Tag: Bristol City Council

The Local Nature Recovery Strategy fails to deliver for Bristol

WEMCA’s Local Nature Recovery Strategy (LNRS) will fail to provide Bristol with the benefits promised for nature. While the new Biodiversity Net Gain (BNG) rules require most development in the city to increase biodiversity by at least 10%, unfortunately the LNRS will not apply to most potential development sites.

The West of England Mayoral Combined Authority (WECA as was) Local Nature Recovery Strategy was published to much fanfare last November. Defra’s blog, Kickstarting local nature recovery: a new strategy for the West of England, hailed it as the first in the country.

The LNRS is a locally led and evidence-based strategy which aims to target action and nature investment where it’s most needed. We’re told that the strategy will also focus on biodiversity net gain by increasing the strategic significance of specific habitats. However, it is hard to imagine how the LNRS will help to enhance biodiversity net gain in most, if not all, potential development sites in the city.

We might have been better off, at least as far as the application of biodiversity net gain to new development is concerned, by asking the LPA to specify alternative documents (such as those listed at the end of this article) for assigning strategic significance instead.

The issue

When calculating the impact of a proposed development on biodiversity, one factor taken into account is the strategic significance of any habitat found on a focus area for nature recovery site (coloured purple in the map above). If strategically significant habitats are created or enhanced, then their strategic significance is set to High in the Statutory Metric calculator tool and a 15% uplift to the calculation of its value is applied. Subject to which of the six LNRS areas is being considered, these are the strategically significant habitats in the city:

  • Ditches
  • Ecologically valuable lines of trees
  • Ecologically valuable lines of trees – associated with bank or ditch
  • Grassland – Floodplain wetland mosaic and CFGM
  • Grassland – Lowland calcareous grassland
  • Grassland – Lowland meadows
  • Heathland and shrub – Mixed scrub
  • Heathland and shrub – Willow scrub
  • Individual urban or rural trees
  • Lakes – Ponds (priority habitat)
  • Priority habitat (on the River Avon and the Riparian buffers)
  • Species-rich native hedgerow with trees – associated with bank or ditch
  • Species-rich native hedgerow with trees
  • Species-rich native hedgerows – associated with bank or ditch
  • Species-rich native hedgerows
  • Urban – Open mosaic habitats on previously developed land
  • Urban – Biodiverse green roofs
  • Woodland and forest – Lowland beech and yew woodland
  • Woodland and forest – Lowland mixed deciduous woodland
  • Woodland and forest – Other woodland; broadleaved
  • Woodland and forest – Wood-pasture and parkland

However, a detailed examination of the LNRS map reveals that not all parks and green spaces have been designated as focus area for nature recovery sites. It’s only those which are in one or both of the following:

  • a location where they can make a greater contribution to ecological networks
  • deprived areas with a lack of access to nature.

These designations were based on Bristol’s previous work on ecological networks within the city and where wildlife-friendly interventions are most likely to be feasible. This means that the existence, creation or enhancement of these special habitats outside these areas will not attract the 15% strategic significance uplift.

The BNG requirements

The now compulsory Statutory Metric Guide, used for calculating Biodiversity Net Gain (BNG), advises (at page 27) that: ‘Strategic significance is the local significance of the habitat based on its location and habitat type. You should assess each individual habitat parcel, both at baseline and at post-intervention, for on-site and off-site.’

If the LPA has adopted an LNRS then only the High or Low strategic significance multipliers can be used (High – formally identified in local strategy = 1.15. Low – area compensation not in local strategy = 1). If it has not adopted an LNRS, then the Medium strategic significance multiplier may also be used (Location ecologically desirable but not in local strategy = 1.10).

Where an LPA has adopted an LNRS, all those sites which have not been identified as a focus area for nature recovery site will be designated as having Low strategic significance and so attract no uplift, even if they’ve been identified as important habitats in the Local Plan or in another strategic document adopted by the Council. These documents (used where an LPA has not adopted an LNRS) can include:

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

Baseline habitats cannot be uplifted

Despite the BNG strategic significance guidance, Defra has stated that LNRS designations only apply to the creation or enhancement of post-development biodiversity mitigation habitats. They don’t apply if these habitats – called the baseline habitats – are found on the site before development begins.

This means that the 15% strategic significance uplift can only be applied where offsite biodiversity mitigation is being delivered in a focus area for nature recovery site. If these habitats are being delivered elsewhere, the uplift may not be applied.

However, even if the baseline habitats were included, it is unlikely to make any difference This is because the focus area for nature recovery sites identified in Bristol are, for the most part, located in public parks or green spaces, on river banks, in riparian buffers or on railway margins, none of which are likely ever to be developed or, in many cases, used to offset habitat lost to development elsewhere.

So far, no announcement has been made as to whether any of Bristol’s focus area for nature recovery sites will be made available for offsite habitat mitigation and the proposed new Local Plan does not commit to using these sites for this purpose.

This, combined with the challenge of finding LNRS suitable for offsite habitat mitigation, registering them as biodiversity gain sites and then managing them, effectively, in perpetuity, suggests that few feasible LNRS sites will be found, especially as many sites are also in demand for public access for recreation.

We set out the process used to assess the strategic significance of habitats on our blog, Assessing habitat parcels: strategic significance explained.

Why we must protect the trees we love

Paul Sander-Jackson, who helped to plant the Baltic Wharf trees, returns to Bristol shocked to learn that they will now be felled.

We came back to live in Bristol nearly two years ago. After living in Somerset for 32 years, and in Bristol 12 years before. Much has changed in the city, but much has remained – the best bits, and especially the trees.

Our new home backs on to Oldbury Court – which has an astonishing range of trees and plants, as well as a river and rocks and old quarries. Our garden has a lime tree – probably about 80 to 90 years, just outside its boundary fence.

In Somerset, we became very involved, in the later stages of life there, in planting new trees and woodlands, hedges and copses. The organisation we were involved with – Reimagining the Levels – has been responsible for planting over 100,000 trees in the past few years. But that is addressing a major problem in Somerset – a tree cover of only between 6% and 7%.

Coming back to Bristol, I wondered where my energy should go. But a few months ago, an old friend mentioned that I might like to get involved in Bristol Tree Forum. The rest is (personal) history. My partner and I are now joint Tree Champions for the Frome Vale ward.

It was a great shock when I was made aware of the application then pending on the Baltic Wharf Caravan Club site, particularly because when I used to do landscaping and gardening for a livelihood in the late eighties and early nineties, I had helped plant trees on that site, and carefully undertaken structural pruning and maintenance. And now a planning application was threatening to fell 80 of them.

“The Baltic Wharf trees were at least 35 years old, providing numerous ecological ‘services’ to the area”

As I made further enquiries, it turned out that there were over 590 objections to the application, with six statements in support. Six!! The trees represented over a quarter of the tree cover in the immediate area. They were at least 35 years old, providing numerous ecological “services” to the communities of Bristol.

And then the terrible shock of a unanimous – yes unanimous – planning committee decision to go ahead without amendments to the felling of the trees, with no objection from the responsible tree officer.

This left me realising many things. How naïve I have been about the problems nature, and especially trees, face in this lovely city. How we need to struggle and advocate for every one. Trees offer so many positive benefits for all creatures, including humans. I reflect on the wonderful life in ‘our’ lime tree.  Pigeons, starlings, sparrows, crows, squirrels. Life in all its varied forms. Leaves, blossoms, growth.

And perhaps most of all, I recognise that in Bristol, in 2024, there is perhaps an equal if not greater task to planting new trees. To protect the ones we have, and love. And to share that love with as many people, in our local communities and beyond, that we can.

“Maybe we can teach even more people how important it is to retain trees and how we should never allow a good tree in a good place to be arbitrarily felled”

My partner and I began our life in Bristol in St Werburghs, starting the City Farm there in 1980. As it got going, with great help from some wonderful City Council officers in the planning and parks departments, we planted trees with children from six local primary schools. Those children, I hope, will always carry the memory of that planting. And I hope they go and visit the trees – now over 40 years old and flourishing in the wondrous environment of the City Farm.

It is about a will, an attitude, a set of values. Above all, it is about respect for our fellow plants and creatures, who share this planet and this city with us.

Interested in becoming a Tree Champion like Paul? Click below to learn more.

Find out about tree champions

Why we need a new Bristol Tree Replacement Standard

We believe the time has come to revise the Bristol Tree Replacement Standard (BTRS), to reflect our changing understanding of the vital importance of urban trees to Bristol and how they contribute to biodiversity gain.

The current BTRS Standard, adopted nearly a decade ago in July 2014, provides a mechanism for calculating the number of replacements needed for any trees that are removed for developments. It was ground-breaking in its time as it, typically, required more than 1:1 replacement of trees lost to development.

Since then, Defra has published the statutory version of the Biodiversity Metric (SM) (on 29 November 2023), which became mandatory on 12 February 2024. In addition, Bristol has adopted Climate and Ecological Emergency Declarations, so an updated BTRS would be an important part of implementing these declarations. It would require all new developments, subject to some exceptions, to achieve a Biodiversity Net Gain (BNG) of at least 10%. Where deveelopments are exempt, BTRS will still apply.

Although Councillors rejected our proposals for a new Standard at their meeting on 31 October last, we’ve revisited our July 2023 proposals and recast our calculations. These proposals, set out below, provide a mechanism for complying with the new requirements and align the BTRS with the BNG provisions of the EA 2021.

The purpose of the BTRS is that it should only ever be a last resort and not the default choice – which, unfortunately, it has become. When considering any development involving established trees, the presumption should always be that trees will be retained. If this is not possible, then the impact of the proposed development must be mitigated. Only if this is impossible, should compensation for their loss be considered. This is the meaning of the Mitigation Hierarchy, as set out in paragraph 180 a) of the National Planning Policy Framework, which states:

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, then planning permission should be refused.

This is reflected in the Bristol Core Strategy, policy BCS9 (page 29),which states that:

Individual green assets should be retained wherever possible and integrated into new developments.

This is repeated in the proposed replacement for BCS9 – Policy BG1: Green infrastructure and biodiversity in new development (page 124) – which ‘aims to ensure that green and blue infrastructure and provision for nature is incorporated into new development’ so that, among other things:

The provision of green infrastructure in new development should … Retain and incorporate important existing green infrastructure such as trees (Policy BG4 ‘Trees’), hedgerows and water features …

It is a shame that the requirement is only an aspiration, not an obligation.

Background

Under the new proposed policy – BG4: Trees (page 131) – trees lost to development will be replaced using this table:

Table 1 The proposed BG4 tree replacement table.

However, when the balance of EA 2021 takes effect, the current version of the BTRS will not, in most cases, be enough to achieve the 10% BNG minimum required for nearly all developments. A new Section 90A and Schedule 7A will be added to the Town and Country Planning Act 1990 and will set out the level of BNG required.

Paragraph: 001 Reference ID: 74-001-20240214 of the Biodiversity net gain guidance states:

Under the statutory framework for biodiversity net gain, subject to some exceptions, every grant of planning permission is deemed to have been granted subject to the condition that the biodiversity gain objective is met (“the biodiversity gain condition”). This objective is for development to deliver at least a 10% increase in biodiversity value relative to the pre-development biodiversity value of the onsite habitat. …

Many development proposals will aim to achieve more than the minimum 10% gain voluntarily. Others may not but will still need to achieve much more in order to comply with the SM trading rules (page 140). This is based on the habitat type lost and its distinctiveness. In the case of Individual tree habitats – Urban or Rural –­ losses must be replaced within the same broad habitat (i.e. more Individual trees) or with a habitat of a higher distinctiveness.

However, for the sake of certainty, we propose only using the minimum 10% BNG required.

Our proposed new BG4 (BTRS) model

We propose that the table in BG4 be amended to reflect the requirements of the EA 2021 and SM and that the BG4 table (Table 1 above) be replaced with Table 2 below:

Table 2 Our proposed BG4 tree replacement requirement

The Replacement Trees Required number is based on the habitat area of each of the four SM tree category sizes (Table 13 below), divided by the area habitat of one BNG 4.0 Small category tree (see section 3 below) plus a 10% net gain. This is rounded up to the nearest whole number (since you can’t plant a fraction of a tree).

The reasoning for our proposal is set out below:

1. Applying the Biodiversity Metric to Urban trees

The most recent Statutory Biodiversity Metric User Guide defines trees as Individual trees habitats as follows:

When to record individual trees

Use the broad habitat type ‘Individual trees’ to record trees where:

  • they are found as an individual or as part of a group;
  • are over 7.5cm in diameter at breast height (DBH).

Individual trees should also be recorded where they meet the definition of an irreplaceable habitat but would not otherwise be recorded.

Do not otherwise record individual trees if they occur within an area habitat type characterised by the presence of trees, examples of these are:

  • woodlands
  • orchards
  • wood-pasture and parkland

Individual trees are classed as ‘urban’ or ‘rural’. You should consider the degree of ‘urbanisation’ of habitats around the tree and assign the best fit for the location.

2. Calculating Individual trees habitat

Table 13 in the SM User Guide is used to calculate the ‘area equivalent’ of individual trees:

The biodiversity metric uses set values to represent the area of trees depending on their diameter at breast height. This value is a representation of canopy biomass, and is based on the root protection area formula, derived from BS 5837:2012.

You should report the number of individual trees within your project and input tree count into the ‘tree helper’ within the biodiversity metric tool to generate area values for data input. For multi-stemmed trees, use the DBH of the largest stem. You should:

  • account for each individual tree within a group or block of trees.
  • record the habitat underneath the tree canopy separately.
  • not reduce any area generated by the tree helper.
  • not deduct the area of individual trees from other habitats.
  • make clear in the user comments how many trees contribute towards the total area.

Recording trees within private gardens

You should assess most individual trees that are recorded in private gardens. You should record:

  • any medium, large and very large trees as individual trees
  • any small trees that are ancient or veteran

Recording trees within hedgerows

You should assess most individual trees that are recorded within hedgerows. You should record:

  • any medium, large and very large trees as individual trees
  • any small trees unless they are ancient or veteran.

You must assess the linear value of hedgerows within the hedgerow module separately.

Individual Tree habitats have medium distinctiveness and so, under Rule 1 of SBNG, ‘Losses must be replaced by area habitat units of either medium band habitats within the same broad habitat type or, any habitat from a higher band from any broad habitat type.’

3. Forecasting the post-development area of Individual trees

The SBNG User Guide provides this guidance:

You should use the tree helper to calculate the area for created trees.

You should categorise most newly planted individual trees as ‘small’, unless the tree is medium sized or above at the time of planting.

You should not factor in the age of nursery stock when using the ‘creation in advance’ function. The ‘creation in advance’ function should only be used where trees are planted in advance of the development (for example, as screening or as structural landscaping).

Exceptions

You cannot count:

  • newly planted trees within private gardens
  • natural size increases of baseline trees
  • trees planted as part of hedgerow creation or enhancement as individual trees.

Our calculations are based on Small category replacement trees being planted as per the SM guidance.

4. The likely impact of this policy change

We have analysed tree data for 1,038 surveyed trees taken from a sample of BS:5837 2012 tree surveys submitted in support of previous planning applications. Most of the trees in this sample, 60.5%, fall within the SM Small tree category, 32.9% are within the Medium tree category, 5.4% are in the Large tree category with the balance, 1.3%, being categorised as Very Large.

Table 4 below sets out the likely impact of the proposed changes to BG4. It assumes that all these trees were removed (though that was not the case for all the planning applications we sampled) and replaced with SM Small category trees:

Table 4 Proposed BG4 impact analysis.

The spreadsheet setting out the basis of our calculations can be downloaded here – RPA Table Statutory BNG 13 table Comparison.

The saga of the SNCI at Yew Tree Farm continues

What does ‘harmful impact’ mean?

When the Development Control Committee last met to discuss the Council’s application to extend the cemetery at South Bristol into the SNCI at Yew Tree Farm on 6 September 2023, we were disturbed to hear the Chief Planner’s interpretation of the meaning of ‘harmful impact’, as set out in the Local Plan policy, DM19 – ‘Development which would have a harmful impact on the nature conservation value of a Site of Nature Conservation Interest will not be permitted.’

We even wrote an open letter to the Chief Planner asking them to explain their reasoning. We published this as a blog: It seems that SNCIs are nothing special – an open letter to Bristol’s Chief planner.

Update

Unbeknown to us, it seems that the Council’s Nature Conservation officer did comment on the Chief Planner’s earlier advice to the Committee:

This document was disclosed on 1 December 2023 as a result of our Freedom of Information request of 01 November 2023. This appears to have formed the basis of the answers given below.

Update Ends

As we received no reply at the time, we took the opportunity to ask again when the Committee reconvened to make its decision on 29 November 2023. We asked two questions – see page 9 of the Public Forum. As the responses still didn’t really satisfy, we asked two supplementary questions:

  1. When you say, ‘the site’, what do you mean? Is it within the redline boundary or something else such as within the SNCI’s boundary?
  2. You say ‘The crucial additional clarification to highlight, is that to be in alignment with this policy it is NOT the overall biodiversity gain that is determinative. There rather needs to be an assessment that establishes whether there is harm with reference to the specific characteristics that make the site special.’

Does this mean that the replacement of one habitat which forms part of the ‘specific characteristics that make the site special’ – such as a replacing the Grassland Habitat that forms part of the current SNCI designation with a Lake Habitat that does not form part of the current SNCI designation, or that the provision of offsite mitigation measures to compensate for onsite habitat losses (in this case -6.44%) – would not be acceptable?

These were the replies:

To question 1

By ‘the site’, it’s the site as set out in the application document, so it’s the SNCI as contained in the application document the area in the redline boundary.

To question 2 (as it is quite complex, we have reproduced it verbatim)

You need to take the application as a whole and where it is demonstrated as that with regard to the features, particularly the grassland, that there is no impact ultimately or, if anything, a slight enhanced impact.

We intervened to ask – So you are saying that the substitution of the grassland habitat for a lake habitat…?

I am not saying that at all, I am saying that the grassland, actually that there is more grassland and that’s what the ecology report also says – more grassland of the type for which the SNCI is designated will be there through this application than before… within the redline boundary.

Here is the recording of this exchange – https://www.youtube.com/watch?v=-8EvqLA8-Lg (08:05 minutes from the start to 11:30 minutes).

What’s a redline boundary?

Anyone who wants to develop land must produce a location plan of the area proposed for development, delineated by a red line – the so-called ‘redline boundary’.[1]

When planning permission is granted, only the area within the redline boundary may be developed (though ancillary works may take place elsewhere).

Here is the location plan for the South Bristol Cemetery Extension application:

The South Bristol Cemetery Extension location plan (North is at the top)

The redline boundary here is quite complex because it’s made up of two burial areas, in the north and south, and an attenuation pond to collect runoff from the northern burial ground through a series of drains (the southern burial ground runoff will drain straight into Colliter’s Brook to the west). The area within the blue line is also owned by the Council and so is under their control.

The redline boundary is also important when it comes to calculating the biodiversity value (BNG) of the development site. All the habitats within the redline boundary are treated as ‘onsite’, while those outside the boundary are treated as ‘offsite’.

So, when we are told that ‘… there is more grassland and that’s what the ecology report also says – more grassland of the type for which the SNCI is designated will be there through this application than before… within the redline boundary,’ it’s just the onsite area that’s being referred to. This is important, as we show below.

The headline results shown in the most recent BNG 3.1 calculation relied on by the Council[2] show that 6.44% of the baseline onsite area biodiversity will be lost as a result of the development (see Figure 1).

Figure 1: The BNG 3.1 Headline BNG results.

Figure 2 shows the net losses of the onsite grassland habitat:

Figure 2: Grassland Area & Habitat Unit analysis (HUs)

Under the BNG Trading Rules, Medium Distinctiveness grassland habitats may only be replaced with the other Medium Distinctiveness grassland habitats or with habitats of a Higher Distinctiveness. So, in order to achieve the net 2.93% BNG which the Council claims will result from the development, it will be necessary to compensate for these losses by crediting 3.25 Habitat Units of High Distinctiveness Lakes habitat by creating the attenuation pond.

This is not what we are told is happening and it certainly cannot be said that: ‘… there is more grassland … of the type for which the SNCI is designated … within the redline boundary,’ This is plainly untrue and, even on the Chief Planner’s definition (which we do not accept), it is clear that this application will ‘have a harmful impact on the nature conservation value of a Site of Nature Conservation Interest.’ This is contrary to DM19.

What’s more, even if the proposed offsite habitat mitigations were taken into account, there’d still be a net loss of -0.47 HU of Medium Distinctiveness grassland habitat (see Figure 4 below).

Figure 4: Net Medium Distinctiveness habitat losses

There’s one other serious flaw in the application, which was not brought to the attention of the Development Control Committee at its meeting. There’s a shortfall of -0.11 Habitat Units of the High Distinctiveness habitat, Species-rich native hedgerow with trees. Lost High Distinctiveness habitats may only be replaced like-for-like. This has not happened. As a result, the application is in breach of the BNG Trading Rules and should not have been approved.

We have brought this to the attention of the Council and the LPA.

These are just some of the important reasons why we say that the Development Control Committee was wrong to grant this flawed application.

A copy of this blog can be downloaded here – The saga of the SNCI at Yew Tree Farm continues

[1] It seems that no one thought of those with red/green colour blindness, who might find it difficult to see this red line.

[2] 22_05714_FB-SOUTH_BRISTOL_CEMETERY_BNG__25TH_AUGUST_23_-3540800

Developing a Tree Strategy for Bristol

Bristol City Council is currently writing a tree strategy for Bristol. This is welcome news, as we have been calling for such a strategy to be developed for more than a decade.

For example, in 2020 we wrote a Manifesto for Protecting Bristol’s Urban Forest.

A tree strategy should be an evolving process rather than a document which may quickly become out of date. This is particularly true in our rapidly changing world – environmentally, climatically and politically.  To provide an effective response to the challenges these present, a group of representatives from both civic and professional groups (along the lines of the Bristol Advisory Committee on Climate Change (BACCC), should be established to help coordinate further research and make recommendations to Bristol City Council and other stakeholders as the situation changes.

We also recommend that the development of a tree strategy should take full advantage of exemplars from other local authorities[1]. We should have the ambition to make Bristol’s tree strategy the best.

Here follow 18 key points that we would expect to see included in a strategy.

  1. Buy in from all the stakeholders involved. Many council departments (as well as Parks, there is Highways, Education and Planning) have a role to play in the management of Bristol’s trees. We need to see evidence that all such departments are fully involved in the development of the strategy. In particular, with the current review of the Local Plan, it is essential that Planning is fully engaged with the strategy, and that the two documents are consistent and properly cross-referenced. The tree strategy needs to be incorporated into the new Local Plan. In addition, other important landowners (such as the universities, utilities providers, housing associations, schools and hospitals) have a role to play in contributing their expertise to the strategy and implementing its goals. As well as the Bristol Tree Forum, many community groups have an interest in tree planting in Bristol and should be involved and consulted.
  2. When council trees are removed, they must be replaced. At present there are more than 800 street tree stumps and empty tree pits around the city – sites where trees once grew. A plan to plant all these missing trees within five years needs to be included. In the future, when any council trees are damaged or felled, they should be replaced within the next planting season.
  3. There needs to be community engagement in tree management decisions both at the level of individual trees and in strategic decisions. In recent years we have seen a rise in community led campaigns to protect trees, such as the Ashley Down Oak, the M32 maples and Baltic Wharf, and this is indicative of a disconnect between the Council and the communities it serves. When the balance of the Environment Act 2021 takes effect later this year, Councils will be obliged to consult when street trees are being considered for removal[2]. This is too narrow and should be extended to include where any public tree is being considered for removal. Therefore, part of the strategy should be promoting community engagement, providing mechanisms for engagement and then taking account of the concerns of the community and tree campaigners alike.
  4. There should be one person responsible for trees within Bristol City Council. At present we have tree planning officers, tree maintenance officers and tree planting officers with no single individual or office accountable overall, often resulting in a lack of appropriate action or people working at cross-purpose. It is also concerning that Highways are able to remove street trees without any consultation.
  5. There needs to be a plan to address the massive inequality in tree cover in Bristol, which often mirrors social and financial deprivation in the City. For instance, additional protections could be given to trees, and tree planting prioritised, especially in deprived areas such as the City Centre, Harbourside and St Pauls.
  6. When developers remove trees, the replacements required should be planted by BCC. Too often developers have shown themselves incompetent or unconcerned when planting trees, so the trees fail or are never planted. In the case of Metrobus, there has been a more than 100% failure rate of trees in some places (trees have been replaced multiple times). We have an excellent tree planting team in Bristol and we should benefit from requiring them to organise and implement the planting required. The cost should be funded by the developer.
  7. Retaining existing trees must be a major part of the strategy. A tree strategy cannot be just about planting new trees, the benefits of which will not be realised for decades, but crucially about retaining and protecting existing trees and the benefits they are already providing. As such, the strategy must address the threats to existing trees. Planning is crucial in this so we would expect major engagement with Development officers to address the current and future problems.
  8. Planning Enforcement must address the illegal removal of or damage to trees. At the moment there are no consequences following the unauthorised damage or destruction of trees. This must change. Other neighbouring local authorities manage to do this but not Bristol. A strategy must include a review of the reasons for the existing lack of effective enforcement and make recommendations as to how this can be rectified.
  9. Developments should be built around existing trees as is already required[3]. Other local authorities do this but not Bristol. This will require a change of culture in the planning department so that pre-application discussions with developers make it clear that this will be required.
  10. The sites for the replacement trees must be agreed before Planning Applications are approved. This is required by planning policy (BCS9 and DM17), but currently developers are being allowed to, instead, pay a “fee” into Section 106, and frequently the replacement trees are never planted. Trees form an important part of our urban habitat. The calculation of tree replacements required to compensate for their loss must be aligned with the Biodiversity Metric as adopted under the Environment Act 2021.
  11. Spend the £ 900K+ reserved for tree planting. Connected with the above point, a strategy needs to include a mechanism for spending the existing £900K+ of unspent tree planting Section 106 money within the next three years.
  12. A strategy to increase Bristol’s tree canopy cover (or at the minimum, maintain existing canopy cover) needs to have a route to implementation This must include addressing the loss of street tree canopy cover by being bolder in selecting new tree planting sites and planting large-form trees wherever possible. Trees such as rowans and flowering cherries are short-lived and will never provide much canopy or become robust enough to survive our challenging urban environment in the long-term.
  13. Canopy Cover needs to be measured with an agreed methodology with confidence limits (levels of doubt in the estimate) made clear. In the first instance, we need to establish the baseline year and percentage tree cover from which progress will be measured. Only then will it be possible to show whether a trend has been determined. Two measurements using different methodologies should not be used to claim an increase in canopy cover. The metric should take account of trees lost so that the figure reflects the true increase, or loss.
  14. Include trees within road changes. There needs to be proper engagement with Highways at early stages of the design process for road changes to look at retaining the maximum number of existing trees and including innovative planting opportunities for new large-form trees, such as pavement build-outs.
  15. For new developments, trees should be properly considered at the pre-application stage, with appropriate consultation with stakeholder groups. Too often, the mitigation hierarchy requiring the removal of trees to be a last resort is disregarded, so that it is only after the design has been finalised that the existing trees are considered and removed where they conflict with the design scheme.
  16. Biodiversity Net Gain (BNG) calculations need to be checked by the Local Planning Authority and biodiversity loss must not be monetised as BTRS has been. BNG, if properly implemented, makes sure that biodiversity on development sites is properly measured and will provide a net gain (soon to be least 10%) is factored in. However, at present, developers’ calculations are not being checked. When we have provided properly evidenced calculations, these have been dismissed by the LPA as mere differences of opinion. You cannot have differences of opinion on facts. The LPA must require that BNG calculations are presented in a way that can be checked by anyone interested and actually do the checking. In addition, ensuring BNG must require that the development site does not lose its biodiversity. If this is not possible, then its immediate local environment must be used to offset any onsite losses. Onsite losses must not be compensated for in some faraway place completely removed from Bristol.
  17.  Planning Applications involving trees must mention this fact in the title. Too often, applications that involve the loss of important trees (or plans to avoid the planting of new trees[4]) do not even mention this fact in the title. This means that it is extremely difficult for community organisations to engage.
  18. Once a planning application has been issued, no removal of trees. A moratorium should be placed on any tree felling pending the outcome of the planning application. This includes applications to demolish buildings which should exclude tree or other habitat removal.

A copy of this blog is available here.

02 May 2023

[1] See for example the Wycombe Council Canopy Cover Doc https://buckinghamshire-gov-uk.s3.amazonaws.com/documents/Canopy-Cover-SPD_3qAkk4z.pdf

[2] https://www.legislation.gov.uk/ukpga/2021/30/part/6/crossheading/tree-felling-and-planting/enacted

[3] Bristol Core Strategy, policy BCS9 states that, “Individual green assets should be retained wherever possible and integrated into new Developments.”

[4] See the Avon Crescent Application pp136 – 155 https://democracy.bristol.gov.uk/documents/g10675/Public%20reports%20pack%2010th-May-2023%2014.00%20Development%20Control%20B%20Committee.pdf?T=10

Our proposal for a new Bristol Tree Replacement Standard using Biodiversity Metric 4.0

The latest version of the Biodiversity Metric (BNG 4.0), just published by Natural England, is likely to become mandatory when the balance of the Environment Act 2021 comes into force later this year. We have revisited our June 2022 proposals and reviewed our calculations. Here is the revised version.

The Bristol Tree Replacement Standard (BTRS), adopted a decade ago, provides a mechanism for calculating the number of replacements for any trees that are removed for developments. It was ground-breaking in its time as it, typically, required more than 1:1 replacement of trees lost to development.

The presumption when considering any development involving established trees should always be that trees will be retained. The application of BTRS should only ever be a last resort. It should not be the default choice which it seems to have become.

The starting point for any decision on whether to remove trees (or any other green asset for that matter) is the Mitigation Hierarchy. Paragraph 180 a) of the National Planning Policy Framework sets it out as follows:

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, then planning permission should be refused.[1]

BTRS is and should always be ‘a last resort’. This is reflected in the Bristol Core Strategy, policy BCS9 adopts this approach and states that:

Individual green assets should be retained wherever possible and integrated into new developments.[2]

However, with the development of a new Local Plan for Bristol, we believe that the time has come for BTRS to be revised to reflect our changing understanding of the vital importance of urban trees to Bristol in the years since the final part (SADMP) of the Local Plan was adopted in 2014.

In addition, Bristol has adopted Climate and Ecological Emergency Declarations so a new BTRS will be an important part of implementing these declarations. Nationally, the Environment Act 2021 (EA 2021) will come force later this year. This will require nearly all developments to achieve a Biodiversity Net Gain (BNG) of at least 10%. Our proposal provides a mechanism for complying with this new requirement and so aligns BTRS with the BNG provisions of the EA 2021.

Background

Under current policy – BCS9 and DM17[3] – trees lost to development must be replaced using this table:

Table 1 The Current DM17/BTRS replacement tree table.

However, when the balance of EA 2021 takes effect, the current version of BTRS will not, in most cases, be sufficient to achieve the 10% BNG minimum that will be required for nearly all developments. A new section 90A will be added to the Town and Country Planning Act 1990 and  set out the level of BNG required (see Schedule 14 of EA 2021).

The Local Government Association says of BNG that it:

…delivers measurable improvements for biodiversity by creating or enhancing habitats in association with development. Biodiversity net gain can be achieved on-site, off-site or through a combination of on-site and off-site measures.[4]

GOV.UK says of the Biodiversity Metric that:

where a development has an impact on biodiversity, it will ensure that the development is delivered in a way which helps to restore any biodiversity loss and seeks to deliver thriving natural spaces for local communities.[5]

This aligns perfectly with Bristol’s recent declarations of climate and ecological emergencies and with the aspirations of the Ecological Emergency Action Plan,[6] which recognises that a BNG of at least 10% net gain will become mandatory for housing and development and acknowledges that:

These strategies [the Local Nature Recovery Strategies] will guide smooth and effective delivery of Biodiversity Net…

Our proposed new BTRS model

We propose that the Bristol Tree Replacement Standard be amended to reflect the requirements of the EA 2021 and BNG 4.0 and that the BTRS table (Table 1 above) be replaced with Table 2 below:

The Replacement Trees Required number is based on the habitat area of each of the three BNG 4.0 tree category sizes (Table 8-1 below) divided by the area habitat of one BNG 4.0 Small category tree (see section 3 below) plus a 10% net gain. This is rounded up to the nearest whole number – you can’t plant a fraction of a tree.

The reasoning for our proposal is set out below.

Applying the Biodiversity Metric to Urban trees

The most recent Biodiversity Metric (BNG 4.0) published by Natural England this April, defines trees in urban spaces as Individual trees called Urban tree habitats. The User Guide states that:

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.

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.

Calculating Individual trees habitat

Table 8-1 in the BNG 4.0 user guide is used to calculate the ‘area equivalent’ of individual trees:

Note that the tree’s stem diameter will still need to be ascertained using BS:5837 2012,[7] and that any tree with a stem diameter (DBH) 7 mm or more and of whatever quality (even a dead tree, which offers its own habitat benefits) is included. Under the current DM17/BTRS requirement, trees with a DBH smaller than 150 mm are excluded, as are BS:5837 2012 category “U” trees. This will no longer be the case.

The Rule 3 of the BNG User guide makes it clear that like-for-like replacement is most often required, so that lost Individual trees (which have Medium distinctiveness) are to be replaced by Individual trees rather than by other habitat types of the same distinctiveness.[8]

Forecasting the post-development habitat area of new Individual trees

The BNG 4.0 User Guide provides this guidance:

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.

Our calculations are based on ‘small’ category replacement trees being planted.

The likely impact of this policy change

We have analysed tree data for 1,038 surveyed trees taken from a sample of BS:5837 2012 tree surveys submitted in support of previous planning applications. Most of the trees in this sample, 61%, fall within the BNG 4.0 Small range, 38% are within the Medium range, with the balance, 1%, being categorised as Large.

Table 4 below sets out the likely impact of the proposed changes to BTRS. It assumes that all these trees were removed (though that was not the case for all the planning applications we sampled):

The spreadsheet setting out the basis of our calculations can be downloaded here – RPA Table BNG 4.0 8-1 table Comparison.

Our proposed changes to BTRS are set out in Appendix 1.

A copy of this article is available here.

Appendix 1 – Our proposed changes to BTRS

See the Planning Obligations Supplementary Planning Document at page 20.

Trees – Policy Background

The justification for requiring obligations in respect of new or compensatory tree planting is set out in the Environment Act 2021, Policies BCS9 and BCS11 of the Council’s Core Strategy and in DM 17 of the Council’s Site Allocations and Development Management Policies.[9]

Trigger for Obligation

Obligations in respect of trees will be required where there is an obligation under the Environment Act 2021 to compensate for the loss of biodiversity when Urban tree habitat is lost as a result of development.

Any offsite Urban tree habitat creation will take place in sites which are either on open ground or in areas of hard standing such as pavements and are located as close as possible to the site of the lost tree.

Where planting will take place directly into open ground, the contribution will be lower than where the planting is in an area of hard standing. This is because of the need to plant trees located in areas of hard standing in an engineered tree pit.

All tree planting on public land will be undertaken by the council to ensure a consistent approach and level of quality, and to reduce the likelihood of new tree stock failing to survive.

Level of Contribution

The contribution covers the cost of providing the tree pit (where appropriate), purchasing, planting, protecting, establishing and initially maintaining the new tree. The level of contribution per tree is as follows:

  • Tree in open ground (no tree pit required) £765.21
  • Tree in hard standing (tree pit required) £3,318.88[10]

The ‘open ground’ figure will apply where a development results in the loss of Council-owned trees planted in open ground. In these cases, the Council will undertake replacement tree planting in the nearest appropriate area of public open space.

In all other cases, the level of offsite compensation required will be based on the nature (in open ground or in hard standing) of the specific site which will has been identified by the developer and is approved by the Council during the planning approval process. In the absence of any such agreement, the level of contribution will be for a tree in hard standing.

The calculation of the habitat required to compensate for loss of Urban trees is set out in Table 8-1 of the Biodiversity Metric (BNG), published by Natural England. This may be updated as newer versions of BNG become mandatory under the Environment Act 2021.

The following table will be used when calculating the level of contribution required by this obligation:

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

[2] https://www.bristol.gov.uk/files/documents/64-core-strategy-web-pdf-low-res-with-links/file at page 74.

[3] https://www.bristol.gov.uk/files/documents/5718-cd5-2-brislington-meadows-site-allocations-and-development-management-policies/file page 36.

[4] https://www.local.gov.uk/pas/topics/environment/biodiversity-net-gain.

[5] https://www.gov.uk/government/news/biodiversity-30-metric-launched-in-new-sustainable-development-toolkit.

[6] https://www.bristol.gov.uk/documents/20182/5572361/Ecological_Emergency_Action_Plan.pdf/2e98b357-5e7c-d926-3a52-bf602e01d44c?t=1630497102530.

[7] https://knowledge.bsigroup.com/products/trees-in-relation-to-design-demolition-and-construction-recommendations/standard

[8] Table 3-2 Trading rules (Rule 3) to compensate for losses. Any habitat from a higher distinctiveness band (from any broad habitat type) may also be used.

[9] These references may need to be changed to reflect any replacement policies adopted with the new Local Plan.

[10] These values should be updated to the current rates applicable at the time of adoption. The current indexed rates as of May 2023 are £1,143.15 & £4,958.07 respectively.

Trees for Streets – will we see more trees being planted in more Bristol streets? Hopefully.

You will all have seen young trees planted in vacant tree pits in the streets of Bristol. These trees are replacement trees. There was once a tree growing there before – maybe some time ago.

These replacement trees are paid for by sponsorship, or by funds paid by Developers when they have felled trees on a building site and there is no room to replace the felled trees on the building site. In the latter case more than one tree has been “lost” – the one on the building site and the one that was previously in the tree pit.

In order to increase Bristol’s tree canopy – vital in this time of a climate emergency – we must see trees being planted in new places as well as getting all the “old” sites being filled more quickly.

Trees for Streets

To try to get this initiative going, Bristol has joined Trees for Streets.

Quotes from the Flyer for Trees for Streets

‘Bristol City Council has joined the Trees for Streets national street tree sponsorship scheme, which aims to plant thousands of additional trees in streets and parks across the city, by supplementing the council’s tree budgets through public and corporate sponsorship.’

and

‘Trees for Streets is the National Street Tree Sponsorship Scheme from the urban tree charity Trees for Cities, funded by the government’s Green Recovery Challenge Fund and City Bridge Trust. The project uses technology to empower people and makes it easy for residents and organisations to get involved in greening their communities.’

and

‘Our mission is to fund the planting of more than 250,000 additional street trees nationwide over the next ten years by hosting online tree sponsorship schemes on behalf of local councils and delivering local promotion and engagement activity to bring these schemes to life.’

Comment

Bristol has long had a Tree Sponsorship scheme, run by TreeBristol (part of Bristol City Council).

In the 2021/2022 planting season £456,000 was spent by Bristol Council in planting of trees. A portion of this money is retained by BCC for maintaining the trees planted 55% of this money came from mitigation funds paid by Developers who had felled trees somewhere in the city in order to build on the land released. (So, the money was not being spent on NEW trees, just on replacements).

10% of that money came from sponsorship, with 6.5% coming from private sponsorship (individuals and groups) and 3.5% coming from business sponsorship. Even then a lot of that money was spent on replacing trees which had been lost i.e., not on providing trees in new sites. It is a difficult “sum” to achieve. Money from Developers is for the replacement of trees lost to development. The Bristol Tree Replacement Standard achieves an amount for replacement trees based on the size of the trees lost. Eventually the trees may grow to a size which more than compensates for the environmental value of trees lost. But it remains true that each replacement tree goes in to a tree site that has lost a tree formerly growing there – so the Council is spared the expense of replacing lost trees that it owned.

Representatives of the Bristol Tree Forum have attended two meetings now where this new scheme has been explained and described.

The Trees for Streets scheme is not going to fund the trees, nor plant the trees, so we would have worded the sentence “Our mission is to fund the planting of more than 250,000 additional street trees…….” slightly differently with instead “Our mission is to facilitate and organise the funding of the planting of more than 250,000 additional street trees…”

The Trees for Streets scheme is similar to Bristol’s former scheme in that it will provide a web based choosing and ordering and paying for system, whereby residents and organisations and businesses can find available tree sites for planting trees in Streets and Parks.

There are differences between the Trees for Streets Scheme and Bristol’s former scheme, and they are:

  • Bristol’s former sponsorship scheme was largely one of replacement for trees lost. A sponsor (an individual, a group or a business) would select, from the Council’s mapping, a site where formerly there had been a tree, and would pay for its planting. New site planting came from One Tree per Child (whips) or from national grants where Bristol would win a bid for a grant and spend the money.
  • The new scheme hopes to facilitate, through sponsorship, the planting of a new tree in a new site. These sites have to be found, and checked for Services (underground utility provision), and then put forward in the Council mapping for planting with a tree.
  • Residents, and other types of sponsor, will be able to suggest new sites for trees by answering the question “Where would you like to see a tree planted?” with their own suggestions.
    The sponsor would need to pay for the tree, but Trees for Streets might be able to assist with organising the funding, using their funding know how.
  • Initially this kind of new planting of Street Trees will only be possible in streets that currently have green verges, or in new sites in Parks.
  • (Trees in “hard ground” – pavements, plazas, city squares, etc. will need to be planted in engineered tree pits – and that is expensive. If a sponsor (which can be an individual, a group or a business) is prepared to meet that cost, then efforts will be made to agree suitable sites and then check them for Services and other criteria, such as the width of the pavement.)
  • Trees for Streets has national funding and this gives it an improved platform with web support and advertising which could see many more trees sponsored. Maybe businesses reached by the advertising will see a role in supporting tree planting in the more “tree poor” areas of Bristol?
  • Bristol is to offer residents the option to water their sponsored tree when it is outside their property – at a reduced cost (£160/tree v £295/tree).  It gives people an option at a lower cost – and it avoids trucks driving about with lots of water in a bowser.  It has worked elsewhere, and Bristol is going to try it.
  • DEFRA has provided funds for the setting up of Trees for Streets, and maybe future DEFRA grants will be channelled through this new national scheme. Bristol has, by making individual bids, obtained grants for tree planting from DEFRA in the past, and will still want to continue to make these bids for new funding for the actual purchase and planting of trees for new sites.

How it will work:

  1. Go to the Trees for Streets website at https://treesforstreets.org.bristol.
  2. Choose the location of your tree from the map or suggest a spot in a grass verge in your street or neighbourhood. The questions on the website take you through the choices.
  3. Answer a few questions about the location and you.
  4. If all works out your tree will be planted during the next available planting season.

Bristol Tree Forum’s Tree Champions are to be offered training from Bristol’s Tree Officers so that they can help residents, organisations and businesses with determining the suitability of sites that are suggested.

Our proposal for a new Bristol Tree Replacement Standard

The Bristol Tree Replacement Standard (BTRS), which was adopted nearly a decade ago in 2013, provides a mechanism for calculating the number of replacements for any trees that are removed for developments. It was ground-breaking in its time as it typically required more than 1:1 replacement.

The presumption should always be that trees should be retained. The application of BTRS should only ever be a last resort. It should not be the default choice, which it seems to have become.

The starting point for any decision on whether to remove trees (or any other green asset) is the Mitigation Hierarchy[2] which states, firstly, avoid; then, if that is not possible, minimise; then, if that is not possible, restore; and, as a last resort, compensate (the purpose or BTRS). BCS9 adopts this approach and states that:

Individual green assets should be retained wherever possible and integrated into new developments.

However, with the emergence of a new Local Plan for Bristol, we believe that the time has come for BTRS to be revised to reflect our changing understanding of the vital importance of trees to the city in the years since the last version of the Local Plan was adopted in 2014.

In addition, Bristol has adopted Climate and Ecological Emergency Declarations so a new BTRS will be an important part of implementing these declarations. Nationally, the new Environment Act 2021 (EA 2021) is coming into force late next year.

Our proposal provides a mechanism for complying with the new legal requirement for 10% Biodiversity Net Gain (BNG) which will be mandatory when EA 2021 takes effect.

Background

Under current policy – BCS9 and DM17 – trees lost to development must be replaced using this table:

Table 1 The Current BTRS replacement tree table

However, when the balance of the Environment Act 2021 (EA 2021) takes effect late in 2023, the current version of BTRS will not, in most cases, be sufficient to achieve the 10% biodiversity net gain (BNG) that will be required for nearly all developments. Section 90A will be added to the Town and Country Planning Act 1990 and will set out the level of biodiversity net gain required ( Schedule 14 of the EA 2021).

The Local Government Association says of BNG that it:

…delivers measurable improvements for biodiversity by creating or enhancing habitats in association with development. Biodiversity net gain can be achieved on-site, off-site or through a combination of on-site and off-site measures.[3]

GOV.UK says of the Biodiversity Metric that:

where a development has an impact on biodiversity, it will ensure that the development is delivered in a way which helps to restore any biodiversity loss and seeks to deliver thriving natural spaces for local communities.[4]

This aligns perfectly with Bristol’s recent declarations of climate and ecological emergencies and with the aspirations of the Ecological Emergency Action Plan,[5] which recognises that a BNG of 10% net gain will become mandatory for housing and development and acknowledges that:

These strategies [the Local Nature Recovery Strategies] will guide smooth and effective delivery of Biodiversity Net…

Our proposed new BTRS model

We propose that the Bristol Tree Replacement Standard be amended to reflect the requirements of the EA 2021 and BNG 3.1 and that the BTRS table (Table 1) be replaced with Table 2 below:

Table 2 The proposed new BTRS tree replacement table

The Replacement Trees Required number is based on the habitat area of each of the three BNG 3.1 tree categories (Table 7-2 below) divided by the area habitat of one 30-year old BNG 3.1 Small tree (Table 3 below) plus 10% net gain. This is rounded up to the nearest whole number since you can’t plant a fraction of a tree.

The reasoning for our proposal is set out below:

Applying the Biodiversity Metric to Urban trees

The most recent Biodiversity Metric (BNG 3.1) published by Natural England, defines trees in urban spaces as Urban tree habitats. The guidance states that:

the term ‘Urban tree’ applies to all trees in urban situations. Urban trees may be situated within public land, private land, institutional land and land used for transport functions.

Table 7-1 divides Urban tree habitats into three categories:

Paragraph 8.5 of the 3.1 BNG Guidance makes it clear that lines of trees in an urban environment should not be treated as a linear habitat:

Urban trees are considered separately to lines of trees in the wider environment, since they generally occur in an urban environment surrounded by developed land. 

Calculating Urban tree habitat

Urban tree baseline habitat area is measured in hectares and is based on the Root Protection Area[7] (RPA) of each tree impacted by a proposed development. RPA is used instead of tree canopy because it is considered to be the best proxy for tree biomass.

In most cases, RPA is obtained from an Arboricultural Impact Assessment (AIA), which complies with British Standard 5837 2012 – Trees in relation to design, demolition and construction (BS:5837).

Where no AIA is available, Table 7-2 is used:

Note that the tree’s size will still need to be ascertained, and that any tree with a stem diameter (DBH) 75mm or more and of whatever quality (even a dead tree, which offers its own habitat benefits) is included . Under BTRS, trees with a DBH smaller than 150 mm are excluded, as are BS:5837 category “U” trees.

The guidance also makes it clear that, given the important ecosystem services value provided by trees, where possible like-for-like compensation is the preferred approach, so that lost Urban trees are replaced by Urban trees rather than by other types of urban habitat.[8]

Replacing lost trees

To calculate the number of trees required to replace Urban tree habitat being lost, table 7-2 above is used on this basis:

Size classes for newly planted trees should be classified by projected size at 30 years from planting.

We have used the median DBH sizes for new stock trees as set out in BS 3936-1: Nursery Stock Specification for trees and shrubs as the basis for calculating the eventual size of a newly planted trees after 30 years and assumed that a tree adds 2.54 cm (1”) to its girth annually.

This results in a predicted stock tree size after 30 years’ growth. This is then assigned to one of the three Urban tree categories set out in table 7-2: Small, Medium or Large. In all cases save for Semi-mature tree stock, the eventual size of stock trees after 30 years falls within the BNG 3.1 size category Small, which has a habitat area of 0.0041 hectares. This value is then used to calculate how many new trees will be required to replace trees lost to the development, plus a 10% biodiversity net gain. This gives a compensation size per replacement tree of 0.0045 ha (0.0041 hectares + 10%).

Table 3 below shows the basis our our calculation:

Table 3 Annual stock tree growth predictions

The Trading Rules

It may be that a notional positive biodiversity net gain can be achieved by replacing fewer trees than this analysis indicates. However, this is not enough. The calculation should also comply with the Trading Rules that apply to Urban tree habitats.

Paragraph 7.6 of the 3.1 BNG Guidance states:

The mitigation hierarchy and trading rules apply to Urban trees. Given Urban trees are a ‘Medium’ distinctiveness habitat, trading rules stipulate that the same broad habitat type (or a higher distinctiveness habitat) is required. However, given the important ecosystem services value provided by trees, where possible ‘like for like’ compensation is the preferred approach (i.e. where possible any loss of Urban trees should be replaced by Urban trees – rather than other urban habitats).

Rule 3 of the User Guide states: ‘”Trading down’ must be avoided. Losses of habitat are to be compensated for on a ‘like for like’ or ‘like for better’ basis. New or restored habitats should aim to achieve a higher distinctiveness and/or condition than those lost…’

The likely impact of this policy change

We have analysed tree data for 1,038 surveyed trees taken from a sample of AIAs submitted in support of previous planning applications. Most of the trees in this sample, 61%, fall within the BNG 3.1 Small range, 38% within the Medium range, with the balance, 1%, categorised as Large.

Table 4 below sets out the likely impact of the proposed changes to BTRS. It assumes that all these trees were removed (though that was not the case for all the planning applications we sampled):

Table 4 Proposed BTRS impact analysis

The spreadsheet setting out the basis of our calculations can be downloaded here – RPA Table 7-2 Comparison.

Our proposed changes to BTRS (published in the Planning Obligations Supplementary Planning Document, page 20) are set out in Appendix 1.

This article was amended on 7 November 2022 to include references to Lines of Trees in the urban environment, the application of the Trading Rules to Urban tree habitats and fix a broken link.

Appendix 1

Our proposed changes to BTRS, set out in the Planning Obligations Supplementary Planning Document, page 20.

Trees – Policy Background

The justification for requiring obligations in respect of new or compensatory tree planting is set out in the Environment Act 2021, Policies BCS9 and BCS11 of the Council’s Core Strategy and in DM 17 of the Council’s Site Allocations and Development Management Policies.

Trigger for Obligation

Obligations in respect of trees will be required where there is an obligation under the Environment Act 2021 to compensate for the loss of biodiversity when Urban tree habitat is lost as a result of development.

Any offsite Urban tree habitat creation will take place in sites which are either on open ground or in areas of hard standing such as pavements.

Where planting will take place directly into open ground, the contribution will be lower than where the planting is in an area of hard standing. This is because of the need to plant trees located in areas of hard standing in an engineered tree pit.

All tree planting on public land will be undertaken by the council to ensure a consistent approach and level of quality, and to reduce the likelihood of new tree stock failing to survive.

Level of Contribution

The contribution covers the cost of providing the tree pit (where appropriate), purchasing, planting, protecting, establishing and initially maintaining the new tree. The level of contribution per tree is as follows[9]:

  • Tree in open ground (no tree pit required) £765.21
  • Tree in hard standing (tree pit required) £3,318.88

The ‘open ground’ figure will apply where a development results in the loss of Council-owned trees planted in open ground. In these cases, the Council will undertake replacement tree planting in the nearest appropriate area of public open space.

In all other cases, the level of offsite compensation required will be based on the nature (in open ground or in hard standing) of the specific site which will has been identified by the developer and is approved by the Council during the planning approval process. In the absence of any such agreement, the level of contribution will be for a tree in hard standing.

The calculation of the habitat required to compensate for loss of Urban trees is set out in Table 7-2 of the Biodiversity Metric (BNG), published from time to time by Natural England. This may be updated as newer versions of BNG are published.

The following table will be used when calculating the level of contribution required by this obligation:

A copy of this blog can be downloaded here:

BTF proposal for a new Bristol Tree Replacement Standard

[1] Biodiversity Metric 3.1 – Auditing and accounting for biodiversity – USER GUIDE.

[2] https://nationalzoo.si.edu/ccs/mitigation-hierarchy.

[3] https://www.local.gov.uk/pas/topics/environment/biodiversity-net-gain.

[4] https://www.gov.uk/government/news/biodiversity-30-metric-launched-in-new-sustainable-development-toolkit.

[5] https://www.bristol.gov.uk/documents/20182/5572361/Ecological_Emergency_Action_Plan.pdf/2e98b357-5e7c-d926-3a52-bf602e01d44c?t=1630497102530.

[6] DBH = Diameter at Breast Height. RPAr = Root Protection Area radius. Area = the calculated BNG habitat area.

[7] RPA area = π × r2 where r is 12 x the tree’s DBH for a single stemmed tree. For multi-stemmed trees, the DBH of the largest stem in the cluster should be used to determine r.

GOV.UK advice is that r should be at least 15 times larger than DBH – https://www.gov.uk/guidance/ancient-woodland-ancient-trees-and-veteran-trees-advice-for-making-planning-decisions.

The Woodland Trust also recommends that r be set to 15 x DBH for ancient and veteran trees – https://www.woodlandtrust.org.uk/blog/2021/04/root-protection-areas.

[8] Paragraph 7.8 – Trading Rules.

[9] These values should be updated to the current rates applicable at the time of adoption. The current indexed rates as of April 2022 are £1,041.6 & £4,517.89 respectively.

[10] DBH = Diameter at Breast Height. RPAr = Root Protection Area radius. Area = the calculated BNG habitat area.

Hundreds of trees threatened at Hengrove Park

The Council’s Development Control A Committee will meet at 6 pm on Wednesday, 16th October at The City Hall to decide the fate of more than 850 parkland trees. We have submitted this statement:

Hengrove Park is just under 51.5 hectares in area and contains 545 mapped trees comprising 37 species. There are many more unmapped trees also growing there.

These trees have a Capital Asset Valuation of Amenity Trees (CAVAT) (One of a range of tools recommended by The Trees and Design Action Group (TDAG) for valuing trees and green infrastructure ) value of at least £5.2 million, a valuation which is based on measurements of the tree diameters made at least 10 years ago. In the meantime, the trees will have continued to grow, making the current CAVAT value even greater.

The Bristol Tree Forum (BTF) was not consulted about the proposed development of this site, which will result in the removal of hundreds of these trees. Many local residents have submitted comments expressing concern about this aspect of the development.

BTF’s starting position is that trees should not be felled if at all possible, and that everything that can reasonably be done to avoid this should always be considered before a felling decision is made. If trees must be felled, then compensatory planting should be undertaken in such a way that there is no net environmental loss.

In order to implement the Council’s recent declaration of a climate emergency, increase net biodiversity and help double tree canopy cover, this development needs to be redesigned to fit around the existing trees, not remove them.

The current documents make various assertions as to the numbers of trees to be lost and the calculations for replacements required under the Bristol Tree Replacement Standard. This can be addressed by the imposition of our proposed planning conditions (see below).

Implementing Bristol’s declaration of a climate emergency

Bristol City Council was the first UK local authority to declare a climate emergency. As Professor Corinne Le Quéré FRS has said, “Actions to tackle climate change have to penetrate all the decisions that we take in society.”

The Government’s 25-year environment plan states that it will strengthen existing requirements for net gain for biodiversity in national planning policy. As it is, we have calculated (appendix 1) that this scheme, if permitted, will result in a net environmental loss of just over £3.65 million – Our CAVAT valuation of the trees potentially lost to this development is nearly £3.8 million (point 8 of Appendix 1). If the figures for tree felling relied on by the Council are accepted, then the figure will be much higher.

Bristol also has ambitious plans to double its tree canopy by 2046. If it is to implement this, and is serious about its declaration of a climate emergency, and wishes to achieve a net gain in biodiversity, then developments like this need to be radically rethought so that we build houses around existing trees rather than felling them, thereby avoiding or at least minimising the loss of our precious existing tree stock.

In addition, we note that the plan is also to remove a row of black poplar trees, a key landscape feature of the site. This is contrary to Policy BCS9 of the Bristol Core Strategy.

Conflicting figures for the calculation of replacement trees under the Bristol Tree Replacement Standard

The figures for the number of trees to be felled differ within the various planning documents and the BTRS calculations are confusing. We address this in detail at Appendix 1.

A technical note (23rd September 2019) identifies 859 trees to be felled, to be replaced by 1,280 new trees.  Elsewhere in the note, a table lists the values given for each BTRS category, which come to a total of 181 trees to be felled with 294 replacements. The table produced at paragraph 5.5.17 of the Environmental Statement Addendum gives different values again – 674 trees to be felled with 986 replacements.

These serious discrepancies need to be resolved before the Committee can form any clear idea of the impact of this development on the park’s trees. We propose a number of planning conditions, set out below, to ensure that the BTRS calculations are correctly made.

We are also concerned to read the Tree Officer’s report which states “As a number of the proposed trees are extra heavy standards it is considered that these can count as three new trees and overall the BTRS is met”.  This is simply wrong. The BTRS contains no such protocol.

The care of replacement trees after planting

Many trees that have been planted as a result of large schemes like this fail because they are not properly looked after.  A recent example is the Metrobus scheme, in which large numbers of trees were planted but have failed, probably due to lack of watering or, in some cases, vandalism. As far as we are aware, Metrobus (the developer) has not given any indication that it will replace these lost trees.

In our view, any replacement planting must be done under British Standard BS8545:2104 (Trees: from nursery to independence in the landscape) with a detailed specification in these terms being made a condition of the development. This should include a clear obligation placed on the developer to replace trees which fail within, say, five years of planting.

Planning conditions requested by BTF

The information that has been used to undertake the BTRS calculation is both incorrect and two years out of date.

If the Committee allows this proposal to proceed despite this, we request that the following planning conditions be imposed:  

  • No felling and replacement of any of the trees on the site should take place unless and until an updated survey is undertaken and the actual numbers and DBH values of all the trees (both individually and in groups) identified for felling are ascertained.
  • The BTRS replacements required are agreed with the Bristol Tree Forum and a Planning Arboricultural Officer.
  • All tree planting conforms with British Standard BS8545:2104 (Trees: from nursery to independence in the landscape).
  • A condition of the development includes a clear obligation on the developer to replace trees which fail within, say, five years of planting.

Here is the full statement we have submitted – BTF Full Statement, plus the one page summary that we have been asked to submit for the committee meeting – BTF Summary Statement.

We also link to the Statement submitted by Treespect which we wholly endorse.

You can link to the Council’s application here, via our BTF Planning Portal – 19/02632/PB.

Appendix 1

The application of BTRS requires that the trunk diameter (called Diameter at Breast Height, or DBH) of each tree identified for felling be measured. This measurement is then used to calculate the number of trees to be planted as replacements for the felled tree using this table:

This planning application is based on a tree survey that was undertaken some time in November 2017 and set out in an Arboricultural Impact Assessment dated May 2019. Part of this survey was updated in Appendix C of an Environmental Statement Addendum dated 4th September 2019. However, the DBH values have not been changed, so these values are now two years out of date. The trees will have grown in the meantime.

There is also a technical note dated 23rd September 2019 which identifies 859 trees to be felled, to be replaced by 1280 new trees. The following table is produced on page 5 of this note:

However, the values given for each BTRS category come to a total of 181 trees to be felled with 294 replacements, not the totals shown above.

The table produced at paragraph 5.5.17 of the Environmental Statement Addendum gives different values again: 674 trees to be felled with 986 replacements. However, this excludes the number of individual trees within groups G1, G354, G355, G380 and G417, so it is impossible to make any like-for-like comparison.

Having collated the two surveys published in the Arboricultural Impact Assessment and in Appendix C of the Environmental Statement Addendum into a spreadsheet (click here to download), we note the following:

  1. 533 individual trees have been identified and their DBH values recorded. Of these, 167 are identified for felling.
  2. 43 tree groups have also been identified, 13 of which are listed for removal or part removal.
  3. Save for groups G347, G347b and G347c (which have 5, 24 and 7 trees respectively in them) the number of trees in each group (or the number of trees to be removed) is not given.
  4. Save for groups G347, G347b and G347c (which have 5, 22 and 7 DBH values respectively listed), only one DBH value is given for each group.
  5. If we assume one tree per species listed for each unnumbered group,[1] then 228 trees in total are identified for felling.
  6. This produces a BTRS value of 294 replacement trees (again, if we assume one tree per species for each unnumbered group and that all these trees have the same DBH[2] as that given).
  7. Of the trees surveyed, 176 are given an ‘Estimated Remaining Contribution’ (life expectancy) of 10+ years; 46 have a life expectancy of 20+ years; and the remaining six have <10 years of life left. These 10+ and 20+ values are meaningless as they give no upper range. The CAVAT approach is to set life expectancy within these bands:
    • <5 years.
    • >=5 & <10 years.
    • >=10 & <20 years.
    • >=20 & <40 years.
    • >=40 & <80 years.
    • >=80 years.
  8. Applying a life expectancy of between 40 and 80 years and a CTI factor for Bristol of 150,[3] we calculate that the 228 trees we have identified for felling have a CAVAT value of £3,784,282. Using the same factors, the 294 BTRS trees (assuming standards with a DBH of 5 cm) would have a CAVAT value of £134,184, a net environmental loss of £3,653,652.

[1] We accept that each group probably contains more trees than our working assumption.

[2] We accept that the DBH values will vary from tree to tree.

[3] A CTI factor is applied to the base CAVAT value to account for population density. Bristol has a population of 459,300 and a land area of 10,970 hectares. This gives a population density per hectare of 41.9 and so a CTI Index of 150.

Changes agreed to Bristol Tree Replacement Standard

‘Only when the last tree has died, and the last river has been poisoned and the last fish has been caught, will we realise that we cannot eat money.’ – A Cree Indian speaking in the 19th Century.

Members of the Bristol Tree Forum (BTF) recently met with senior Planning Officers and the two Arboricultural Officers working in the Department. We wanted to raise a number of planning issues that have been concerning us.

The Bristol Tree Replacement Standard (known as BTRS – you can find it at page 21 of the Council’s Planning Obligations Supplementary Planning Document) is a flagship policy copied by other planning authorities. Bristol should be proud of it. We are because it goes a long way towards making sure that trees and tree canopy lost to development is replaced at the expense of the developers.

This is how the BTRS formula is applied (the diameters shown are in centimetres):

However, in the years since its inception about ten years ago it has become apparent to us that the policy could be improved if some changes to the way it is applied were made to it. Two things that have particularly concerned us are:

Firstly, it had become apparent that developers and householders developing land in Conservation Areas were avoiding their obligation to mitigate tree loss by submitting two separate planning applications – the first for the trees to be felled (usually for some spurious reason), then, months later, a substantive application to develop the now tree-free land.

Outside Conservation Area, where there is no protection for trees (unless they have a TPO) at all, the trees were simply being felled, sometimes in large numbers, some time before an application to develop the land was submitted.

In either situation, if the development was permitted, the trees were lost, never to be replaced, because the loss was not considered to be “in association with” the development of the land.

Secondly, if developers or householders were developing land and the BTRS was being applied, we noticed that in some cases, hedging was being approved as a replacement for the lost tree canopy. Whilst grand hedging might indeed be appropriate as part of the planning proposal – say as screening or as a pollution mitigation measure – we do not believe that it can ever be used as an adequate substitute for lost tree canopy.

In particular, we noticed that this option was being proposed by those developers who had filled nearly all of the site so that there was little, or no room left for replacement tree planting on site. In our view this was being done to avoid having to pay the Council (us really) for replacement trees to be planted nearby.

We are pleased to report that, after several meetings with Officers to discuss our concerns, the following has finally been agreed:

  1. Where there is evidence of prior felling, BTRS will be applied retrospectively to include all trees felled within the year before the planning application. In this way any trees felled before the development will be taken into account when considering the application of BTRS.
  2. Other than in exceptional circumstances, hedges will no longer be acceptable as mitigation for tree canopy loss when applying BTRS.
  3. If council officers think it is necessary, these new protocols will be written into the Council’s Planning Practice Note so that there is no possibility of any future misunderstandings by either developers or planning officers how BTRS is the be applied.

BTF has more ideas which we believe will strengthen the application of BTRS (for instance, why should trees under 15 cm not be replaced?; should BTRS be applied in non-development tree felling applications?) . We will continue to advocate for these and other possible changes.

We accept that there is always going to be development, but we must try to ensure that the city’s tree cover is, at the very least, protected and maintained in keeping with SDG 15 – Life on Land of the One City Plan Sustainable Development Goals which commit to doubling tree canopy cover by 2046.