated. Level monitoring displayed a seasonal and cyclical pattern of movement, with an amplitude of up to 28mm, consistent with significant subsidence.

“[The tree] was pruned by a 30% crown reduction in October 2019 but this was not enough to prevent ongoing subsidence of at least 10mm in summer 2020.

“Further crown reduction could be contemplated, and this would need to reduce the height of the tree to no more than 14m (and a corresponding reduction in crown width), with pollarding thereafter at intervals not exceeding three growing seasons. Level monitoring would need to continue to confirm the efficacy of pruning.

“Felling [the tree] would remove its influence from the building and would be the surest way of stopping ongoing damage.

“The level monitoring suggests that subsidence is completely seasonal and that there has been no build-up of a persistent soil moisture deficit. I consider that removal of the tree will not result in a risk of heave.”

Further to their report, the independent expert added that pruning works when an oak tree is more than 10m away from the affected property and when foundation movements are less than about 15mm. In this case the tree is closer than 10m and the movements were larger than 15mm.

Vassili Papastavrou is the secretary of the Bristol Tree Forum

Main photo: Martin Booth

Read more: Felling of historic oak tree is ‘unavoidable’