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When Does Biodiversity Net Gain Apply?

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What is biodiversity net gain?

Biodiversity net gain refers to the process of increasing biodiversity in a given area over and above the pre-development levels as a result of new development projects. Essentially, it involves designing and implementing development projects in a way that enhances and improves biodiversity, rather than just avoiding or minimizing negative impacts on biodiversity.

The concept of biodiversity net gain is increasingly being adopted by governments and businesses as a way to address the ongoing loss of biodiversity and habitat destruction caused by human activities. It is often seen as a key strategy for achieving sustainable development and mitigating the impacts of climate change.

To achieve biodiversity net gain, developers must first assess the existing biodiversity in the area where their project is to be located, and then develop plans and strategies to enhance and improve it. This might involve measures such as habitat restoration, rewilding, the creation of new wildlife corridors, or the introduction of new species.

The aim of biodiversity net gain is to ensure that new development projects contribute positively to the overall health and diversity of local ecosystems, rather than further degrading them.

When does biodiversity net gain apply and become mandatory?

So, when will biodiversity net gain apply and become 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 Bill 2021 allows a transitional two-year period for local authorities to get their policies and processes smoothly in place before BNG becomes mandatory in November 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 biodiversity net gain 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” (LNRS) 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.
  • Requiring local authorities to prevent local air quality issues.
  • 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.

Implementing BNG

If you have queries surrounding planning application and the biodiversity net gain requirements then you should contact your local planning authority and an experienced ecologist. Our ecologists can assess whether your development plans meet the necessary standards and recommend any measures that may be required to comply with the biodiversity standards. With our team’s extensive experience in completing BNG, we can offer guidance throughout the planning process. Our experienced ecologists can also visit your development site to create and develop any necessary biodiversity net gain plans and required BNG reports.

We conduct a habitat classification assessment, and the data obtained is used in a metric to measure the natural environment’s changes pre- and post-development. This metric is currently known as Defra Metric 4.0. Landscape planting plans and management plans are employed to determine post-development biodiversity measures.

Biodiversity net gain principles

The Chartered Institute of Ecology and Environmental Management (CIEEM) have outlined ten good practice principles of biodiversity net gain. A brief overview of these principles can be found below:

  • Utilise the mitigation hierarchy to minimise the impact on biodiversity
  • Eliminate any negative impacts on biodiversity
  • Communicate each BNG outcome with complete transparency
  • Cover all areas of sustainability, including societal and economic factors
  • Involve any pre-development and post-development stakeholders in creating mandatory net gain solutions
  • Focus on producing long-term environmental benefits from BNG
  • Understand the variable factors and potential risks in order to achieve biodiversity and deliver net gain
  • Offer nature conservation that exceeds the stated BNG requirements
  • Determine a suitable method in order to secure measurable biodiversity net gains
  • Ensure the best possible results from biodiversity net gain.


What is required from developers under The Environment Act 2021?

All developers in England need to understand and apply the rules laid out in the Environment Act for BNG planning moving forward. The legislation aims to inform developers about the considerations needed for biodiversity right from the acquisition stage to the design and development stage of a project, saving both time and money for those involved if guidelines are followed from the outset.

A shift in the planning process will be the main difference noticed by developers, as local planning authorities are required to develop fresh nature restoration tactics that comply with The Environment Act 2021 standards.

Furthermore, the act necessitates that developers devise a pre-development biodiversity net gain plan, demonstrating how their project will fulfill the biodiversity net gain requirements. In England, planning permission will be granted once this plan is completed. Therefore, seeking help from a biodiversity net gain consultant is crucial to creating a comprehensive plan that satisfies the planning permission requirements.

How do you calculate biodiversity net gain?

When biodiversity net gain applies it is calculated by comparing the biodiversity value of a site before development to the value after development, focusing on losses and gains of biodiversity.

To calculate BNG, the following steps can be taken:

1. Identify the baseline biodiversity value of the site before development. This can be done by conducting a habitat survey to identify the different habitats and species present on the site and their relative importance in terms of biodiversity.

2. Determine the biodiversity value of the site after development. This involves assessing the quality and quantity of the habitats that will be created or enhanced as a result of the development. The value of the habitats can be assessed using the standardized DEFRA biodiversity metric version 4.0, which takes into account factors such as habitat quality, rarity of species, and connectivity with other habitats. For small development sites, metric users can utilise the small site metric version can be used, which is a simplified version of the 4.0 metric.

3. Calculate the net gain in biodiversity. This is done by subtracting the baseline biodiversity value from the biodiversity value after development. If the biodiversity value after development is higher than the baseline value, the net gain will be positive.

4. Implement measures to enhance biodiversity on site if necessary to achieve a positive net gain. This may involve incorporating features such as green roofs, planting native vegetation, and creating wildlife corridors to improve habitat quality and connectivity.

It’s important to note that the biodiversity net gain metric 4.0 is a complex process that requires input from ecologists, planners, and other experts. It’s recommended that you work with a qualified professional to ensure that your calculations are accurate to achieve biodiversity gains.

How can we assist?

If you are a developer or land owner and are looking for more information about when biodiversity net gain applies then our team of experienced Ecologists are here to help.

We can ensure your project is conforming to the current legislation, saving you both time and money. 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. 

Our team’s experience and special scientific interest in BNG means we can support our clients efficiently, calculating their pre development biodiversity measurements to ensure the required gain is made post development in order to reach the required bracket that is becoming law in late 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.

To find out more how CWE can help you with your queries surrounding when biodiversity net gain will apply then please do not hesitate to get in touch with us to discuss your queries. Contact us on 01204 939 608 or use the online form below.


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