Developers have new guidance from Defra on private gardens, trees

New guidance on private gardens tops the list of updates to Defra’s Statutory Biodiversity Metric tool, released on July 23, 2024. 

The Statutory Biodiversity Metric builds on prior versions of the biodiversity metric developed with input from Natural England, Environment Agency, and the Forestry Commission, as well authors and other contributors to earlier versions. Defra has released updated guidance on private gardens and urban trees, and has reformatted the guidance document to provide additional clarity throughout.

AiDash Biodiversity Net Gain Management System (BNGAI) closely follows updates to the metric tool, and quickly incorporates changes within the BNGAI platform, so BNG planning applications are always in line with metric guidance.

Defining private gardens

The newly released version expands on the definition of private gardens. Defined as gardens within the curtilage of a privately owned or tenanted dwelling house, private gardens require additional consideration as the post-development private garden has no public access, and biodiversity net gains cannot be legally secured.

Working with private gardens within the Biodiversity Metric

The newly released also provides additional clarity and detail on recording habitats within gardens in both baseline and post-development plans.

The earlier, Statutory Biodiversity Metric user guide, released with the tool in February 2024, offered a simple directive regarding private gardens:

Where private gardens are created, any tree planting within the created garden should not be included within post-development sheets of the metric. The habitat type “urban – vegetated garden” should be used.

The updated guide directs you to record any newly created private gardens as either urban – vegetated garden or urban – unvegetated garden. And it further instructs you not to record additional habitats within new gardens.

The updated guidance notes that private gardens can contain important features for biodiversity, including mature trees and hedgerows, which may require recording in the baseline.

To prevent under-recording of biodiversity, the guide recommends that you report individual trees (medium, large, and very large individual trees), hedgerows and other habitats, such as ponds within private gardens as individual habitat parcels in the baseline. Note that, if such habitats remain after development, you should record them as retained and guidance on retention should still be followed.

However, as there is no public access for the private garden once development is completed and biodiversity net gains cannot be legally secured, enhancements to these baseline habitats should not be recorded in the post development plan.

Recording individual trees and rural lines of trees within the metric

Defra has also expanded its guidance in the new metric regarding recording individual trees, particularly in urban areas. In determining whether the tree is urban or rural, the updated guide advises you to consider the degree of urbanization of habitats surrounding the tree.

The user should use the habitat term “individual trees” for the following:

• Individual rural trees
• Individual urban trees
• Lines, blocks, or groups of trees found within and around the perimeter of urban land

The user guide states that individual trees should only be recorded when they occur within a habitat that is not characterized by the presence of trees (such as in a woodland), unless they fit into specifications within the “recording individual trees at baseline” section of the updated guide. However, independent of location, the label “individual trees” should be used for all ancient and veteran trees, even those within hedgerows, rural lines of trees, and woodlands.

The updated guidance has now clarified that that hedgerow module classifications “line of trees” and “ecologically valuable line of trees” should be used only for rural lines of trees and therefore should not be recorded in urban environments.

Other new clarifications regarding individual trees include:

• Any individual trees that will be removed for any purpose, including development, disease, or safety must be recorded in your baseline as lost.
• In the urban environment trees within overgrown non-native and ornamental hedges should not be recorded as individual trees but rather as ornamental hedges in the hedgerow unit.

These and future updates will be reflected on the BNGAI platform to ensure a successful BNG planning application. For more information about how the platform streamlines and simplifies compliance, click here.

Lauren Weller
Senior Ecologist and R&D, EMEA

Lauren is currently working on the application of AI to geospatial and earth observation data to solve environmental challenges including biodiversity loss. Her previous work experience includes data analysis of water quantity and quality for farm-based research projects, environmental management and due diligence of mining and exploration projects throughout the African continent, and environmental consulting and advisory to the mining industry. She is interested in biodiversity, soil health, and sustainable agriculture — specifically the role of carbon in agricultural landscapes, and the science of teaching and learning.