Ecologically Valuable Line of Trees BNG Units
High
Hedgerows and Lines of trees
Trusted by Developers and Landowners
What are Ecologically Valuable Line of Trees?
An Ecologically Valuable Line of Trees is a high-distinctiveness linear habitat consisting of a continuous or near-continuous arrangement of trees over 20 metres in length, typically less than 5 metres wide between major stems, and distinguished by structural features that support specialist wildlife. Unlike standard lines of trees, this habitat includes at least one tree with veteran characteristics or natural ecological niches such as cavities, standing or attached deadwood, ivy cover or loose bark.
Why It Matters for BNG
Ecologically Valuable Lines of Trees carry a high distinctiveness score (6), meaning they generate more hedgerow biodiversity units per kilometre but also trigger higher replacement obligations if removed. Because units must be replaced within the hedgerow module and cannot be offset with woodland or grassland, early identification is critical to managing planning risk, cost exposure and design flexibility.
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Where Are They Found?
Ecologically valuable lines of trees are typically found along historic field boundaries, estate drives, parkland edges and rural corridors where long-term continuity has allowed trees to mature and develop veteran features. They often occur in traditional agricultural landscapes where boundaries have remained undisturbed for decades.
Soil & Site Requirements
They occur across a wide range of soil types including brown earths, clay loams, calcareous soils and moderately acidic substrates. To achieve high condition, the site should support long-term tree growth, maintain adequate rooting depth, and include an undisturbed vegetated buffer strip of at least 6 metres on both sides to protect from cultivation, spray drift and mechanical disturbance.
How New Ecologically Valuable Line of Trees Are Created
Inputs
• Establish a continuous linear corridor over 20 metres in length
• Plant ≥70% native UK tree species to meet condition thresholds
• Space trees approximately 3–6 metres apart to secure future canopy continuity
• Include a mix of fast-maturing pioneer species and long-lived canopy species with veteran potential
• Secure a minimum 6-metre undisturbed vegetated buffer on both sides
• Avoid non-native or ornamental dominance
Management
• Protect young trees from grazing, compaction and vandalism
• Allow natural canopy development; avoid heavy or routine pruning
• Retain standing and attached deadwood where safe
• Encourage development of ivy and natural cavities over time
• Monitor and infill canopy gaps below the 5-metre threshold
Landscape
• Reinforce historic field boundaries and estate alignments
• Connect woodland blocks, hedgerows and riparian corridors
• Maintain wide buffer strips to reduce agricultural disturbance
• Avoid fragmentation through excessive removal or infrastructure encroachment
How Existing Ecologically Valuable Line of Trees Are Improved
Inputs
• Increase native species proportion to ≥70% where below threshold
• Undertake selective infill planting to restore canopy continuity
• Introduce long-lived native species to secure future veteran potential
• Expand buffer strips to at least 6 metres where feasible
Management
• Reduce pruning intensity to retain ≥75% canopy cover
• Encourage development and retention of veteran features
• Protect root protection areas around mature trees
• Address tree health issues early to maintain ≥95% healthy trees
• Control invasive species and prevent mechanical damage
Landscape
• Strengthen ecological connectivity across agricultural landscapes
• Buffer with semi-natural grassland to enhance structural complexity
• Integrate into wider BNG habitat networks
• Retain mature trees during development to preserve high distinctiveness status
Target Condition
An Ecologically Valuable Line of Trees in defined BNG Good condition should:
• Contain at least 70% native tree species across its length
• Maintain a predominantly continuous canopy, with total gaps under 10% and no individual gap exceeding 5 metres
• Include at least one tree with veteran features or ecological niches, such as standing or attached deadwood, cavities, loose bark or significant ivy growth
• Be protected by a minimum 6-metre undisturbed vegetated buffer strip on both sides (or appropriate root protection areas around veteran trees)
• Demonstrate high overall tree health, with at least 95% of trees free from significant damage or disease
The BNG Value of Ecologically Valuable Line of Trees
• Distinctiveness: High
• Condition Potential: Strong uplift through buffer expansion, canopy repair and structural enhancement
• Restoration Pathway: Long-term maturation with focus on veteran features
• Strategic Value: High-functioning linear corridors linking woodland, hedgerows and riparian habitats
Species Typical of Ecologically Valuable Line of Trees
Canopy or Primary Layer
• Oak (Quercus robur, Quercus petraea)
• Ash (Fraxinus excelsior)
• Beech (Fagus sylvatica)
• Field maple (Acer campestre)
• Alder (Alnus glutinosa)
Shrub or Secondary Layer
• Hawthorn (Crataegus monogyna)
• Hazel (Corylus avellana)
• Holly (Ilex aquifolium)
• Blackthorn (Prunus spinosa)
Ground Flora or Margin Layer
• Dog’s mercury (Mercurialis perennis)
• Cow parsley (Anthriscus sylvestris)
• Red campion (Silene dioica)
• Rough grasses and nectar-rich herbs depending on soil context
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Frequently Asked Questions
What is an Ecologically Valuable Line of Trees?
Ecologically Valuable Line of Trees is a continuous line of trees over 20 metres long that includes at least one tree with wildlife features such as deadwood, cavities or loose bark. It is classed as high distinctiveness under BNG and sits in the hedgerow module.
How is BNG measured for Ecologically Valuable Lines of Trees?
BNG is measured by recording the length of the tree line and assessing its condition, including native species, canopy continuity, buffer protection, and tree health. It generates hedgerow biodiversity units only.
How can I achieve BNG with Ecologically Valuable Lines of Trees?
You can create new native tree lines with proper spacing and buffers, or improve existing ones by increasing native species, filling gaps and encouraging veteran features.
What is the BNG target condition?
At least 70% native trees, a mostly continuous canopy, one or more veteran features, a 6-metre buffer strip and healthy trees across the line.
What management is required?
Long-term management includes protecting roots, keeping buffer strips undisturbed, avoiding heavy pruning, retaining deadwood where safe and monitoring tree health over time.
Exploring Other Habitats?
Line of Trees
A Line of Trees in BNG is a row or corridor of trees forming a clear linear feature in the landscape. It is made up of individual trees spaced closely enough to create a recognisable boundary or route through farmland, estates or river corridors. These lines often follow historic field edges, green lanes or trackways and can include banks or ditches alongside them.
Some lines are simple boundary features, while others hold greater ecological value because they contain mature or veteran trees, standing deadwood, cavities and other natural features that support birds, bats and invertebrates.
Native Hedgerow
A Native Hedgerow BNG habitat is a linear woody habitat where more than 80% of the shrub and tree cover consists of native species. Structurally, native hedgerows consist of a dense shrub layer commonly dominated by species such as hawthorn, blackthorn and hazel, often with standard trees including oak or ash emerging above the canopy.
Ecologically Valuable Line of Trees
An Ecologically Valuable Line of Trees is a high-distinctiveness linear habitat consisting of a continuous or near-continuous arrangement of trees over 20 metres in length, typically less than 5 metres wide between major stems, and distinguished by structural features that support specialist wildlife. Unlike standard lines of trees, this habitat includes at least one tree with veteran characteristics or natural ecological niches such as cavities, standing or attached deadwood, ivy cover or loose bark.
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