Biodiversity Net Gain Consultant

Biodiversity net gain consultant: practical support for development

A biodiversity net gain consultant helps you understand what your development must deliver for nature and how to demonstrate it through the planning process. Working with a BNG consultant early can connect your habitat baseline, layout, biodiversity metric and long-term management commitments before decisions become expensive to change. Collington Winter Environmental provides biodiversity consultancy throughout England, helping applicants, landowners and design teams turn BNG requirements into a clear, evidence-led delivery strategy. Our role is to explain the ecological implications of your proposals and support a solution that can be implemented, managed and checked.

BNG consultants do more than calculate a percentage. A credible assessment must reflect the habitats actually present, the development that will be built and the management that can realistically take place. A BNG ecologist should also recognise when protected species, designated sites or other ecological constraints require separate investigation. Biodiversity net gain complements those responsibilities; it does not replace them or make an otherwise unacceptable ecological impact acceptable.

What does a BNG consultant do?

Establish a defensible habitat baseline

The starting point is an accurate picture of the site before development. Your consultant reviews available information, identifies survey requirements and maps habitats within the application boundary. Habitat type, extent and condition inform the baseline calculation. For habitats requiring condition assessment, the evidence should explain why the selected condition is justified rather than simply assigning a convenient score.

Survey findings need to be traceable to mapped parcels and the correct metric entries. A grassland parcel, hedgerow or watercourse cannot be treated as interchangeable just because it occupies the same development site. Some habitats require specialist assessment, and seasonal limitations can affect the confidence of survey conclusions. Identifying these issues early helps establish what information is needed before the planning application is prepared.

Calculate losses, retention and proposed gains

The consultant models your proposals using the statutory biodiversity metric, or the Small Sites Metric where the development is eligible. The calculation distinguishes retained habitats from those lost, enhanced or created. It considers factors including distinctiveness, condition and strategic significance, alongside the delivery risks associated with proposed habitats. Read more about our approach to biodiversity metric calculations.

The result is a decision-making tool, not a substitute for ecological judgement. If a layout generates a deficit, your consultant can explain whether retaining additional habitat, changing the landscape proposals or securing appropriate off-site units would address it. The metric's trading rules must also be satisfied, so achieving an overall percentage does not automatically mean the scheme complies.

When do you need a biodiversity net gain consultant?

In England, mandatory BNG generally requires at least a 10% increase in biodiversity value for development within scope. The framework was introduced through the Environment Act 2021 and Schedule 7A of the Town and Country Planning Act 1990. It commenced for major development from 12 February 2024 and for small sites from 2 April 2024, subject to exemptions and transitional arrangements.

You should seek advice before submitting an application if your project may affect habitats, if the council requests BNG information or if you are uncertain whether an exemption applies. Even a modest development can require a proper assessment. Conversely, some developments are exempt, and permitted development is outside this mandatory planning framework. Our guide to when BNG assessments are required explains the starting questions.

Early advice is particularly valuable when acquiring land, establishing development capacity or reviewing planning risk. An apparently straightforward landscape scheme may not provide enough suitable habitat to achieve the required outcome. Discovering that after the layout has been fixed can restrict your options, especially where access, drainage, utilities and public use compete for the same land.

The process from baseline to biodiversity gain plan

1. Scope the project and check applicability

We start with the planning route, application history, site boundary and development proposals. This helps identify whether statutory BNG applies and whether earlier permissions or relevant exemptions need closer review. We also consider whether the full statutory metric is required or whether the Small Sites Metric is suitable. A small site does not qualify automatically: habitat and species constraints can make the simplified tool inappropriate.

At this stage, useful information includes a location plan, existing and proposed layouts, any previous ecological reports and details of intended phasing. A clear brief helps avoid gaps between the ecological assessment and the planning consultant's submission strategy. It also establishes which surveys or supporting assessments fall outside the BNG calculation itself.

2. Survey habitats and prepare the baseline

A suitably competent surveyor records habitat parcels and the evidence needed for the selected metric. The baseline date must be appropriate to the statutory framework, and earlier habitat degradation may need to be considered. Clearing or degrading habitat before an application is not a reliable way to reduce BNG obligations; the legislation contains safeguards addressing relevant earlier degradation.

The baseline should be consistent across the metric, survey report and habitat plan. Clear parcel references allow the planning authority to follow the calculation and help the wider project team understand which areas are important to retain. Where information is uncertain, that uncertainty should be identified and resolved rather than hidden within a spreadsheet.

3. Test the design against the biodiversity gain hierarchy

Avoiding habitat loss and retaining valuable features should be considered before relying on replacement habitat. Your consultant can work with landscape architects, engineers and planners to test realistic design changes. This might involve retaining a boundary hedgerow, improving an existing grassland parcel or moving infrastructure away from habitat that would be difficult to replace.

The biodiversity gain hierarchy guides consideration of on-site avoidance, mitigation, enhancement and creation before appropriate off-site provision and, finally, statutory credits. The aim is not to maximise an attractive spreadsheet result at the expense of deliverability. Proposed habitats must suit the soil, hydrology, available space and future use of the site if they are to achieve their target condition.

4. Resolve any off-site requirement

Where a residual shortfall remains, we can help establish the type and quantity of off-site biodiversity units required. Units from a habitat bank must meet the development's needs after the metric's trading rules and spatial risk multiplier are applied. A nearby offer is not necessarily suitable if it provides the wrong habitat category or lacks a clear route to registration and allocation.

Off-site gains must be legally secured and registered on the biodiversity gain site register run by Natural England before they can be relied on in the approved gain plan. Our habitat banking guide explains the relationship between landowners, habitat delivery and development demand. Statutory biodiversity credits are a last resort, not the normal starting point for sourcing a shortfall.

5. Support the biodiversity gain plan and delivery arrangements

The biodiversity gain plan is normally submitted after planning permission has been granted and must be approved before development commences under the statutory biodiversity gain condition. The application stage still requires baseline information and enough explanation for the authority to understand the proposed approach. Leaving every BNG question until after permission risks an undeliverable condition.

The gain plan needs to align with the final metric, habitat plans, off-site allocations and management arrangements. Significant on-site enhancements and registered off-site gains must be secured and maintained for at least 30 years under the applicable framework. A habitat management and monitoring plan translates the ecological proposals into practical tasks, responsibilities, monitoring and corrective action.

How to choose BNG consultants

Ask who will undertake the survey, who will complete the metric and who will review the proposed habitats for deliverability. Experience with planning submissions matters, but so does the ability to explain assumptions clearly. Look for a consultant who can distinguish statutory minimum requirements from local policy expectations and who will identify missing information before it becomes a planning issue.

A useful scope should state the surveys, plans, calculations and written outputs included, as well as exclusions such as protected species work, legal drafting or ongoing monitoring. Ask how design revisions will be handled and what information is needed from your team. Comparing only the headline fee can obscure substantial differences in the work being offered and the risks left unresolved.

Why choose Collington Winter

Collington Winter Environmental is based in Bolton and we work throughout England. Managing Director Olivia Collington is a Chartered Environmentalist with the IES and holds Natural England bat and great crested newt licences, together with GCN and badger mitigation licences. Her experience includes the DEFRA Statutory Biodiversity Metric and habitat bank offsetting, supporting joined-up consideration of assessment, delivery and planning obligations.

We focus on clear advice that connects ecological evidence with the practical needs of your project. Whether you need an initial applicability review or support progressing from survey to gain plan, the objective is an understandable route forward. For background, explore what biodiversity net gain means and whether BNG is mandatory.

Speak to a BNG consultant

Bring us your site plan, planning history and any ecological information already available so we can discuss the next steps. To talk about biodiversity consultancy for your development, call 01204 939 608 or use our contact page.