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Hedgerow loss and biodiversity net gain in Gravesham: the planning obligation under the Environment Act 2021

Planning permissions in England have been subject to a biodiversity net gain condition since 12 February 2024 for major development and 2 April 2024 for most smaller sites. Unless an exemption applies, a development that affects a hedgerow, whether by removal, fragmentation or damage, must deliver a minimum 10 percent biodiversity net gain under the Environment Act 2021. The rule is not satisfied by a token replanting gesture. It requires a metric calculation, a Biodiversity Gain Plan approved by the council, and a commitment to secure the gain for at least 30 years. For the farmers and developers working on hedge-bounded land in DA11 and DA12, this is a separate legal framework that sits alongside, and does not replace, the Hedgerow Regulations 1997 notice obligation.

What the law says

Section 98 of the Environment Act 2021, together with Schedule 14 of that Act, inserted a new Schedule 7A into the Town and Country Planning Act 1990. Schedule 7A introduced the "biodiversity gain condition": a mandatory pre-commencement planning condition that must be attached to every qualifying planning permission in England. Until a Biodiversity Gain Plan is submitted to, and approved by, the local planning authority, no development works may lawfully begin.

The Biodiversity Gain Plan must demonstrate that the proposed development will achieve at least a 10 percent net gain in biodiversity units compared to the pre-development baseline. The calculation is made using Natural England's statutory biodiversity metric, or the simplified Small Sites Metric where it is available for qualifying small sites.

Mandatory from:

• 12 February 2024 for major development, as defined in the Development Management Procedure Order, where the application was made on or after that date.
• 2 April 2024 for non-major development, where the application was made on or after that date, unless an exemption applies.

Enforcement: development commenced without an approved Biodiversity Gain Plan is a breach of the pre-commencement condition. Gravesham Borough Council, as the local planning authority, can take enforcement action, and GOV.UK says the council has a role in monitoring the Biodiversity Gain Plan once development has started.

This obligation is entirely separate from the Hedgerows Regulations 1997 (which govern removal notification for qualifying agricultural hedgerows), from the section 211 conservation area notice, and from the Tree Preservation Order regime. All of these frameworks may apply simultaneously to the same site: satisfying one does not discharge the others.

The hedgerow metric: why hedges have their own unit type

The statutory biodiversity metric divides habitat features into three categories, each measured and scored separately:

• Area habitats: grassland, woodland, scrub, bare ground and similar, measured in hectares.
• Linear habitats: hedgerows, lines of trees, and ditches with hedgerow character, measured in kilometres.
• Watercourses: rivers and streams, measured in kilometres.

Each category has its own biodiversity unit calculation, and units from one category cannot substitute for units from another. This is the point that catches many applicants by surprise. If a development removes 100 metres of hedgerow on the eastern boundary of a Gravesham field, the developer cannot compensate for that loss by planting wildflower meadow or adding trees elsewhere on the site. The metric requires hedgerow units to be replaced with hedgerow units, either on-site or through a registered off-site hedgerow gain. Area habitat units cannot fill a hedgerow deficit.

Within the linear habitat category, each hedgerow receives a condition class (good, moderate or poor) based on a field assessment. A good-condition hedge is worth significantly more biodiversity units per kilometre than a poor-condition one. The condition assessment follows the metric's own criteria, which cover things such as hedge height and width, gaps, the vegetation beneath and beside it, standard trees and non-native species. A dense, species-rich mixed hedge of hawthorn, blackthorn, field maple and hazel with occasional standards is likely to score in the good condition class. A thin, gappy leylandii boundary hedge in a suburban garden will score poor. The difference in units per kilometre is material: a good-condition hedge that is removed creates a larger BNG obligation than a poor-condition one of the same length.

The practical consequence for any application involving hedgerow loss in Gravesham is that the condition of the existing hedge drives the scale of the replacement obligation. A well-managed, species-rich agricultural hedgerow is the most biodiversity-valuable hedge type in the metric: removing one triggers a proportionately larger gain requirement than removing a monoculture boundary hedge.

Does BNG apply to your planning application? A qualifying check

Work through the following before preparing a Biodiversity Gain Plan or commissioning a baseline survey:

• Does the project require a planning application? BNG applies only to development requiring planning permission. Works carried out under permitted development rights (authorised by the Town and Country Planning (General Permitted Development) (England) Order 2015 without an application) are outside the BNG framework. Note: Article 4 Directions removing permitted development rights operate in several of Gravesham's conservation areas. If your development is in a conservation area and you are unsure whether PD rights apply, confirm with Gravesham Borough Council before assuming no application is required.
• Is the project within the exemptions? The exemptions are set out in the Biodiversity Gain Requirements (Exemptions) Regulations 2024. They include householder applications and permitted development. There is also a de minimis exemption for development that does not affect priority habitat and affects less than 25 square metres of habitat and less than 5 metres of linear habitat such as a hedgerow, so a short gap for an access may fall inside it but a longer length will not. For applications made on or after 6 August 2026, a further exemption covers sites no larger than 0.2 hectares that do not affect priority habitat. Confirm which applies with a planning consultant or the council.
• What is the application date? BNG applies to applications made on or after 12 February 2024 (major development) or 2 April 2024 (non-major development). Applications submitted before these dates are not subject to the mandatory condition, even if the development is ongoing.

If BNG applies, the next step is a baseline hedgerow survey. The survey must be completed before the Biodiversity Gain Plan can be prepared, and the timing of that survey is governed by a separate set of legal constraints.

The seven steps for a BNG-compliant application affecting a hedgerow

1. Commission a baseline hedgerow survey. A qualified ecologist (or, for small sites using the Small Sites Metric, a competent person following Natural England's field guidance) must survey all hedgerow features on the site and assign each a condition class using the statutory biodiversity metric field methodology. The survey records hedge length, woody species present, connectivity, management history and any notable features. For small sites, Natural England's Small Sites Metric tool does not require a full ecologist's condition assessment, but the hedgerow length and species-richness data must still be gathered on site. Plan survey timing around the nesting-season constraint above.

2. Run the Biodiversity Metric calculation. Enter the baseline survey data into Natural England's statutory biodiversity metric calculator (or the Small Sites Metric tool for qualifying applications). The tool produces a baseline biodiversity unit figure broken down by area habitats, linear habitats and watercourses. For a hedgerow-affected application, the key output is the number of linear biodiversity units in the pre-development hedgerow, calculated from the hedge's length, distinctiveness type and condition class. This is the starting point for the 10 percent gain target.

3. Design the development to avoid or minimise hedgerow loss. The National Planning Policy Framework requires applicants to demonstrate that they have sought to avoid harm to biodiversity before mitigating or compensating for it. For a hedgerow, this means exploring whether the development footprint can be adjusted to retain the hedge, or whether gaps can be limited to the minimum necessary for access. A retained hedge in good condition scores better than a new hedge of equivalent length: retention reduces the BNG burden and is the preferred outcome under both the NPPF and Natural England's guidance. Document the avoidance and minimisation steps taken, as Gravesham Borough Council's ecology officer may require this as part of the Biodiversity Gain Plan.

4. Identify where the 10 percent gain will be achieved. The hierarchy is: on-site gain first, then off-site registered gain, then government statutory biodiversity credits as a last resort. For hedgerow loss, on-site gain means planting new hedgerow of equivalent or greater length and a target condition class. Off-site gain requires registering a parcel of land on the national Biodiversity Gain Site Register and securing a legal agreement for at least 30 years of hedgerow management on that land. Government biodiversity credits are purchased from DEFRA for a fee: confirm the current credit price with DEFRA or Natural England before including credits in any BNG plan, as prices are subject to revision. Credits are a last resort and are not intended to substitute for on-site or off-site hedgerow creation where those options are feasible.

5. Secure the gain for 30 years. Any habitat created or enhanced to deliver the BNG obligation must be maintained and monitored for a minimum of 30 years. For on-site hedgerow gain, this is typically secured by a planning condition requiring submission and approval of a Habitat Management and Monitoring Plan. For off-site gain, a section 106 legal agreement or conservation covenant under the Environment Act 2021 is used. The 30-year management obligation runs with the land and binds future owners: it should be noted in any title documents or solicitors' enquiries on sale.

6. Prepare and submit a Biodiversity Gain Plan. The Biodiversity Gain Plan is a formal document setting out the pre-development baseline units (from the metric calculation), the post-development units (after any on-site or off-site gain), the 10 percent minimum gain demonstrated, and the mechanism by which the gain will be secured and managed. It must be submitted to Gravesham Borough Council as part of the planning application. For small sites using the Small Sites Metric, Natural England publishes a standard Biodiversity Gain Plan template and a Habitat Management and Monitoring Plan template: use these rather than creating bespoke documents, as they match what the planning officer will expect to see.

7. Apply to discharge the pre-commencement biodiversity gain condition. Once planning permission is granted, the biodiversity gain condition will appear as a pre-commencement condition (typically worded to the effect that development shall not begin until a Biodiversity Gain Plan has been submitted and approved in writing by the local planning authority). Submit a formal application to Gravesham Borough Council to discharge this condition, including the approved Biodiversity Gain Plan and any supporting Habitat Management and Monitoring Plan. Development may not lawfully start until written discharge confirmation is received.

How BNG and the Hedgerow Regulations 1997 interact

For agricultural or rural hedgerows in the Gravesham borough, the Hedgerow Regulations 1997 and the BNG requirement under the Environment Act 2021 operate as two separate and parallel legal obligations. Both may apply to the same hedgerow removal. The Hedgerow Regulations require a written Hedgerow Removal Notice submitted to Gravesham Borough Council at least 42 days before removal: this is a standalone notification process with its own penalty regime. BNG requires a Biodiversity Gain Plan approved before development works begin: this is a planning condition under a separate statutory regime.

Completing the 42-day Hedgerow Regulations notice does not satisfy the BNG obligation. Preparing a Biodiversity Gain Plan does not substitute for the Hedgerow Removal Notice. An applicant removing a qualifying rural hedgerow in Gravesham as part of a development that also requires planning permission must comply with both, in sequence.

A planning permission that includes hedgerow removal as part of the consented development may itself deal with the Hedgerow Regulations position, by means of a condition or by the planning officer's assessment: check the specific wording of the planning permission and any pre-commencement conditions carefully. Do not assume that a grant of planning permission overrides the Hedgerow Regulations obligation; it may not, and the two regimes are administered under different statutory routes.

Gravesham: agricultural land, Thames corridor development and the hedgerow unit value question

The farmland between Gravesend town and the villages of Higham, Chalk, Shorne, Cobham and Meopham is divided by mixed hedgerow networks, and many of them may be old and species-diverse enough to score in the good condition class under the metric. A good-condition hedgerow of 200 metres creates a larger BNG obligation on its removal than a comparable length of poor-condition hedge. Applications for residential subdivision, access creation or equestrian development on agricultural land are likely to involve precisely these higher-value hedge types.

Check with Gravesham Borough Council, or a planning consultant familiar with its ecology requirements, whether its local plan policies ask for anything beyond the national 10 percent minimum before finalising a Biodiversity Gain Plan.

Part of the south of the borough lies within the Kent Downs National Landscape (formerly the Area of Outstanding Natural Beauty). Development in or affecting a protected landscape is subject to additional policy scrutiny under the National Planning Policy Framework, and a hedge there may carry both Hedgerow Regulations protection and a significant BNG obligation: the two compound, they do not substitute for one another.

Sources: Environment Act 2021, section 98 and Schedule 14 (legislation.gov.uk); Town and Country Planning Act 1990, Schedule 7A as inserted (legislation.gov.uk); The Biodiversity Gain Requirements (Exemptions) Regulations 2024 (legislation.gov.uk); Natural England, statutory biodiversity metric and Small Sites Metric calculation tools (gov.uk); GOV.UK, "Biodiversity net gain" planning practice guidance; DEFRA Environment blog, "Biodiversity net gain now applies to small developments" (defraenvironment.blog.gov.uk, 2 April 2024); Ground Control, "How hedgerows contribute to Biodiversity Net Gain" (ground-control.co.uk); National Planning Policy Framework (DLUHC, 2023 ed.); Hedgerows Regulations 1997, SI 1997/1160 (legislation.gov.uk); Wildlife and Countryside Act 1981, section 1 (legislation.gov.uk).