Allocation

The planned habitat set aside by a BGS site to meet the offsite BNG requirements of a specific development.

API

An Application Programming Interface is a set of rules and protocols that allows different software systems to communicate and exchange data with each other in a standardized way, without users needing to know the intricate details of how each system is built.

Baseline habitat

The pre-existing habitat of a site before that site is developed.

Biodiversity Gain Site (BGS)

An area of land or habitat designated to create or enhance habitats for wildlife, leading to a measurable increase in biodiversity. Only sites listed on the BGS Register are eligible for this designation.

The Biodiversity Gain Site Register Regulations 2024

Condition

The ecological health and functional status of a habitat, indicating its resilience and how well it supports its ecosystem. It's assessed using criteria for specific habitat types, often resulting in a rating - good, moderate or poor - which is based on factors like species presence, management and disturbance.

Decile

A decile is calculated by ranking the 33,755 neighbourhoods in England from most deprived to least deprived and dividing them into 10 equal groups (i.e. each containing 3,375 or 3,376 neighbourhoods). These deciles range from the most deprived 10 per cent of neighbourhoods nationally to the least deprived 10 per cent of neighbourhoods nationally.

Deprivation

Deprivation refers to people's unmet needs, a lack of access to opportunities and resources which we might expect in our society.

Habitat

An environment or area that supports living organisms, including plants, animals and fungi.

Habitat Unit (HU)

A quantitative measure of the value of a natural habitat, used in Biodiversity Net Gain calculations. It is calculated based on a habitat's size (area or length), distinctiveness, condition and strategic significance, with higher values indicating better ecological quality and greater biodiversity.

Local Nature Recovery Strategy (LNRS) site

An England-wide system of spatial strategies required by the Environment Act 2021 that identifies priorities and maps proposals for nature recovery at the local level. These strategies are designed to map existing important habitats, identify areas for new or improved habitats, set out priorities for action, and integrate with the planning system to support wider environmental benefits like biodiversity, flood management, carbon storage, and water quality. See Local nature recovery strategies policy paper.

Local Planning Authority (LPA)

A local government body, often a council department, responsible for managing land use and development in a specific area. Its functions include deciding on planning applications, preparing and implementing local plans, and enforcing planning policies to ensure that development is sustainable and balances economic, environmental and social considerations.

Lower Layer Super Output Areas (LSOAs)

LSOAs are small areas designed to be of a similar population size, with an average of approximately 1,600 residents or 650 households. There are 33,755 LSOAs in England. They are a standard statistical geography and were produced by the Office for National Statistics for the reporting of small area statistics. LSOAs are referred to as 'neighbourhoods' .

Deprivation in England (2025)..

National Character Area (NCA)

A distinctive and recognisable unit of England's landscape, defined by a unique sense of place resulting from its specific natural, cultural and economic features. NCAs follow the natural lines of the landscape, rather than administrative boundaries like counties, making them a useful framework for planning and decision making for landscape and environmental projects. There are 159 NCAs in England, and each has a detailed profile outlining its characteristics and how it functions and can be sustained. See National Character Area Profiles.

Parcel

A discrete habitat within a larger site containing a single, consistent type of habitat in a particular condition.

Responsible Body

An organisation designated by Defra to hold and administer conservation covenants for BNG projects, monitoring and enforcing habitat improvement plans to ensure long-term conservation. See Conservation covenants: criteria for being a responsible body guidance.

Sankey diagram

Sankey diagrams are a data visualisation technique or flow diagram that emphasises flow/movement/change from one state to another or one time to another, in which the width of the arrows is proportional to the flow rate of the depicted transformation.

Size

The size of area habitats is measured in hectares (ha). Linear habitats - hedgerows and watercourses - are measured in kilometres (km).

SRM

The spatial risk multiplier is a factor used in the statutory BNG metric to reduce the measured ecological value of off-site habitat compensation based on its distance from the development site.

Trading Rules

The trading rules require that lost habitats must be compensated for with habitats of equal or higher value on a 'like-for-like or like-for-better' principle.