Collington Winter Environmental

When Will Biodiversity Net Gain be Mandatory? All You Need to Know

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What is biodiversity net gain?

The UK has already made it well-known that Biodiversity Net Gain (BNG) is a part of legislation across all of the local planning authorities in the country. But when will biodiversity net gain be mandatory? BNG is set to become mandatory for all development and planning applications by the end of 2023.

Biodiversity net gain plans ultimately ensure developers must consider the impact their project or development has on the local environment and surrounding irreplaceable habitats. As such, developers must change and adapt their planning processes to safeguard the local ecosystems and encourage habitat enhancements to ensure no damage is caused.

Leaving an environment in a better condition than it was prior to development is the ultimate aim of biodiversity net gain, and it can be accomplished by creating or enhancing a habitat surrounding and within the development itself.

To obtain planning permission for projects and developments, local planning authorities are commonly asking developers to meet the requirement for BNG before it becomes mandatory. This is ultimately in hopes that the developers can demonstrate how their project will benefit the environment around them.

BNG essentially acts as a planning condition as well as a policy requirement for planning consent. As such, complying with biodiversity net gain is a significant factor in whether planning permission is granted or denied.

When will biodiversity net gain be mandatory?

So, when will biodiversity net gain be mandatory? Local planning authorities require all permissions they grant to achieve at least 10% biodiversity following the Environment Act 2021. A provision for secondary legislation has been put into place from the act, which will set a date in which the mandate will come into force. Currently, the mandate is expected to come into force towards the end of 2023.

The Environment Act 2021 allows a transitional two-year period for local authorities to get their policies and processes smoothly in place before BNG becomes mandatory in 2023.

The current national policy in England, The National Planning Policy Framework (NPPF) Paragraph 179 states:

  • “To protect and enhance biodiversity and geodiversity, plans should:
  • “Identify and pursue opportunities for securing measurable net gains for biodiversity.” 

Paragraph 180 states:

  • “When determining planning applications, local planning authorities should apply the following principles: opportunities to improve biodiversity in and around developments should be integrated as part of their design, especially where this can secure measurable net gains for biodiversity” 

Many Local Planning Authorities have already been requesting the assessment for BNG for a number of years already, and many of them are beginning to amend local developers’ processes to ensure they meet the set standards as part of the local policy.

The Act will require the key points:

  • Developers must deliver BNG at a minimum of 10% through their schemes. This will be measured through a metric, currently Biodiversity Metric 4.0. This tool can help to identify your biodiversity unit score and translate it into the standards of local planning authorities.
  • A developer will need to demonstrate how biodiversity gain will be delivered on developed land. This will be demonstrated through the production of detailed Landscape Planting Schemes, Landscape Management Plans and Monitoring assessments for on and/or off-site.
  • A mitigation hierarchy is to be followed and demonstrated to avoid, minimise or compensate. If it is not possible to compensate on the development site, then offsetting will be required elsewhere.
  • Developers will have to guarantee the biodiversity gain is maintained for at least 30 years (as outlined in Landscape Management Plans).
  • New “local nature recovery strategies” will be prepared to geographically cover England by “responsible authorities”. This will encourage habitat creation and enhancement in the right places.
  • Conservation covenants will be a mechanism used to deliver this (this approach is in preparation by Defra and Natural England).
  • A national register of land used for biodiversity gain will be established. This will involve setting up a new biodiversity credits market.
  • Metrics are only concerned with habitats and do not take protected species into consideration.
  • Other ecological legislation and policies still apply. 

The Act ultimately endeavours to encourage developers to think about the mandatory biodiversity net gain before and during the acquisition of land to avoid changing plans and calculation further down the line once processes have already begun. Having to adapt an on-going development to meet BNG will lead to delays and financial loss to name but a few problems they may encounter.

How can we help?


Staying up to date with current and new legislation and laws surrounding the Environment Bills will make your development project run more smoothly, saving you both time and money in the long run. Following the guidance and rules surrounding biodiversity net gain will help you gain the required planning permissions from your local authorities to carry out your project.

Regulations regarding planning permission can vary across local authorities so it can be confusing and time consuming for developers to ensure they are following the correct rules. Our team of ecologists are experts in BNG and can keep you up to date with the current legislation and regulations.

Our team’s experience and qualifications in BNG means we can support our clients pre and post development in order to reach the required mandatory biodiversity net gain bracket that is becoming law in autumn 2023. We can offer a range of services including consultations on site and off site, protected species surveys and expert advice and planning surrounding BNG.

We can assist by providing:

BNG assessments

Site condition assessments

– Advice on planning

-BNG mitigation


To find out more how our team of biodiversity net gain consultants can help you with your biodiversity plans then please do not hesitate to get in touch with us to discuss your queries. Contact us using the details below. 


Registered Office

23 Bark Street East, 1st Floor, Bolton



01204 939 608


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