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Preparing for Biodiversity Net Gain

April 2023

By Mark Richards, Associate Planning Consultant

In February 2023 Natural England issued new guidance in respect of biodiversity net gain (BNG). At the same time, the Government also published its response to last year’s consultation on BNG regulations and implementation. These publications provide a number of important updates that will need to be understood by developers, landowners and local planning authorities (LPAs) ahead of the introduction of mandatory BNG later this year.

This Briefing Note provides a refresher on the basics of BNG, along with a summary of the most recent announcements from the Government and Natural England.

Key Points
  • Mandatory BNG will apply to most new development types from November 2023
  •  Small sites will remain exempt from BNG until April 2024
  • It will be possible to ‘stack’ credits for BNG and nutrient neutrality
  • LPAs may set their own policy requirements for BNG.

What is biodiversity net gain?
BNG is an approach to new development and land management that aims to leave the natural environment in a measurably better state than before. 

The concept of BNG is not new. In fact there has been a requirement for new developments to deliver BNG enshrined in the National Planning Policy Framework (NPPF) for several years. However, in the absence of mandatory targets or a statutory method for measuring the value of habitats, it has generally been sufficient to demonstrate modest BNG based on the professional judgement of ecology specialists.

This approach is set to change with the introduction of a mandatory requirement for new developments to deliver a measurable 10% BNG over and above a site’s pre-existing level. This gain will be calculated using a standardised biodiversity metric prepared by Natural England.

When will mandatory BNG be required?
From November 2023 a minimum of 10% BNG will become a mandatory requirement for most types of development in England as set out by the Environment Act 2021. 

What types of development must deliver mandatory BNG?
All major residential, industrial, commercial and mixed-use developments will be required to achieve a minimum of 10% BNG from November 2023. 

The Government has confirmed that small sites will remain exempt from mandatory BNG until April 2024. This is to give smaller developers and LPAs greater time to adapt and prepare before expanding it to a wider scope of application types. Small sites are defined as follows:
  •  Residential - where the number of dwellings to be provided is between one and nine on a site of less than one hectare, or where the number of dwellings to be provided is not known, a site of less than 0.5 hectares. 
  • Non-residential - where the floor space to be created is less than 1,000 square metres or where the site area is less than one hectare.

Nationally Significant Infrastructure Projects (NSIPs) will also not be required to deliver mandatory BNG until November 2025.

The Government has confirmed that permitted development and householder applications will remain exempt from mandatory BNG.

How is mandatory BNG calulated? 
Mandatory BNG must be calculated using a standardised metric prepared by Natural England. Following a consultation in the Autumn of 2022 Natural England has now published an updated version of the metric (iteration 4.0). 

The metric is a tool to measure a site’s existing value to wildlife, taking account of factors including habitat type, size, condition, distinctiveness and location. These habitats are then converted into measurable ‘biodiversity units’. Although the metric is publicly available it should be completed by a competent person. In most cases this will require a qualified ecologist.

It is important to note that river, hedgerow and area habitats are considered independently and are not interchangeable. For example if you have a negative score for hedgerow habitat this cannot be compensated by delivering a substantial improvement to river habitat.

How is BNG delivered and managed?
All habitat enhanced or created for the purposes of mandatory BNG must be secured, managed and maintained for at least 30 years. 

In seeking to achieve mandatory BNG there will be a preference to maximise delivery on-site as part of the development. Where it is not practical to achieve 10% BNG on-site then applicants may secure any outstanding balance through off-site habitat creation or enhancement within the local authority area. This might be achieved on land within the applicant’s ownership or by purchasing credits from landowners or from habitat banks.

As a last resort, where mandatory BNG cannot be delivered on-site or elsewhere in the local authority area, it will be possible to purchase statutory credits from Natural England who will deliver strategic projects elsewhere in England. Statutory credits will be priced deliberately high so as to incentivise local solutions wherever possible.

Can landowners stack BNG credits alongside other environmental credits?
If you use your land to undertake environmental projects, you may be able to sell these services as credits or units to developers who require an off-site project to achieve their mandatory BNG requirements. In February 2023 the Government confirmed that where nature based interventions deliver both BNG and nutrient benefits, it will be possible to sell credits for both. This is commonly referred to as ‘stacking’.

Can local planning authorities set higher BNG requirements?
Yes. Although this briefing note relates to statutory BNG it is important to note that local planning authorities (LPAs) may set their own policies to require BNG ahead of November 2023 and even set a higher minimum threshold than the 10% set by Government.

There are examples across the south west region where LPAs are already requiring applications to demonstrate BNG using the metric, including Cornwall Council and Bath and North East Somerset Council.

Overall Conclusions
The latest updates serve as a timely reminder that mandatory BNG is fast approaching and will soon be a standard requirement for the majority of applications for new development. It is therefore strongly advised that applicants seek professional advice on all current and future projects to ensure that the implications of BNG are understood and factored in at the earliest possible opportunity. 

For more information contact our Development Land & Planning department here.

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