West Sussex BNG / County planning guidance
Biodiversity net gain in West Sussex depends on your planning route, the habitats on your site and the authority considering your application. Start with the site boundary, then connect the design to local nature recovery.
ACP helps developers, architects, planners and landowners establish the requirements, survey habitats and prepare practical BNG delivery plans.
Reviewed 7 November 2026 · West Sussex LNRS published June 2026
District / National Park / county matters
The correct authority is not always the council named in your postal address. First, check whether the site is inside the South Downs National Park. The National Park Authority is the planning authority for land within its boundary, although Chichester District Council may handle an application on its behalf.
Outside the National Park, ordinary development applications generally go to Adur, Arun, Chichester, Crawley, Horsham, Mid Sussex or Worthing, depending on the location. West Sussex County Council usually handles relevant minerals, waste and county development proposals.
Use the four route checks below before selecting a Local Plan or preparing the metric.
The South Downs Local Plan and its Biodiversity Net Gain Technical Advice Note guide sites in the National Park. That includes parts of West Sussex. The National Park boundary also crosses into neighbouring counties, but the West Sussex Local Nature Recovery Strategy remains the relevant LNRS for land within West Sussex.
Even if a district council processes your paperwork, do not substitute its outside-Park Local Plan for the South Downs policies. Check the application record and responsible case officer if there is any doubt.
Four practical checks / site boundary first
Work through these four checks before commissioning the metric. They help you identify the authority and documents to use.
Yes: South Downs National Park Authority is the planning authority. Chichester District may process the application for SDNPA, but Park policies apply.
No: move to the type of proposal. Check the boundary rather than relying on a postal town.
Minerals, waste or county Regulation 3 development: check West Sussex County Council’s jurisdiction outside the Park. For a Park site, confirm the SDNPA route.
Other development outside the Park: identify the relevant district or borough using the red-line boundary.
Check the application date, full red-line area, priority habitat impacts, proposal type and transitional rules. From 6 August 2026, qualifying sites of 0.2 hectares or less may be exempt where no on-site priority habitat is affected.
However, ecological evidence and protected-species duties may still apply.
Read the adopted Local Plan and current validation list. Gather the required habitat survey, condition evidence, maps, BNG statement, metric and delivery information.
Then review the West Sussex LNRS and Local Habitat Map. Where the statutory gain condition applies, obtain approval of the Biodiversity Gain Plan before development starts.
Statutory objective / exemptions / metric methods
The statutory BNG process compares the biodiversity value of habitats before and after development. The statutory metric considers habitat type, area or length, condition, distinctiveness and other prescribed factors. It also accounts for proposals to retain, enhance and create habitats.
You normally assess the existing site, explore layout and habitat options, and prepare the required metric and supporting evidence. Where the statutory biodiversity gain condition applies, a Biodiversity Gain Plan must be approved before the permitted development starts.
The process should inform design choices rather than become a calculation added after the layout is fixed. This is particularly important where hedgerows, woodland, watercourses or higher-value habitats affect the result.
No. The statutory framework contains exemptions and transitional rules. An application made on or after 6 August 2026 can qualify for the 0.2-hectare site exemption if its red-line area is no larger than 0.2 hectares and the development does not impact a priority habitat on site.
Other rules cover householder applications, certain negligible habitat impacts and some temporary development. However, the former self-build and custom-build exemption does not apply to new applications made from 6 August 2026.
An exemption does not automatically remove ecological surveys, protected-site requirements or relevant local biodiversity evidence. For example, Arun’s current validation guidance requests a BNG statement for all development. This is a council information requirement; it does not turn an exempt proposal into a statutory 10% BNG scheme.
The latest statutory biodiversity metric workbook was updated to version 1.1.0 on 3 November 2026. A simplified Small Sites Metric may be available for eligible, straightforward schemes, but a site being “minor” does not automatically make that tool appropriate.
The statutory calculation assesses area habitats, hedgerows and watercourses in separate unit categories. Their unit scores cannot simply be added together to offset one another. For watercourses, use the current user guide and catchment assessment.
If you are unsure which approach applies, commission an eligibility and baseline review before starting the calculations.
For the full method, see our statutory biodiversity metric guide. Where appropriate, our Small Sites Metric service explains the simplified route.
Seven district and borough councils / adopted policy
Local policies and validation lists are not identical across the county. The table gives an initial guide to the adopted policy framework and the evidence worth checking. It does not replace the latest council checklist or advice on a specific application.
| Planning authority | Adopted biodiversity policy or framework | Practical check before submitting |
|---|---|---|
| Adur | Adur Local Plan 2017, Policies 30 and 31; June 2026 Green Infrastructure and Biodiversity SPD | Check the adopted SPD, BNG Technical Advice Note and, where relevant, the Shoreham Harbour plan. |
| Arun | Arun Local Plan 2018, ENV DM5 | Check Arun’s local BNG statement request and the habitat, condition and metric evidence relevant to the application. Record any statutory exemption separately. |
| Chichester | Chichester Local Plan 2021–2039, adopted 2025, NE5 | Use the latest adopted plan, not superseded 2015 policies. Check ecological networks, designated sites and district validation. |
| Crawley | Crawley Local Plan 2023–2040, GI3; 2026 Green Infrastructure SPD | Consider local BNG statement and urban greening evidence where applicable. |
| Horsham | Horsham District Planning Framework 2015, Policy 31 | Council's BNG statement is a local validation requirement; check the separate significant on-site gain guidance. |
| Mid Sussex | Mid Sussex District Plan 2014–2031, DP38 | Check the council's Local List, metric, mapping and Biodiversity Gain Plan evidence. |
| Worthing | Worthing Local Plan 2020–2036, DM18 and DM19; June 2026 SPD | Review Worthing's adopted SPD and the joint Adur/Worthing BNG advice. |
| South Downs National Park | Adopted South Downs Local Plan 2019, SD9 | Verify the National Park boundary and SDNPA's current BNG technical advice, even when a district host processes the case. |
| West Sussex County Council | Applicable county waste/minerals plans and county development policies | Use the county local validation list for minerals, waste and Regulation 3 development outside the National Park. |
Several replacement district plans are being prepared. An emerging or examined plan is not automatically adopted. In particular, Horsham's 2023–2040 plan remained under examination in October 2026; Mid Sussex's 2021–2039 review remained in examination in early November; and Chichester began scoping a further plan to 2045. Use the plan status relevant to your decision date.
The current NPPF limits higher mandatory BNG targets to justified, deliverable, specific site allocations. Decision-makers should give no weight to other policies requiring gains beyond the statutory framework.
Therefore, distinguish ecological information requests from a requirement to deliver extra biodiversity units. Read NPPF policies N1(2) and N2(3) with the application date, exemptions and relevant plan.
A Biodiversity Gain Plan brings the agreed delivery evidence together before commencement.
24 priorities / 108 measures / published June 2026
The West Sussex Local Nature Recovery Strategy (LNRS) was published in June 2026. Prepared under the leadership of West Sussex County Council, it sets out priorities and mapped opportunities for restoring habitats and helping wildlife recover.
The published strategy contains 24 priorities and 108 measures, supported by a Local Habitat Map and information about 166 priority species. It considers how habitat restoration, improved connections and targeted management could contribute to nature recovery.
For a development or off-site habitat proposal, the LNRS can help answer an important question: could the habitat improvements contribute to an identified local nature recovery priority?
The map is not a list of approved off-site BNG sites. It does not override protected-site rules, landownership or the metric's trading requirements. However, used with professional judgement, it can help make a stronger connection between development and local ecological recovery.
Explore the published West Sussex LNRS and Local Habitat Map.
Chalk / woodland / river valleys / coastal habitats
Different landscapes offer different opportunities and constraints. The starting point is a field-based habitat survey and the site's actual design, not a generic county habitat list.
Chalk grassland, woodland edges, scrub and connected hedgerows can be ecologically important. However, creating a rich grassland habitat depends on suitable soils, management and realistic delivery times. Within the National Park, landscape and biodiversity policy apply alongside the statutory metric.
The Weald includes woods, hedgerows, farmland and streams. Ancient woodland and veteran trees need particular protection, and neither can be treated as an ordinary replaceable habitat. Strengthening habitat connections may be appropriate, but first establish what can be retained and what ecological constraints apply.
The Arun and Adur catchments, floodplains and watercourses require careful consideration of water conditions, riparian habitat and flood management. A river or stream can trigger a separate watercourse unit assessment and may require specialist input or other consents.
Coastal locations around Chichester and Pagham Harbours and other shoreline habitats can be sensitive to development pressures. In towns, opportunities may include better urban green infrastructure, native planting and well-designed drainage features. Nevertheless, neither BNG nor a landscape scheme replaces any assessment required for protected sites.
Natural England withdrew the Sussex North water-neutrality position statement on 31 October 2025. That former blanket planning requirement is no longer in force, although separate ecological and water-related assessments may still be necessary.
Read the county’s water-neutrality update. Check any separate water, habitat and protected-site issues for the actual proposal.
Application route / registered units / long-term stewardship
BNG should start with protecting the best habitats that can realistically remain. Next, test suitable on-site creation and enhancement options against the layout, ecology and long-term management requirements.
For eligible non-major applications from 6 August 2026, relevant on-site and registered off-site gains sit at the same level of the hierarchy. Major schemes and earlier applications can follow different rules. Therefore, confirm the application date and route before choosing the delivery strategy. Statutory biodiversity credits remain a last resort.
For West Sussex off-site habitat proposals, it is sensible to review the local recovery strategy and local ecological connections. However, units must be real, meet the metric and trading rules, and have the appropriate registration, legal agreements, allocation and management arrangements.
A Habitat Management and Monitoring Plan (HMMP) can define the intended habitats, establishment work, management methods, responsibilities, monitoring and corrective actions. Significant on-site gains and registered off-site gains are generally secured for at least 30 years.
A plan should also consider access, future land use, drainage, soil and the practical costs of habitat maintenance. Without a workable management approach, a favourable headline metric result may be difficult to deliver.
If off-site delivery is needed, compare the requirements for off-site biodiversity units. Our habitat management and monitoring plan guidance covers delivery responsibilities and monitoring.
Eight checks / coordinated planning evidence
Use this checklist before instructing surveys or submitting an application. It helps your team coordinate the site information and identify questions for the planning authority.
Scope / survey / delivery
We review your location, planning stage, proposed works and existing evidence. First, we help identify the relevant authority, BNG applicability questions and likely ecological inputs. We then explain the recommended scope and assumptions.
Where instructed, we prepare the agreed baseline survey, habitat mapping, metric calculations and related reporting. We can work with your planning and design team to check how layout changes affect the evidence.
We help set out the relevant Biodiversity Gain Plan information, habitat management and monitoring requirements, and practical issues to resolve for any on-site or off-site approach. The work and responsibilities are agreed in the project scope.
For a coordinated submission, see our BNG report for planning service. Explore BNG across South East England for the wider regional context.
Practical answers / application planning
No. The statutory regime normally requires at least 10% BNG for non-exempt development, but exemptions and transitional rules apply. Separately, local biodiversity policies and protected-species duties may still affect an exempt proposal. Check the application date, site and council guidance before assuming either outcome.
A qualifying application made on or after 6 August 2026 may be exempt if the red-line site is no larger than 0.2 hectares and the development does not impact on-site priority habitat. Other conditions and application routes still need checking. The rule is about the site area, not simply the building footprint.
If the site is inside the National Park, SDNPA is the planning authority. However, Chichester District Council may process applications in its district under the National Park's delegated arrangements. Check the map, planning application portal and responsible case officer rather than relying on a postal address.
Use the adopted Local Plan for the authority and boundary that cover your land. There are separate district and borough plans, plus the South Downs Local Plan inside the Park. An emerging plan can be relevant as a material consideration, but it must not be described as an adopted replacement.
Yes. The West Sussex LNRS was published in June 2026. It has its own priorities, species information and Local Habitat Map. East Sussex and Brighton & Hove share a separate strategy, so choose the correct mapped area.
No. Mapped measures are evidence to examine, not an automatic approval or unit uplift. Strategic significance requires a justified relationship between the proposed habitat, its location and the applicable published strategy and metric guidance. Site-specific ecological judgement remains essential.
Where the rules permit, registered off-site biodiversity units can address a calculated shortfall. Check unit type, trading rules, registration, allocation and legal security. The relevant gain hierarchy also depends on the application date and whether the scheme is major or non-major. Statutory credits are a distinct last-resort mechanism.
For planning permission subject to the statutory biodiversity gain condition, the BGP must be approved before development commences. A council may also ask for supporting strategy, metric and management details earlier to understand whether the proposed development can deliver BNG.
It can be suitable for eligible smaller schemes with appropriate habitats and proposals. However, exemption from statutory BNG and eligibility to use the Small Sites Metric are different questions. Complex habitats and off-site proposals can require the full statutory metric. Confirm the latest eligibility rules before relying on the simplified tool.
Hedgerows and watercourses are assessed separately from area habitats in the statutory metric. They can need their own survey, condition evidence and unit calculations. A gain in one category cannot simply cancel a deficit in another, and separate ecological or regulatory consents may apply.
The specific Natural England Sussex North water-neutrality position statement was withdrawn on 31 October 2025. The former blanket planning evidence requirement has ended. Nevertheless, consider any separate habitat, water-quality, protected-site or project-specific issues with the correct planning authority.
Significant on-site gains and registered off-site gains are generally legally secured and managed for at least 30 years. The required HMMP, monitoring, ownership and enforcement arrangements depend on the scheme and authority. Do not assume every small piece of routine landscaping needs an identical legal agreement.
Talk to ACP / Site enquiries
Tell us where the site is, what you plan to build and how far the application has progressed. We’ll use that context to discuss the surveys, calculations or plans your project needs.
What to have to handA red-line plan, an existing ecology report or a request from the council can help us scope the work. Start with whatever you already have.
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West Sussex BNG
Reviewed 7 November 2026.
Adur supplementary planning guidance
Arun — BNG and validation guidance
Chichester — adopted Local Plan 2021–2039
Crawley — Green Infrastructure SPD
Horsham — BNG application guidance
Horsham — Local Plan examination update
Mid Sussex — adopted District Plan
BNG and Local List guidance — Mid Sussex
