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Biodiversity Net Gain Guidance

Biodiversity net gain (BNG) in planning terms is an approach to development that aims to leave biodiversity in a better state than beforehand. The planning system already seeks to minimise impacts on and secure improvements to biodiversity, but the Environment Act 2021 which became law on 9th November places BNG on a statutory footing, introducing a mandatory requirement for developments to demonstrate a measurable 10% increase in biodiversity.

This guidance has been prepared to explain what BNG means and how it operates.  The mandatory requirement for BNG is governed by the implementation of the Environment Act and associated regulations that are still to be issued, but it had been expected to apply to relevant planning applications submitted from November 2023, and for applications on small sites from April 2024. On 27th September 2023 DEFRA announced that it would publish further regulations and guidance by the end of November 2023, and that major developments submitted from January 2024 would be required to deliver mandatory BNG.

Making improvements to biodiversity is already recognised as a crucial component of sustainable development which must be taken into consideration in the existing planning process, and the measurement of BNG is already well-established. Developments are able to provide net gains for biodiversity now through a number of different measures, and this is not reliant on the implementation of the Act. The information contained in this guidance is therefore of relevance to developers today in the design of their proposals.  Existing ecological features on site such as trees, hedgerows and streams should be retained wherever possible, and opportunities taken to enhance biodiversity through the appropriate design of green infrastructure, landscaping and open space.  

It is the intention that this page will be updated as further information, guidance and resources become available.  

1.1    What is Biodiversity?

Biological diversity, or ‘biodiversity’, is the variety of all life on earth, encompassing genes, species and ecosystems .   The term includes all species of plants, animals and microorganisms, the genetic diversity within them, and the variety of ecosystems and component habitats that support them.  These range from deserts, mountains, forests, and wetlands, to grasslands, lakes and rivers and marine ecosystems.  Man-made agricultural and urban landscapes are also included.

1.2    Why is Biodiversity Important?

Biodiversity is important for its own sake and intrinsic value, but it also supports the vital benefits humans get from the natural environment. Studies such as the National Ecosystems Assessment (NEA)  illustrate the value of biodiversity as the building block of habitats and ecosystems, providing the goods and services crucial to wellbeing and social and economic prosperity.  These nature-derived benefits, or ‘ecosystem services’, include essentials such as food, fresh water and clean air, but also protection from flood and natural disasters, climate regulation, water purification, crop pollination , and other services such as recreation and tourism. Biodiversity is thus an integral component of sustainable development:

  • Providing goods such as food, fresh water, wood, wool, fibre, pharmaceuticals and fuels; 
  • Through its intrinsic value and contributing to our aesthetic, spiritual, cultural educational and    recreational experiences, promoting  well-being; 
  • Supporting processes such as nutrient recycling, decomposition, soil formation and oxygen production; 
  • Capturing carbon dioxide which mitigates climate change; 
  • Helping to reduce the magnitude of flood events, protecting soils from erosion and reducing the likelihood of landslips; 
  • Crucial to Improvements to air and water quality, and waste purification; and 
  • Species and genetic diversity is important for improvements to crops and livestock, and resistance to disease.   

The loss of biodiversity is therefore not just of significance ecologically, it also has serious implications for humanity which is dependent upon a healthy natural environment for the provision of natural resources, a good physical environment, a functioning climate, and for general health and wellbeing.  Biodiversity is essentially key to the survival of life on Earth, its loss depriving future generations of irreplaceable genetic information and compromising sustainability .

1.3    What is Happening Now? 

Statistics compiled for The State of Nature Report (2019)  demonstrate that the abundance and distribution of the UK’s species has, on average, continued to decline since 1970, and the rate of decline appears to be increasing.  Prior to this 1970 baseline, it is accepted that the UK’s wildlife had already been massively depleted by centuries of persecution, pollution, habitat loss and degradation. Statistics indicate that over the last decade nearly half of the species for which data exists have shown strong changes in abundance, and nearly half have shown strong changes in distribution. In the UK, more than one in seven (assessed) wildlife species have become extinct or threatened with extinction in the last forty years. 

The drivers of biodiversity loss and pressures on wildlife have been identified, including: 
•    Intensive agriculture; 
•    Overconsumption, and the exploitation of organisms and production of waste and pollution; 
•    Climate change impacts; 
•    Non-native invasive species; 
•    Hydrological change; and
•    Land-use changes, including deforestation and urbanisation 

Urbanisation has a direct effect upon wildlife in terms of changes to land use and the nature of land cover alterations, but also through the creation of barriers between habitats, isolating some populations and in turn reducing their genetic health. Whilst a range of green spaces exist within urban environments, their biodiversity value varies with their degree of habitat fragmentation, management, local population density and surrounding land uses.  Air, light and noise pollution, human disturbance and predation by domestic animals are all factors affecting biodiversity in urbanised areas.

1.4    Achieving Net Gains for Biodiversity
Achieving net gains for biodiversity rather than just stemming further losses is essential to counteract its long term decline.  Net gain for biodiversity is achieved by land management practices or ‘interventions’ that deliver more or better habitat for biodiversity through habitat creation or enhancement on an identified piece of land. Improvements could arise from the way the land is managed, for example maintaining natural wildflower areas in public parks, or through the provision of additional habitat such as ponds, hedgerows or woodland.

More specifically in planning terms ‘biodiversity net gain’ (BNG) is an approach to development which seeks to leave the natural environment in a measurably better state than beforehand. It is a means of delivering measurable improvements for biodiversity by creating or enhancing ecological features and natural habitats for wildlife in association with development after avoiding or mitigating harm. Biodiversity Improvements can be delivered on-site, through a combination of on-site and off-site measures, or in some circumstances entirely off-site where developers pay a levy or tariff for habitat creation or improvement elsewhere.  The concept at its most simple level is illustrated in figure 1.

Fig 1: Concept of BNG

Some local authorities already have planning policies that require development to deliver specific net gains for biodiversity, but the Environment Act establishes a mandatory requirement for BNG as a condition of planning permission, and quantifies the amount of gain that is to be achieved.

The following sections provide an outline of the existing legislative and planning policy context relating to biodiversity, and an overview of the changing approach to the restoration of the natural environment.  Subsequent sections summarise the relevant measures in the Environment Act itself, and the operation of the BNG regime.

3.1    Making Space for Nature

In a review of wildlife sites and ecological networks, the Making Space for Nature report (or ‘Lawton Report’) (2010)  concluded that England’s protected wildlife areas did not represent a coherent and resilient ecological network capable of responding to climate change and other pressures. Whilst nature conservation had traditionally focused on protecting specific sites, the report recommended a step-change from this piecemeal approach to wildlife conservation to an integrated landscape-scale approach of large-scale habitat restoration and re-creation.  

The establishment of viable ecological networks – groups of high quality wildlife sites containing biological diversity, with connections between them enabling species, or their genes, to move - was recognised as key to responding to the fragmentation and isolation of wildlife habitats.  Making the network of sites, ‘bigger, better and more joined up’ would require improved protection and management of designated wildlife sites, increasing their size, enhancing connections between them by creating new wildlife corridors or stepping stones, creating new sites, and increasing protection for non-designated wildlife sites. 

Fig 2: The 'Bigger, better, more joined up' Approach

This thinking was reflected in the Natural Environment White Paper (2011)  and the government’s strategic plan for biodiversity, Biodiversity 2020 (2011) , which endorsed an integrated landscape-scale approach to nature conservation, the need to create healthy, well-functioning ecological networks, and moves towards net gains for biodiversity. 

A Biodiversity offsetting pilot programme was established to trial a system in which conservation activities or ‘biodiversity offsets’ would deliver measurable biodiversity benefits to compensate for losses and damages to nature caused by development that could not otherwise be avoided or mitigated.  A measuring tool or ‘metric’ was developed by DEFRA and Natural England to quantify losses and gains to biodiversity, and Nature Improvement Areas (NIA) were set up to examine landscape-scale approaches to achieving better places for wildlife, delivered on a partnership basis.  Recognising that government action alone would not bring about sufficient improvements to biodiversity, Local Nature Partnerships incorporating a broad range of organisations, businesses and individuals were established to lead nature recovery in local areas, working alongside Local Enterprise Partnerships to ensure that nature would be fully considered in local decisions for the benefit of nature, people and the economy.

As a priority, the government committed that it would, “through reforms of the planning system, take a strategic approach to planning for nature within and across local areas. This approach will guide development to the best locations, encourage greener design and enable development to enhance natural networks. We will retain the protection and improvement of the natural environment as core objectives of the planning system.”  

3.2    The 25 year Environment Plan

A Green Future: Our 25 Year Plan to Improve the Environment (2018)  is the government’s long term management strategy for the environment, setting out how their ambition ‘to be the first generation to leave the environment in a better state than we inherited it’  will be achieved.  It includes goals and targets for arresting the decline in native species and restoring biodiversity.  Building on previous initiatives, the plan seeks to embed a net environmental gain approach to development in policy making and decision-taking, in which measurable environmental benefits are delivered in association with development.  It commits to the establishment of a Nature Recovery Network to meet the challenges set out in the Lawton Report - a national network of wildlife rich places, to improve, extend and connect habitats across towns, cities and the countryside to help address wildlife decline.  
The Environment Act 2021 which received Royal Assent on 9th November 2021 is the legal mechanism designed to deliver the vision set out in the Environment Plan to protect and improve the natural environment and to reverse biodiversity losses.

4.1    The Environment Act

The Environment Act is the key legislative instrument designed to secure improvements to nature and deliver Government pledges to protect and restore the natural environment after leaving the EU.  It establishes a new domestic legal framework for environmental governance, creating an independent Office for Environment Protection and including provisions on specific environmental policy areas including waste and resources efficiency, air quality, water quality and nature and biodiversity.   

Part 6 of the Act 'Nature and Biodiversity', and Part 7 of the Act 'Conservation Covenants', sets out a package of interrelated measures designed to support nature’s recovery and deliver gains for biodiversity in line with the objectives of the 25 Year Environment Plan.  Key to this is the introduction of a mandatory requirement for BNG as a condition of planning permission, establishing for the first time a standardised approach for the delivery of net gains for biodiversity through the planning system. Relevant developments will be required to demonstrate a 10% increase in biodiversity on or near the development site. 

The Act became law on 9th November 2021 with a two year transitional period. Further regulations will be issued through secondary legislation to guide implementation and provide further details on its operation.

4.2    Biodiversity Net Gain (BNG)

As outlined in section 1.4 BNG in planning terms is an approach to development which seeks to leave the natural environment in a demonstrably and measurably better state than beforehand. In terms of the Environment Act, it is a means of delivering improvements for biodiversity by creating or enhancing ecological features and natural habitats for wildlife in association with development, firstly on-site, through a combination of on-site and off-site measures, or in some circumstances entirely off-site where developers pay a levy or tariff for habitat creation or improvement elsewhere. 

BNG involves developers undertaking an assessment of the type and quality of habitat on their site before development, and then demonstrating how biodiversity is improved as part of any proposals, such as through the creation of green corridors, planting more trees, or forming local nature spaces.  Site surveys are expected to inform development schemes, avoiding harm to existing biodiversity assets and habitats, and identifying opportunities for enhancement.  If net gain cannot be achieved wholly on site, then off-site habitat enhancement or creation will need to be provided, before the purchase of biodiversity credits from a government-run statutory credit scheme is considered (see section 4.4).  Figure 3 illustrates the broad mechanisms through which a residential development could achieve BNG.  

Fig 3: BNG in Practice: Broad mechanisms through which a residential development could achieve BNG

4.3    Mandatory 10% Biodiversity Net Gain (BNG) & the Biodiversity Gain Plan (BGP)

The Act establishes a mandatory requirement for 10% BNG as a condition of all planning permissions , with a stipulation that a Biodiversity Gain Plan (BGP) demonstrating how the gains will be achieved must be submitted and approved before development can commence. A statutory biodiversity metric tool must be used to measure and assess biodiversity losses and gains which are expressed in terms of biodiversity units. The tool specified is currently the Natural England Biodiversity Metric 4.0 published in March 2023. If net gain is not achievable on-site, the biodiversity gain plan will need to include off-site habitat enhancements secured through a planning obligation or conservation covenant for a minimum of 30 years. If habitats are significantly enhanced within the development site, these improvements must be secured in the same way or through a planning condition. Finally there is the option to purchase biodiversity credits from a government-run statutory credit scheme.

The Act also provides for the creation of a publicly-accessible biodiversity gain site register, in which off-site biodiversity gain and its allocation to a development must be recorded. Natural England will be the register operator, responsible for establishing and maintaining the register. Biodiversity gain sites can be registered from November 2023.

The requirement to achieve BNG will apply to all relevant planning applications submitted after BNG comes into effect in November 2023, or April 2024 for small sites.  Small sites are defined for the purposes of the BNG as:

  • For residential: where the number of dwellings to be provided is between one and nine inclusive on a site having an area of less than one hectare, or where the number of dwellings to be provided is not known, a site area of less than 0.5 hectares.
  • For 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

There are exemptions to the BNG requirement for 'permitted development' (development granted planning permission by virtue of the Town and Country Planning (General Permitted Development) (England) Order 2015 , as amended) and the Secretary of State also has the authority to issue further exemptions. Nationally Significant Infrastructure Projects (NSIPS) are the subject of separate legislative requirements.  The government response to its consultation on BNG Regulations and Implementation (February 2023) sets out other exemptions to the BNG requirement which will be implemented through secondary legislation:

  • Development impacting non-priority habitat of an area below a ‘de minimis’ threshold of 25 metres squared, or 5m for linear habitats such as hedgerows and watercourses.
  • Householder applications
  • Biodiversity gain sites (where habitats are being enhanced for wildlife)
  • Small scale self-build and custom housebuilding.

4.4    Biodiversity Credits

The Act enables the establishment of a framework for the provision of a biodiversity credit system for habitat compensation.  Developers unable to achieve on-site BNG or off-site BNG locally to meet the mandatory 10% requirement would be able to pay the government for a specified value of credits which would be included in the biodiversity gain plan. Proceeds from the sale of credits are to contribute to strategic ecological networks and provide long-term benefits. The intention is that the price of a biodiversity credit is set at a level that does not discourage the development of local habitat market schemes and habitat creation projects.

4.5    Local Nature Recovery Strategies (LNRS)

The preparation of Local Nature Recovery Strategies (LNRS) or ‘spatial strategies for nature’ which will cover the whole of England is a requirement of the Act.  For the area that it covers (determined by the Secretary of State), each LNRS will map the most valuable existing habitat for nature and also specific proposals for creating or improving habitat for nature and wider environmental gain.   With an emphasis on local leadership and a partnership approach to their production, the LNRS is a tool designed to help inform nature recovery and direct actions and investment for improvements for nature.  It will identify local opportunities and priorities for enhancing biodiversity and supporting other objectives such as mitigating or adapting to climate change. 

LNRSs are expected to guide the effective delivery of BNG and other nature recovery measures by helping developers and planning authorities avoid the most valuable existing habitat, and focus habitat creation or improvement where it will achieve the most benefits to nature and people. The LNRS is the foundation of a key commitment in the Environment Plan,  the Nature Recovery Network, a national network of wildlife-rich places that will improve extend and connect habitats to help address wildlife decline. 

4.6    Species Conservation Strategies and Protected Sites Strategies

These strategies are targeted measures that support the design and delivery of strategic approaches for the protection of specific species or specific sites. They are an approach in which developers avoid the need to identify precise project-level solutions.

Species conservation strategies prepared by Natural England would set out policies to help the conservation of a particular species at greatest risk in a particular area.  Initially they would be prepared where the conservation of a species is impacted primarily by housing development.  The district level licensing scheme introduced in parts of the country for great crested newts is an example of such a scheme . 

Protected sites strategies relate to the conservation and management of a protected site such as a SPA, SAC or SSSI . The strategy would include measures on how to manage the impact of development pressures on the site and any approach to mitigation or compensation that is wider than the individual project level. Nitrate credit trading to protect the Solent is cited as an example of a protected sites strategy.   

The Act places a duty on Local Planning Authorities to cooperate with Natural England and other public bodies in the establishment and operation of the Strategies. Where they are created, the relevant measures that they propose will be integrated into the LNRS for the area.

4.7    A strengthened Biodiversity Duty

Amendments to section 40 of the NERC Act 2006 strengthen and expands the duty on public bodies from “conserving” to “conserving and enhancing” biodiversity, taking into account any LNRS and Species Conservation and Protected Sites Strategies.  Public authorities will have a more active requirement to consider what action they can take to “further the general biodiversity objective” of conserving and enhancing biodiversity, producing a Biodiversity Report within a year of the bill coming into effect, and every five years thereafter.  It is intended that the Biodiversity Report will report on action taken across all of the measures supporting nature recovery and their impact, which can then be used to guide further action. The report will also include a summary of action taken under the Biodiversity Net Gain Policy, which will also be informed by details on the Biodiversity gain site register. 

4.8    Conservation Covenants

Conservation covenants are a means by which developers can demonstrate that the biodiversity gains in its biodiversity gain plan are assured.  The developer has a duty to maintain biodiversity enhancements delivered through the BNG regime for at least 30 years after completion of work on the development site.  Part 7 of the Act legislates for the introduction of voluntary legally binding agreements between landowners and ‘responsible bodies’ such as conservation charities or public bodies as designated by the Secretary of State, to conserve and enhance a specified piece of land in a particular way in order to achieve BNG.  Binding on subsequent landowners, the covenants are a mechanism to secure long-term conservation benefits delivered by BNG on a piece of land, which would be registered as a land charge. Landowners can be released from conservation covenant obligations after parting with their interest in the land, but these obligations will then lie with their successor.

Although the Environment Act introduces a mandatory requirement for BNG of 10%, the existing planning policy framework does already support and promote the conservation of the natural environment, the protection and enhancement of biodiversity, and the achievement of net gains for biodiversity as part of development.


5.1    National Planning Policy Framework (NPPF, 2021)

The National Planning Policy Framework (NPPF) sets out the Government’s planning policies for England, providing the framework for local development plans that guide development, and as a material consideration in the determination of planning applications.  The NPPF encourages net gains for biodiversity to be sought through planning policies and decisions.  

Paragraph 8 requires opportunities to be taken to secure net gains across all three overarching objectives of the planning system that contribute to the achievement of sustainable development: economic, social and environmental. The environmental objective is to protect and enhance the natural, built and historic environment, which includes improving biodiversity.

Chapter 15 relates specifically to how planning policies and decision-making should contribute to the conservation and enhancement of the natural environment, referencing the protection and enhancement of sites of biodiversity value, the minimization of impacts on biodiversity, and the provision of net gains for biodiversity (para 180). 

Opportunities to improve biodiversity improvements in and around development should be integrated as part of their design, and especially where measurable net gains for biodiversity can be secured or public access to nature enhanced where appropriate (paras 179 - 180).  

Key principles that local planning authorities are expected to apply in determining planning applications are outlined, including the biodiversity mitigation hierarchy (para 180): 

  • if significant harm to biodiversity resulting from a development cannot be avoided (through locating on an alternative site with less harmful impacts), adequately mitigated, or, as a last resort, compensated for, then planning permission should be refused; 
  • development on land within or outside a Site of Special Scientific Interest (SSSI), and which is likely to have an adverse effect on it (either individually or in combination with other developments), should not normally be permitted. 
  • development resulting in the loss or deterioration of irreplaceable habitats (such as ancient woodland and ancient or veteran trees) should be refused, unless there are wholly exceptional reasons and a suitable compensation strategy exists; and 
  • development whose primary objective is to conserve or enhance biodiversity should be supported; while opportunities to improve  biodiversity should be integrated as part of their design, especially where this can secure measureable net gains for biodiversity or enhance public access to nature where this is appropriate.


5.2    The National Design Guide and the National Model Design Code

Section 12 of the revised NPPF places greater emphasis on the design quality of new development. Local Planning Authorities are expected to prepare design guides or codes consistent with the principles and guidance set out in the National Design Guide (NDG) and National Model Design Code (NMDC). These documents are to be used to guide decisions on applications in the absence of locally produced design guides or design codes, and both reference nature and biodiversity net gain. The Contribution of trees to the character and quality of the urban environment is also recognised.

The National Design Guide illustrates government priorities for well-designed places in the form of 10 Characteristics of good design. Nature is recognised as a critical component of well-designed places, to be enhanced and optimised through the incorporation of existing and new natural features that support and enhance quality of place, rich and varied biodiversity, and water management.  Well-designed development includes site specific enhancements to achieve biodiversity net gains at neighbourhood, street and household level, and open spaces offer the opportunity to include well integrated drainage, ecology, shading, recreation and food production that achieves net gains for biodiversity as required by the 25 year environment plan.

The National Model Design Code expands on the 10 NDG characteristics, setting out design considerations that local planning authorities are expected to take into account when developing local design codes and guides and when determining planning applications.  In the absence of local design guides planning authorities are expected to defer to the NDG and NDC.
The Code sets out the expectation that nature and green space is woven into the fabric of villages, towns and cities, providing benefits to health and wellbeing, biodiversity, and climate and flood mitigation. Development should enhance the natural environment, with schemes being expected to follow national policy by achieving a minimum 10% net gain in biodiversity through the creation and enhancement of habitats. 

Further detail is included in the Guidance Notes for design codes , emphasizing the need for new development to use, retain and improve existing habitats or create new habitats to achieve measureable gains for biodiversity, and highlighting the role of landscaping and tree planting. It points out the need to address the enhancement and protection of natural assets and the consideration of priority habitats and priority species in the design process, and adherence to the mitigation hierarchy.

The NPPF is clear that development that is not well designed should be refused, especially where it fails to reflect local design policies and government design guidance.

5.3    National Planning Practice Guidance (NPPG) 

National Planning Practice Guidance (NPPG) provides supplementary guidance to assist the implementation of the NPPF.  The National Environment Section explains key issues in implementing policy to protect and enhance the natural environment.  Paragraphs 10 - 35 relate specifically to Biodiversity, geodiversity and ecosystems, updated in 2019 to include a new section on biodiversity net gain (paras 20-28).

The guidance recognizes the potential of planning decisions (and development plans) to affect biodiversity inside and outside designated areas, as well as the opportunities they present to conserve and enhance biodiversity and contribute to habitat connectivity.  Factors to consider are listed, which include:

  • Commitments in the government’s 25 Year Environment Plan;
  • Up-to-date plans and strategies for biodiversity and nature recovery;
  • The potential effects of a development on the habitats or species listed under Section 41 Natural Environment and Rural Communities Act 2006 (Priority Habitats and Species); 
  • Opportunities to restore or enhance local ecological networks, including those that contribute to the wider Nature Recovery Network; and
  • How to secure net gains for biodiversity as part of green infrastructure provision.  

In outlining the principles of BNG and how it operates, planning conditions or obligations are identified as mechanisms to provide for works that will achieve BNG in appropriate circumstances.  The potential for applicants to propose unilateral undertakings to increase biodiversity is also referenced. 

Examples of works that may be involved in increasing biodiversity are included in the guidance - the creation of new habitats, enhancing existing habitats, providing green roofs, green walls, street trees or sustainable drainage systems.  The benefits to wildlife of even small features within development is highlighted, such as incorporating ‘swift bricks’ and bat boxes or providing safe routes for hedgehogs between different areas of habitat.  Off-site measures for biodiversity enhancement and ‘habitat banks’, comprising areas of enhanced or created habitats which generate biodiversity unit ‘credits’, are also touched upon .  

The need to ensure that any agreed gains will lead to genuine and demonstrable benefits for biodiversity is stressed; discussions with local wildlife organisations and the use of assessment tools such as the Biodiversity Metric  are suggested as a means of identifying appropriate solutions and determining whether BNG is likely to be achieved.  

The importance of and need for ecological evidence and rationale supported by appropriate expertise is recognised as being crucial to the assessment of opportunities and proposals to secure BNG.   Relevant local planning policies will also need to be taken into account, such as those relating to open space, health, and green infrastructure, and whether BNG provisions will be resilient to future pressures from further development or climate change, and are supported by appropriate maintenance arrangements.

The guidance emphasizes the operation of the mitigation hierarchy set out in the NPPF, in seeking to firstly avoid impacts on biodiversity, and the fact that BNG does not override the protection for designated sites, protected and priority species and irreplaceable or priority habitats.  BNG habitat improvement needs to be a genuine additional benefit, beyond any measures required to implement a compensation strategy.

The guidance directs that new or improved off-site habitat needs to be located where it can best contribute to local, national and international biodiversity restoration, including the Nature Recovery Network proposed in the 25 Year Environment Plan (see section 1.5), or other locally identified ecological or green infrastructure networks and biodiversity opportunity areas.  It highlights that management plans may be necessary to ensure appropriate management of the habitat in the long term, alongside appropriate monitoring on how the habitat creation or enhancement is progressing, and whether any remedial action may be needed.


5.4    Allerdale Local Plan (Part 1) (ALPP1) Adopted July 2014

The ALPP1 sets out the strategic and development management policies that guide development in the borough (outside the Lake District National Park).  It highlights the quality of Allerdale’s natural environment and its recognition on an international and national scale.  Sites within the north of the district and the Solway Firth are internationally designated as a Ramsar Site, Special Areas of Conservation (SACs), and Special Protection Areas (SPAs) and afforded the highest levels of protection. There is also an extensive range of nationally protected Sites of Special Scientific Interest (SSSI) throughout the plan area, in addition to sites of County importance. (The hierarchy of designated sites in the plan area are listed in appendix 2) 

The Borough also hosts a range of important habitats for a number of key protected and priority species. Coastal areas are recognised as being home to Natterjack Toads and the Small Blue Butterfly, and Great Crested Newts, Otters and Red Squirrels are also found throughout the Plan Area. The area in and around Dean Moor is recognised as a Hen Harrier Protection Zone, and the marshes of northern Allerdale provide important habitat for wild geese and swans.  

A key priority of the plan is to promote sustainable development whilst conserving and enhancing the borough’s biodiversity and geodiversity.  The plan sets out a vision of Allerdale as a place adapted to meeting the challenges of climate change, with a diverse and extensive network of accessible green infrastructure, unspoilt landscape and coastline and areas rich in biodiversity and geodiversity. Specific reference is also made to the protection and enhancement of the quality of the local environment and biodiversity assets in rural areas.

Five of the plan’s strategic objectives relate directly to the natural environment:

  • SO6a    Protect and enhance the natural and historic landscape, including ancient woodland and geological assets, from unnecessary and harmful development, particularly within the Solway Coast AONB and areas adjoining the National Park; 
  • SO6b    Protect and enhance biodiversity and geodiversity, notably the Natura 2000 sites  and create ecologically diverse habitats across Allerdale and ensure the ability of habitats and species to adapt to climate change;
  • SO6c Promote opportunities to improve access to the countryside and coast;
  • SO6d    Ensure high levels of water, and air quality are retained and where necessary improved, and safeguard agricultural land; and
  • SO6e    Promote, protect and provide a comprehensive network of green infrastructure, incorporating multi-functional green and blue spaces both within developments, and linking across and between settlements throughout the area.

Policy S2, Sustainable Development Principles, sets out the principles fundamental to sustainable development, including the need to protect, maintain and re-connect the range and vitality of habitats and species, and enable species to adapt to climate change and create viable ecological networks within and outwith the plan area.

Policy S6 (a-f) sets out the more distinctive area based policiesfor the six localities within the plan area, addressing themes on housing, the economy, communities and infrastructure, the built environment, and the natural environment.  Matters within the natural environment sections include, where relevant, support for the English Coastal Path, flood management, protection of landscape character, and the safeguarding of protected areas within the AONB.  There is a strong emphasis on the protection and enhancement of biodiversity and geodiversity within all of the localities, as well as references to more specific natural assets, which include

  • The River Derwent and River Derwent Corridors (Workington S6a, Cockermouth S6c); 
  • Siddick Ponds SSSI (Workington S6a);
  • Internationally protected Natura 2000 sites (Wigton S6d, Silloth S6e, Aspatria S6f); and
  • The SSSIs of the Solway Mosses and Marshes (Wigton S6d);

Policy S35 Protecting and Enhancing Biodiversity and Geodiversity, is the key policy within the plan relating to the Council’s objectives of conserving and enhancing biodiversity and Geodiversity, making positive improvements to the natural environment and achieving net gains for biodiversity.  It also reflects national policy in respect of mitigation and compensation; where a development poses significant harm to an irreplaceable habitat which cannot be mitigated or compensated for, permission will be refused. 
Developments, projects and activities are expected to:
a)    Protect and enhance key ecological habitats and wildlife corridors and stepping stones including watercourses and wetlands; 
b)    Maintain, and where appropriate enhance, conditions for priority habitats and species identified in the Cumbria and UK Biodiversity Action Plan Priority Species and habitats  or the Cumbria Biodiversity Data Centre at Tullie House; 
c)    Maintain and where appropriate enhance recognised geodiversity assets identified in the Local Geodiversity Action Plan for Cumbria; 
d)    Protect soil and water resources in line with Policy S36; 
e)    Contribute to Allerdale’s green infrastructure network in line with Policy S24;
f)    Protect existing trees, hedgerows and woodland (including ancient trees and hedgerows) that are considered important to the local community, contribute positively to the character of the area and/or are of a nature conservation value.

The value of biodiversity assets in urban settings is recognised; vacant brownfield/ previously developed land can provide ideal habitats for specific plant and animal species, and existing features of green infrastructure such as parks, roadside verges and domestic gardens can contribute to a network of biodiversity corridors and stepping stones in which wildlife can reside and/or travel.  It is therefore important to ensure that development in all settings does not damage habitats or encroach upon land forming part of the wider network of wildlife habitats. It is emphasized that the consideration of biodiversity is not limited to protected sites.

Although Policy S35 is the overarching biodiversity policy applicable to all development, the need to consider nature conservation features, biodiversity and geodiversity, including Natura 2000 sites, habitats and species is further embedded throughout the plan, referenced within a range of different policies including: 

S11    Gypsy, Traveller, and Travelling Showpeople Sites
S13    Energy Coast Innovation Zone
S18    Derwent Forest, Policy 
S19    Renewable Energy and Low Carbon Technologies, 
S24    Green Infrastructure, 
S32    Safeguarding amenity, 
S33    Landscape, 
S37    Shoreline management and coastal development, 
DM5    Farm Diversification, 
DM6   Equestrian and Agricultural Buildings, and 
DM13  Telecommunications Development.

Policy DM14, Standards of Good Design further highlights that development should take advantage of existing green infrastructure and biodiversity assets with the retention of existing features of interest within the site including trees, hedgerows, becks and streams, and the nature conservation and biodiversity value of development should be maximised through the incorporation of hard and soft landscaping features that facilitate the creation of wildlife habitats.


5.5    Allerdale Local Plan (Part 2) (ALPP2) Adopted July 2020

The Allerdale Local Plan (Part 2) ALPP2 is the site allocations development plan document that identifies or ‘allocates’ land to deliver the development strategy set out in the ALPP1.  It also includes other supporting policies that guide development.  Each of the individual policies relating to the sites identified for development such as housing or employment outlines the ecological survey work required and opportunities for ecological enhancement.  Supporting polices also contribute to nature conservation and biodiversity objectives:

Policy SA32 relating to Tourism, Coastal and Countryside Recreation replaces Policy S17 within the ALPP1.  The policy continues to seek the promotion and diversification of the tourism economy whilst prioritizing the conservation and protection of sensitive landscapes, habitats, species and biodiversity.  Measures that would relieve tourism pressure on these attributes in the most sensitive parts of the borough are supported. 

Policy SA49 provides a development framework for the Lower Derwent Valley, where proposals are expected to deliver a measurable biodiversity net gain.  The River Derwent corridor in Workington is an important feature in terms of biodiversity, green infrastructure, and for informal recreation, and the River Derwent is also designated as a Special Area of Conservation (SAC) in recognition of its international importance for biodiversity.


Policy SA51 Amenity Greenspace acknowledges the contribution of greenspaces in terms of visual amenity, the health and well-being of communities and by supporting biodiversity and wildlife conservation as part of the green infrastructure network.

Policy SA52 Protecting and creating Green Infrastructure sets out the council’s approach to major development and green infrastructure (GI) within the principal and key service centres, identifying a network of GI assets on the polices map.  Development proposals are expected to take account of the mapped network at the design stage, and incorporate existing GI assets and secure opportunities to strengthen and connect with the wider GI network in order to deliver multiple benefits which can include wildlife linkages and gains for biodiversity. 


The BNG regime is a mechanism to deliver measurable improvements to biodiversity in association with development. Improvements to biodiversity can be met in a combination of the following ways:

  • Firstly, through the enhancement, restoration, management and/or creation of wildlife habitats on-site as part of the development;
  • The enhancement, restoration, management and/or creation of wildlife habitats locally off-site;
  • The payment of a nationally set tariff for offsite habit creation and improvement elsewhere.

In order to demonstrate that the mandatory requirement of a 10% increase in biodiversity is delivered, biodiversity losses and gains associated with development and land management practices must be measured in a consistent, robust, and transparent way. 

6.1    The Biodiversity Metric 4.0 and Calculating BNG
The Biodiversity Metric 4.0  is a spreadsheet-based tool designed to measure biodiversity losses and gains using habitat as a proxy for biodiversity.  It is the statutory biodiversity metric tool that the Environment Act specifies must be used by developers to demonstrate how they will meet their requirement to deliver 10% BNG.

Fig 4: The Biodiversity Metric 4.0

Biodiversity losses and gains are calculated through the assessment of habitat and its quality. The metric quantifies the existing biodiversity value of habitats on a piece of land, and then calculates the losses and gains in biodiversity associated with a proposed development and any related habitat creation, restoration or enhancement.  Information from habitat surveys of the site before development, and for habitats proposed within the development plus any off-site habitat improvement is used to populate the metric spreadsheets. 

The metric translates the habitat distinctiveness, condition, size, and strategic importance into a score, which is then converted into measureable Biodiversity units.  

Fig 5: The Biodiversity Metric Main Menu

The post-development calculation of biodiversity value takes into account risks in delivering habitat creation or enhancement.  Linear habitats/features such as hedgerows, lines of trees, and rivers and streams are assessed separately within the metric to properly account for their biodiversity value. 

To achieve net gain, a development must have a higher biodiversity unit score after development than beforehand (see fig 6). 

Natural England’s suite of guidance on the operation of the metric is available online (see appendix 4 ). 

Fig 6: General approach to calculating the biodiversity value of a habitat

6.2    The Baseline for Assessing BNG

The existing biodiversity value of a development site or ‘baseline’ is assessed at the point that planning permission is applied for, although if any harm to this biodiversity value has taken place in the recent past (for example through hedge or tree removal), this would need to be accounted for to ensure that proposals achieve genuine BNG. Schedule 14 of the Environment Act enables Local Planning Authorities to recognise any habitat degradation since 30th January 2020.

The site is surveyed, mapped and divided into parcels of distinct habitat types present using the ‘UKHAB’ habitat classification system. All surfaces present including built surfaces are included.  The biodiversity ‘value’ of a habitat parcel is evaluated on the basis of its area in hectares and the relative quality of its habitat. Quality is determined by three components:

  • Distinctiveness: A score based on the type of habitat present. Habitats are assigned to ‘distinctiveness’ bands based on an assessment of their features including species richness, rarity (at local, regional, national and international level), and the degree to which a habitat supports species rarely found in other habitats. The distinctiveness band of each habitat is pre-assigned based on whether the habitat is of high (e.g. native broadleaf woodland) or low (e.g. improved/amenity grassland) value to wildlife. 
  • Condition: Based on the quality of the habitat, whether the habitat is a good example of its type. For example whether a woodland is in peak condition (which might mean it can better support rare species) or whether it is full of invasive species or is overcrowded. 
  • Strategic significance: Strategic significance relates to a landscape scale approach based on whether the location of the development and/or off-site work has been identified locally as significant for nature, taking account of published local biodiversity plans, National Character Area objectives , and local plans for targeting green infrastructure and biodiversity. This component gives extra value to habitats that are located in optimal locations to meet biodiversity and other environmental objectives.  

The metric operates by applying a score to each of these elements for a habitat  parcel. A calculation using the scores and the area of the habitat gives a number of  biodiversity units that represents the biodiversity value of that habitat parcel. The initial calculation determines the ‘baseline’ value in biodiversity units. 

6.3    Post-Development Calculation of BNG

The process is repeated using a ‘post development’ scenario to account for the impact of the development including any on site measures to retain, enhance or create biodiversity.  Additional factors to account for the risk associated with the creation, restoration or enhancement of habitats are incorporated within the metric: 

  • Difficulty of creating or restoring a habitat:  This component recognises the difficulties in creating or restoring some habitat types, and the related uncertainty of outcome this creates. Uncertainty in achieving the target outcome for each habitat is addressed by a habitat-specific ‘difficulty’ multiplier.
  • Temporal risk:  If there is a gap between a negative impact on biodiversity and compensation habitat reaching the required quality or level of maturity, there will be a loss of biodiversity for a period of time. This issue can be managed by the creation of compensation habitat ahead of the impact taking place through the setting up of habitat banks or, for projects with a long lead in, by commencing offset work ahead of the development. Even where the management to create compensation habitat starts in advance, the time taken for habitats to mature means that there is almost always a time lag. Where a time lag occurs, a ‘Time to target condition’ multiplier is applied to take account of it. 
  • Spatial Risk:  This component reflects the fact that habitat created at a great distance from the site of habitat losses carries a risk of depleting local areas of natural habitats, and of depriving communities experiencing development of the associated benefits. The multiplier is simple and should be applied as a rule but with the discretion of the Local Planning Authority (for example, where a development creates compensatory habitat locally, but technically in a separate planning area).

The value of biodiversity units ‘post development’ is deducted from the baseline value to quantify the extent of change. If net gain can be achieved on site there is no need to consider off site measures. If the calculation does not result in a sufficient net gain in biodiversity units the development proposal can be revisited to improve the number of biodiversity units obtained or, if there is no scope for additional on-site compensation or enhancement, off-site measures will need to be considered.

Fig 7: The Development Process

If off site measures are required, the same assessment process has to be undertaken to establish biodiversity unit values on the offsite land ‘pre intervention’ and ‘post intervention’ to calculate how many units that land can contribute as compensation. The change in biodiversity units on site is then added to the change in units off site to provide a total change in biodiversity units for the development. The total change in units needs to be sufficient to ensure a ‘Net Gain’ is achieved.

Fig 8: Example of BNG

6.4    The Mitigation hierarchy

The mitigation hierarchy is the cornerstone of BNG.  The effective operation of the BNG regime relies on the principles of and adherence to the biodiversity mitigation hierarchy established in planning policy, to avoid, minimise, remediate, and compensate for losses to biodiversity (para 180 NPPF).  BNG is in addition to the application of the mitigation hierarchy, not instead of.

Fig 9: The Mitigation Hierarchy

Application of the hierarchy means retaining habitats on site or avoiding habitat damage in the first instance.  BNG is easier to achieve where habitat impacts are avoided due to the way that risks associated with habitat creation or enhancement are accounted for in the Biodiversity Metric. 

BNG is not a justification for on-site biodiversity losses simply compensated for by the payment of a levy for habitat improvement elsewhere. The Mitigation hierarchy must be applied, and development schemes are still expected to comply with relevant planning policies requiring the protection and enhancement of ecological features such as trees, hedgerows and streams within the application site boundary, and incorporate green infrastructure and open space within development design.

6.5    Protected Sites and Species

BNG does not override the various existing statutory legal and policy protections in place for designated (protected) sites, protected or priority species and the habitats that support them, and irreplaceable or priority habitats.   

Internationally and nationally designated sites (appendix 1 ) are largely excluded from the BNG regime. BNG cannot be used as a justification for otherwise unacceptable development on such sites. They are legally protected and should already be managed in a way that preserves and enhances their biodiversity value. Non-designated features of such sites may be suitable for enhancement, but DEFRA is to provide further guidance on the circumstances in which statutory protected sites can be enhanced for BNG.

The potential impact of new development on a protected site outside the development site boundary has to be considered in the usual way in accordance with statutory obligations. Any compensation or mitigation that may be required in this respect can contribute towards BNG but only to achieve no net loss. At least 10% of the post-development biodiversity score should be met by measures not undertaken to address impacts on protected sites. 

Development should also avoid impacts on irreplaceable habitats or features such as ancient woodland or veteran trees; these cannot be restored, re-created or replaced, and impacts cannot be offset to achieve BNG. The Environment Act empowers the Secretary of State to set out what other features or habitat constitutes ‘irreplaceable’, and this will be defined in secondary legislation. It is the intention that there will be separate information requirements for irreplaceable habitats, as a separate element in the biodiversity gain plan or in a supplementary report that can be used by the LPA to determine planning applications. There will also need to be a robust statement of reasonable alternatives explored for the development that would avoid the loss of irreplaceable habitat and why they were not feasible. On 5th October DEFRA confirmed an initial list of irreplaceable habitats for BNG:

  • Ancient woodland
  • Ancient and veteran trees
  • Blanket bog
  • Limestone pavements
  • Coastal sand dunes
  • Spartina saltmarsh swards
  • Mediterranean saltmarsh scrub
  • Lowland fens

The presence of protected and priority species also needs to be assessed in line with their differing legal and policy protections, and an understanding of how the existing site habitat supports them.  The Biodiversity Metric quantifies biodiversity outcomes based on habitat alone; it does not account for the presence of specific species on the site.  They will need to be assessed and carefully considered separately in any ecological evaluation of the site. Compensation and mitigation needed to comply with legislation in connection with protected or priority species can contribute towards BNG  but only to achieve no net loss. At least 10% of the total post-development biodiversity score should be from measures which are not undertaken to address impacts on protected species.

A thorough understanding of a site’s habitat, the presence of protected and priority species, and the potential impacts arising from proposed development including on biodiversity outside the application site is all needed, and for which ecological expertise is required.  

6.6    ‘Trading down’ of Habitats 

New or restored habitats should result in an improvement in the extent or quality of the habitat affected. They should achieve a higher distinctiveness and/or condition than those lost. Compensation measures should not result in “trading down”, for instance in the replacement of a habitat of high distinctiveness with creation or restoration of a greater amount of habitat of a lower distinctiveness. Losses of habitat of a high distinctiveness are expected to be compensated on a “like for like” basis. Trading rules are incorporated within the metric.
6.7    Off Site Biodiversity Gain 

Where off-site measures are needed to meet the 10% biodiversity net gain uplift requirement, it is expected that the off-site habitat enhancement or creation will be local to the development site.  It should as a minimum be comparable to the habitat that has been lost, and contribute to the delivery of the Cumbria Local Nature Recovery Strategy (LNRS) and Cumbria Nature Recovery Network which are currently in formulation (section 6.8). The LNRS and NRN help direct where investment should go and help identify suitable receptor sites.  Developers may not own or be able to undertake appropriate works close by, but it is the intention that the biodiversity gain register will include eligibility criteria for land to be registered as suitable for habitat enhancement for the delivery of off-site BNG.  This would not preclude other sites coming forward or being considered.  All enhanced and new habitats will need to be maintained for a minimum of 30 years secured by a S106 agreement or Conservation Covenant. 

6.8    Cumbria Local Nature Recovery Strategy and Nature Recovery Network

Cumbria is one of 5 Pilot areas in England that trialled the development of a Local Nature Recovery Strategy (LNRS) referred to in the Environment Act. The purpose of the LNRS is to restore and link up habitats so that species can thrive, and agree the best places to help nature recover, plant trees, restore peatland, mitigate flood and fire risk, and create green spaces for local people to enjoy. 

As the acting ‘Responsible Authority’ at the time Cumbria County Council led the work on the draft Cumbria LNRS, which involved mapping existing sites and habitats that are important for biodiversity and nature recovery, identifying priority outcomes for enhanced nature recovery across the county and potential measures to achieve these outcomes, and mapping suitable locations for delivery of these measures. Together the Local Habitat Map produced and the Statement of Biodiversity Priorities forms the draft Cumbria Local Nature Recovery Strategy.

Work on the Pilot schemes commenced in September 2020, and the Draft Cumbria LNRS has now been published. As this strategy was produced as part of a pilot scheme, further work on it will be necessary following the Environment Act becoming law and to accord with statutory guidance issued in 2023. The LNRS will form the foundation for the Nature Recovery Network, upon which the Cumbria Local Nature Partnership has commenced work.

6.9    National Biodiversity Credits Scheme and Off Site Habitat Market

As a last resort and in the absence of any suitable local sites there will also be the opportunity for developers to purchase statutory biodiversity credits from an offsite habitat market to help them meet their biodiversity gain requirements. Operated through Natural England, funds from the purchase of biodiversity credits would be used to fund off-site habitat enhancements, purchase interests in land with a view to carry out enhancement works, or undertake the operation and administration of enhancement works. The biodiversity net gain credits scheme is linked to the statutory biodiversity metric and the price of credits is set by the Secretary of State. Indicative prices for credits published in July 2023 range from £42,000 to £65,000 per credit depending on the habitat type involved and condition.

6.10    The Biodiversity Gain Plan 

To demonstrate how the BNG requirement is to be achieved as part of each development, the Environment Act requires developers to submit a Biodiversity Gain Plan (BGP) to the Local Planning Authority for approval as a pre-commencement condition of planning approval. Incorporating information obtained using the biodiversity metric the plan is expected to include

  • The steps taken to minimize the adverse effect of the development on the biodiversity of the on-site habitat, demonstrating the application of the mitigation hierarchy;
  • The baseline (pre-development) biodiversity value of the site;
  • The post-development biodiversity value of the site;
  • The biodiversity value of any off-site biodiversity gain allocated to the development; 
  • Any biodiversity credits purchased for the development;
  • A demonstration that the ‘post-development’ biodiversity value of the development is greater than ‘pre-development’ biodiversity value by at least 10 per cent.

The government is currently preparing a biodiversity gain plan template and will also clarify the level of information that must be submitted upfront with the planning application.  Separate guidance is to be provided on irreplaceable habitats. It is intended that any development on irreplaceable habitats would be accounted for in a separate section of the gain plan or in a separate report, including a robust summary of reasonable alternatives to avoiding the loss of irreplaceable habitats and why they are not feasible. Statutory biodiversity credits cannot be use to compensate for the loss of irreplaceable habitat.

Any land which is the subject of a biodiversity gain plan including compensatory habitat sites will be recorded in the publicly available biodiversity gain site register.

6.11    Summary of Principles and Rules in Applying the Biodiversity Metric

Key principles involved in the application of the Biodiversity Metric 4.0 include:

  1. The metric does not change existing biodiversity protections, statutory obligations, or policy requirements.  The use of the metric does not override the ecological mitigation hierarchy and other requirements (such as consenting or licensing processes, for example woodlands).
  2. The metric should be used in accordance with established good practice guidance and professional codes. 
  3. The metric is not a complex or comprehensive ecological model and is not a substitute for expert ecological advice.
  4. Biodiversity units are a proxy for biodiversity and should be treated as relative values.
  5. The metric is designed to inform decisions in conjunction with locally relevant evidence, expert input, or guidance.
  6. Habitat interventions need to be realistic and deliverable within a relevant timeframe.
  7. Created and enhanced habitats should seek, where practical and reasonable, to be local to any impact and deliver strategically important outcomes for nature conservation.
  8. The metric does not enforce a minimum habitat size ratio for compensation of losses.  However, proposals should aim to:
  • maintain habitat extent (supporting more, bigger, better and more joined up ecological networks) and
  • ensure that proposed or retained habitat parcels are of sufficient size for ecological function. 

Key Rules  involved in the application of the metric:

  • Competency requirements must be complied with. The person completing the metric (on behalf of the developer) is expected to be a competent person; someone who can demonstrate they have acquired through training, qualifications or experience, or a combination of these, the knowledge and skills enabling that person to perform specified tasks in completing and reviewing metric calculations.  
  • Biodiversity unit outputs are unique to the metric.  The results of other metrics, including previous versions of this metric, are not comparable to those of this metric.  The three types of biodiversity units generated by the metric (area, hedgerow and watercourse) cannot be summed, traded or converted between modules. 
  • Trading rules of the metric must be followed. Trading down must be avoided – losses of habitat are to be compensated on a like or like for better basis.  New or restored habitats should aim to achieve a higher distinctiveness and or/condition than habitats lost. 
  • Losses and deterioration of irreplaceable or very high distinctiveness habitat cannot be accounted for through the metric.
  • In exceptional ecological circumstances deviation from the metric methodology may be permitted by the relevant planning authority but this would need to be fully justified and evidenced.

6.12    The Small Sites Metric

The Small Sites Metric  is a simplified version of the Biodiversity Metric intended for use in connection with small development sites which do not contain any protected species or high distinctiveness or priority habitats, and meet the following criteria:

  • For residential developments the number of dwellings to be provided is between 1 and 9 inclusive with a site area of less than 1 ha. Where the number of dwellings is not known the site area is less than 0.5 ha.  For all other development types where the site area is less than 0.5 ha; AND
  • Where there is no priority habitat present within the development area (excluding hedgerows and arable margins)

This metric is unsuitable to calculate offsite losses and gains.

Fig 10: The Small Sites Metric

7.1    Submitting a planning application

Information on biodiversity impacts and opportunities is needed to inform all stages of development, including site selection, design, construction, implementation and operation.  It is also needed to prepare the Biodiversity Gain Plan (BGP) that is required by the Environment Act to demonstrate how BNG is to be achieved as part of any proposals. 

Fig 11: Summary of Planning Process

Planning and budgeting for BNG at an early stage in the development process is essential, and appropriate ecological assessment is crucial to the effective and viable delivery of BNG.  BNG can be achieved by avoiding areas containing high levels of biodiversity in the first instance, by using alternative sites or different development designs. 

The Biodiversity Gain Plan (BGP) is a new obligation that developers will have to fulfil. However, it builds on the preliminary ecological work and surveys already undertaken to establish the potential impacts of development on designated sites and priority habitats, protected and priority species, and the scope to avoid or mitigate any such impacts. Developers are able to use the BGP mechanism now to demonstrate how their proposals are achieving BNG.    

The BGP does not override the need to meet legal or policy requirements regarding protected species and designated sites, or priority species and habitats; BNG must be considered in addition to any mitigation that may be needed - compensation measures for protected sites or species can only achieve no net loss.  Further details on the survey work currently required to accompany planning applications lies within the local validation checklist and associated appendix E  for the former borough of Allerdale. 

It is expected that all ecological surveys, impact assessments and mitigation, and preparation of the BGP will be carried out by suitably qualitied ecologists.

Fig 12: Integration of Biodiversity net gain in the planning process

7.2    The Biodiversity Gain Plan (BGP)

The BGP will include:

  • The baseline (pre-development) biodiversity value of the site;
  • The steps taken to minimize the adverse effect of the development on the biodiversity of the on-site habitat, demonstrating the application of the mitigation hierarchy;
  • The post-development biodiversity value of the site;
  • The biodiversity value of any off-site biodiversity gain allocated to the development (pre and post development); 
  • Any biodiversity credits purchased for the development;
  • A demonstration that the ‘post-development’ biodiversity value of the development (including any off-site gain and biodiversity credits) is greater than ‘pre-development’ biodiversity value by at least 10 per cent; 
  • The metric spreadsheets behind the calculations to enable interrogation; 
  • A costed management plan designed to deliver the required measurable biodiversity gain.

The biodiversity value must be calculated using the DEFRA Biodiversity Metric 3.0 or subsequent revised version (see appendix 4 );

Habitat and management to enhance biodiversity is expected to be maintained for a minimum of 30 years, and secured by means of a S106 or conservation covenant.

7.3    Site Survey

A clear understanding of the existing biodiversity on the proposed development site is needed to determine the baseline (pre-development) value of the site for the BGP, and to assess the impacts of development.  

The presence or otherwise of protected or priority species must be established, how the development will impact these species, and whether the development has the potential to affect designated sites or protected species outside the application site boundary.

The Initial site survey, a phase 1 Habitat Survey, sometimes also referred to as a Preliminary Ecological Appraisal, consists of desk-based research using local records from Cumbria Biodiversity Data Centre (CBDC) , and a walkover survey designed to map the site based on the habitats present, and assess a site’s potential to support protected species (such as bats, great crested newts, badgers, reptiles and nesting birds).  The findings will inform whether further detailed botanical or species surveys are needed. 

Habitat surveys are ideally undertaken between April and October when deciduous and annual plant species are identifiable. Some survey work for particular species must only be undertaken at certain times of year (See appendix 5 ), which will need to be factored into the timing of any planning submission.

Ecological assessments are expected to be proportionate to the nature and scale of development proposed and likely impacts on biodiversity; guidance indicates that Local Planning Authorities should require ecological surveys only where clearly justified.  A Phase 1 habitat survey may not necessarily be appropriate for some small scale sites, depending on their characteristics, but an assessment will still be needed to underpin the biodiversity net gain appraisals.

The change of use of a building in a town location may result in no impact on biodiversity, and householder developments may also be exempt from the need for ecological appraisal, although in some circumstances bat or other protected species surveys may be necessary (for example bats), or the proximity of a protected site might also be a relevant consideration.

7.4    Assessment of Impact on Biodiversity (Ecological Impact Assessment)

An evaluation of the impact of the development proposal on the biodiversity of the site is undertaken based on the information collected as part of the initial survey. This assessment, sometimes referred to as an Ecological Impact Assessment (EcIA), will reflect the nature, scale and complexity of the development proposal, and the risk to biodiversity and ecosystem function.  It may be part of the ecological report or a standalone document, and is likely to include:

  • Details of any biodiversity features affected by the implementation of the development scheme or its subsequent operation.  This will include features which are present on the development site or on any areas indirectly affected.
  • Identification of any impacts on protected or priority species on or adjacent to the site, and how  these could be affected by the scheme
  • Identification of residual impacts on biodiversity features that could be expected should the development be implemented and the significance of these impacts.
  • How biodiversity impacts have been avoided;
  • Demonstrate how during implementation and operation of the development impacts and risks will be reduced (for example appropriate timing of works to avoid disturbance, inclusion of pollution prevention measures, sensitive site lighting design and inclusion of access points in fences). 

This assessment will help inform the Biodiversity Gain Plan

7.5    Protected Species

As outlined in previous sections protected and priority species require consideration that accords with their level of statutory and policy protection, separate to the habitat assessment that forms part of the Biodiversity Metric. If development impacts on protected or priority species can be mitigated, the mitigation would not contribute towards Biodiversity Net Gain.   

7.6    Sources of Information

DEFRA’s ‘ MAGIC ’ interactive mapping tool shows the location and extent of internationally and nationally designated and protected sites (see appendix 1 ).

An inventory of ancient woodland is also available on the MAGIC map, although this is not comprehensive.  Ancient woodlands and planted ancient woodlands (PAWS) of less than 2ha are not mapped, and therefore smaller woodlands close to or part of any application site will need to be assessed to consider their status.

The Cumbria Biodiversity Records Centre is the biological records centre for Cumbria, and can supply information on local designations such as County Wildlife Sites (see appendix 1 ).

Sites may exist that meet the designation criteria for a County wildlife Site, but have not been previously identified, and will need to be taken into account in the planning process accordingly. 

Priority Habitats (Habitats of Principal Importance) (appendix 1 ) are also identified on the MAGIC Map, although these records are incomplete; priority habitats exist outside those areas shown on the map.  Additional information may be available from CBDC, but priority habitats should be identified as part of the phase 1 habitat survey.

CBDC also holds records of observations of protected, priority, rare and scarce species.  The absence of a record does not necessarily mean that a species is absent. Key species data also identifies zones that have known species interest within them.  These areas do not represent the full knowledge of any species distribution, but identify areas that are associated with a particular set of species, and help inform survey work. 

It is expected that records from the CBDC will form the basis for the desk based survey that forms part of the initial Preliminary Ecological Survey, and that suitably qualified ecologists will be engaged in the process. 
7.7    Biodiversity Offset Gains

As outlined in section 6.6, newly created or restored habitat provided to meet BNG requirements is expected to be of higher distinctiveness and/or condition than habitat lost.  It should also be local to the development site.  
In developing offsite measures to achieve BNG, the local priorities set out in the Cumbria Local Nature Recovery Strategy and the identified Cumbria Nature Recovery Network are key considerations, and to which offsite gains should contribute.  
Other useful sources of information include the Cumbria Habitats and Species Statements available on the CBDC website and the environmental opportunities set out in the National Character Area Profiles for the area in which the development site lies  

Developers of large scale schemes are expected to engage with local communities and stakeholders when evolving their plans to achieve BNG.
7.8    Small-scale Applications

Small-scale development forms a significant proportion of planning applications received, and collectively can make a sizeable contribution to BNG.  However, the Biodiversity present may be too small to apply the metric in a meaningful way. The small sites metric is in development to help address this issue, and there are other ways in which small scale developments can contribute to improvements to Biodiversity.

Ciria’s ‘Biodiversity Net Gain: Good Practice Principles for Development’ points out that traditionally small-scale development has sought to enhance biodiversity by simply installing nesting boxes or bat boxes. It notes that although these can be beneficial in the right location, they are often included without sufficient consideration of the type of boxes that would most benefit local biodiversity, whether the site is close to wider habitat needs such as foraging habitat, and whether there are the necessary habitat connections to enable species to commute to and from the nesting or roosting boxes.
If bird or bat boxes are to be included, the following questions need to be answered to help determine whether their installation will offer a positive enhancement.

  • Which Species are local nature conservation priorities, and are the boxes the right specification for these species?
  • Has the correct height and orientation for the box been specified, and is there a clear flight path to the box?
  • Are there records for the target species locally? Check with CBDC and MAGIC map?
  • Does the wider area have the right habitat, and habitat that is connected for the species?
  • Is there a shortage of nesting or roosting locations for the species?
  • Will the operation of the site create disturbance or detractors that will deter the target species (eg light, noise, odour, people movement, pets etc.)?

Further guidance on the appropriate use of bat and bird boxes is available from The Bat Conservation Trust and RSPB.  

Other options available to small-scale low impact development sites to enhance biodiversity include, where appropriate:

  • Green roofs with a diversity of plant species (could be a small section of the development if not all of the roof area);
  • Brown roofs with a range of substrates (could be a small section of the development if not all of the roof area);
  • Rough or natural stone walls with holes for invertebrates and small birds to use;
  • Species rich native hedgerows as boundary features;
  • Habitat creation for locally relevant wildlife habitat types (this can be beneficial on a small scale if it adds to the habitat resource locally)
  • Pond creation (not fish-stocked), with an irregular shallow sloping edge (these should be combined with stone and log piles close by to provide refuge for amphibians;
  • Green walls with planting locations built in, or a planting framework added externally;
  • Nectar-rich native planting and native species with berries within formal landscaping;
  • Native wildflower mixes as an alternative to amenity grassland or verges;
  • Garden boundaries with gaps to allow small animals to move between them (hedgehog highways);
  • Early flowering plants that provide a nectar source for early invertebrates such as bees;
  • South facing banks with some bare ground (particularly beneficial for reptiles and invertebrates);
  • Habitat corridors across a site to make a connection with wider habitats;
  • Architectural features that provide nesting or roosting habitat (such as slit holes)
  • Range of bug hotels with dead wood and stone piles, or purpose built bug boxes or bee bricks;
  • Information packs and interpretation material for the development end users;
  • Habitat creation that targets locally important species with isolated habitat patches;
  • Biodiversity focused design of sustainable urban drainage, for example with open and naturally vegetated swales.
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