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England's off-site Biodiversity Net Gain (BNG) market is now estimated at £143 million, up from £93 million in July 2026, according to the November 2026 report from broker Biodiversity Units UK, reported by The Dirt on 10 November 2026 [1]. The figure landed eight days after the 10% net gain duty became mandatory for Nationally Significant Infrastructure Projects (NSIPs) on 2 November 2026 [2]. For anyone commissioning a biodiversity net gain habitat banks ecology survey, the headline number matters less than the detail underneath it: supply is uneven, many banks have never sold a unit, and the evidence behind every unit purchase is now being tested harder than ever.
Key Takeaways
- The BNG market is estimated at £143m in November 2026, with 414 registered habitat banks, up from 186 a year earlier [1].
- Half of English local planning authorities still have no habitat bank, and 39% of registered banks have yet to sell a unit [1].
- Mandatory 10% BNG now applies to NSIP development consent order applications submitted on or after 2 November 2026, with its own metric and baseline rules [2][3].
- Unit scarcity in specific habitats and locations is the most likely trigger for planning-condition, section 106 and conservation covenant disputes.
- Ecological reports increasingly serve as expert evidence, so CPR Part 35 duties and professional conduct rules apply from the first site visit.
What the November 2026 Biodiversity Net Gain Habitat Banks Data Shows
The Biodiversity Units UK report draws its pricing from 305 of the 414 registered banks and tracks allocations recorded on the national register [1]. The key figures are set out below.
Developer purchases split roughly a third each between local, neighbouring-area and wider sources [1]. Unit prices have eased for most habitats since July, although the report cautions that some larger price moves rest on limited data [1].
"More habitat banks nationally does not necessarily mean buyers can find the right units close to their development.", Ian Hambleton, founder and director, Biodiversity Units UK [1]
That sentence explains the roughly £36m spent on additional units to cover spatial risk. When a developer buys units outside the local planning authority or National Character Area, the statutory metric applies a spatial risk multiplier, so more units must be bought to deliver the same gain. The report also notes that registration alone does not show whether a bank is actively seeking buyers [1]. With 39% of banks having sold nothing, a map of registered sites overstates real supply, so a biodiversity net gain habitat banks ecology survey of the sourcing options for a scheme has to confirm habitat type, condition, distance, legal security and whether the operator is actually trading.
NSIP Net Gain From 2 November 2026: A Different Regime
The Government confirmed in April 2026 that a minimum 10% net gain duty would attach to development consent order (DCO) applications for NSIPs submitted on or after 2 November 2026, under the Planning Act 2008 rather than the Town and Country Planning Act 1990 [2][3]. The main technical differences are:
- A new "BNG boundary". Only land disturbed permanently or temporarily within the DCO Order Limits goes into the baseline; undisturbed habitats within the Order Limits are excluded [2][4].
- Irreplaceable habitat is excluded from the baseline and from the 10% obligation, and cannot be compensated through credits [2].
- No spatial risk multiplier penalty in most cases where off-site gains are delivered within the same local authority or National Character Area, except for watercourse units spanning more than one catchment [2].
- Statutory biodiversity credits remain a last resort behind on-site and off-site delivery [2].
- An NSIP-specific metric and Biodiversity Gain Statements laid before Parliament, which take effect like national policy statements [2].
Asked whether NSIP demand could cause undersupply, Hambleton said: "Potentially in particular habitats and locations, but we would be cautious about predicting a nationwide reversal." [1] He also expects larger infrastructure buyers to apply tougher due diligence to the banks they use [1].
The TCPA regime also changed on 31 July 2026: a 0.2 hectare de minimis exemption replaced the self-build exemption, and temporary development of five years or less became exempt, following Defra's consultation responses of 15 April 2026 [4]. BNG itself derives from the Environment Act 2021, inserted as Schedule 7A to the Town and Country Planning Act 1990, and has applied to major development since February 2024 with a 30-year habitat management and monitoring requirement [5].
What This Means for Baseline Surveys and Metric Work
Every unit allocation starts with a baseline. The November data increases the stakes for three parts of the ecology survey process.
UKHab Baseline Surveys
The baseline fixes how many units a scheme must deliver. On NSIPs, drawing the BNG boundary correctly is now a survey task as much as a legal one: the ecologist must distinguish habitat that will be disturbed, even temporarily, from habitat that will not [2]. Over-mapping disturbance inflates the obligation; under-mapping invites challenge at examination.
Condition Assessments
Condition scores drive unit values on both the development site and the receptor site. Where units are scarce locally, buyers may be offered banks whose condition targets look optimistic. An independent condition assessment of the receptor habitat, against the published metric criteria, is the simplest protection against paying for units that cannot be delivered.
Metric Calculations and Trading Rules
The metric's trading rules and the spatial multiplier determine whether a bank 40 miles away is cheaper or dearer than one next door. With unit prices easing for most habitats but data thin in places [1], a biodiversity net gain habitat banks ecology survey should test more than one sourcing scenario and record the assumptions, because those assumptions will be read again by a planning officer, an examining authority or, in a dispute, a judge.
Why Local Unit Scarcity Leads to Disputes
Half of local planning authorities have no habitat bank [1]. That gap produces recognisable disputes:
- Planning conditions and biodiversity gain plans. Development cannot lawfully begin until the biodiversity gain plan is approved. If the off-site units named in the plan are not available when needed, the condition cannot be discharged and the start on site is delayed.
- Section 106 and conservation covenant obligations. Off-site gains must be secured for at least 30 years. Disagreements arise over who bears the cost when a bank fails to reach its condition targets, or when monitoring reports show a shortfall.
- Failed off-site deals. Allocation agreements signed before the register entry is confirmed, or before the bank's legal agreement is in place, can collapse, leaving the developer to buy replacement units at a different price or location.
- Monitoring breaches. The 30-year management period means habitat monitoring reports become evidence of compliance or breach for decades.
In each scenario the ecologist's survey, metric calculation and monitoring report are the documents everyone turns to. That is where expert evidence begins.
Expert Ecological Evidence: Ecologists as Expert Witnesses
Ecological evidence is tested in three forums: planning appeals before an inspector, DCO examinations before an examining authority, and civil proceedings in court over contracts, covenants and negligence.
Duties Under CPR Part 35
In court, an expert's overriding duty is to the court, not to the party paying the fee, and the report must comply with Part 35 and Practice Direction 35, including a statement of truth and a summary of instructions [6]. Experts of the same discipline can be ordered to discuss the issues and produce a joint statement. An ecologist whose baseline survey was commissioned for a planning application may later have to defend it under cross-examination, so survey dates, weather, methods and limitations should be recorded as if that will happen.
Professional Conduct
Members of the Chartered Institute of Ecology and Environmental Management are bound by its code of professional conduct, which requires competence, objectivity and evidence-based opinion. Where the expert is a chartered surveyor, the RICS professional standard Surveyors acting as expert witnesses, 5th edition, takes effect on 30 November 2026 and sets expectations on independence, instructions, conflicts and report content.
What Good Expert Ecological Evidence Looks Like
- A clear statement of what was surveyed, when, by whom and under what conditions.
- Metric inputs that can be traced to survey records and photographs.
- An explicit account of alternative sourcing options considered, including why a local bank was or was not used.
- Separation of fact, assumption and opinion.
- Disclosure of any interest in a habitat bank or unit broker.
Biodiversity Surveyors provides UKHab baseline surveys, BNG assessments and expert ecological reports for developers, landowners and their advisers.
Frequently Asked Questions
Does the £143m figure mean units are easy to buy?
No. The figure measures value allocated across England. Half of local planning authorities have no bank and 39% of banks have not sold a unit, so local availability varies widely [1].
Can a planning-stage ecology report be used as expert evidence?
It can be relied on, but if a dispute goes to court the author will usually need to produce a Part 35-compliant report and may be cross-examined on the original survey [6].
Who is liable if an off-site habitat bank fails?
It depends on the terms of the allocation agreement, the section 106 agreement or conservation covenant, and the monitoring evidence. This is general information, not legal advice.
Conclusion
The November 2026 data confirms that BNG is a functioning but uneven market: £143m in value, 414 banks, and large gaps in local supply [1]. With NSIP net gain live from 2 November 2026 [2], demand for specific habitats in specific places is likely to tighten, and the survey and metric work behind each allocation will face closer scrutiny.
Practical next steps for developers, landowners and advisers:
- Commission the UKHab baseline early and record it to an evidential standard.
- Verify any habitat bank's condition, legal security and trading status before relying on it in a biodiversity gain plan.
- Model more than one sourcing scenario and keep the workings.
- Treat every ecology report as a document that may one day be expert evidence.
This article is general information and does not constitute legal or professional advice.
References
- Bng Market Value Climbs to 143m as Activity Grows. thedirt.news.
- Biodiversity Net Gain Requirements Extended Nov 2026. pinsentmasons.com.
- Government Confirms Biodiversity Net Gain for Major Infrastructure From November 2026. cieem.net.
- Key Changes Confirmed to Biodiversity Net Gain. cla.org.uk.
- Understanding Biodiversity Net Gain. gov.uk.
- Part35. justice.gov.uk.