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Last edited 06 Jun 2024

Biodiversity net gain, tools, tips and terms for small sites

1 Environmental biodiversity
2 Challenges facing Biodiversity Net Gain in the long term
3 Defining small developments for BNG
4 Supporting tools specifically for small developments
5 Ten tips from Natural England for planning BNG with small sites
6 Terms, approaches and strategies for net gain
7 Related articles on Designing Buildings
8 External Links

[edit] Environmental biodiversity

The environment, or habitat of the earth, can refer to the built environment of modern humans as well as the natural environment, while biodiversity represents the variety of life forms residing in both built and natural habitats. Biodiversity includes plants, animals, microorganisms, their genes, and the terrestrial, marine, and freshwater ecosystems, as well as, in the strict sense, humans.

The United Nations Framework Convention (UNFC) Rio Summit created three strands of global concern, which included the Convention on Biological Diversity (UNCBD or CBD) as well as the well-known Convention on Climate Change(UNFCC), most commonly referred to as COP or UNCCCOP. In 2020, the UN produced a report that noted the unprecedented rate of biodiversity loss, with around 1 million species threatened with extinction, highlighting the need for policy interventions, including biodiversity offsetting and mitigation measures on a global scale.

In the UK, the Environment Act received royal assent on November 9, 2021. The Act followed UN reports and increased government awareness, including studies that showed the UK losing more biodiversity than any other G7 country. The Environment Act replaced many aspects of UK legislation that were covered by European law prior to Brexit and were no longer applicable after the UK left the European Union. It also introduced concepts around biodiversity gain.

The general aims of the Act focused on reducing landfill, improving air and water quality, and protecting biodiversity and wildlife. It originally set out a number of components relating to biodiversity net gain (BNG), including amending the Town and Country Planning Act (TCPA), requiring a minimum 10% biodiversity gain, significant on-and off-site habitat to be secured for at least 30 years, with evidenced interventions, a national register for net-gain delivery sites, and a biodiversity credit scheme.

[edit] Challenges facing Biodiversity Net Gain in the long term

Biodiversity Net Gain (BNG) means that large and small new developments have to increase biodiversity levels compared to those that existed previously on a site, aiming to provide nature-friendly environments that are good for residents, wider communities, and biodiversity.

Biodiversity Net Gain (BNG) is now a mandatory scheme for both major developments (as of February 12, 2024) and for small sites or minor developments (as of April 2, 2024), as well as nationally significant infrastructure projects planned for 2025. The changes to standard development processes are significant while also representing challenges in terms of management, implementation, and enforcement. A recent report published by the National Audit Office and the Department for Environment, Food, and Rural Affairs, 'Implementing biodiversity net gain', highlighted risks to the long-term effectiveness of the biodiversity net gain scheme.

[edit] Defining small developments for BNG

Minor residential developments are defined as one to nine dwellings, inclusive, on a site having an area of less than one hectare, or, where the number is not known, a site area 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.

Developments that exceed this, so 10 dwellings or more, are defined as major developments, with these exemptions: development impacting a habitat area below 25 m2 or 5 m for linear habitats such as hedgerows, householder planning applications, and small-scale self-build custom buildings.

There are are certain specific definitions relevant to developments that involve the winning or working of minerals, land-use for mineral-working deposits or waste developments. But essentially, for residential development, it means a development with nine houses or fewer on less than one hectare of land. There are exemptions to biodiversity net gain, so not all small developments will have this requirement, but in general, the biodiversity net gain process is the same for small and major developments.

[edit] Supporting tools specifically for small developments

[edit] Small Sites Metric calculation tool (SMM)

There is a simplified version of the statutory biodiversity metric calculation tool, which calculates biodiversity value for biodiversity net gain. It has been designed by experts and is called the Small Sites Metric Calculation Tool (or SSM). The tool makes some reasonable ecological assumptions, which means that an ecologist does not need to complete it.

There is also a simplified version of the Habitat Management and Monitoring Plan Template available, which has been published by Natural England. This will help users provide the details of how they will be managing and monitoring habitats over at least 30 years.

For further information visit Calculate biodiversity value with the statutory biodiversity metric and to The small sites metric and a detailed user guide.

[edit] Small Sites Habitat Management and Monitoring Plan (HMMP) Template

The Small Sites Habitat Management and Monitoring Plan (HMMP) template can only be used on sites that meet the criteria for 'small sites’ as defined in the Small Sites Metric (Statutory Biodiversity Metric).

For further information visit Habitat Management and Monitoring Plan Template (JP058) and here to download the Small Sites Metric HMMP Template.

[edit] Small Sites Habitat Management and Monitoring Plan (HMMP) Guide

The Small Sites Habitat Management and Monitoring Plan (HMMP) Guide provides descriptions of proposed habitat types and conditions allowed in the Small Sites Metric (SSM). The purpose is to assist SSM users, who may not be professional ecologists, in preparing plans for long-term management. The Habitat Guide is not suitable for informing the management and monitoring plans for BNG associated with major developments or more complex habitats.

For further information visit Habitat Management and Monitoring Plan Template (JP058) and here to download the Small Sites Metric HMMP Guide.

[edit] Ten tips from Natural England for planning BNG with small sites

'Everything counts when it comes to nature'. Through mandatory BNG, small developments have an important role in supporting nature’s recovery and enhancement. Here are some tips for small sites in meeting BNG, quoted from the government blog and written by Julia Baker (Technical Director, Nature Services, Mott MacDonald), Isabelle Carter (Regional Director and Landscape Architect, Stride Treglown) and Emma Toovey (Chief Ecology Officer, Environment Bank) for Natural England. For more information about the article, follow the link here.

[edit] Tip 1: Collaborate on BNG as early as possible

"There are great landscape designs for small urban developments that create green spaces for people and habitats for wildlife. Even if wildlife habitats cover small areas, they can create stepping stones throughout a locality as well as refuge for wildlife. This needs an integrated approach to BNG and landscape designs, and the best, most efficient way is for ecologists and landscape architects to collaborate from the start."

[edit] Tip 2: Keep track of the developments in green infrastructure

"Green infrastructure (GI) is an exciting, fast-moving space with new and improved products and technologies coming to market. Do keep track. There is an increasing range of green walls, urban planters such as lamp posts, bike racks, and other GI features that can fit a variety of developments. All add up to create more green space."

[edit] Tip 3: Think Sustainable Drainage System!

"There are really good guidelines on designing biodiverse Sustainable urban Drainage Systems (SuDs). There are many case studies demonstrating biodiverse SuDs within a variety of small-scale development settings. This makes for a great link between BNG and SuDs, and it’s key to consider this join-up from the start.

We often work on small or constrained sites in both urban and rural contexts. They can add real value for BNG if you consider the site holistically, looking beyond the boundaries for local and regional GI networks to tap into."

[edit] Tip 4: Start with biodiversity

"By looking at the biodiversity at the design stage, you can make the most of existing natural habitats and features, such as trees, hedgerows, or grasslands. Understanding the baseline and site conditions early on allows you to tailor your proposals to make the most of the opportunities in aspect and microclimate. Do not forget to use water, as this can really add habitat value in the form of swales, ponds, and rain gardens. Drainage can create vibrant features in small areas."

[edit] Tip 5: Maximise planting mixes

"Make planting mixes. work hard in small areas to extend pollinator seasons and tolerate drought and flood conditions. This could be achieved by: including floral lawns and meadows instead of standard amenity grasses; adjusting mowing and cutting regimes to allow flowers to grow; leaving things over winter rather than clearing debris; and being led by nature rather than trying to control it. To quote Professor Dave Goulson ‘tidiness is the enemy of biodiversity’."

Tip 6: Use buildings and structures

"Biodiversity is not just to do with landscape areas. Use vertical and horizontal building areas as well, such as for green roofs and walls. This will make a significant contribution to BNG on a small site. Look at the Stride Treglown Biodiversity Design Guide for further ideas. It outlines a concise but robust set of concepts to embed biodiversity in the design process."

[edit] Tip 7: Habitat Banks: small site solutions

"Habitat banks are forward-funded projects that do not rely on the sale of any units to kick-start the project. Habitat creation works can start straight away, with the units ‘banked’ for future sale to multiple developers. Habitat bank providers can service very small transaction sizes. They can provide teeny fractions of a unit and can offer units ‘off the shelf’. This could avoid lengthy negotiations, hefty legal costs, or potential programme delays. Some providers may have a minimum unit transaction size or administrative fee; this will typically be small and offer a much more viable solution for smaller developments."

[edit] Tip 8: Love thy neighbour

"The BNG off-site market is hotting up, but many local planning authorities (LPAs) and national character areas still lack accessible off-site solutions. Especially in urbanised LPAs where land is scarce. All is not lost! The Statutory Biodiversity Metric allows for the delivery of BNG across boundaries. This means you can use habitat banks nationwide, even for small requests. A consequence of this is that multipliers in the metric result in an increase in land requirements. This is at a rate of either: 33.3% extra for an adjacent delivery, 100% extra for a national delivery. Leveraging habitat banks nationally can help small development sites to mitigate BNG challenges, albeit potentially at a higher cost. I recommend incorporating this cost into your project right from the outset."

[edit] Tip 10: Strength in numbers

"Collaborating with local developer groups strengthens negotiations. The buying power of a developer cluster should not be underestimated! Engage with a trusted habitat bank operator and secure ‘off-the-shelf’ biodiversity units where and when you want them. Early engagement with operators will give you the greatest chance of success."

[edit] Terms, approaches and strategies for net gain

[edit] Biodiversity metric

The biodiversity metric is an official and statutory term referring to a way of measuring biodiversity value for the purposes of the Biodiversity Net Gain (BNG) regulations. The approach uses biodiversity units to assess a habitat before development takes place and what is needed to replace any equivalent habitat lost in order to achieve 10% BNG. It takes into consideration the size, condition, strategic significance, and type of habitat under consideration. For habitats that are enhanced or newly created, the formula also takes account of the difficulty of creation or enhancement, the time needed, and the distance from the area of habitat loss. It measures all types of habitat, including grassland, hedgerows, lakes, woodland, and watercourses such as rivers or streams.

[edit] Biodiversity net gain units

Biodiversity net gain units are measures before and after an intervention to calculate an improvement, these can be habitats on-site, off-site, or as a last resort through contributions, using the statutory (official) biodiversity metric calculation tool. Three types of biodiversity units, calculated in three separate modules of the metric covering area units, hedgerow units and watercourse units. A professional ecologist will usually use the available metric tool for a particular project and take on the role of gathering, inputting, and assessing data. There is also a Small Sites Metric calculation tool (or SSM).

[edit] Biodiversity gain plan

Biodiversity gain plan (BGP) is a document that shows how biodiversity net gain (BNG) will be achieved, according to the regulations and law. It can be submitted to the local planning authority after the planning application has been approved.

[edit] Biodiversity net gain agreement

Biodiversity net gain agreements are legal agreements to support the obligation to enhance and maintain a habitat, refer ring to off or on site gains, they must last for at least 30 years. The first type is a planning obligation (section 106) with the Local Planning Authority (LPA), the second is a conservation covenant agreement with a responsible body. Both mean the developer or client via a sub-contracted third party, commits to creating or enhancing habitats and managing the habitats for at least 30 years and must be in writing, signed by all parties.

[edit] Local nature recovery strategies

Local nature recovery strategies (LNRSs) are 48 areas across England without gaps or overlaps, where local authorities agree and set priorities for nature recovery, propose actions that make particular contributions, a local habitat map and statement of biodiversity priorities for public, private, and voluntary sectors to focus where action is most effective.

[edit] Habitat management and monitoring plan

A habitat management and monitoring plan (HMMP) outlines how a parcel of land will be managed and monitored over at least 30 years to create and enhance habitats for biodiversity net gain. These are encouraged to capture relevant information for significant on-site enhancements or off-site gains, whilst planning authorities are encouraged to set specific proportionate monitoring requirements as part of planning conditions and obligations to secure habitat enhancements.

Natural England has published a template to help structure management and monitoring plans and demonstrate how habitat creation, enhancement, management, and monitoring will be undertaken for projects of all sizes, on and off-site.

[edit] Biodiversity gain site register

The biodiversity gain site register is a national register of land used for biodiversity gains. The Biodiversity Net Gain (BNG) site register will provide a publicly accessible source of information about on- and off-site gains across England, recording outputs from the BNG metric tool, completed by professional ecologists. It will be operated by Natural England on behalf of Defra and includes a collection of new digital and other services that local planning authorities, developers, landowners, and others will need to be BNG compliant,

[edit] Statutory biodiversity credits

Statutory biodiversity credits are proposed as a last resort in the mitigation hierarchy so that, as well as, or instead of, creating and enhancing biodiversity on or off a development site, developers can make a financial contribution that counts towards their mandatory 10% BNG. Contributions are used to fund biodiversity enhancements across England, with prices based on the cost to create, maintain, and monitor different habitat types.

[edit] Nature recovery networks

A national network of wildlife-rich places set aside to increase and restore nature, and the role of the delivery partnership and management group.

[edit] Habitat banks

Habitat banks are parcels of land set aside in order to allow for biodiversity improvement; they are in effect biodiversity banks in the simplest terms, but they also have potential links to financial models through the BNG credit system. There are now a number of financial institutions offering habitat bank investment as part of their service.