Category: Ancient and veteran trees

Biodiversity Metric 4.0: what’s it all about?

On 24 March 2023 Natural England published Biodiversity Metric 4.0. This revised metric will revolutionise the way we value urban tree habitats, making it clearer than ever that they are a very important habitat.

It is anticipated that BNG 4.0 [1] will be given statutory force when the biodiversity elements of the 2021 Environment Act [2] take effect later this year (see Measuring biodiversity net gain – Publication of Biodiversity Metric 4.0). All new planning applications issued after 24 March, where a Biodiversity Net Gain (BNG) calculation is required, will be required to use it.

Unlike several neighbouring local authorities (e.g., BANES & South Gloucestershire County Council), which have already adopted Supplementary Planning Documents to protect their biodiversity, Bristol City Council has decided not to require this as part of current planning applications until the rest of the EA 2021 comes into force. The failure to do this will have a negative ecological and social impact for the many current planning applications. In the meantime, only developers will benefit.

Given Bristol’s declaration of an ecological emergency in 2020, BNG 4.0 must now be implemented in Bristol. This is a key environment measure which could be adopted at no cost to the council.

The NPPF basis for achieving biodiversity net gain

Paragraph 180 a) of the National Policy Planning Framework [3] (NPPF) echoes the overarching Mitigation Hierarchy principles and obliges local planning authorities to refuse planning permission:

if significant harm to biodiversity resulting from a development cannot be avoided (through locating on an alternative site with less harmful impacts), adequately mitigated, or, as a last resort, compensated for…

Paragraph 179 c), states that plans should:

…pursue opportunities for securing measurable net gains for biodiversity.

BNG 4.0 has been designed to give effect to these two core planning goals.

Pending planning applications

Natural England advises that:

‘Users of previous versions of the Biodiversity Metric should continue to use that metric (unless requested to do otherwise by their client or consenting body) for the duration of the project it is being used for. This is because users may find that certain biodiversity unit values generated in biodiversity metric 4.0 will differ from those generated by earlier versions.‘

Given that the approach to valuing urban trees has fundamentally changed, we urge all ‘consenting bodies’ (LPAs for most of us) to require developers to adopt this new methodology, for Individual trees habitats at least.

We have always argued that the old Urban tree habitat area calculation methodology used in BNG 3.0 is flawed and unworkable, and we advocated for the use of the calculation method given in BNG 3.1, if only for Urban tree habitat area calculations. With the advent of BNG 4.0, we plan now to argue instead for the BNG 4.0 Individual trees habitat methodology to be used.

The BNG 4.0 Guide

Here is a link to the BNG 4.0 User Guide, which was published with BNG 4.0 (the quotes in italics below are taken from it). We set out below the salient points that cover most trees growing in an urban setting.

What is Individual trees habitat?

BNG 4.0 has made a substantial change to the way trees growing in the urban space will be valued and introduces a new broad habitat category called Individual trees (to replace the Urban tree habitat category first published with BNG 3.0):

8.3.1. The broad habitat type ‘Individual trees’ may be used where a tree (or a group of trees) over 7.5 cm in diameter at breast height (DBH) does not meet or contribute towards the definition of another broad habitat type.

8.3.2. Individual trees should not be recorded separately where they occur within habitat types characterised by the presence of trees, such as orchards, lines of trees or wood-pasture and parkland, but can be recorded where they do not form part of a primary habitat description.

8.3.3. Ancient and veteran trees are irreplaceable habitats and the broad habitat ‘Individual trees’ must not be used to record these.

Even though all irreplaceable habitats fall outside BNG 4.0, they should still be recorded in the metric calculation. A special form for this has been built into the calculator and special rules apply.

Note: Paragraph 8.3.1 refers to trees ‘over 7.5 cm in diameter’ but table 8-1 below refers to trees that are ‘greater than 7 cm’. BS5837:2012 requires all trees 75 mm or over to be surveyed – at paragraph 4.2.4.

Broad habitat type Individual trees can be in either ‘urban’ or ‘rural’ habitats:

8.3.4. Individual trees may be classed as ‘urban’ or ‘rural’. Typically, urban trees will be bound by (or near) hardstanding and rural trees are likely to be found in open countryside. The assessor should consider the degree of ‘urbanisation’ of habitats around the tree and assign the best fit for the location.

8.3.5. Individual trees may also be found in groups or stands (with overlapping canopies) within and around the perimeter of urban land. This includes those along urban streets, highways, railways and canals, and also former field boundary trees incorporated into developments. For example, if groups of trees within the urban environment do not match the descriptions for woodland, they may be assessed as a block of individual urban trees.

Either way, they have the same Medium habitat distinctiveness, so the difference is perhaps academic.

Developers may seek to argue that some urban trees in groups or blocks are a woodland habitat or a ‘Hedgerow – line of trees’ habitat and not Individual trees habitat. BNG 4.0 and earlier versions use a different approach to calculating their habitat sizes. This approach is based on canopy area for woodland habitats and a linear measurement for ‘Hedgerow – line of trees’ habitats. However, it is the degree of ‘urbanisation’ that is key.

Trees in private gardens

Individual trees habitats within private gardens are also to be recorded in the baseline calculation, but should not form part of the post-development BNG calculation:

8.3.6. Established trees within gardens should be recorded in a site baseline.

8.3.7. Where private gardens are created, any tree planting within the created garden should not be included within post-development sheets of the metric. The habitat type ‘Urban – Vegetated garden’ should be used.

This is an important distinction and means we should be alive to any attempt to include newly created habitat in private gardens into post-development BNG calculations. The logic is that, as private space is outside the control of the developer, any post-development habitat management obligations they have cannot be applied to these spaces, and so should be excluded from the post-development calculation.

Measuring Individual trees habitat size

Habitat size is one of the key parameters used for calculating a habitat’s value – called Habitat Units (HUs). For baseline area habitats, the formula is based on four parameters:

HU = Area in hectares x Distinctiveness x Condition x Strategic significance.

Note: For linear habitats, length in kilometres is used instead of area.

The way BNG 4.0 measures the habitat area of Individual trees has reverted to the methodology used in BNG 3.0 but, thankfully, now uses a table that works!

The effect is far more generous than the one used in BNG 3.1 as it values all the trees in the bottom two categories, Small & Medium, at the top of their range. All Large category trees are given the same habitat value as a tree with a stem diameter (called DBH – diameter at breast height) of 130 cm. [4] Given that the vast majority of urban trees fall within this range – with DBHs of between 7cm and 130 cm – this has the effect of greatly enhancing their habitat value.

The following graph illustrates the effect on a range of DBHs from 7 cm to 160 cm; RPA refers to root protection area and the orange stepped lines are the BNG 4.0 habitat area values assigned to each DBH. [5]

This difference is significant. For example, in a recent application we were involved with, trees on the site that had a baseline Urban tree habitat area of 0.7056 ha using BNG 3.1 now have an Individual trees habitat area of 4.3144 ha when the BNG 4.0 methodology is applied. This makes their habitat unit value much greater than it was before.

Here is the BNG 4.0 Individual trees habitat area measurement methodology:

8.3.8. Once the size, number and condition of trees is known, assessors should generate an area equivalent value using the ‘Tree helper’ within the metric tool ‘Main menu’ (Figure 8-2). The ‘area equivalent’ is used to represent the area of Individual trees. This value is a representation of canopy biomass, and is based on the root protection area formula, derived from BS 5837:2012.

8.3.9. Table 8-1 sets out class sizes of trees and their area equivalent. For multi-stemmed trees the DBH of the largest stem in the cluster should be used to determine size class.

Note: The correct metric equivalent area of Large category trees is 0.0765, not 0.0764.

This same approach applies to Individual trees habitats in groups or blocks:

8.3.12. Assessors should account for the size class (Table 8-1) of each Individual trees within a group or block. The number of Individual trees present within a group or block should be entered into the tree helper to calculate area equivalent. Do not reduce any area generated by the tree helper even if tree canopies overlap.

Assessing baseline Individual trees habitat condition

As ‘condition’ is one of the parameters used for calculating the habitat’s value, each Individual trees habitat tree, group or block needs to be assessed against the following criteria. [6]

Condition Assessment Criteria
AThe tree is a native species (or at least 70% within the block are native species).
BThe tree canopy is predominantly continuous, with gaps in canopy cover making up <10% of total area and no individual gap being >5 m wide (Individual trees automatically pass this criterion).
CThe tree is mature (or more than 50% within the block are mature).
DThere is little or no evidence of an adverse impact on tree health by human activities (such as vandalism, herbicide or detrimental agricultural activity). And there is no current regular pruning regime, so the trees retain >75% of expected canopy for their age range and height.
ENatural ecological niches for vertebrates and invertebrates are present, such as presence of deadwood, cavities, ivy or loose bark.
FMore than 20% of the tree canopy area is oversailing vegetation beneath.
Number of criteria passed
Condition Assessment Result (out of 6 criteria)Condition Assessment Score
Passes 5 or 6 criteriaGood (3)
Passes 3 or 4 criteriaModerate (2)
Passes 2 or fewer criteriaPoor (1)
Note that ‘Fairly Good and Fairly Poor’ condition categories are not available for this broad habitat type.

In our experience, very few Individual Urban tree habitats will ever be assessed as in ‘Good’ condition and many will only ever achieve a ‘Poor’ score. Many urban trees are not native, [7] few survive to become mature, most are subject to some form of management or show ‘evidence of an adverse impact on tree health by human activities’, and most trees in a public space will never be allowed to develop ‘natural ecological niches’ as these often also present a public safety risk.

The same challenges will also apply when attempting to assess the future condition of post-development Individual Urban tree habitats after 30 years have passed (we discuss this below). In our view, every such tree should always be assessed as having a ‘Poor’ outcome given the uncertainties they face.

Assessing baseline Individual trees habitat strategic significance

Strategic significance is the fourth parameter used in calculating HUs. There are three categories – High, Medium and Low:

To qualify as ‘High’, the following evidence needs to be available:

5.4.3. Assessors must provide evidence by referencing relevant documents. If published, the relevant strategy is the Local Nature Recovery Strategy (LNRS). If an LNRS has not been published, the relevant consenting body or planning authority may specify alternative plans, policies or strategies to use.

5.4.4. Alternative plans, policies or strategies must specify suitable locations for habitat retention, habitat creation and or enhancements, and might, for example, be:

  • Local Plans and Neighbourhood Plans
  • Local Planning Authority Local Ecological Networks
  • Tree Strategies
  • Area of Outstanding Natural Beauty Management Plans
  • Biodiversity Action Plans
  • Species and protected sites conservation strategies
  • Woodland strategies
  • Green Infrastructure Strategies
  • River Basin Management Plans
  • Catchment Plans and Catchment Planning Systems
  • Shoreline management plans
  • Estuary Strategies

5.4.5. If no alternative is specified, agreement should be sought from the consenting body or Local Planning Authority when determining strategic significance.

In many cases, the proposed development site will fall within one of the criteria above (especially where the authority has adopted a well-designed tree strategy) and so should be given ‘High’ strategic significance.

If it does not then, given that trees nearly always provide ‘a linkage between other strategic locations’, we suggest that Individual trees habitats should always be assigned ‘Medium’ strategic significance.

It is notable that the Medium strategic significance dropdown option in the Metric calculator is still labelled ‘Location ecologically desirable but not in local strategy’. This suggests a wider definition than is perhaps suggested above.

Post-development Individual trees habitat creation. 

Post-development Individual trees habitat creation also uses the same parameters for the HU calculation discussed above, but with a time-to-target factor added. This is the time it will take the new habitat to reach its target condition. If the created Individual trees habitat condition will be Poor, the time-to-target period is ten years, if it will be Medium, it is 27 years, and if it will be Good, it will be 30+ years.

These periods can be increased or reduced in yearly increments if, somehow, habitat creation has been advanced or delayed.

These are then factored into the calculation to allow for the future habitat created using the 3.5% discount tables – so x 0.700 for ten years, x 0.382 for 27 years and x 0.320 for 30+ years.

The calculation also assesses the difficulty of creating the target habitat. For Individual trees habitats, this is pre-set to Low (score 1), so does not affect the eventual calculation.

Existing habitats can also be enhanced on or off site or created off site. We do not discuss this here.

Post-development Individual trees habitat area forecasting 

This assumes that any new tree planted will grow into a Small category tree at the end of the ‘project timeframe’. This is likely to be 30 years by default, as per Part 1 s.9 of Schedule 14 of the 2021 Environment Act. [8] This is the approach advised in the Guide:

8.3.13. Size classes for newly planted trees should be classified by a projected size relevant to the project timeframe.

  • most newly planted street trees should be categorised as ‘small’
  • evidence is required to justify the input of larger size classes.

8.3.14. When estimating the size of planted trees, consideration should be given to growth rate, which is determined by a wide range of factors, including tree vigour, geography, soil conditions, sunlight, precipitation levels and temperature.

8.3.15. Do not record natural size increases of pre-existing baseline trees within post-development calculations.

If a larger Individual trees habitat area projection is advanced, this will need to be justified.

The evidence of tree growth rates is patchy at best – see the About section in our Tree Canopy Prediction tool. To overcome this, we have adopted the simple rule-of-thumb approach commonly used by arboriculturists and assume that a tree’s girth grows by one inch (2.54 cm) a year. We then apply this to the standard tree sizes adopted in BS 3961-1 – Nursery Stock Specification to Trees and Shrubs [9] to calculate the eventual size of a tree 30 years after it has been planted. In all cases, save for semi-mature trees, the tree will be a BNG 4.0 Small category tree.

Here is the model we use:

The age of the tree being planted should not be ‘credited’ when calculating the time-to-target period. Sadly, BNG 4.0 does not take account of mortality rates, which are high for urban trees.

The Trading Rules

Individual trees habitats are given Medium distinctiveness in BNG 4.0 and so are subject to the Rule 3 Trading Rules:

3.2.1. Rule 3 is automatically applied by the metric and sets minimum habitat creation and enhancement requirements to compensate for specific habitat losses (up to the point of no net loss). These requirements are based on habitat type and distinctiveness, as set out in Table 3-2 (below).

In effect, any habitat losses may not be traded down. In this case, the broad habitat category is Individual trees. Given that there are very few habitats with high or very high distinctiveness that are likely to be either applicable or feasible, this will mean that Individual trees habitats will mostly need to be replaced like-for-like.

In our view, urban trees are too important to be substituted by any other, non-tree habitat.

The effect of these rules is that, not only will the proposed project have to achieve at least 10% biodiversity net gain when the Environment Act 2021 takes effect later in 2023, it will also need to comply with the Trading Rules. In some cases, this will mean that far more than the minimum 10% net gain will need to be achieved.

We look forward with interest to seeing how developers will ‘manage’ this new metric.

A copy of the article can be downloaded from here – Biodiversity Metric 4.0: what’s it all about?

[1] http://publications.naturalengland.org.uk/publication/6049804846366720

[2] https://www.legislation.gov.uk/ukpga/2021/30/contents/enacted

[3] https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1005759/NPPF_July_2021.pdf

[4] This is a girth of 4.08 metres.

[5] This is the spreadsheet it is based on – BNG 4.0 – Individual trees BNG Analysis.xlsx

[6] See Biodiversity Metric 4.0 – Technical Annex 1 – Condition Assessment Sheets and Methodology & Biodiversity Metric 4.0 – Technical Annex 2 – Technical Information

[7] See table 2 of the Woodland Condition Survey forms linked to https://woodlandwildlifetoolkit.sylva.org.uk/assess for the list of recognised native tree and shrub species.

[8] https://www.legislation.gov.uk/ukpga/2021/30/schedule/14/enacted

[9] https://www.thenbs.com/PublicationIndex/documents/details?Pub=BSI&DocID=16650

In Defence of Dead Wood

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.

The fall of a tree opens up new opportunities…

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.

Left to fade away…

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.

St Andrews Park – The fallen Black Poplar

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.

A monolithed Beech on the Granny Downs

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.

@NTGates Feb. 2020

The trees at Stoke Lodge Park and Playing Fields – a letter to the Council

5th February 2020

Dear Bristol City Council Parks Department,

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:

  1. 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.
  2. The potential for damage being caused to the trees growing within the new fence being caused by the school’s grass mowing regime.
  3. 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.

The new vehicle access point at the eastern end.

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.

The eastern end of the fields.
The path leading to the Pavilion on the northern boundary.
created by dji camera
The path leading to the Pavilion.

These images show how the current mowing regime encroaches within the root zone of one of the Turkey oaks inside the fence.

The Turkey growing at the eastern end of the playing fields seen from above.
The Turkey growing at the eastern end of the playing fields – the mowing line is clearly visible.

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?

Best Regards,

The Bristol Tree Forum

Council no longer manages trees on educational sites – Part I

There are some 166 educational sites and 63 playing fields across the city. Together they cover over 560 hectares and form a significant proportion and an important part of the city’s open, green spaces.

This is the Part I of a two-part blog – here is Part II.

Despite this, Bristol City Council no longer manages trees growing on many of these sites and their related playing fields. We are not certain, but we imagine that this situation has come about as a result of the decline in local authority control over state educational provision with the rise of independent Academies.

We issued a Freedom of Information request (FoI) to try to find out which sites remain under the control of the Council, but our request has been refused on the grounds that answering it would impose a significant burden on the council. Our more generic request at the end has also been refused on the same grounds.

The trees at Stoke Lodge Playing Fields

Recent events at Stoke Lodge and the playing fields there perhaps best illustrate our concerns and the potential threats to the many trees growing on land set aside for educational purposes.

The site was leased for 125 years to Cotham School in August 2011. Interestingly, the Council agreed to retain its responsibility for all the trees growing on the site. It also agreed to indemnify the school for any damage the school might cause to the trees and to insure against this risk.

Stoke Lodge Playing Fields are located to the west of the city in Stoke Bishop ward and cover some 8.7 hectares of open space. Historically they were part of the grade II listed lodge (now an adult learning centre) of the same name which covers about two more hectares and contains an arboretum of important trees (the survivors of a collection that formerly spread right across the historic lodge grounds).

Unlike most of the land around it, this part of Stoke Bishop is not in a Conservation Area. For some 70 years, the whole estate, which until recently had never been seen as a divided space, has been used by the local community and is designated an important open space. Nearly all the trees on the Stoke Lodge estate are subject to Tree Preservation Orders (TPO) which were placed on the trees in early 2012.

The TPO trees and canopies

In the summer of 2018 Cotham School announced that it intended to erect a fence along the boundary of its leased land. They stated that they did not require prior planning permission to do so because they were exercising their statutory Permitted Development rights. After an initial dispute about whether the school could indeed use Permitted Development rights, in January 2019 work began to erect the fence.

It was at this point that the Bristol Tree Forum became involved after it became clear that the proposed route of the fence would pass through the root zones of a large number of important trees, many of which were the subject of a TPO.

The original plan – the fence passing through the root zones of many protected trees.

There then followed a protracted period of back and forth representations while we and the local community fought to get the fence relocated to avoid damaging the trees. This was partly successful. Where it was not, we were able to insist that the methodology for erecting the fence where it still passed through tree roots was modified to minimise damage. Even so, it took the constant vigilance of the local community and BTF representatives to ensure that Cotham School did not ignore the conditions placed upon it.

Setting aside the issue of the siting of the fence, our primary argument has always been that TPO law requires a prior planning application to be made (and approved) before any work is undertaken that could cause damage to TPO trees. Initially, the Council rejected this argument, effectively stating the Permitted Development rights trump primary TPO legislation. It also argued that, anyway, it could not proactively prevent damage to TPO trees, but had to wait until the damage has been done, which is, frankly, absurd. We continued to challenge these interpretations and, eventually, the Council conceded our points, though only after the fencing had been completed.

Things then appeared to return to normal,except that the community was now largely confined the unfenced areas around the boundaries of the site. As a result, the trees around the boundary are being exposed to heavier traffic through their root zones. We are concerned that this may have a long-term, adverse impact on their health.

Then, in August of this year, and without any warning, contractors arrived to lay cable ducting across the site so that video surveillance equipment could be installed. Using a mini digger they immediately set about driving over and cutting through the root zone of a TPO Common Ash growing on the boundary of the site. Other non-TPO trees (some privately owned) were similarly damaged.

Digger in amongst the TPO Ash roots

It soon became clear that the contractors had neither been advised of the TPO status of the tree nor of the proper methods to use when working within tree root zones as set out in BS 5837 (Trees in relation to design, demolition and construction – Recommendations), or in the NJUG Guidelines for the Planning, Installation and Maintenance of Utility Apparatus in Proximity to Trees. This was despite the Council being aware of, and engaged with the school’s plans.

We lodged a complaint with the Council’s Planning department. As a result, enforcement proceedings were commenced and the school, whilst narrowly avoiding prosecution, was obliged to take remedial action to try to mitigate the damage caused to the tree. The council also felt obliged to remind the school of its obligations to TPO trees:

And this is a site where the trees are still under the ‘guardianship’ of the Council! What about those sites where the care is vested with the school?

Our concerns remain for the future health of those trees whose root areas had been invaded by the fence installation. We have also continued to express fears about other continuing threats to the trees arising as a result of other activities on the site. So far, our concerns have been ignored.

For example, continuing root compaction and branch damage is being caused to the Persian walnut growing by the gate close to the rear car park and to the trees growing beside the Parrys Lane entrance. This is the result of grass mowers and other service vehicles using these entrances to gain access to the site. We are told the access point has been moved to the Parrys Lane entrance, though that too involves vehicles passing over tree roots.

Driving over the walnut’s roots on the way to mow the playing fields

Historically, it looks like vehicles accessed the site from behind the Children’s Play Ground on the southwest of the site, so did not need to drive over any tree roots. The presence of the fence and lack of any gate there has now closed off that option.

The school’s contractors also continue to mow within the root zones of the two large Turkey oaks (BCC-77025 on the eastern end & BCC-77059 on the western end) that grow inside the playing fields fence.

The eastern Turkey oak

However, the Council and the school decline to address these issues saying that they have made adequate arrangements to safeguard the trees.

STOP PRESS – 4th January 2020 – since writing this blog, Cotham School has felled a TPO protected Elder (plus five others) on the Eastern side of the playing fields and poisoned it with Glyphosate. We have informed Bristol Council Parks and Planning Departments and asked them to investigate. They advise:

“The felled Elder trees were not included within or protected by the TPO covering the adjacent Sycamore tree.

It is very unlikely that roots from the Elder trees will have grafted with the roots from the Sycamore tree. Also translocation of herbicide between grafted roots is very unlikely.*

We are not aware of any plans to fell the twin stemmed Oak beside the white shed at the eastern end of Stoke Lodge Playing fields.”

But, when we asked Parks if these works were done with their prior knowledge and agreement, or if the department had approved the application of Glyphosate to the tree roots, or if they had seen the School’s Aboricultural Management Scheme, they answered ‘No’.

It seems that the school had complied with their obligation to get consent from the Council, their Landlord, but that the Council’s Education Asset Management team had failed to consult Park’s specialist tree officers about the plans.

More details can be found here.

Before the Elders were felled
The aftermath

Cotham School has issued these FAQs – 33 to 38 in response to this issue.

The fate of other educational sites

In the meantime, we have no idea if or how other schools are managing the trees on their sites, or if the Council is consulted when they do.

Even though, in most cases, educational sites are still on Council-owned land, the Council only needs to be told if the trees have a TPO or are growing in one of the city’s 33 conservation zones (or, we assume, if the Council’s lease with the school keeps the management of the trees in the control of the Council – as was the case at Stoke Lodge).

Given that Bristol City Council does not normally issue TPOs for trees on its own land, arguing that it is a good landlord and will look after important trees appropriately, it is unlikely that trees that have been handed over on other educational sites will have been protected by a TPO. Perhaps the council should now review its policy where it no longer manages trees growing on educational sites in light of this history.

Certainly it seems that new tree planting need no longer involve the Council. For example we recently observed that several newly planted trees at Cotham School’s main site had died. It was only when we noted that the dead trees were missing from the Council’s tree stock data for the school that we learned that they were no longer responsible for the trees on the site. We have now been told by the school that the trees were planted as part of a recent development and that the failure of these dead trees will be ‘rectified’ soon. Meanwhile, it seems that these new trees are no longer selected, managed or mapped as part of the Council’s wider tree stock strategies and that the existing trees on the site are no longer the Council’s concern.

Presumably, similar arrangements are happening across the city with other educational sites being left to make their own, ad hoc arrangements to plant trees or not. Given that the One City Plan aims to double tree canopy cover over the next 25 years, it seems a great shame that this important land bank of possible new planting sites might have been excluded from helping to achieve Bristol’s plans.

We are also 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 tree stock places upon them. As a result, they are likely to have to buy in (at our expense) ad hoc expertise, thereby possibly overlooking the wider strategic considerations that are needed when it comes to managing trees across the city.

This, coupled with the distinct possibility that well-meaning but unqualified Council officers may be making critical decisions about the welfare of trees on educational sites, makes for a very worrying situation.

*Here is a contrary view about using Glyphosate around and on trees – Tree pits: plants vs glyphosate

Redland Hill street trees felled by the Council. Why? An explanation…

We have now received an explanation, via a local Councillor, for why the trees on Redland Hill were felled – see our recent blog – Redland Hill street trees felled by the Council. Why?As we are anxious to update the record as soon as possible, we have decided to make it public. Here it is, received just yesterday:

“Contractors removed some of those trees along this strip in error. The contractor is planting replacements free of charge (hence the blue markers) [small posts painted blue, which we noticed had recently been inserted in a line along the wall – just visible in the image below].

The history I’m told goes as follows: 

The tree officer selected and marked the specific trees to be removed with a green paint spot. The thinning out was necessary due to the lack of space on the narrow strip of verge. It is good arboricultural practice.  It has been suggested this row used to be part of an old beech hedge, this isn’t the case because the trees removed were a mix of species, ash, sycamore and elder.

Unfortunately other trees, without the green spots and which were scheduled to remain, had previously been marked up with orange paint spots. It was made clear to the contractor’s manager when they met the Council’s tree officer on site which trees were to be removed and which should stay. 

The contractor’s team leader who subsequently carried out the felling work had not been given the full information from the manager and felled all the trees except the large Beech on the corner. The felling was also done much quicker than expected which is why the Councillors weren’t notified in advance thus compounding the error.

[The Trees and Allotments Manager] has discussed this communication error with the contractors and they have agreed to replace the trees that were incorrectly felled (i.e. the orange spot ones). The new replacement trees will be much better suited to the location than the original species. The new trees are birch with a very narrow and upright form. This will be much more suited to the narrow planting location and should have potentially less conflict in the future with pedestrians with pushchairs and will be easier to maintain next to the highway.  They will all be planted by the end of tomorrow.”

Here they are…just planted…and we are very pleased to see them.

The view after planting – 13 birch planted in six groups

We have asked the Council to comment. We await their response, though we see that they have already commented to BristolLive.

Councillor Clive Stevens (and ex-Chair of Bristol Tree Forum) commented: “Although conspiracy theories are more fun to read about, sometimes it is due to a good old fashioned cock-up. Lessons to be learned on communication with the public which I think was the main theme of the Tree Forum’s original blog is the need for more and better consultation. That applies to many things the Council does. If the Government decided to increase the duty to consult on tree works lets hope they provide some extra money to pay for someone to do it. And secondly, often the Council takes a while to respond and in this case probably because they wanted to finalise the solution first; its the same department dealing with Stoke Lodge and ex Wyevale Garden Centre situations and probably a hundred or so other active planning applications all with tight deadlines which take priority.”

As a precaution, we have asked the Council to take urgent steps to protect the last remaining beech tree on the boundary wall with a Tree Preservation Order. This is partly because of what has happened, but also because we have had to advise the Planning Department that someone on the site has dumped a large amount of builders rubble and other materials on the tree’s roots on the other side of the wall from the tree. Clearly this important tree (the last vestige of a historic hedge which probably predates both the wall and the buildings nearby) is still under threat and needs protection.

We are sad to have lost what was once a significant aspect of one of the approaches to the Downs, but are pleased to see the whole sorry saga resolved. We hope that lessons have been learned and look forward to watching the replacement birches grow and flourish.

Redland Hill street trees felled by the Council. Why?

Until a few weeks ago there was a lovely informal stand of trees along Redland Hill, which is a busy road that I walk up twice a day to get to the Downs.

As it used to look – Google Street View – July 2018

Rush hour stationary traffic belches out pollution and the trees provided some respite.  I have watched over the years as several of the old beech trees were removed.  They were probably once part of a beech hedge that predates the existing buildings (and the wall): now only one is left.  Instead, an informal collection of ash and other trees grew in their place.  This was a great place to see Broomrape, a parasitic plant that grew at the base of some trees.

How it now looks…All gone – just one lonely beech and some street furniture left to improve the view.

There was no consultation of any kind with the community. One day the trees were there, the next they were gone. Without any involvement from the Bristol Tree Forum, the local councillor or the local community, we can only guess why the trees were removed. Perhaps it was concerns about the nearby wall.  A careful examination shows that there are no obvious cracks, even close to the one remaining beech tree.  Was a proper engineer’s survey done? In days gone by a Bristol City Council Tree Officer defended a tree, similarly close to a garden wall, that the owners wanted to cut down, even obtaining an engineer’s report. Even if there were substantial damage to the wall, other options were possible, such as thinning out the trees (only some were marked with green paint) or laying them as a hedge as was recently done in Redland Green.

…just sawdust, rubbish and some ivy (now hacked down), nothing else.

Of course the removal may be for a different reason. Maybe what the developers really wanted to do was to create views for their flats and successfully put pressure on the council? Perhaps the pavement will be widened?  Or perhaps the area will be dug up for services. I don’t think the removal of trees was in the planning application.

J

At this time, with the threat of Ash die-back disease we should be looking to keep healthy ash trees in case by chance they turn out to be the ones that are resistant. Cutting down healthy ash trees is misguided.

The money that was spent cutting down these trees should have been used for planting new street trees, something that Bristol City Council says it has no funds to do. I’m guessing more money will now be spent to tarmac over the area where the trees once were. 

Bristol City Council should have thought differently. For example, it should have enforced a root protection area for the last remaining beech tree. This was apparently not done and I guess we will see that last tree fail in the next ten years.

At present, Bristol City Council refuses to consult over tree felling decisions, despite requests from the Bristol Tree Forum for a decade. It is almost as though the council thinks there are no inhabitants in the urban forest and that they always know best. Unilateral decisions such as this show how important the government’s proposal is to require local authorities to properly consult before removing street trees. 

Bristol has an ambitious plan to double its tree canopy by 2050. Yet all over Bristol, on an almost daily basis, tree canopy is being lost – for multiple reasons. Just in the local area, about half a dozen really large trees have gone and the canopy cover has decreased. We did manage to get one new street tree, in the middle of Redland roundabout but it took a four year battle and the help of our local MP to get it planted. Trees are lost very gradually in our bit of Bristol and are often not replaced.  So the change in canopy is not obvious. Fisheries biologists have coined the term “shifting baselines”, where each generation sees only minor negative changes. But the effect over a long period is substantial.

As Professor Corinne Le Quere has said, “actions to tackle climate change have to penetrate all the decisions that we take in society”. We are hoping that we can get this point across to the decision makers in Bristol City Council.

The Bristol Tree Forum will now be campaigning for these trees to be replaced.

Vassili Papastavrou.

The Stoke Lodge Lucombe Oak wins Bristol Tree of the Year 2018

We are delighted to announce that the winner of the inaugural Bristol Tree Forum’s Tree of the Year competition is the Lucombe Oak, submitted by the community group We Love Stoke Lodge. The Lucombe Oak was a clear winner with 584 votes out of the 1,269 confirmed votes cast for the eleven entries. 

We Love Stoke Lodge is an informal community group of local residents based around Stoke Lodge, a 26-acre park and recreational area in Stoke Bishop in the north-west of Bristol.

The group writes:

The Lucombe Oak is a cross between a Turkey Oak and a Cork Oak. It was first raised by an Exeter nurseryman, William Lucombe, in 1762. It is unusual in the fact that it keeps its leaves over winter. The story goes that William Lucombe was so attached to his special oak that he felled the original specimen to provide wood for his own coffin and kept the boards under his bed until he died. However, he lived an exceptionally long life, dying at the age of 102 years, by which time the planks had decayed in the Devon damp. To quote an article from Royal Botanical Gardens, Kew, this showed ‘that Lucombe knew more about growing trees than preserving them’. On his death timber from one of his early propagations was used to make his coffin instead.

Notwithstanding the tree’s fascinating history, so many of our community hold treasured memories of this tree dating back over four generations. At a recent community picnic those in their nineties sat alongside primary school children of today talking about the best picnics they have had under our beloved tree and sharing tips on how to climb it wonderful branches. This tree is the meeting point for many sports and well-being groups. Its branches shade baby groups, yoga classes, families and friends from the sun (and the rain) every day – as it has done for hundreds of years ! This tree is a not just located in the centre of our community, it is part of it.

The runner-up is the Brislington Brook Plane Tree, with 399 votes and submitted by Friends of Brislington Brook, a community group which works to enhance and look after the green spaces that are Nightingale Valley and St Annes Wood. 

The group writes:

This giant London plane tree that dominates an area of Brislington’s Nightingale Valley is, together with the nearby pack-horse bridge, one of the features that help define this unexpected green haven. Its trunk was once an open hollow, tempting the mischievous to light fires within it so a few years ago a local action group walled it up. This has given rise to a legend that a witch is entombed within. Many generations of Brislingtonians have picnicked in its shade, swung across the brook from ropes attached to its boughs or caught tiddlers beneath it. It has a symbolic significance: It’s tall, it’s strong, it’s seen adversity, it endures.

We would like to thank all those who submitted a nominee. We were delighted to receive such a varied and eclectic range of wonderful and inspiring trees, both living and dead. An inspiration for next year’s competition.

Our congratulations to the winner and the runner-up and thank you to all those who voted.

For more information about the competition and the votes cast for each entry, click on this link – Bristol Tree of the Year 2018.

Ancient and Veteran Trees explained

These two terms are in common use, but they have specific meanings when it comes to their conservation. All ancient trees are veterans, but a tree may qualify as a veteran without being ancient.  Most British trees increase in girth over their lifetimes by 2.5 cm a year. They grow faster when young, when in the open as opposed to woodland, and when in good soil rather than bad. They grow slower as they get older. Some species grow faster than average, such as Black Poplar, Plane, and Wellingtonia, and some more slowly, especially Limes and Hawthorns.

Trees are very good at vegetative reproduction, so that they are effectively eternal. Some create their own clumps, each tree being a clone. They do this by branches that arch down to the ground, root, and send up new vertical trees. The Tortworth Chestnut, which was regarded as ancient in King Johns reign, is a good example, but some of the limes on the Downs are doing this. Some trees send up new shoots from the base of the trunk which eventually replace the original tree. Many trees if cut to the ground, by storm or men, will promptly create new shoots, and this is the basis of coppicing which was a standard woodland management tool from at least Roman times. There is a Small-leaved Lime at Westonbirt Arboretum that now consists of a ring of clones about forty metres in diameter.

Ancient trees should be at least two hundred years old, and hence have a girth of more than five metres. I have measured 120 trees in Bristol with this girth, and there are many more in Ashton Court that I have not checked.   They matter because they provide a range of habitats to a range of species. They are always hollow, often squat,  having long since lost their upper branches, their hearts eaten out by fungi and beetles, full of nooks and crannies, and often clothed in lichens and ferns. They are most frequently Oaks, Sweet Chestnuts, Planes and Cedars.

Veteran trees are defined by their individuality. They will be mature, around 140/150 years old, about three metres in girth, mostly still standing tall. Fine, significant specimens of their species both in form and biodiversity. They are candidates to become Ancient, they may be starting to go hollow, and hence be of concern. They may need management to avoid their becoming top heavy, or developing a dangerous lean. They will stand out from other trees in their particular locality and may have planning protection as a consequence. They may also have special features of note, such as being multi-trunked.

Trees and Planning

The National Policy Planning Framework document (issued in July 2018) has the following definitions at Appendix 2: Glossary.

Ancient or veteran tree: A tree which, because of its age, size and condition, is of exceptional biodiversity, cultural or heritage value. All ancient trees are veteran trees. Not all veteran trees are old enough to be ancient, but are old relative to other trees of the same species. Very few trees of any species reach the ancient life-stage.

Ancient Woodland. An area of woodland that has been wooded continuously since at least 1600 AD. It includes ancient semi-natural woodland and plantations on ancient woodland sites.

Irreplaceable habitat: Habitats which would be technically very difficult (or take a very significant time) to restore, recreate or replace once destroyed, taking into account their
age, uniqueness, species diversity or rarity. They include…ancient woodland and ancient and veteran trees….

Paragraph 175 (at page 51) of the framework states:

When determining planning applications, local planning authorities should apply the following principles:

c) development resulting in the loss or deterioration of irreplaceable habitats (such as ancient woodland and ancient or veteran trees) should be refused, unless there are wholly exceptional reasons and a suitable compensation strategy exists;

Paragraph 2.17.6 of DM17: Development Involving Existing Green Infrastructure – part of the Bristol Local Plan echoes this:

Due to their characteristics and value, Aged and Veteran trees are considered to be of relatively greater importance than other trees and even trees of a similar species. Aged trees, by definition, have developed characteristics associated with great age and often have particular landscape and townscape value. Veteran trees are considered to have particularly important nature conservation value. Both will often have significant visual amenity, and potentially historic and cultural importance. As such their loss or harm will not be permitted, and the design and layout of development will be expected to integrate them into development.

These guidelines apply whether the tree or woodland grows in a public or a private place.

R L Bland

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