Your say / Trees
‘We might still be able to save the trees on the centre’
Without consultation, five London plane trees (Platanus x hispanica) will be removed from the Centre Promenade outside the Hippodrome in proposals for redeveloping the site.
We’re told that these trees have outgrown the containers in which they were planted some 24 years ago, and therefore can’t be retained.
The trees are to be replaced with five smaller Judas trees (Cercis siliquastrum), which are better suited, we’re told, to being grown in raised planters.
is needed now More than ever
The Judas tree is a small bushy tree with striking pink blossom in spring; it can grow to an ultimate height of eight to ten metres and live to be 50 years old (100 years in the wild).
Plane trees, on the other hand, can grow to 37 metres and live for several hundred years. They have been a popular urban tree since the 17th century.
Many plane trees are planted across the city, including the magnificent boulevard of plane trees planted by Frank Kelf on nearby Narrow Quay as part of the Plant a Tree in ’73 campaign.
The condemned trees form part of an avenue of trees sweeping up from Narrow Quay to the Cenotaph and provide far more shade in our warming world than their replacements are ever likely to do.
Some vital statistics
Bristol City Council hasn’t responded to our request for their evidence about the trees, so we asked our own arborist to survey the trees.
This is what they found:
We calculate that these five trees have already sequestered around 3.72 tonnes of carbon to date. Using the CAVAT calculation, a standard used throughout the UK, they are worth over £191,000 altogether.
If these five trees were removed as part of a development rather than as Highways works, then 19 replacements would be required under Bristol’s tree replacement standard (BTRS) at a cost of nearly £100,000 if planted in tree pits. However, only five replacements are planned.
Under the recent introduction of the new biodiversity gain obligations, these trees are now given a far greater biodiversity value than under BTRS.
Using the mandated statutory metric, we calculate that 29 trees would have to be planted just to offset their lost habitat, with another three needed to achieve the ten per cent minimum net gain which the legislation requires.
It’s ironic that under the biodiversity gain legislation, the Ecological Emergency Action Plan and its proposed new Local Plan, the council requires developers to achieve at least ten per cent biodiversity gain, yet somehow this does not apply to the council’s own developments.
In this case, the trees will only be replaced one-for-one.
We understand that the city centre remodelling has to be funded from (unverified) savings made by removing the existing fountains and that there’s no extra money to do anything more complex.
Even so, it’s possible that other options might be worth considering that will not involve the loss of these trees.
The Centre is built on top of St Augustine’s Trench where the River Frome was re-routed in the 13th century – photo: Martin Booth
Can the trees be saved?
It’s clear that the trees have outgrown their planters. With hindsight, container planting of plane trees was unwise, but the failure of the post-planting maintenance regime has compounded this, with the problems caused by the growth of the tree left unresolved.
The photo below shows how the original watering site has been allowed to become incorporated into the tree and how the roots were left to destroy the facing of their containers.
We are also told that the root growth is damaging the nearby pavers.
The trees on the centre have clearly outgrown their planters – photo: Martin Booth
We’re not engineers so we can’t say whether the state of the trees creates a safety hazard.
The council has this expertise but hasn’t made its conclusions public. Their web page makes no mention of any such risk.
If there is concern about the risk of the trees falling over, this could be determined by professionals using techniques such as a pull test, where the trees’ movement under load can be determined.
It’s also been suggested that the trees are growing on a concrete structure used to cap the old dock beneath.
We have no idea if this is correct, although a line drawn from the edge of the extant wharf at Narrow Quay into the centre using Google Earth (the image below) suggests that this might not be the case and that there is ground beneath the planters.
We also note that the plane trees on the north and west side of the site are not in planters, even though they also appear to be planted over the old dock.
This should at least be explored before the trees are condemned. If ground can be accessed by the trees, they wouldn’t need to be removed.
Maybe tree roots have already found their way out of the bottom of the planters and the trees are perfectly stable as a result. This should be investigated.
Lines showing the apparent extent of the old docks -photo: Google Earth
Even if there is no ground into which the trees can grow, there may be other options.
Might it not be possible, with the trees in situ, carefully to dismantle the planters, prune their roots and pollard their branches, and stabilise them before constructing bigger planters?
We can’t say whether this is practicable, but we’d welcome an opportunity to discuss this and other possibilities before the plans proceed.
However, if, having explored all the options and decided that retention of the trees is impossible, the council should follow the legislation and its own policies and properly compensate for the loss of these trees.
We plan to include these trees when we join Notice this Tree on their intervention on Sunday.
Notice This Tree is taking place in Bristol on Sunday – photo: Martin Booth
This is an opinion piece written by Mark Ashdown, chair of Bristol Tree Forum
Main photo: Martin Booth
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