Trees valued at over £4.6m are under threat at Bonnington Walk, Lockleaze

Whatever the merits of this application of achieving its primary goal to provide much needed housing may be, it should not be permitted to proceed unless and until it has properly addressed how it will replace and build upon the Green Infrastructure (including trees) that will inevitably be lost if this application proceeds as presently formulated.


Summary of our submission

We object to this application for the following reasons.

Bristol City Council has:

Declared climate and environmental emergencies.

Committed to becoming carbon neutral by 2030.

Committed to doubling tree canopy cover by 2046.

As currently formulated, these plans to build new houses can only set back the work needed to resolve these emergencies and achieve these commitments.

  1. The need to build housing to meet sustainable economic or social development objectives should not be allowed to take precedence over ensuring that the development is also both environmentally sustainable and meets Net Gain objectives.
  2. Whatever the merits of this application of achieving its primary goal to provide much needed housing may be, it should not be permitted to proceed unless and until it has properly addressed how it will replace and build upon the Green Infrastructure (including trees) that will inevitably be lost if this application proceeds as presently formulated.
  3. The existing trees have a significant asset value which should not lightly be ignored. Using CAVAT, we have valued them at £4,674,918.
  4. Under the Mitigation Hierarchy, trees should not be removed unless there is no realistic alternative. One alternative would be to build around the trees rather than remove them.
  5. BCS9 of the Core Strategy also states that “Individual green assets should be retained wherever possible and integrated into new development”. Clear felling nearly all the trees to the east of the cycle/footpath should not, as it so often is, be the default option.
  6. Trees should not be removed merely because they are diseased or self-sown, or because they are small or not perfect specimens of their species.
  7. The removal of existing trees inevitably means that the eco-services they provided will not be replaced for decades, if at all.
  8. The adverse knock-on environmental impact on biodiversity of removing existing trees far outweighs any short-term benefits achieved by replacing them.

Our submission

The planning background

The National Planning Policy Framework

The National Planning Policy Framework (NPPF) seeks to ensure that new development is sustainable. It stresses the importance of Green Infrastructure as one of three overarching, interdependent objectives – economic, social, and environmental. This means that the presumption in favour of sustainable environmental development is just as important as any in respect of economic or social development objectives.

Trees are an integral part of this because of the importance of trees in relation to the management of air, soil and water quality along with other associated ecosystem services, climate change adaptions and beneficial health effects. The NPPF also seeks to achieve the protection and enhancement of landscapes and achieve Net Gain in biodiversity.

The Natural England Joint Publication JP029 – Biodiversity Metric 2.0 (BDM2) provides a way of measuring and accounting for biodiversity losses and gains resulting from development or land management change. It defines Net Gain as an:

“approach to development that aims to leave the natural environment in a measurably better state than beforehand. This means protecting existing habitats and ensuring that lost or degraded environmental features are compensated for by restoring or creating environmental features that are of greater value to wildlife and people. It does not change the fact that losses should be avoided where possible, a key part of adhering to a core environmental planning principle called the mitigation hierarchy.”

The Mitigation Hierarchy

Avoid – Where possible habitat damage should be avoided.

Minimise – Where possible habitat damage and loss should be minimised.

Remediate – Where possible any damage or lost habitat should be restored.

Compensate – As a last resort, damaged or lost habitat should be compensated for.

This is a cascading decision process – only if the preceding choice is unavailable is the next considered.

Local Planning Authorities (LPA) in the UK have a statutory duty to consider both the protection and planting of trees when considering planning applications. The potential impact of development on all trees is therefore a material consideration. In particular, BCS9 of the Core Strategy states that “Individual green assets should be retained wherever possible and integrated into new development”.

We have summarised Bristol’s planning policies as they relate to trees here – Planning obligations in relation to trees in Bristol.

Summary of the proposal in relation to trees

This site covers just over six hectares. The Lockleaze Allotments (a 0.8 hectare Statutory Allotment[1]) is located to the south east of the widest part of the site. It appears to be disused. Most of the substantial trees growing on the site are growing in or around this allotment or to the north of it. We have calculated that, taken together, they cover at least 1.3 hectares of the site – a tree canopy cover (TCC) of around 20% which is well above the estimated TCC for Bristol as a whole which is just under 12%.

All our calculations, summarised below, can be examined in this linked spreadsheet.

The Arboricultural Impact Assessment Report (the AIS) dated June 2020 (based on a survey done on the 19th and 20th of September 2019) identified a combined total of 58 individual trees and 40 tree group features. The number of trees in each group is not given, so it is not possible to say how many trees in total are growing on the site.

Of all the trees growing on site 24 individual and at least 251 group trees are identified for removal. The trees growing in Groups G69 and G74 are all to be removed, but the number of trees in each group is not identified so we have not been able to include or count these in our calculations.

The only reason for given for felling these two groups is because they show evidence of Ash Dieback (Hymenoscyphus fraxineus). As the AIS recognises, the mere presence of Ash Dieback is not a sufficient reason for the removal of a tree. We oppose the removal of these tree unless it can be shown that they there is a better reason for their removal.

The CAVAT calculation

Using CAVAT we have calculated that those identified trees which have a measured stem Diameter (DBH) are worth £4,674,918.  As the AIS fails to give the upper life expectancy ranges[2] of the majority of trees, we have assumed that all those trees given a 10+ or 20+ years life expectancy will survive between 40 and 80 years. This attracts a 5% discount on the base valuation. We have applied a CTI factor for Bristol of 150[3]. All the other factors are set to their default values.

The BTRS calculation

These two tree groups and five individual trees are categorised as Category ‘U’ trees under BS5837:2012 Trees in relation to design demolition and construction, and so have not been taken into account for the purpose of the Bristol Tree Replacement Standard (BTRS) calculation. A further 10 trees are also excluded from the BTRS calculation because their stem diameters are under 15 cm. We advocate that all trees identified for removal should be replaced no matter what their size.

Notwithstanding this and based on the current guidance, we have calculated the BTRS value at 455 trees as per the AIS calculation.

Net Gain calculation

No Net Gain calculation has been undertaken using BDM2 in support of this application.

We have undertaken our own BDM2 calculation in respect of just the trees surveyed in support of this application. A full calculation needs to be undertaken in respect of the whole of the site. This will inform any future decision about achieving Net Gain if this development is to be allowed to proceed.

Using BDM2, we have calculated that the combined tree canopy cover[4] of just the known, measured trees is 1.21 hectares. We have set the A-1 Site Habitat Baseline Habitat Type to Urban – Street Tree in the calculation. This assumes, amongst other things, that any replacement trees will reach maturity in 27 years and so uses a multiplier of 0.3822 to reflect this.

This gives Base Habitat Units of 5.864 and a Base Replacement value of 3.17 hectares. If we add an arbitrary Net Gain value of 10%[5], then the Base Habitat Units increases to 6.451 and the Base Replacement value to 3.49 hectares. Assuming that a 27-year-old tree has a canopy of .00403 hectares, then 866 replacement trees are needed to replace what has been removed and to achieve Net Gain.

Loss of the ecosystem services of trees

We invite you to consider the decades-long damage that felling just one tree (let alone over 277 trees) will cause by inputting the DBH of any tree identified for removal into our Tree CO2 Calculator.

As you will see, when an equivalent tree is replaced on a one-for-one basis, the lost CO2e is never recovered. Even when the largest tree (with a DBH of 100 cm) is replaced with eight trees in accordance with BTRS, it will still take some 40 years to recover the 10.4 tonnes of lost CO2e. And this is just one of the eco-services that trees provide us!

Impact on wildlife from tree loss

We endorse the following passages from the Bonnington Walk Breeding Bird Survey Report which observes at 5.2 Habitat Loss:

The Proposed Development will include the loss of scrub, trees and buildings which provide habitat for breeding birds. The extent of habitat loss is likely to include all the scrub and trees in the centre of the Site with some edge habitat along the boundaries retained…The loss of this habitat will have an impact on any birds using it for foraging or breeding at the time. The Site is located within an urban landscape with limited natural habitats. Alternative habitats are not readily available adjacent to the Site, though alternative habitat is available in the wider landscape including Stoke Park Estate and connected habitats further east. Habitat loss on Site will have an impact at a Local level by reducing breeding bird habitat in the local area…

and at 6.2.1 Habitat Loss:

Where possible, habitat loss should be avoided, and natural habitats retained. Scrub and trees are of most value to breeding birds at this Site. When natural habitats are retained these should be protected during construction to prevent damage including root compaction and knocking off or damaging over hanging limbs.

This is just one example of the likely adverse impact on wildlife resulting from these tree removal plans. There is evidence of a diverse range of both flora and fauna that likewise will also be adversely affected by the loss of these trees.

The Bristol Tree ForumJuly 2020

You can find more detail about the application here:

20/02523/FB – Land on south side of Bonnington Walk, Bristol


[1] Owned by BCC under its asset number 8397.

[2] CAVAT uses six age ranges to set the discount factor.

[3] Bristol has a population of 459,300 and a land area (as opposed to the Administrative area which covers large parts of the River Avon and coastal margins) of 10,970 hectares. Using this gives a population per hectare of 41.9 (459,300/10,970) and so a CTI Index value of 150.

[4] Under BDM2 each tree’s Root Protection Area (RPA) is calculated at 12 times its stem diameter. RPA is roughly equivalent to a tree’s canopy.

[5] The choice is arbitrary chosen only for the sake of illustration. We are not advocating a Net Gain of 10%, though the concept of Net Gain implies an improvement on the base values.

Author: BristolTreeForum

We are a group of volunteers dedicated to increasing the tree canopy cover of Bristol.

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