You are here: 11.0 Land Use and Ecology > LE 03 Minimising impact on existing site ecology

LE 03 Minimising impact on existing site ecology

Number of credits available	Minimum standards
2	Yes

Aim

To minimise the impact of a building development on existing site ecology.

Assessment criteria

The following is required to demonstrate compliance:

Two credits - Change in ecological value 1

The change in ecological value of the site is equal to or greater than zero plant species, i.e. no negative change, using the methods outlined in either (a) or (b) below:
1. Determine the following information and input this data in to the BREEAM LE 03/LE 04 calculator:
  1. The broad habitat type(s) that define the landscape of the assessed site in its existing pre-developed state and proposed state (see Table 56 ).
  2. Area (m²) of the existing and proposed broad habitat types.
  OR
2. Where a Suitably Qualified Ecologist (SQE) has been appointed and, based on their site survey, they confirm the following and either the assessor or ecologist inputs this data in to the BREEAM LE 03/LE 04 calculator:
  1. The broad habitat types that define the landscape of the assessed site in its existing pre-developed state and proposed state.
  2. Area (m²) of the existing and proposed broad habitat plot types.
  3. Average total taxon (plant species) richness within each habitat type.

One credit - Change in ecological value 2

Where the change in ecological value of the site is less than zero but equal to or greater than minus nine plant species i.e. a minimal change, use the methods outlined in either 1(a) or (b) above.

Checklists and tables

Table 56 Broad habitat types (Source: Countryside Survey 2007)

Broad habitat type	Description
Acid grassland	Vegetation dominated by grasses and herbs on a range of lime-deficient soils which have been derived from acidic bedrock or from superficial deposits such as sands and gravels. They characteristically include a range of calcifuge or ‘lime-avoiding’ plants.
Arable and horticultural	Includes all arable crops such as different types of cereal and vegetable crops, together with orchards and more specialist operations such as market gardening and commercial flower growing. Freshly ploughed land, fallow areas, short term set-aside and annual grass leys are also included in this category.
Boundary and linear features	This habitat includes a diverse range of linearly arranged landscape features such as hedgerows, lines of trees (whether they are part of a hedgerow or not), walls, stone and earth banks, grass strips and dry ditches. These features may occur separately or in combinations forming multi-element boundaries. This habitat type also includes some of the built components of the rural landscape, including roads, tracks and railways. The narrow strips of semi-natural vegetation along verges or cuttings are also included.
Bracken	Stands of vegetation greater than 0.25ha in extent which are dominated by a continuous canopy cover (> 95% cover) of bracken (Pteridium aquilinum) at the height of the growing season.
Built-up and gardens	Covers urban and rural settlements, farm buildings, caravan parks and other man-made built structures such as industrial estates, retail parks, waste and derelict ground, urban parkland and urban transport infrastructure. It also includes domestic gardens and allotments. This category has been split in to three individual broad habitat categories for the purpose of BREEAM: Gardens, allotments and urban parkland Built-up (maintained buildings and infrastructure) Derelict land (where the land was previously used for major historical industrial use or development). This split is to reflect the differing impact of development in these types of habitats.
Broad-leaved, mixed and yew woodland	This form of woodland is dominated by trees that are more than 5m high when mature, which form a distinct, although sometimes open, canopy with a cover of greater than 20%. It includes stands of native broad-leaved trees (such as oak, ash and beech), non-native broad-leaved trees (such as sycamore and horse chestnut), and yew trees, where the percentage cover of these trees in the stand exceeds 20% of the total cover of the trees present. Scrub vegetation, where the woody component tends to be mainly shrubs (usually less than 5m high), is included if the cover of woody species is greater than 30%.
Calcareous grassland	Vegetation dominated by grasses and herbs on shallow, well-drained soils, which are alkaline, as a result of the weathering of chalk, limestone or other types of base-rich rock. They characteristically include a range of calcicoles or ‘lime-loving’ plants.
Coniferous woodland	Dominated by trees that are more than 5m high when mature, which form a distinct, although sometimes open, canopy which has a cover of greater than 20%. It includes stands of both native conifers (Scots pine but not yew) and non-native conifers (such as larch and Sitka spruce) where the percentage cover of these trees in the stand exceeds 80% of the total cover of the trees present.
Mixed woodland	This is not a category in its own right, but has been included separately by BRE Global for clarification. Many areas of woodland contain both broad-leaved and coniferous trees. There is not a separate Broad habitat type for mixed woodland. Instead where mixtures occur they are assigned to the broad-leaved, mixed and yew woodland habitat type if the proportion of conifers is less than 80%. The separation of coniferous from broad-leaved, mixed and yew habitat is applied at a stand or sub-compartment level within large woodlands to avoid areas that are predominantly coniferous being treated as mixed because they are part of a larger wood, of which 20% consists of pure broad-leaved trees. Therefore, most areas of mixed woodland that are assigned to the broad-leaved, mixed and yew woodland habitat type would normally have much more than 20% broad-leaved or yew trees.
Dwarf shrub heath	Vegetation that has a greater than 25% cover of plant species from the heath family or dwarf gorse species. It generally occurs on well-drained, nutrient-poor, acid soils.
Improved grassland	Occurs on fertile soils and is characterised by the dominance of a few fast-growing species, such as rye grass and white clover. These grasslands are typically used for grazing and silage, but they can also be managed for recreational purposes. They are often intensively managed using fertiliser and weed control treatments, and may also be ploughed as part of the normal rotation of arable crops but if so, they are only included in this Broad habitat type if they are more than one year old.
Inland rock	Habitat types that occur on both natural and artificial exposed rock surfaces, such as inland cliffs, caves, screes and limestone pavements, as well as various forms of excavations and waste tips, such as quarries and quarry waste.
Neutral grassland	Found on soils that are neither very acid nor alkaline. They support different types of vegetation communities compared to acid and calcareous grasslands in that they do not contain calcifuge (‘lime-avoiding’) plants which are found on acid soils, or calcicole (lime-loving) plants which are found on calcareous soils. Unimproved or semi-improved Neutral grasslands may be managed as hay meadows, pastures or for silage. They differ from Improved grassland in that they are less fertile and contain a wider range of herb and grass species. Usually the cover of rye grass is less than about 25%.

Table 57 Inclusive analysis of average total taxon richness by broad habitat in Fields and Other Main Land Cover Parcels plots in Great Britain.

Broad habitat type	Previously undeveloped land	Previously developed land (within broad habitat type) & ** (Time period that the site has been unoccupied/unmaintained and therefore derelict)
	Average total taxon (plant species) richness*
		< 5 Years	5-10 Years	10 - 20 Years	20 - 30+Years
Acid grassland	19.58	0	5.87	14.69	19.58
Arable and horticultural land	10.25	-	-	-	-
Boundary and linear features	15.42	-	-	-	-
Bracken	19.29	-	-	-	-
Built-up (buildings and infrastructure)^&*	-	0	-	-	-
Calcareous grassland	43.02	0	12.91	32.27	43.02
Coniferous woodland	14.05	-	-	-	-
Derelict land**	-	0	6.00	14.99	19.99
Gardens, allotments and urban parkland***	19.99	0	6.00	14.99	19.99
Dwarf shrub heath	15.87	0	4.76	11.90	15.87
Improved grassland	14.28	0	4.28	10.71	14.28
Inland rock	16.74	-	-	-	-
Mixed, broad-leaved and yew woodland	20.91	-	-	-	-
Neutral grassland	20.44	0	6.13	15.33	20.44
Source: Acknowledgement - Countryside Survey data owned by NERC – Centre for Ecology and Hydrology. Countryside Survey © Database Right/Copyright NERC– Centre for Ecology and Hydrology. All rights reserved.
Total taxon richness is higher plant species only, no bryophytes (non flowering plants). Figures are based on the average species richness per 200m² plot. The derelict land and built-up figures are not from the Countryside Survey data (see Additional information). BRE Global has split the 'Built-up and gardens' Countryside Survey category into these headings to reflect the differing impact of building on these types of land. **The ecological value of derelict sites is time dependent; a linear scale has been used to determine intermediate values between zero ecological value, where development occurs within 5 years from the end of occupation and maintenance works, and the value at 30 years based on the full species richness for the relevant broad habitat. This presents a minimum figure which can be amended on the advice of a Suitably Qualified Ecologist and their site survey.

Compliance notes

Ref	Terms	Description
Shell and core
CN1	Applicable assessment criteria	Both options: All criteria relevant to the building type and function apply. Refer to Appendix D – BREEAM UK New Construction and Shell and Core Project Assessments for a more detailed description of the above shell and core assessment options.
Simple buildings
CN2	Applicable assessment criteria	All criteria relevant to the building type and function apply.
General
CN3	Assessment of a single development on a larger site	Where the assessment is of a single building that forms part of a larger development and the soft landscape and ecological features form a common part of the whole site, for the purpose of assessing this issue the broad habitat types for the entire site must be used.
CN3.1	Infill developments on existing occupied site	Where a new building is an infill on an existing occupied site, then the construction zone for the new building would be the area of site assessed for the purposes of this issue.
CN3.2	Site clearance prior to purchase of the site	Refer to BREEAM issue LE 02 Ecological value of site and protection of ecological features – Compliance notes
CN3.3	Green roofs/walls See criterion 1b.	The contribution of plant species on a green roof can only be incorporated within the calculation where a Suitably Qualified Ecologist has been appointed to advise on suitable plant species for the roof. Presently green walls cannot be considered compliant within this BREEAM issue due to concerns over high maintenance requirements which are often not self-supporting/sustainable, resulting in deterioration of these plants. If the assessor feels that the green wall specified meets the aims of this issue and will be self-sustaining, details can be sent to BRE Global for consideration. Ground planted plants trained up a framework supported by the building would be acceptable (confirmed by the SQE) as these are not so dependent on systems and maintenance.

Methodology

Calculating the change in ecological value for a site

The change in ecological value is determined by measuring the diversity (species richness and cover) of plants on the site immediately before site clearance/preparation and after construction of the assessed development. The ecological value is expressed as an area-weighted average of plant species richness for the site’s broad habitat types. This enables BREEAM to use plant species as an indicator of the development’s impact on the site’s existing ecological value.

A simple example of the calculation is outlined below.

Calculate the ecological value of a previously developed existing site:

A 2065m² existing site consists of the following types of land and, using data from the table above, plant species richness:

1. 1865m² hard landscape = 0 species
2. 200m² urban parkland = 19.99 species

The ecological value of the site in its existing condition is calculated as follows, for each broad habitat type;

Number of species on broad habitat type x broad habitat type area as % of total area.

Therefore, for the example site:

1. Hard landscape: {(0 species x (1865m²/2065m²)} = 0
2. Urban parkland: {(19.99 species x (200m²/2065m²)} = 1.94
3. Ecological value of the existing site = 0 + 1.94 = 1.94

Calculate the ecological value of the site in its proposed, post-developed state

The 2065m² post construction-site consists of the following types of land:

1375m² of building = 0 species.
550m² of hard landscape = 0 species
140m² has remained as urban parkland = 19.99 species

The ecological value of the proposed site is as follows:

Building: {(0 species x (1375m²/2065m²)} = 0
Hard landscape: {(0 species x (550m²/2065m²)} = 0
Urban parkland: {(19.99 species x (140m²/2065m²)} = 1.36
Ecological value of the proposed site = 0 + 0 + 1.36 = 1.36

The ecological impact is the difference between the two ecological values:

Change in ecological value: 1.36 (after) – 1.94 (before) = - 0.58

Therefore, as the ecological value has decreased by no less than minus nine, for this example one credit can be awarded.

Evidence

Criteria	Interim design stage	Final post construction stage
All	One or more of the appropriate evidence types listed in The BREEAM evidential requirements section can be used to demonstrate compliance with these criteria.
1, 2	Where relevant: A completed copy of the BREEAM LE 03/LE 04 calculator	As per interim design stage. For large mixed use/multi-building developments, where the whole site has not been completed and ecological enhancements have not yet been added, or where features are being added at a later date in an appropriate planting season: Evidence from the client or principal contractor confirming planting will be completed within 18 months from completion of the development.
1, 2	Documentary evidence supporting the data used to complete the Calculator tool.	As per interim design stage

Criteria

Interim design stage

Final post construction stage

All

One or more of the appropriate evidence types listed in The BREEAM evidential requirements section can be used to demonstrate compliance with these criteria.

1, 2

Where relevant:

A completed copy of the BREEAM LE 03/LE 04 calculator

As per interim design stage.

For large mixed use/multi-building developments, where the whole site has not been completed and ecological enhancements have not yet been added, or where features are being added at a later date in an appropriate planting season:

Evidence from the client or principal contractor confirming planting will be completed within 18 months from completion of the development.

1, 2

Documentary evidence supporting the data used to complete the Calculator tool.

As per interim design stage

Additional information

Relevant definitions

Average total taxon (plant species richness): The ecological value of a site expressed as an area weighted average of plant species richness for a site's broad habitat types.
Note: BREEAM uses plant species richness as an indicative measure of ecological value of the assessed site and therefore an indication of ecological impact resulting from its development.
Assessment zone: Refer to BREEAM issue LE 02 Ecological value of site and protection of ecological features.
Suitably Qualified Ecologist (SQE): Refer to BREEAM issue LE 02 Ecological value of site and protection of ecological features.

Other information

See LE 02 Ecological value of site and protection of ecological features ‘Other information’ for information that also applies to LE 03 Minimising impact on existing site ecology.

Where green roofs are specified The GRO Green Roof Code1The GRO Green Roof Code: Green Roof Code of Practice for the UK 2014, Groundwork Sheffield. provides guidance on green roof design, installation and maintenance and maximising their environmental benefits.

Countryside Survey (2007) data

The data used in this BREEAM issue has been obtained from the Countryside Survey 2007 tables; www.countrysidesurvey.org.uk

Broad habitat definitions have been sourced from: www.countrysidesurvey.org.uk

Some of the Countryside Survey broad habitat data have not been used within this BREEAM issue either because the broad habitat supports no taxon richness or because it is unlikely that buildings will be constructed within these habitat types e.g. bog, fen etc.

BREEAM assumptions

In order to use the Countryside Survey data within BREEAM, BRE Global has made the following assumptions:

Built-up (maintained buildings and hard landscaping) have a plant species richness of zero.
The previously developed land category is relevant for derelict sites within a broad habitat type where plant species found in that habitat are likely to reclaim the site if left to do so over a defined period of time. BRE Global has assumed this is the case for land found within the grassland, heath, derelict, gardens, allotments and urban parkland habitats. It has not been assumed for other categories as BRE Global is unable to confirm an appropriate period over which planting will re-establish itself on derelict land within these other broad habitat types.
A period of 5 to 10, 10 to 20 and 20 to 30 year’s dereliction is used; the species richness figures against each period for a particular habitat type are based on a re-establishment rate of 30% of richness, 75% and 100% respectively.
BRE Global has split the ‘Built-up and gardens’ category from the Countryside Survey into ‘Gardens, allotments and urban parkland’, ‘Derelict’ and ‘Built-up’ habitat types. This split is to reflect the differing impact of building on this type of land.