The UK aims to be carbon neutral by 2050. Bristol is more ambitious and aims to reach that goal in 2030. Both are massive challenges in which trees have been enrolled to play their part in mitigating the carbon dioxide (CO2) created by human activity.
There are plans for extensive tree-planting. The government pledged to plant 30 million trees a year, nationally. This a huge challenge partly because seedlings and land has to be found for these trees. However even when planted, these trees will take a long time to grow and extract CO2 from the air. We in Bristol Tree Forum are concerned that not enough attention is given to the role of existing mature trees.
Trees grow and add to their mass each year. Most of this mass is in the form of cellulose and lignin and about 50% of those organic compounds is carbon, obtained through photosynthesis using the energy of sunlight and CO2 from the atmosphere. The rate at which mass is accumulated increases with age so whilst a 10 year old tree might put on a few kilograms a year, a 50 year old tree might add 50 kg. So the older the tree the better for CO2 fixation. However mature trees are constantly under threat – from development for housing and industry, from home owners overshaded by large trees, from councils assessing maintenance costs and risks.
Here in Bristol, the Bristol Tree Replacement Standard (BTRS) is part of local planning regulations and specifies how many replacement trees are needed to be paid for by the developer and planted to mitigate the loss of mature trees. The BTRS is a very welcome and forward-thinking strategy, but is it enough to support the Carbon Neutrality goals? Should BTRS apply also to council-owned and indeed privately owned trees for which no funded replacements are available?
The Bottom Line
In an attempt to understand how this standard works in practice, we have developed an on-line calculator to explore different scenarios.
The general conclusion from this analysis is stark: it will take 25 to 40 years before the replacement trees are able to compensate for the loss of the mature tree.
The graph shows the scenario of the replacement of a mature tree such as a Maple with a diameter of 60 cm by the 6 trees as determined by BTRS which are faster growing but shorter lived such as Rowens.
Assuming that the original tree is felled, chipped and used as fuel in a biomass boiler (the practice in Bristol), the carbon stored in the mature tree is returned to the atmosphere within months of felling. The replacement trees start to grow, but absorb much less carbon than the original mature tree would have done, so they take many years to catch up. In the case shown in the graph, it takes 35 years (ie, to 2055) before the new trees mitigate the loss of the original tree.
A model of this scenario needs to take into account:
the rate at which different species of tree grow at different ages in different conditions.
the estimated mortality of the tree over time.
the calculation of a tree’s biomass from its girth for different species.
the relationship between the tree’s biomass and the amount of carbon stored.
There is a lot of uncertainly in these relationships, partly because of the paucity of data on urban, as opposed to forest, trees. Urban trees are under threat not only from natural processes and disease, but also from the vagaries of vehicles and humans. Planting sites are often less than optimal and urban trees have no support from the ‘wood wide web’.
The interactive calculator allows the user to vary the parameters of the model using the sliders. This allows the sensitivity of the overall outcome to variation in values to be tested. Different policy choices can also be explored and can be used in a predictive sense to determine the number of replacements needed to achieve a given carbon neutral date.
Documentation on the website explains the thinking behind the model in more detail, and the sources of data used. The model is still under development, in particular to make it easier to select conditions for different species and situations, and to improve the quality of the model itself. The research literature is extensive but often of limited applicability to urban conditions.
We would be grateful to receive additional or better sources of this information, and indeed any comments on the model itself at email@example.com.
We want to put on record our congratulations for the successful bid that your Parks Strategy team led for Bristol City Council to the DEFRA Urban Tree Challenge Fund (UTCF). It has been some time in the resolution, but it is great that we now know for sure that it has succeeded.
We are delighted that there will now be more funds available to plant and maintain trees in the streets and green spaces of local communities that have perhaps been been overlooked in the past.
Thanks to you and to your excellent tree planting team, the Council has built an enviable reputation for planting urban trees across the city. Long may it continue!
We look forward to helping you with the planning and consultation that will be needed for adding these UTCF trees to next winter’s tree planting season.
We also applaud your decision to involve us in the collaborative partnership preparing the initial bid. As the only group specialising in protecting and caring for Bristol’s urban forest, we are very pleased to have been able to:
Survey a representative sample of some of the 1,471 sites you have identified across the city, thereby relieving overstretched BCC officers who simply didn’t have the time to undertake this work.
Develop our Tree Care site which communities will be able to use for post-planting tree maintenance and care – an important part of match funding the UTCF grant.
We have also developed a comprehensive network of ward-based tree champions who are ready to be involved both in engaging with their local communities in the planned consultation and in helping with the ongoing care of newly planted trees.
As you can imagine, it was a lot of work, but we believe that it provided the sort of detail that helped clinch the bid.
Now that the funding has been secured, we look forward to meeting with you and the other partners to help with the next important planning phase of engaging with local communities and getting trees actually planted come next winter.
It was once believed that when a tree died, it was no longer of use. For decades, we have actively removed trees at the first signs of rot or fungal attack, felling them at the base and removing all evidence of their existence…
Our guest editor, Nick Gates, Naturalist, writes
Storm damaged trees are hastily sectioned for firewood or bio-fuel. Sometimes, we replace them with a new, younger version of themselves. It was thought that this in turn kept other trees healthy, and that the wider environment benefited as a result.
But nothing is further from the truth. By removing this deadwood, we are stripping out a most vital layer of the natural world. Because when a tree dies, it isn’t actually dead.
As a tree grows, its core begins to die. Have you ever looked at a majestic old oak, its core completely hollowed out, and wondered how on earth it was still producing green leaves and fresh shoots? The reason is that only the outer layers of the wood, just below the bark, are alive. They transport all the water and nutrients that a tree needs to survive. Simultaneously, under the soil, a massive network of fungi around its roots help the tree collect all of the vital nutrients and minerals it needs. As the tree grows, the wood core, the growth rings left behind and superseded from previous season, slowly dies.
Over time, this core wood is slowly broken down by fungi. In the very oldest trees, the core is lost completely. Perhaps the most famous of these wood-feeding specialists is one you may well have eaten, the Shiitake mushroom. The fungi in turn are eaten by many species, from bacteria to nematodes, insects to mammals, whilst the rotten wood supports many more. Therefore, this soft rotting deadwood actually hosts a complex living food web.
An oak tree supports over 350 different varieties of insect. But over half of these feed on dead parts of the oak tree. Bats rely on deadwood cavities to roost, whilst feeding on many species of night-flying beetle that feed solely on deadwood. Redstarts require hidden cavities to nest, whilst searching for bark beetles and moths that grew up in the deadwood. Everything from blue tits to woodpeckers and wood mice to tawny owls rely on deadwood for some part of their existence. By the time an old tree falls completely, upended from its rotting root network, the wood may be dead but the vast diversity of creatures it is feeding are very much alive.
When we strip out deadwood from a natural environment, often under an aesthetic tidiness premise, we aren’t just taking the wood away. We are slowly eroding the complex living food web that the deadwood feeds. The Bristol Downs has suffered from this for many years. We could have hedgehogs snaffling snails from deadwood retreats and spotted flycatchers nesting amongst the craggy cavities in gnarled out stumps. Animals just need food and shelter to thrive. By removing deadwood, we take away both. There are many ways of leaving deadwood that look aesthetic whilst appreciating the enormous ecosystem service it provides. Good signage can help explain this.
In a time of unprecedented ecological collapse, we must all do what we can to help the natural world. Leaving deadwood in situ is one of the easiest ways to do this. So please, next time you see a fallen tree, don’t look on it as an untidy addition to the landscape, but enjoy it as the next opportunity for nature to reclaim a part in our everyday lives.
Everyone from all sides of the political spectrum is talking about planting trees. We fully endorse this, but it will take time for these new trees to mature. In the meantime, retaining existing trees will have the biggest immediate effect.
We propose that
There needs to be genuine community engagement in Bristol’s tree management decisions. The council needs to listen to communities that want to save trees, not just to those who want to remove them.
Urban trees (planted or self-sown) have a tough life. Many bear the wounds and scars of previous damage or interventions. These trees, though they may not be perfect, should be valued for the ecosystem services they provide and retained with appropriate and careful management wherever possible.
Alternatives to felling must be given priority, whether for street trees, or for those threatened by planning applications, or for other trees in the public or the private space.
We need to strengthen planning policies to help retain trees on development sites by building around them, especially when the trees are on the edge of the site.
Veteran and ancient trees require specialist management to ensure their retention whenever possible.
When surveys identify trees that present a risk, there should be consultation about the range of options available to mitigate the risk. This should always balance risk with the benefits the tree provides. Felling is only ever a last resort.
If trees must be felled, then more trees need to be planted to replace them. This should be based on well-established metrics used to calculate how to increase (not just replace) the natural capital of the lost tree.
Click here to print acopy of the manifesto. Candidates are welcome to download and use to support our aims.
Our Blogs contain many examples of the sorts of issues that have caused us to write this manifesto.
As you are aware, we have been expressing our continuing concerns about the welfare of the trees growing at Stoke Lodge Park and Playing Fields for the best part of a year now.
At the moment, our particular concerns are threefold:
The potential for damage to trees caused by pedestrians being obliged to pass over their root zones and under their canopies since Cotham School erected its boundary fence last year.
The potential for damage being caused to the trees growing within the new fence being caused by the school’s grass mowing regime.
The potential for damage to trees caused by vehicles passing over their root zones and under their canopies.
To a large extend, our concerns about issue three may have been allayed by the school’s adoption of a new access point at the eastern end of the fields, but we will have to see how this develops.
As for the other two issues, we attach images showing how the very muddy and disturbed path running around the outside of the school’s fence is causing disruption to the root zones of a number of trees – these are not all the trees being affected by this.
These images show how the current mowing regime encroaches within the root zone of one of the Turkey oaks inside the fence.
Here is a video which shows the mowing issue more clearly.
In our view, something needs to be done about this before any damage being caused becomes irreversible.
Can you advise me what action the Council plans to take to protect these trees, please?
Trying to avoid the Council’s earlier refusals to answer our earlier FoIs about this, we asked for the same information as before, but just about one school which we selected randomly.
The school’s identity has no particular significance. We believe that these responses reflect the same situation across many other schools in Bristol (and the rest of the country?) – the lease disclosed is a ‘Department for Education (DfE) standard Academy Lease’.
[We] have been advised that Bristol City Council no longer maintains or manages trees growing on some sites owned by it.
In respect of Henleaze Junior School, is it a site where the responsibility for the care of the trees growing on its site has been passed to the school?
If so, please provide the following information:
1. Does the Council retain the ownership of the trees on the site? 2. If it no longer retains ownership, who does? 3. Does the Council still retain liability for any damage caused by trees on this site? 4. If it no longer retains liability, who does? 5. is this site available for tree planting by the public through sponsorship schemes such as TreeBristol or through tree-planting initiatives such as One Tree Per Child or the Urban Tree Challenge Fund? 8. Who makes decisions about the planting, maintenance or felling of trees on this site? 9. If it is not the Council, is the decision maker obliged to consult the Council before proceeding to maintain or fell a tree, whether or not the tree is growing in a Conservation area, or is protected by a Tree Preservation Order or is the subject of a planning application?
Please provide a copy of any lease entered into between to Council and Henleaze Junior School for the lease of its site.
The Council has responded to say…
The site is let to the Academy on a 125 year Department for Education standard Academy Lease. The Council holds the Freehold of the site, but the responsibility for the management of the trees has passed to the Academy and the Council no longer retains liability for any damage caused by trees on this site? The Academy does.
While the the site is available for tree planting by the public through sponsorship schemes such asTreeBristol or through tree-planting initiatives such as One Tree Per Child or the Urban Tree Challenge Fund, consent by the Academy is required for this.
The Academy is not obliged to consult the Council regarding the maintenance, removal or planting of trees on site and has the sole responsibility for these activities. This is subject only to any Tree Protection Orders (TPO’s) and/or Conservation Area requirements that may exist for trees on the site. In these cases, a planning application must first be made and permission given before the school can proceed.
A copy of the lease is availablehere. There is no mention of trees in the lease.
We are intrigued to note however, that the Council retains the right to develop the school and playing fields – Schedule Three – Rights Excepted and Reserved:
It appears very likely that similar arrangements to this will be found across most of the city’s 78 Academy schools (and possibly many Maintained and Special schools), by leaving them to make their own ad hoc arrangements to care for and/or plant trees as they may/or not desire.
Given that theOne City Plan aims to double tree canopy cover over the next 25 years, it seems a great shame that this important land bank (we estimate some 188 hectares – land and buildings – for Academies alone) of possible new planting sites might have been excluded from helping to achieve Bristol’s ambitious plans.
What about protecting all the trees with a TPO?
There are already at least 3,400+ established trees growing on educational sites that could be at risk. As far as we can tell, very few of these trees are protected by a TPO, though some will be are growing in a Conservation area.
So, is it possible possible to protect all the remaining unprotected trees with TPOs? At least then all schools would be obliged to get planning permission before removing or ‘managing’ trees and we will be able to see what is planned.
Local Authorities have the power to make four types of TPO:
Individual TPOs:A single tree, illustrated as a trunk and approximate canopy spread. If trees merit protection in their own right, authorities should specify them as individual trees in the Order.
Group TPOs:A group of trees, usually shown as a canopy, or group of canopies, with or without stems shown. The group category should be used to protect groups of trees where the individual category would not be appropriate and the group’s overall impact and quality merits protection.
Woodland:Shown as an area of land. The woodland category’s purpose is to safeguard a woodland as a whole. So it follows that, while some trees may lack individual merit, all trees within a woodland that merits protection are protected and made subject to the same provisions and exemptions.
Area TPO:Shown as an area, without stems highlighted. The area category is one way of protecting individual trees dispersed over an area. Authorities may either protect all trees within an area defined on the Order’s map or only those species which it is expedient to protect in the interests of amenity.
We were recently been copied this answer when this issue was raised about some trees growing in the Bearpit:
Thank you for your email requesting a Tree Preservation Order for trees within the St James Barton roundabout/ Bearpit area. We have reviewed these trees following your TPO request. We understand that you are concerned about any future plans for the Bearpit which could affect these trees and the amenity they provide.
“though some trees or woodlands may merit protection on amenity grounds it may not be expedient to make them the subject of an Order. For example, it is unlikely to be necessary to make an Order in respect of trees which are under good arboricultural or silvicultural management.”
Furthermore, the potential effect of development on trees, whether statutorily protected (e.g. by a tree preservation order or by their inclusion within a conservation area) or not, is a material consideration. This means that tree matters must be taken into account by Bristol City Council as the Local Planning Authority when dealing with planning applications, and when undertaking consultations, and that members of the public can make clear their views.
Given that these trees are already under existing arboricultural management, and that they would automatically be a material consideration should any future planning application come forward, it is not expedient or necessary for a Tree Preservation Order to be placed on these trees.
It appears that trees on educational land can, in theory, have TPO protection if it can be shown that they are not ‘under good arboricultural or silvicultural management’. But, how can the Local Authority know this?
However, our experience when we have requested that TPOs are made, is that the council will rarely do so, unless the trees are considered to have Amenity valueand they are shown to be under immediate threat of destruction or damage. But, how can the Local Authority know this if the school is not obliged to tell them?
And…bitter experience has taught us that, whilst ‘…the potential effect of development on trees, whether statutorily protected…or not, may be ‘a material consideration’, other considerations often result in the welfare of trees being a very distant secondary consideration, with the result that they are frequently sacrificed to the too-oft-repeated argument that it is either the development or the trees, when there is no reason why it cannot be both.
So, the reality is that these trees are unlikely to be granted TPO status, save in exceptional circumstances and, even if they are, this is no guarantee of their future protection.
Our original concerns remain
We remain concerned that school governors (quite apart from lacking the necessary skills to manage the trees growing on their sites) may not yet have realised the full implications of the practical and strategic obligations that taking on such an important part of Bristol’s Natural Capital places upon them.
As a result, they are likely to buy in (at our eventual expense) ad hoc expertise, with the risk that they will overlook the wider strategic considerations that are needed when it comes to managing and promoting Bristol’s trees.
This, coupled with the distinct possibility that well-meaning, but unqualified Council officers in departments with no expertise in the management of trees may be making critical decisions about the welfare of trees across a wide range educational sites across the city, makes for a very worrying situation.
Our view is that the Council should take back the control and management of trees growing on land owned by it whether it is leased or not. Only then can we be assured that there is at least some degree of oversight and accountability, while helping us to achieve the wider strategic vision for the development of Bristol’s urban forest.
Bristol has declared a climate emergency. There is an urgent need for all council departments to re-think the way that they work.
At the time of writing, four of the trees in this image have been felled (two Norway Naples and two Indian Bean trees on a different plot). The value of the five maple trees along Lower Ashley Road was calculated at £200,000 using CAVAT. Local residents are desperately trying to save the three remaining maples.
This blog discusses six changes that are desperately needed to protect trees on development sites.
Planning Decisions regarding important or TPO trees should be considered by committee and not delegated to one officer.
It is practically impossible for local residents and other stakeholders to wade through all planning documents online. Planning Officers must highlight important tree issues and have a duty of care to act positively in favour of trees.
Bristol should implement policies to retain trees on development sites in the way that has been done in London, Oxford and elsewhere. This includes enforcement and a presumption to retain trees at the edge of development sites.
An emergency number to address immediate tree felling issues.
It is a false choice to say that we can either have social housing or trees. With clever designs, we can retain existing trees and have better social housing.
Replacing felled trees, even when applying the Bristol Tree Replacement Standard, is second best to retaining existing large urban trees. We get the benefits from existing trees now – we have to wait decades for their replacements to grow.
Over the last six months there have been half a dozen articles in the local press and now one Guardian article about the shocking planning decision to allow removal of five Norway maple trees with Tree Preservation Orders (TPOs) on Lower Ashley Road, one of the most polluted streets in Bristol. There have been two meetings with the mayor who also visited the site and there is now a vigil by protesters on the site: police have been called on several occasions. All this indicates a planning process that has marginalised local residents and failed to take into account the value of the trees.
The Bristol Tree Forum appreciates the efforts by Mayor Marvin Rees to try and resolve the situation after the event. He visited the site and then convened two meetings in City Hall which he chaired. We have been impressed by his serious engagement and the way that he has brought all the interested parties into the room and handled the discussion. But, as we think he would agree, this is the wrong way around. Discussions such as this should happen before the planning decisions are taken so that there is community engagement in the decision making.
Planning Decisions regarding important or TPO trees should be considered by committee and not delegated to one officer
That we have got to this stage shows a serious failure of both Bristol City Council Planning policy and its implementation. The decision to remove the trees was taken in 2015/16 by one planning officer as a reserved decision. It did not go for to the Planning Development committee for a considered decision. Looking over the documents it doesn’t seem that any time or thought was given to the trees. The Arboricultural Report provided by the developer does not even state whether the trees had TPOs, and indeed there is no discussion of the TPOs in any of the documents in that planning application, with the only mention on the “constraints” page. In 2015, The Bristol Tree Forum commented in opposition to the proposal but even the BTF was unaware that the trees had TPOs. Whilst BCC insists that the decision was “valid”, without a mention of the TPOs there was insufficient information to allow intelligent consideration of the proposal, so we question that decision. Sufficient information for intelligent consideration is one of the fundamental principles of a “proper consultation” as decided by Lord Woolf*. The first mention of the TPOs in a document is in the Officer’s Report outlining the delegated decision.
Unfortunately this is not an isolated failure: trees all over Bristol are being unnecessarily sacrificed as a result of applying ideology from the 1960s. For example a single planning officer gave the green light for the removal of some 25 trees on the Redland Girls School site, in a conservation area, despite the fact that the removal is purely for landscaping.
It is practically impossible for local residents and other stakeholders to wade through all planning documents on line. Planning Officers must highlight important tree issues and have a duty of care to act positively in favour of trees
Important tree issues need to be highlighted and openly discussed during the planning process. Planning Officers already implement policy regarding flood risk, traffic management and other construction matters. The Bristol Tree Forum is asking that tree protection is included too as is done in other local authorities (Examples are Oxford and Islington, below). In addition, trees on or near active development sites must be properly protected.
We see applications with no information on the Bristol Tree Replacement Standard calculations, or obviously incorrect information being supplied. Documents such as these should be rejected by the planning officer.
An emergency 24-hour number to address immediate tree felling issues.
Bristol is at risk of becoming known as a Mad Max world now that unqualified people are wielding chainsaws from ladders above passing pedestrians with no enforcement consequences, often on public holidays, sometimes in the evenings and even at night. A proper approach for addressing this problem needs to be developed in collaboration with the police. It is unfair to send a single tree officer on their own to deal with issues of public order. Multiple phone calls and sometimes hundreds of emails to numerous council departments very quickly overload already overstretched council officers. It is no good passing the buck to the Health and Safety Executive. Therefore we need one emergency Bristol City Council number.
Bristol should implement policies to retain trees on development sites
Where possible we should build developments around existing trees. There should be a presumption to build around existing trees and particularly to retain trees at the edge of development sites.
The developer’s arboricultural report for Lower Ashley Road states that “In order to retain the trees within any new scheme, the front of any new building will need to be sited a minimum of ten metres from the existing site boundary”. We have heard this assertion stated by developer and planner as “the ten metre rule”.
There are many examples where mature trees are retained close to new buildings, in London, Oxford and elsewhere. This must become commonplace in Bristol too. A Trees and Design Action Group article describes the construction of the Angel Building (Islington, London) around existing mature trees. No cowboy chainsawing there. Instead extreme care was taken in a project that was led by landscape architects. For example:
Deliveries needed to be conducted on a daily basis. To enable this, the Tree Protection Plan (TPP) and Arboricultural Method Statement (AMS), developed by appointed tree specialist JCA, in coordination with the project landscape architect and the council tree officer, proposed the use of a porous load-spreading cellular confinement system (Geoweb) braced with timber frames.
All existing trees were irrigated during the two-year construction period following a sporadic pattern imitating rain. Because irrigation was fed with calcium-rich London tap water, the system was fitted with filters to avoid increasing the soil pH.
It is a false choice to say that we can either have social housing or trees.
Although the 2015/16 planning approval that is being used to justify removal of the trees was for student accommodation, the current proposal, still under consideration, is for social housing that Bristol desperately needs. We are surprised that, despite this new undecided application, the developer is still able to undertake work under the old approved application which they no longer intend to pursue. Shouldn’t the slate be wiped clean so we have a chance to revisit the whole plan with the trees still in place rather than be forced to decide without them?
The developer, planners and others have presented a false choice stating either we retain the trees, keep the site derelict and leave 28 families homeless, or we remove the trees.
These trees are right on the edge of the development site. With clever designs, led by a landscape architect (not even apparent that one has been engaged for this project), and carefully constructed foundations (e.g. screw piling), the developer could build close to the existing trees. The result? Better social housing which benefits from existing green infrastructure and provides a more pleasant environment with some protection from the noise and pollution of this busy road.
Lord Woolf MR in R v North and East Devon Health Authority, ex parte Coughlan  QB 213,  3 All ER 850,  as follows: whether or not consultation is a legal requirement, if it is embarked upon it must be carried out properly; to be proper, consultation must be undertaken at a time when proposals are still at a formative stage; it must include sufficient reasons for particular proposals to allow those consulted to give intelligent consideration and an intelligent response; adequate time must be given for this purpose; and the product of consultation must be conscientiously taken into account when the ultimate decision is taken.