Tag: Urban Development

Temporary development, permanent loss: a closer look at the five-year exemption

Two new exemptions from biodiversity net gain (BNG) came into force on 6 August 2026. The first exemption, for sites of 0.2 hectares or less, has drawn the most attention, and it’s the subject of our last post – Small sites, big losses: The BNG exemption is the strongest argument yet for a national tree replacement standard.
The second exemption, Regulation 7B, is for development that’s wholly temporary, where planning permission is granted for five years or less. It deserves a closer look.

What regulation 7B does

The temporary development exemption is regulation 7B of the Biodiversity Gain Requirements (Exemptions) Regulations 2024, inserted with effect from 6 August 2026 by the Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026. It applies where three conditions are met: 

  1. The development doesn’t affect an onsite priority habitat. 
  2. The whole development is temporary. 
  3. The specified period for the development doesn’t exceed five years. 

Individual trees are not priority habitat, so felling them doesn’t disturb the exemption. So far, so unremarkable. The interest lies in how the regulation defines its five years.

The five-year clock includes restoring the land

Under 7B(8)(d), the specified period is the period at the end of which buildings and works must be removed, any use must be discontinued, and — this is the part that matters — ‘any works to reinstate the land are required to be completed’.

Two things follow. First, the clock includes the reinstatement window, not merely the operational life of the development. A scheme needing five years of use plus a restoration period afterwards doesn’t qualify, and falls back into BNG. That’s a real constraint, and one to which an authority can hold a developer.

Second, and more revealingly, the regulation defines temporariness by reference to the land being put back into its pre-development condition. That’s an assumption of reversibility written into the heart of the provision — and it’s precisely the assumption removing a tree undermines. You can reinstate the ground but you can’t reinstate a mature tree, not in five years and probably not in 50. The development is temporary but the loss is effectively permanent.

The impact test also cuts the other way

There’s one further point in 7B(8)(f) that runs in the opposite direction, and it narrows the exemption considerably. This is the condition that the development won’t affect onsite priority habitat, which is habitat being ‘lost or degraded such that there is a decrease in the biodiversity value of that habitat’. There is no de minimis threshold in the definition, and — more strikingly — no temporal qualifier. Nothing requires the decrease to be permanent, or lasting, or significant.

For example, a five-year compound laid across priority grassland which would recover within a decade still causes a decrease in biodiversity value, and so is not exempt. The test is a simple one: on any site carrying priority habitat, an officer must ask whether biodiversity value decreases at all. If it does, regulation 7B doesn’t apply and a biodiversity gain plan is still required.

Note, too, that this is a test of impact, not of presence. A site may contain priority habitat and still be exempt, provided the development genuinely leaves it alone. But with the threshold set at zero, any encroachment into the priority habitat defeats it — even compaction from vehicle movements, storage on the habitat, or trampling on it that would recover in two seasons.

However, individual trees are not a priority habitat and are not protected by regulation 7B. A temporary development may remove trees or tree canopy without restriction. This is why we need to make separate provision to protect trees, especially in urban areas where development pressures are the highest. Imposing conditions when an application is granted is the one tool planning authorities have that can help resolve this.

Drafting reinstatement conditions to protect trees

Section 72(1)(b) of the Town and Country Planning Act 1990 expressly permits a local authority to impose a condition requiring the carrying out of works for the reinstatement of land, and it is for the authority to say what reinstatement requires. Restoring land to its former condition includes its vegetation cover. Replacement planting can therefore come within the condition, provided the authority can point to a policy that justifies it.

The temptation is to put everything into that reinstatement condition and deal with it at the end of the five years, but this is the wrong way round. A tree planted in year one has five years more of growth by the time the compound is dismantled; a tree planted in year five must start from scratch, after five years of canopy loss (though the BNG metric calculator can factor in this delay). The requirement would be better split across two conditions.

Another thing to get right is duration, and here the benchmark is not the usual five-year planning norm but the BNG regime timescales where, in the case of replacement trees, the target final condition is at least 30 years from completion of the development. This can be secured by a planning condition, a section 106 agreement or a conservation covenant. If the local standard is to deliver what the national regime would have delivered, then replacement trees need the same protection. 

A local authority can draft the reinstatement conditions in two ways. 

Condition A — replacement planting at the outset

No development shall commence until a tree replacement scheme has been submitted to and approved in writing by the local planning authority. The scheme shall identify every tree to be removed to facilitate the development together with its size category, assessed in accordance with BS 5837:2012 and the size bands in the statutory biodiversity metric, and shall provide for replacement planting at the ratios set out in policy [X], specifying locations, species, stock sizes, and a management and monitoring plan. The approved planting shall be carried out in the first planting season following commencement of development. The replacement trees shall be maintained in accordance with the approved management and monitoring plan, and retained, for a period of 30 years beginning with the completion of the development. Any replacement tree which within that period is removed, dies, or becomes seriously damaged or diseased shall be replaced in the following planting season with a tree of the same size category and, unless otherwise agreed in writing, the same species.

Reason: to ensure that the loss of trees arising from the development is compensated in accordance with policy [X], that replacement canopy begins to be established at the earliest opportunity, and that it is secured for a period equivalent to that required for habitat enhancements under the biodiversity gain condition.

Condition B — reinstatement at the end of the period

The use hereby permitted shall be discontinued, and all buildings, structures, plant, machinery and hardstanding removed, on or before [date]. The land shall thereafter be reinstated in accordance with a scheme of reinstatement to be submitted to and approved in writing by the local planning authority, all works of reinstatement to be completed on or before [date]. The scheme of reinstatement shall provide for the retention and protection of the replacement trees planted under condition A, and for the making good of any ground disturbance within their root protection areas.

Reason: the permission is granted for a limited period only, and to ensure the land is restored and the replacement planting retained.

Here are four practical notes on using these two conditions:

  1. Both dates in condition B must fall within five years if the applicant is relying on the exemption. The specified period ends when reinstatement is complete, not when the use stops.
  2. All conditions must satisfy the six tests set out in the NPPF and the Planning Practice Guidance: they must be necessary, relevant to planning, relevant to the development to be permitted, enforceable, precise, and reasonable in all other respects.
  3. Secure a 30-year obligation. Defra’s own guidance accepts a planning condition as one of the three mechanisms, so an authority imposing one is following the department’s lead rather than striking out on its own. But a condition is enforced against whoever owns the land at the time, and enforcement 25 years and, say, three owners later is a real practical difficulty. Where the planting is substantial, a section 106 obligation is the better instrument: it runs with the land, binds successors, and is registrable as a local land charge so it shows up on a search. For householder-scale replacement, where such an agreement could be disproportionate, a condition combined with a Tree Preservation Order on the replacement trees could possibly achieve much the same for a fraction of the cost. Monitoring should be proportionate too: reports at years one, three, five and ten will tell an authority what it needs to know without committing anyone to three decades of annual paperwork.
  4. A condition can’t require works on land outside the applicant’s control. This is most important on small sites — a 0.15 hectare plot which loses 18 mature trees can’t physically accommodate 90 replacements. Any workable standard therefore needs an off-site option — planting elsewhere (preferably nearby) in the authority’s area, or a commuted sum calculated on the cost of planting, establishing and maintaining the shortfall for 30 years — secured by a section 106 obligation rather than by condition. For smaller schemes a negatively worded Grampian condition, preventing occupation until the off-site planting has been carried out, is a cheaper alternative. A standard without that option will simply be negotiated down to whatever the developer believes will fit on the plot.

What regulation 7A leaves out

Set the two new exemptions side by side and the small-sites provision looks noticeably thinner than its temporary development counterpart. They share the priority habitat condition and the definition of impact discussed above. The following three things separate them.

There’s no anti-stacking rule. Regulation 7B(7) expressly aggregates successive grants for the same temporary development, so a developer can’t take five years and then another five. Regulation 7A contains no such equivalent. Nothing on the face of it prevents a larger site coming forward as a series of applications each at or below the threshold, every one of them exempt. Authorities can resist using ordinary principles about what constitutes a single development, but that’s a contest on the facts every time rather than a rule. The department plainly considered the risk of gaming the duration. It appears not to have considered the more obvious risk of gaming the area.

‘Site’ is not defined. Regulation 7A(3) refers to ‘a site which has an area no larger than 0.2 hectares’, and the interpretation provision at 7A(6) defines every other term but that one. The red-line boundary is the sensible reading and the one we’ve adopted, but it’s not what the regulation says. One consequence is at least helpful: area is two-dimensional, so canopy oversailing a plot adds nothing to it. The 0.18 hectare site described in our last post, carrying 0.33 hectares of canopy, remains a 0.18 hectare site.

There’s no protection against clearing the site first. The first condition asks whether the development impacts an onsite priority habitat, assessed as matters stand when permission is sought. Where the habitat has already been cleared, there’s nothing left for the development to impact. The BNG regime properly guards against this: habitat degraded since 30 January 2020 otherwise than in accordance with planning permission is assessed at its baseline pre-degradation state. But that guard operates within the definition of pre-development biodiversity value, and 7A doesn’t use that concept. However, this is a question for a planning lawyer rather than for us. If it doesn’t, first-clear-then-apply is a route directly into the exemption.

A circularity at the heart of both exemptions

‘Biodiversity value’ is not a loose description. It’s a statutory term, measured using the biodiversity metric and its guidelines. So the question of whether a habitat is impacted — and therefore whether the developer is exempt from producing a metric — is expressed in terms that only a metric can establish. The test for exemption from the metric is written in the metric’s own currency.

In practice this makes both exemptions self-certifying. The applicant asserts the exemption; without a survey nobody’s in a position to test the assertion, and no survey is required, because the exemption is precisely what removes the gain plan. Where a site plausibly carries priority habitat, the planning authority should ask for enough survey information to satisfy itself that the exemption is properly claimed. This is merely validating a claim, not imposing BNG by the back door.

What we’re asking for

  • Where temporary permission is granted, replacement planting should be required at the outset with the reinstatement condition requiring those replaced trees to be retained and protected. This needs no change to national policy and could be adopted immediately.
  • Replacement trees will be maintained and retained for 30 years from completion of the development, with failures replaced throughout that period — the same protection BNG requires for a significant on-site habitat enhancement.
  • Authorities should ask for enough survey information to satisfy themselves that exemption is properly claimed, rather than accepting the applicant’s assertion.
  • Defra should insert into regulation 7A an aggregation provision equivalent to regulation 7B(7), so that a larger site can’t be brought forward as a series of sub-threshold applications. It should also define what ‘site’ means for the purposes of the 0.2 hectare threshold.
  • Defra should insert an anti-degradation provision to both new exemptions, so that neither the area threshold nor the priority habitat condition can be satisfied by prior site clearing before an application is made.

Notes

A note on citation. The two new exemptions are regulations 7A (small sites) and 7B (temporary development). They’re not part of the original 2026 Regulations themselves: these are amending regulations inserted into the Biodiversity Gain Requirements (Exemptions) Regulations 2024.

The model conditions above are offered as a starting point for discussion, not as approved wording. This post sets out our reading of the regulations; it is not legal advice, and anyone relying on the position for a consultation response, a condition, or an appeal should seek their own expert advice.

A companion post, ‘Too many exceptions: why BNG was never going to protect our trees’, looks at the much longer list of development the biodiversity gain condition has never applied to.

Looking at Bristol’s development sites

Since the Government changed the biodiversity net gain (BNG) rules last month, the smallest development sites – 0.2 hectares or smaller – no longer have to deliver a BNG of at least 10% as part of their proposal. We wanted to know what difference this change will make to the protection of nature, and specifically trees, within Bristol.

We looked at every Full Planning application that Bristol validated between 6 and 31 August 2026  (the applications carrying the suffix ‘/F’, householder applications having their own suffix and their own exemption from the BNG regime). There are 28 of them, and every single one is on a site of 0.2 hectares or less. This means that none of them now needs to deliver any biodiversity gain: all are under the threshold, and none records an impact on a priority habitat.

However, only eight of these applications would have had to deliver BNG before 6 August in any case. Eighteen were already exempt under the de minimus rule (which remains in force, though perhaps now is redundant for small sites like these), while one was covered by the self-build exemption, itself withdrawn on 6 August, and another cannot be decided from the published evidence.

The de minimus rule exempts a development from the BNG regime if it impacts less than 25 square metres of on-site habitat carrying any biodiversity value, and less than 5 metres of linear habitat such as a hedge with biodiversity value, and doesn’t include a priority habitat. The limit is on what the development impacts, not on how big the development is. Sealed surfaces, buildings and hardstanding all score zero in the metric, so a proposal can cover such a site entirely and still impact nothing above the de minimus threshold. Fourteen of the 18 applications are exactly that, even though they are all larger than 25 square metres: they include the installation of shop frontages, air conditioning units and parcel pick-up lockers, a replacement conservatory on to an existing terrace, and a basement-level extension on existing hardstanding.

This leaves eight (almost a third of the sample) that would not have been exempt before 6 August but are now. Each is a dwelling or a subdivision of land that is, or was, garden. The new exemption never asks what stands on the site. It asks only whether a priority habitat is impacted and if the site is 0.2 hectares or less; the habitat on the site is not measured at all. The de minimus rule did measure it — and so a single small tree, which has a habitat area of 41 square metres, would defeat the de minimus exemption if affected. But an individual tree is not priority habitat, so, even if the combined tree habitat area within a development site might be greater than 0.2 hectares, the new exemption still applies.

This is why we are asking for a new way to protect urban trees: a tree replacement standard in every local plan.

This is a follow-up from Small sites, big losses: The BNG exemption is the strongest argument yet for a national tree replacement standard

The full analysis is in the accompanying spreadsheet – Sub 0.2 ha applications – BNG analysis.xlsx.

Small sites, big losses: The BNG exemption is the strongest argument yet for a national tree replacement standard.

Since 6 August this year, the smallest developments in England (those 0.2 hectares or smaller) no longer have to deliver biodiversity net gain (BNG). To understand what this means for trees, we’ve analysed 505 biodiversity gain plans and 320 readable metric calculations gathered from 59 planning authorities.

The answer is uncomfortable: the exemption removes roughly half of all development sites from the BNG regime, and these are precisely the sites on which trees make up the largest share of the habitat being lost.

In December 2023 we argued for a new Bristol Tree Replacement Standard (BTRS) calibrated to the statutory biodiversity metric. That argument was about making the local standard consistent with national policy. It’s now about something much more critical: on half of all sites, a local standard is the only thing left to protect trees being lost to development.

What changed on 6 August 2026

The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026 (SI 2026/790) took effect for planning applications made on or after 6 August 2026. The three changes made matter here:

  1. A site of 0.2 hectares or less, measured by the red-line boundary of the application, is exempt from mandatory BNG unless on-site priority habitat is negatively affected.
  2. Development that’s wholly temporary, with permission granted for five years or less, is also exempt on the same proviso.
  3. For minor development above the area threshold, the mitigation hierarchy has been relaxed: off-site gains are now seen as just as desirable as created or enhanced habitat on the site itself, so a developer may go straight off site without first showing that on-site provision is unachievable.

The self-build and custom-build exemption has also been removed, on the reasoning that most such schemes now fall inside the new small-sites exemption anyway. While applications already submitted before 6 August continue under the old rules, Defra in its 15 April 2026 response to the consultation, estimated that ‘the new area based exemption for sites of less than 0.2 hectares is expected to remove more than 50% of the smallest planning applications which are currently delivering mandatory BNG, from the BNG requirement’.

Trees aren’t priority habitat

The priority habitat proviso sounds protective, and for some sites it is, but it does nothing for trees. Depending on where it is, an individual tree is recorded in the statutory metric as urban tree or rural tree, both of medium distinctiveness; neither is a habitat of principal importance under section 41 of the Natural Environment and Rural Communities Act 2006. Only ancient and veteran trees sit outside these two categories, as irreplaceable habitat, and they are a vanishingly small proportion of the trees felled for development.

So a mature street-side lime, a garden oak, or a row of maturing London planes on the edge of a school playing field — none of these will be protected if they’re in the way of a 0.2 hectare development. Below the threshold, they can be removed without any obligation to count them, replace them, or compensate for their loss anywhere. Unless the tree is protected by a Tree Preservation Order, or unless the local plan says otherwise, nothing now requires their loss to be made good.

This is the gap; and it’s much larger than the word ‘small’ implies.

Half of all development sites now fall outside the system

We measured site area for every gain plan in our dataset that came with a usable metric calculation — 305 sites across 59 authorities. Site area here is the baseline area-habitat total, net of any individual trees, taken from the statutory metric or, for small-sites metrics.

Table 1. Development sites by size, 305 sites with a usable metric calculation
Site size Sites Share Baseline area HUs Post-development area HUs On-site change
0.2 ha or smaller 151 49.5% 48.79 48.67 −0.25%
Over 0.2 ha 154 50.5% 506.88 512.82 +1.17%
All sites 305 100% 555.67 561.49 +1.05%

Habitat units are on-site figures from sections 6.3 and 6.4 of the biodiversity gain plan. Hedgerows and watercourses are excluded as linear features.

Just under half of the sites that have been going through the BNG process fall at or below the new exemption threshold — consistent with Defra’s own estimate. Two further things stand out in that table. First, small sites were barely holding their own on site even under the old regime that’s just been withdrawn: a baseline of 48.79 area habitat units became a mere 48.67 after development, a small net loss, with any gain bought off site from elsewhere. Second, the small-site total is dwarfed by the large-site total, which is exactly why the exemption looked politically cheap. In habitat unit terms these sites are a rounding error. In tree terms, though, they aren’t.

Small sites are where the trees are

Of the 320 metric calculations we could read, 163 relate to sites of 0.2 hectares or less. Sixty of these — 36.8% — record individual trees in the on-site baseline. Between them they carry 3.12 hectares of tree canopy ‘oversailing’ 15.22 hectares of land.

Table 2. Individual trees in the on-site baseline, by site size
Site size Metrics With trees Site area (ha) Canopy (ha) Canopy as % of site area Tree baseline HUs
0.2 ha or less 163 60 (36.8%) 15.22 3.12 20.5% 26.71
Over 0.2 ha 157 81 (51.6%) 219.64 13.79 6.3% 133.22
All sites 320 141 (44.1%) 234.85 16.91 7.2% 159.94

Site area is net of individual trees, because tree canopy oversails the habitat beneath it and is not additional land. Canopy can therefore exceed 100% of the site area it overlies.

That last comparison is the heart of it. On sites above the threshold, tree canopy is equivalent to about 6% of the site area. On sites at or below 0.2 hectares it’s 20.5% — more than three times the share. Small sites are disproportionately tree rich, probably because they’re disproportionately urban: they include infill plots, back gardens, corners of school and hospital grounds, and the fringes of existing built-up land. These are the places where we usually find the mature tree canopy of a town.

The concentration is sharper still for twenty of the 163 small-site metrics, which record canopy covering more than half the site area. Seven record canopy exceeding the whole of it. One example is a 0.18 hectare site at 22 York Road in Sutton, which carries 0.33 hectares of canopy across 18 recorded tree entries — canopy equal to 182% of the site, and worth 3.42 habitat units. At an average of 0.019 hectares of canopy each, these are mature trees, not saplings — on the replacement standard set out below, losing 18 medium trees would require 90 replacements. On an application made today, that site would be exempt and the trees could be removed without any obligation to replace them under the new BNG regime.

Expressed as trees rather than hectares, the 3.12 hectares of canopy on small sites is equivalent to 762 small trees, using the 0.0041 hectares the June 2026 metric assigns to a small tree. Because much of that canopy belongs to medium, large and very large trees, the actual number of trees is likely to be lower — and their replacement cost, in the metric’s own currency, correspondingly higher.

And they’re where the new trees were coming from

The exemption removes an obligation to plant as well as an obligation to compensate. Of the 163 small-site metrics, 72 record individual trees created as part of the post-development scheme.

Table 3. Individual trees created in post-development proposals
Site size Metrics With tree creation On-site trees Off-site trees Total trees
0.2 ha or smaller 163 72 (44.2%) 597 8 605
Over 0.2 ha 157 97 (61.8%) 3,135 205 3,340
All sites 320 169 (52.8%) 3,731 213 3,944

Tree numbers are the recorded habitat creation area divided by 0.0041 ha per small tree, rounded up. Off-site units bought from a registered gain site do not appear here, because they sit in the seller’s metric.

Over 600 trees across a dataset of a few hundred plans covering barely two years and 59 authorities out of 306. If you scale that across every planning authority in England and across the years ahead, the tree planting foregone is substantial.

BNG was never going to save urban trees anyway

It’s worth being clear that the case for a local tree standard doesn’t rest solely on the exemption. Even where BNG still applies, it often doesn’t keep compensation anywhere near the trees that were lost.

The Biodiversity Gain Sites register as of 19 August 2026 — 2,328 developments across 306 authorities — shows that 87% of developments in urban authorities offset outside their own authority area. Those authorities needed 1,835 area habitat units and hosted 889. In London the pattern is near total: 98% of the 113 registered London borough developments offset elsewhere, requiring 46.8 units and hosting 3.3.

The units are real, and the receiving sites may well be excellent. But a habitat unit delivered in a rural county doesn’t provide shade in Bristol, intercept its rainfall, cool it in a heatwave, or stand outside anybody’s window. Urban tree canopy is a local public good, yet BNG systematically moves its replacement to some distant field that few, if any, will ever visit.

Why we need a tree replacement standard

A tree replacement standard is a local plan policy, not a national biodiversity calculation. It attaches to the tree, not to the site area; it applies whether or not a metric has to be completed; and it keeps the replacement in or close to the place where the loss occurred. It’s the mechanism best suited to fill the gap the exemption has opened.

This is not a novel invention. Bristol has operated the BTRS since 2014 under Core Strategy policy BCS9, and a replacement table is carried forward into proposed local plan policy BG4. What we argued in 2023 was that the ratios should be recalibrated so that the standard delivers what the statutory metric would have delivered, plus the 10% uplift. Our proposal was not adopted then, though our argument stands. What’s changed is who needs it: not just Bristol, but every planning authority that wants any control at all over tree loss on the majority of its planning applications.

We would encourage authorities without such a policy to adopt one, and those with one to check that it’s calibrated to the metric rather than to a historic rule of thumb whose rationale was and remains hard to understand. As the standard is a local plan policy, it can be applied to exempt sites without cutting across the national BNG regime: BNG sets a floor for biodiversity, and a replacement standard sets a separate, local requirement for canopy.

Recalculating the standard against the June 2026 metric

Our 2023 proposal derived replacement numbers from the tree area equivalents then in force. Those figures have since changed. Table 15 of the Statutory Biodiversity Metric User Guide (June 2026), at page 62, now assigns the areas set out below. Applying the same method — the area of the lost tree divided by the area of one small tree, since a newly planted tree is recorded as small, plus the 10% net gain, rounded up because a fraction of a tree is not a tree — gives revised numbers.

Table 4. Replacement trees required, recalculated against the June 2026 metric
Tree size (DBH) Area equivalent (ha) Multiple of a small tree Plus 10% net gain Replacement trees 2023 proposal
Small (>7.5–30 cm) 0.0041 1.00 1.10 2 1
Medium (>30–60 cm) 0.0163 3.98 4.37 5 3
Large (>60–90 cm) 0.0366 8.93 9.82 10 10
Very large (>90 cm) 0.0765 18.66 20.52 21 20

Areas are from Table 15 of the Statutory Biodiversity Metric User Guide (June 2026), p62. Replacement numbers are the tree’s area divided by the area of one small tree, plus the 10% net gain, rounded up.

Two categories of tree size move. A medium tree is now worth almost four small trees rather than three, so its replacement requirement rises from three to five. A very large tree rises from 20 to 21. Large trees are unchanged at ten.

The small-tree row needs a decision rather than an arithmetic answer. One small tree replaced by 1.1 small trees rounds up to two, which is a real doubling for the commonest category in the surveyed population. The alternative is to hold the small category at one-for-one and take the 10% uplift from the scheme as a whole. We think the honest position is to state the arithmetic and let the policy make the choice explicitly, rather than round the uplift away in silence.

What we’re asking for

  • That local planning authorities adopt, or retain and strengthen, a tree replacement standard in their local plan, applying to all development including sites exempt from mandatory BNG.
  • That the replacement ratios be calibrated to the current tree area equivalents in the statutory metric, so that a local standard delivers no less than the national regime would have done.
  • That replacement be required within the same authority area and as close to the loss site as is practicable, so that canopy is replaced where people live.
  • That authorities continue to require a BS 5837:2012 tree survey with applications on exempt sites, so that the loss is properly recorded even where no metric is required.
  • That Defra keep the 0.2 hectare exemption under review, and specifically consider whether the priority habitat proviso should be extended to sites carrying significant tree canopy.

The exemption was introduced to reduce costs and delays for small applications. Whatever one makes of that aim, it shouldn’t be paid for with the mature canopy of our towns and cities. A tree replacement standard is a cheap, well-understood, locally enforceable way of making sure it’s not.

About the data

Figures are drawn from the Bristol Tree Forum biodiversity gain plan dataset (v11): 505 gain plans logged from 59 planning authorities, of which 320 carry a readable statutory or small-sites metric calculation and 305 a usable site area. Plans are dated 2024 (58), 2025 (254) and 2026 (165). Register figures are from the Biodiversity Gain Sites register extract of 19 August 2026, covering 2,328 developments and 2,686 allocations across 306 authorities.

Two caveats:

  1. Site area in this analysis is the metric’s baseline habitat area net of individual trees, which is a close proxy for the red-line boundary the exemption uses but not identical to it; a handful of sites near the threshold may fall on the other side of it in practice.
  2. The sample is of applications that produced a gain plan, so it describes the population the exemption removes rather than all development across the country.

Take a look at our recent follow-up which looks at the immediate impact of this new exemption for Bristol :

Looking at Bristol’s development sites

The small-sites rule change that could quietly cost your neighbourhood its trees

From 6 August 2026, a change to the planning rules takes effect that most people will never hear about — but it could reshape the trees on our streets, in our gardens and on the small plots being built on all over the country.

Here is the short version.

What is changing

When land is developed, the law has, since 2024, usually required a small boost to nature — a “Biodiversity Net Gain” of at least 10%. In plain terms, a development is meant to leave nature a little better off than it found it.

From 6 August, the smallest sites — those of 0.2 hectares or less (about 2,000 square metres, roughly a third of a football pitch, or a small cluster of houses and their gardens) — no longer have to do this at all.

For hard-pressed small builders, that is a welcome simplification. But there is a catch for trees.

Why trees are caught in the middle

Under the old rules, removing even a single tree was usually enough to bring a small project into the nature-boost system — because of the way a tree’s protected “footprint” is measured. In practice, that meant a developer could not quietly fell a tree on a small plot without having to make good the loss.

The new rule swaps that “what is the impact?” test for a much simpler “how big is the site?” test. If the site is 0.2 hectares or smaller, the nature rules simply do not apply — however many trees are cleared.

What that means on the ground

On a site right at the new limit, the equivalent of up to 48 small trees — or around a dozen mature ones — could be removed with no requirement to replace or compensate for them under this system. And the trees most exposed are exactly the ones we tend to notice most: established trees on small urban and infill plots.

What still protects trees

It is not a free-for-all. Tree Preservation Orders, conservation-area rules and the special protections for ancient and veteran trees all still apply — they sit entirely outside this change. Some councils also have their own local tree policies: Bristol’s Tree Replacement Standard, for example, still requires replacement planting whatever the new exemption says.

The snag is that these local protections only exist where a council has actually put them in place — and not every council has.

Why it matters

The change is a sensible piece of red-tape reduction for small builders. But it is also, almost by accident, a real step back for the everyday trees that give our neighbourhoods shade, character and wildlife. From August, whether the trees near you are protected will depend less on national nature rules and more on whether your council has its own policies — and on whether a particular tree happens to be covered by an order.

If you value the trees around you, it is worth asking your local council what protections are in place.

We have set out the full detail — the mechanics, the legal position, and what to watch next — in an accompanying briefing note.

Read the full briefing note here.

St Philip’s Marsh: do the green space sums add up?

Bristol’s biggest regeneration plan promises parks within a five-minute walk of every front door. We measured the plan’s own drawings to see whether the promise holds. Here’s what we found.

St Philip’s Marsh is about to become the new place in Bristol to live, work and study. The draft Masterplan, created by the Bristol Temple Quarter Partnership is now out for consultation. It proposes at least 7,000 homes — for roughly 15,000 people — on 94 hectares of old industrial land east of Temple Meads, plus workspace for thousands of jobs and student housing beside the university’s new campus. For an area with almost no publicly accessible green space currently, the Masterplan’s vision of parks, green streets and riverside walks is most welcome, and we want it to succeed.

However, when we measured the plan’s own drawings — every park, square and green corridor, checked against the Council’s own GIS records — the numbers put forward started to wobble.

A table that vanished

The Masterplan’s headline is 22.4 hectares of open space and green corridors, including 8.1 hectares of ‘new open space’. Curiously, the published figure that should show this breakdown contains no numbers at all. The arithmetic survives only in the figure’s hidden accessibility text — the description read aloud by screen readers. This refers to a quantification table ‘overlaid on the side of the plan’. However, this table was removed before publication, and nobody has updated the hidden text. Our own measurements confirm the totals are correctly computed. So why take the table out?

How big is Sparke Evans Park? Pick a number

The document gives three different sizes for the area’s only existing park, Sparke Evans Park: 2.9 hectares in the body text, 2.5 in the hidden arithmetic, and 2.34 as drawn. The Council’s own GIS records 2.3416 ha. A small thing, perhaps — but the body text overstates the park by 24%, which is the baseline everything else is measured from.

A bigger question is how large is the site itself? The Masterplan never says. Its drawn boundary encloses 94 hectares but the council’s investment website says St Philip’s Marsh totals 65 hectares. Nobody reconciles the two. This is important as the site area is the denominator for the plan’s flagship promise of 25% tree canopy. 25% of which number?

What actually counts as a park?

Bristol’s Parks and Green Spaces Strategy is clear that ‘public realm’ — squares, promenades, landscaped frontages — does not count as open space for recreation. Strip those out of the Masterplan’s 8.1 hectares and the qualifying provision shrinks to somewhere between 5 and 6.6 hectares, most generously counted — and only around 2.6 to 4.3 hectares of it is new. The real new parks are two: Chapel Park (1.26 ha) and Fruit Market Park (about 1.3–1.5 ha). Each is roughly the size of College Green. Between them and Sparke Evans Park, they are expected to host school play, neighbourhood events, ecology, gardens and the daily recreation of thousands.

The density arithmetic nobody has published

Bristol’s adopted standard for the city centre zone is 7.75 m² of recreational open space per person — itself barely a quarter of the 33 m² the average Bristolian enjoys citywide. Working through the strategy’s published figures shows that standard has been set with zero headroom: it assumes the central area’s population will rise 65%, offset by just 2.9 hectares of new green space, landing exactly on the 7.75 m² standard adopted.

The St Philip’s Marsh residents will get roughly 3.3 to 4.4 m² of qualifying green space per person on site, about one tenth of the citywide average. And that’s before you include the daytime population, who will share the same spaces: a workforce of 5,000 or more, several thousand students, and those whom the plan rightly invites in, living nearby in The Dings, Barton Hill, Totterdown and Redcliffe — some of the most green-space-deprived communities in Bristol. If the Masterplan’s population exceeds what the strategy assumed — and its unpublished assumptions are a question we’ve put to the Council — the adopted standard is breached simply by the arithmetic.

Five-minute-walk — from the front door, or the tenth floor?

We modelled walk times over the plan’s own street network. The average journey to the nearest named park is about three minutes. This supports the five-minute-walk promise. However, with roughly one in five residents living above the fifth floor in residential towers of ten storeys and more, this will add to the walk time just getting to the ground before setting off. For those households the five-minute promise quickly becomes longer. Sparke Evans Park, in the south-east of the site, is up to 21 minutes from the far north-west corner, while parts of the employment area are 7–10 minutes from any named park.

And five minutes for whom? The plan’s promise assumes a brisk walker covering 400 metres in five minutes. Bristol’s own parks standard describes that same 400 metres as a nine-minute walk — the pace of older people, small children, anyone with a buggy or those whose walking is impaired: exactly the people who parks matter most for. At that pace, every estimate above roughly doubles, and the far corner of the site is nearly 40 minutes from Sparke Evans Park. The five-minute-walk promise is really a 400-metre promise — which should be judged at the speed of the slowest, not the fastest.

Three thousand trees, ready by the 2050s?

The 25% canopy pledge needs 16–19 hectares of new tree canopy: in the order of 3,000 trees. These will largely be planted on streets that must also fit cycleways, drainage and utilities — creating a near-continuous tree ceiling over two-thirds of the public realm. Newly planted trees would deliver under 1% of site canopy on day one and take 25–40 years to mature, on top of the 20 years needed to complete the development. The 25% canopy pledge currently has no target date, no baseline and no monitoring. So for the first couple of decades, a resident on, say, the tenth floor will look down on saplings, not canopy — exactly what the international 3/30/300 benchmark (3 visible trees, 30% canopy, green space within 300 m) aims to prevent.

What we’re asking for

Our submission makes a series of specific requests, including:

  1. Correct the ambiguous reported park sizes.
  2. Reinstate the vanished quantification table.
  3. State the definitive site area and publish the boundary as open GIS data.
  4. Publish a schedule of open space that distinguishes real recreational space from public realm space, and test this against the projected full daytime population.
  5. Publish the population assumptions behind the quantity standard.
  6. Put a date, baseline, funding and monitoring regime on the canopy pledge.
  7. Front-load tree planting.
  8. Adopt 3/30/300 at design-code stage.
  9. Explain how and when the riverside open spaces will be delivered, given their dependency on the Avon Riversides 2100 flood defence programme — for which £88m has been identified against a further £128m still required.

None of this requires redrawing the plan. It just requires the Partnership to show its workings — because on green space, the difference between a promise and a number is where communities lose out, one planning application at a time.

One last thing. This document was meant to be a Supplementary Planning Document — statutory guidance sitting alongside the Local Plan. A change in Government regulations earlier this year means it will now be adopted only as an “endorsed Masterplan”: non-statutory guidance that developers must merely “have regard to”. That makes everything above more fragile, which is why our submission also asks for the green space framework to be secured through Local Plan policy wording, where it will have legal force.

The consultation closes on 28 July 2026. You can respond through the council’s survey or by emailing: hello@bristoltemplequarter.com — and if green space in this new piece of Bristol matters to you, please do.

Read our submission, with methods and maps, here:

SPM Masterplan Consultation – BTF Response

Analysis for this submission included independent measurement of the Masterplan’s Figure 07.34, georeferenced against Bristol City Council GIS data, and walk-time modelling over the illustrative street network, carried out with AI assistance (Claude, Anthropic) under our direction. Methods are set out in full in the submission’s annex.

Understanding Biodiversity Gain Plans

Since BNG became mandatory in February 2024, qualifying developments in England must show how they will deliver at least a 10% gain, to be set out in a Biodiversity Gain Plan (BGP) submitted to the local planning authority. We’ve transcribed 160 BGPs from 21 LPAs into a single, comparable dataset.

What the data shows so far:

  • Just over under 60% (95 of 160) deliver their gain entirely on site. Another 34 use a mix of on-site and off-site measures, while 17 rely wholly on off-site units and 14 did not state an approach. Two bought Statutory Credits.
  • Off-site reliance is a recurring theme. A number of plans record an on-site biodiversity loss offset by purchased habitat units — a legitimate route, but one that moves the gain away from the community where the development happens.
  • Net gain has to be met habitat type by habitat type (area, hedgerow, watercourse), not as a single blended figure. Several plans that pass overall are marginal — or fall short — on an individual module.

Accessing this data was harder than it should be:

  • There is no central register of gain plans – why can’t Defra or Natural England include them in their BGS allocation dataset? These documents should be easily accessible.
  • Each council’s portal has to be searched separately, with no consistent way of identifying the relevant application. Only a few authorities (City of York, Bristol and Cotswold among them) have a dedicated application category for BNG discharges. Otherwise the BGPs sit inside generic “discharge of conditions” applications and are very difficult to find.
  • BGPs are produced in a variety of forms – as clean PDFs, fillable forms, bespoke versions or scanned images requiring OCR – which is challenging, especially if they are hand-written.
  • They are often internally inconsistent: off-site figures just copied from the on-site section, credits confused with habitat-bank units, or headline numbers that do not reconcile.
  • Off-site claims frequently differ from what the Biodiversity Gain Sites register records as allocated.
  • Many applications do not include the required BNG Metric calculation.
  • Some applications can’t be analysed because all that is produced (and approved) is the certificate of the off-site HU purchase – and sometimes not even that. As a result, we’ve been unable to include these in our analysis.

The information exists, but we can only conclude that the planning approval process makes meaningful public scrutiny far harder than it needs to be. Using the available standard Defra form and creating a single searchable register of BGPs would be a straightforward improvement.

The full dataset and analysis are here — comments, corrections and more data are welcome:

BGP Full Data Extract

NB. This analysis will grow as we add more data.

#BiodiversityNetGain #BNG #BGS #Planning #Nature #Transparency

Assessing habitat parcels: strategic significance explained

To calculate the biodiversity value of a habitat, it’s important to assess its strategic significance. A habitat’s strategic significance takes into account both its type and its location. If strategic significance is high, then the habitat’s value will be uplifted by 15%. However, as this article explains, the opportunities for doing this are limited.

A habitat parcel is an area of habitat which is all of the same distinctiveness, condition and strategic significance. Strategic significance refers to the importance of a habitat parcel based on its location and type.

Each habitat parcel needs to be assessed both before, when the baseline habitat is surveyed, and after development, on or off site.

This flowchart sets out how to assess the strategic significance of a habitat parcel. It uses the tables, shown below, from the Statutory Biodiversity Metric User Guide.

Our blog, The Local Nature Recovery Strategy fails to deliver for Bristol assesses the implications of this for Bristol, which recently adopted the WECA LNRS.

These are the tables referred to in the flowchart:

Table 7: strategic significance categories where an LNRS has been published.

Table 8: strategic significance categories where an LNRS has not yet been published.