Since mandatory biodiversity net gain (BNG) became a legal requirement in England on 12 February 2024, biodiversity has become a central consideration within the planning process. Before development can begin, local planning authorities must approve a biodiversity gain plan demonstrating how a development will achieve at least a 10% increase in biodiversity value.
Many developers assume that submitting biodiversity metric calculations alone is enough. In practice, local planning authorities look for much more than a final biodiversity score. They want evidence that biodiversity net gain requirements have been properly considered throughout the design process, that biodiversity gains are realistic and deliverable, and that they will be maintained for at least 30 years.
Understanding what local planning authorities actually look for can help reduce planning risk, avoid delays and improve the likelihood of securing planning permission.
The Purpose of a Biodiversity Gain Plan
A biodiversity gain plan is the document that shows how a development will achieve biodiversity net gain and satisfy the biodiversity gain condition attached to planning permissions. It accompanies the finalised statutory biodiversity metric tool and comprises a simple pro-forma, onto which a number of other documents and agreements may be appended depending on the complexity of the project.
Under the statutory framework, local planning authorities must approve the biodiversity gain plan before development starts. LPAs generally have up to eight weeks to determine whether the submitted gain plan satisfies biodiversity net gain requirements.
The gain plan forms part of the wider biodiversity net gain BNG process and demonstrates how biodiversity value will be protected, enhanced and maintained throughout the lifecycle of a development project.
Accurate Baseline Biodiversity Value Calculations
One of the first things planning authorities assess is whether the baseline biodiversity value has been calculated correctly.
The pre-development biodiversity value establishes the benchmark against which biodiversity gain is measured. Local planning authorities will expect developers to provide accurate habitat surveys undertaken by suitably qualified professionals and supported by ecological expertise.
The statutory biodiversity metric tool must be used to calculate the baseline biodiversity value. Published by Natural England, the current biodiversity metric calculates biodiversity units based on habitat size, condition and distinctiveness.
Local planning authorities will review whether the baseline biodiversity has been assessed accurately within the red line boundary and whether existing habitat conditions have been properly recorded.
Evidence That the Biodiversity Gain Hierarchy Has Been Followed
Many local planning authorities place significant emphasis on the biodiversity gain hierarchy and mitigation hierarchy.
Before considering off-site biodiversity units, developers must demonstrate that opportunities to avoid biodiversity loss have been fully explored. Planning officers want to see evidence that site layouts have been designed to retain valuable habitats, protect biodiversity and minimise impacts on wildlife habitats and wildlife species.
Particular attention is often given to irreplaceable habitats. LPAs will check that adverse impacts on irreplaceable habitats have been minimised and that statutory requirements relating to these habitats have been followed.
Where biodiversity losses cannot be avoided, authorities expect developers to maximise habitat enhancement and habitat creation opportunities within the development site before relying on off-site gains.
Robust Biodiversity Metric Calculations
A biodiversity gain plan must contain clear and transparent biodiversity metric calculations.
Planning authorities will review both the pre-development biodiversity value and the projected post-development biodiversity value to ensure that the biodiversity gain objective is being met.
The statutory biodiversity metric measures biodiversity value before and after development and calculates whether sufficient biodiversity units have been delivered to achieve mandatory biodiversity net gain.
Authorities will scrutinise habitat creation assumptions, habitat enhancement works, habitat condition targets and delivery timescales. Unrealistic assumptions can result in requests for additional information or delays to approval.
Clear On-Site Biodiversity Proposals
Local planning authorities generally prefer biodiversity gains to be achieved on site wherever possible.
A strong biodiversity gain plan should clearly explain how biodiversity gains will be delivered through habitat creation, habitat enhancement and green infrastructure. This may include new woodland planting, species-rich grassland creation, wetland features, wildlife corridors or other measures designed to enhance biodiversity.
Planning officers will assess whether proposed habitats are appropriate for the location and whether they contribute positively to the natural environment and local nature recovery objectives.
Developers should clearly explain how much biodiversity gain can be achieved on site and how these measures contribute to the overall net gain target. Should proposed on-site habitats that contribute to the overall net gain score require specific management regimes, it may be necessary to append a detailed habitat management plan and a 30+ year legal commitment to enact that plan (such as a Section 106 agreement).
Appropriate Off-Site Biodiversity Gains
Where sufficient biodiversity units cannot be achieved on site, LPAs will assess proposed offsite biodiversity units carefully.
If biodiversity gain requirements cannot be achieved on-site, off-site biodiversity gains must be legally secured and registered. Local planning authorities will expect evidence that the proposed biodiversity gain site appears on the Biodiversity Gain Site Register maintained by Natural England.
Authorities will also review whether off-site gain sites align with local nature recovery strategies and broader local nature recovery priorities. Sites that contribute to strategic ecological objectives often carry greater strategic significance within the statutory biodiversity metric.
Many local planning authorities favour off-site biodiversity units located within their own authority area where possible, particularly where these support local habitat creation priorities.
Legal Agreements and Long-Term Security
One of the most important aspects of any biodiversity gain plan is demonstrating that biodiversity gains will be maintained over the long term.
Biodiversity net gain must be secured for a minimum of 30 years. Local authorities therefore require evidence that appropriate legal agreements are in place.
For offsite biodiversity units, this may involve conservation covenants with a responsible body or planning obligations secured through Section 106 agreements. These legal mechanisms ensure biodiversity gain commitments remain enforceable long after planning permission has been granted.
Planning authorities will often review the legal agreement alongside the biodiversity gain plan to ensure habitats are properly protected.
Habitat Management and Monitoring Plans (HMMPs)
Delivering biodiversity gain is only part of the requirement. Authorities also want to understand how habitats will be managed.
A detailed monitoring plan should explain how biodiversity gains will be maintained and monitored over the required 30-year period. The management plan should identify responsibilities, maintenance activities, performance indicators and reporting arrangements. If purchasing biodiversity units from an offset provider such as Civity, they will have their own pre-approved HMMP; however, if providing your own habitats, you may be expected to produce your own project-specific HMMP and to secure it via an appropriate legal agreement over the 30-year period.
Local planning authorities have a duty to monitor biodiversity gains and verify compliance throughout the management period. As a result, clear environmental management arrangements are increasingly important within planning submissions.
Off-Site Units and Statutory Biodiversity Credits
Where offsite biodiversity units are required, planning authorities will expect developers to provide evidence that those units have been secured appropriately.
This includes demonstrating that the biodiversity value of the proposed gains equals or exceeds the value being claimed within the biodiversity metric calculations.
Where developers intend to buy statutory biodiversity credits, LPAs will typically require evidence that statutory credits have been purchased. However, statutory biodiversity credits are intended as a last resort and should only be used where suitable off-site biodiversity gains cannot be secured through the private market. It will be necessary to demonstrate to the LPA that it was not practicable to produce units or purchase them from an offset provider before resorting to purchasing statutory credits. The biodiversity Gain Plan template stipulates that at least three offset providers or a negative search result from online registers is required as evidence, but this should be treated as a minimum requirement and LPAs may have more detailed thresholds.
Alignment with Local Nature Recovery Strategies
Local nature recovery strategies are becoming increasingly influential within planning decision-making.
Many local planning authorities assess whether biodiversity gains contribute towards local nature recovery priorities. Habitat creation proposals that support strategic ecological networks, wildlife habitats and biodiversity enhancement objectives are often viewed more favourably.
Developers who align biodiversity gain plans with local nature recovery strategies can often strengthen their planning submissions while delivering wider environmental benefits.
How Civity Supports Biodiversity Gain Plan Preparation
At Civity, we support developers throughout the biodiversity net gain process, from baseline biodiversity assessments and statutory biodiversity metric calculations through to biodiversity gain plan preparation and off-site biodiversity unit procurement.
Our team works closely with developers, ecologists, land managers and local planning authorities to ensure biodiversity gain plans are robust, compliant and aligned with planning policy requirements. We also help clients identify suitable habitat banks, secure offsite biodiversity units and navigate the legal requirements associated with conservation covenants and planning obligations.
Conclusion
What local planning authorities actually look for in a biodiversity gain plan goes far beyond achieving a numerical biodiversity target.
Planning authorities want evidence that baseline biodiversity has been assessed correctly, that the biodiversity gain hierarchy has been followed, that biodiversity units are calculated accurately and that habitats will be managed successfully for at least 30 years.
Developers who address these requirements early and prepare a comprehensive biodiversity gain plan are far more likely to achieve planning permission efficiently while delivering meaningful biodiversity gains for the natural environment.
