Need a Biodiversity Net Gain assessment?

What is a Biodiversity Net Gain Assessment?

Biodiversity Net Gain (BNG) has become an integral concept in sustainable development, aimed at addressing biodiversity loss by ensuring that new developments leave the natural environment in a measurably better state than before. With BNG now enshrined in law, understanding what a BNG assessment entails is critical for developers, planners and environmental professionals.

This article explores the origins of Biodiversity Net Gain and the purpose behind its introduction, before looking at how a Biodiversity Net Gain assessment is conducted and the practical implications for development projects and achieving planning permission.

Background to Biodiversity Net Gain becoming Law

BNG became a legal requirement as part of a global shift towards halting biodiversity decline. In the UK, the Environment Act 2021 mandates that all developments must achieve at least 10% net gain in biodiversity from a pre-development biodiversity baseline, and the improvements must last for the long term – at least 30 years, which will require future management.

BNG was expected to become law in November 2023 after a two-year transition period following the passing of the Environment Act 2021 by the UK government. However, rollout was delayed until 12 February 2024.

The legislation reflects growing recognition of the need to integrate biodiversity considerations into the planning system, ensuring that economic growth does not have a negative impact on irreplaceable habitat and protected species. BNG is now an integral part of the planning system and it is a developer’s responsibility to fulfil the mandatory bng requirements.

BNG Aims to Boost Existing Protections

BNG was introduced to counteract the alarming rate of habitat lost to urbanisation, agriculture and infrastructure development. The primary aim of BNG is to create a measurable increase in biodiversity through responsible planning and land management.

By enhancing habitats, habitat restoration and promoting sustainable development practices, BNG seeks to balance economic development with ecological preservation: preserving important species and valuable habitat types. It also aims to foster public and stakeholder confidence by demonstrating accountability in managing environmental impacts.

How a BNG Assessment is carried out

A BNG assessment involves a set format to retain consistency and reliability. Initially, a competent person such as an environmental consultant will conduct a desk top study to assess the locality of the development proposal and any known habitats present. This is followed by a site visit to measure biodiversity on-site.

To achieve a baseline habitats figure, surveyors will use the latest version of the Defra biodiversity metric calculation tool to evaluate onsite habitat type, condition, and ecological value. Wildlife species present will be noted, and the findings will be converted into a unit value that can be entered into the statutory biodiversity metric tool to calculate a pre-development biodiversity value of the site.

Features typically providing biodiversity units include hedgerows, linear habitats and watercourses. Using professional judgement, the ecologist will make a post-development biodiversity net gain calculation by assessing the developer’s plans to work out any loss or gain in biodiversity.

Calculate the Number of Biodiversity Units

Using the biodiversity gain hierarchy, the consultant will be able to calculate biodiversity net gain to enhance the site’s biodiversity value in the optimal way. This will vary according the the site, and may well involve creating or enhancing habitats. If it proves impossible to achieve at least 10% uplift through on site enhancements, which is the first option, off-site compensation will be needed. This is the last resort option, involving the creation of habitat on land outside the development site.

As well as referring to the mitigation hierarchy, the surveyor will take into account key considerations that could affect planning applications such as nationally significant infrastructure projects, local nature recovery strategies, protected sites, site of special scientific interest designations, existing local policies, other stakeholders and local plans.

The resulting biodiversity net gain plan will be submitted to the relevant local planning authority at the planning application stage. The proposed approach will contain details of habitat present within the red line boundary along with expected habitat loss and habitat enhancement, suitable mitigation and compensation measures and steps to deliver the required amount of biodiversity gain.

Further surveys

The ecological survey may reveal the presence of protected wildlife species indicating the need for additional surveys. These could also include noise and air quality assessments, tree surveys or an ecological impact assessment.

Key stakeholders in a BNG assessment

BNG surveys involve a range of stakeholders. Developers are responsible for commissioning assessments and implementing biodiversity measures, and ecological consultants conduct surveys, apply the statutory biodiversity metric tool, and provide biodiversity net gain guidance. Local planning authorities evaluate and enforce compliance with BNG requirements. Other key stakeholders include conservation organisations, landowners, and the general public.

Understanding the Biodiversity Net Gain Metric

The Biodiversity Net Gain metric is a standardised tool used to quantify biodiversity loss and gain on a specific development project. It calculates biodiversity units by assessing habitat area, distinctiveness, and condition, alongside strategic significance. This quantification allows for a transparent and consistent evaluation of a development’s impact on biodiversity.

The metric ensures that net gains are measurable and verifiable, providing a reliable framework for decision-making and accountability. For a small development, a specific small sites metric, released on 2 April 2024, can be used.

Delivering On Site Biodiversity

Delivering BNG on a development site involves careful planning and design. Options include enhancing present habitat, creating new habitats, or restoring existing habitats or degraded ones to achieve the biodiversity gain objective and boost ecological connectivity. Bird or bat boxes can prove to be worthwhile site enhancements as part of a biodiversity gain plan.

While on-site delivery of BNG is the optimal approach, if this is impractical due to space constraints or site limitations, off-site compensation measures can be pursued as a last option. This involves enhancing or creating habitats elsewhere, often through agreements with landowners or contributions to conservation projects that create off site biodiversity gains.

Providing biodiversity gain off-site allows the opportunity for buying statutory biodiversity credits of the same quantity needed to meet biodiversity unit value requirements. Off-site biodiversity units may be purchased from land managers who own land designated for biodiversity offsetting: a Biodiversity Gain Site Register holds details of available land in habitat banks. Such sites require ongoing management and conservation covenants: a legal agreement setting out how the habitat parcel will be monitored. A responsible body will monitor such sites.

Common ways to satisfy Biodiversity Net Gain requirements

Whether the requirement is for a residential development, industrial or commercial development or major developments, there are several strategies commonly employed to enhance biodiversity and meet BNG requirements. These include:

Habitat creation:

Establishing new types of habitat, such as wetlands, woodlands, or grasslands, that align with the site’s ecological context.

Site enhancements:

Improving the quality of present habitats through better management or restoration techniques.

Wildlife corridors:

Creating connections between habitats to support species movement.

Green infrastructure:

Integrating features like green roofs and urban planting schemes into developments.

Off-site contributions:

Investing in biodiversity credits or external projects when on-site measures are insufficient.

Leaving the Environment in a Better State

A biodiversity net gain assessment is a vital tool for ensuring that development projects contribute positively to the natural environment. By understanding the legislative background, assessment process, and delivery options, stakeholders can better navigate the complexities of mandatory biodiversity net gain and achieve an outcome that satisfies a local planning authority.

Achieve Planning Consent

Achieving the required biodiversity net gain means that you will be able to meet the necessary planning obligations. By engaging an experienced ecological consultancy to carry out a bng assessment, you will obtain expert advice and the information needed to complete a planning application. By fulfilling this legal obligation, your application should be able to progress through the relevant planning authority planning process. With careful planning and collaboration, BNG has the potential to foster a sustainable balance between development and nature recovery.