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Comparing losses and gains in biodiversity:
Lessons learnt from HS2 Phase One
John Simmons (URS) & David Collins (HS2 Ltd)IEEM Spring Conference, Birmingham
18th March 2014
Environmental Overview Consultants for
HS2 Phase One
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Overview: HS2 Phase One
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• Phase One = 143 mile route London-West
Midlands. Promoted via a hybrid Bill
• Land required to construct and operate
Phase One identified within the hybrid bill.
includes compensatory habitat provision
• ‘Seeking to achieve ‘no net loss’ at the
route wide level’
No formal offsetting agreements with
third parties proposed
Use of an offsetting metric to measure
pre- and post development biodiversity
units
Proposed methodology accompanied ES
in November 2013, following discussion
with Defra & Natural England.
Calculation nearing completion.
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key requirements for an HS2 metric (1)
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• UK Government backed scheme
Defra pilot offsetting metric
• Compatible with scope of habitat
survey methodologies agreed for use
in HS2 Phase One.
• Loss of some ‘irreplaceable habitats’
(principally ancient woodland) &
impacts on land within SSSIs
desire for an all encompassing
calculation.
• Landscape scale scheme
Vital to ensure importance of position
in the ecological network consideredSource: Lawton et al (2010)
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key requirements for an HS2 metric (2)
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Isolated fragment Core area or corridor
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra metric: Distinctiveness
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1. Habitat distinctiveness
• New tier – ‘Very high’ score for Habitats
of Principle Importance (HoPI) which
cannot be adequately recreated
Multiplier of 8 but only available within
pre-development calculation
Compensation for ‘very high’ losses will
not be ‘like for like’ but rather via larger
areas of ‘high’ distinctiveness habitat’
For all other habitats aim to provide
habitats of same or higher
distinctiveness & similar type.
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra metric: Distinctiveness
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Distinctiveness Habitat type Multiplier
Very High(N.B. ONLY USED
IN PRE-
DEVELOPMENT
CALCULATION
Habitats meeting habitat of principal importance definition and
which can not be adequately re-created if lost.
For HS2 Phase One considered: ancient semi-natural
woodland, mature lowland heathland & Lowland fen.
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High Habitats of principal importance which do not qualify under
the definition for ‘very high’ category above.
6
Moderate Other semi-natural habitats that do not fall within the scope of
habitats of principal definitions - includes uncultivated field
margins, road verges and railway embankment (excluding
those intensively managed)
4
Low Improved grassland, arable fields (excluding any uncultivated
margins), built up area, domestic gardens, regularly disturbed
bare ground, intensively managed road verges and rail
embankments.
2
None Transport corridors (without associated verges), hard
standing, landfill sites, spoil heaps.
0
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra metric: Habitat condition
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2. Habitat condition
• No variable condition score for low
distinctiveness habitats.
automatically scored as ‘poor ‘ (1).
• ‘One-step rule’ replaced by ‘cap’ on
target condition scores for post-
development habitats
For high distinctiveness habitats - only
allowed to target a max. of moderate
condition (2) – except hedgerows
Where habitats not to be primarily
managed for their ecological value then
mitigation/compensation can target max.
condition of moderate (2).
Condition
multiplier
Condition
assessment
category
3 Good
2 Moderate
1 Poor
N.B. A condition
score of 1 will
automatically be
applied to all
habitats of low
distinctiveness
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra Metric: Distinctiveness vs condition`
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HS2 methodology
Pilot methodology
Habitat Distinctiveness
Very
High (8)
High (6) Medium
(4)
Low (2)
Co
nd
itio
n
Good (3) 24* 18** 12 2
Moderate
(2)
16* 12 8 2
Poor (1) 8* 6 4 2
*Not available as post-development targets. ** Only available as post-development target in
relation to hedgerows
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra Metric: Position in ecological network
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• Multiplier based on position in ecological network applied to both pre-
and post-development calculations
3 point scoring based on Lawton Review principles of ‘more, bigger,
better and joined’
• Bigger & well connected areas of high distinctiveness habitat are
valuable and help to maintain and enhance value of existing networks
Not intended as a proxy for requirements of individual species
Better acknowledge impact of losses in pre-development calculation
Seeks to encourage provision of compensation in those locations that
make ‘ecological sense’
• In establishing position in the network scores ecologist have considered
habitat data available for within a 500m radius of the land required for
the Proposed Scheme (i.e. the extent of habitat survey undertaken).
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra Metric: Position in ecological network
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Pre-Development
Position within existing ecological network Multiplier
Habitat areas which form part of a contiguous area of habitat(s) of principal
importance which is of more than 1ha in size1 (core habitat block) and have
connectivity with other areas of semi-natural habitat
3
Habitats areas which form part of a contiguous area of habitat(s) of principal
importance which is of more than 1ha in size but have little or no connectivity with
other areas of semi-natural habitat (i.e. those that do not score multiplier of 3 above);
Habitat areas which form part of a contiguous area of habitat(s) of principal
importance which is of between 0.25ha and 1ha in size (regardless of connectivity –
these are considered as stepping stones);
Habitat which forms part of an area of semi-natural habitat which provides
continuous physical connectivity2 between existing ‘core habitat blocks’
2
Any other areas which do not meet the criteria identified for either a multiplier of 2 or
3 above.
1
1 For the purposes of the calculation where areas of habitat of principal importance are separated by gaps of non-
qualifying habitat of 15m or less then these should be considered to be contiguous (unless professional judgement of an
ecologist considers otherwise);2 Defined as a ‘continuous corridor’ of moderate, high or very high distinctiveness habitat parcels. A gap in qualifying
habitat of more than 15m in extent, or a section where minimum width drops below 5m in width is considered a break in
connectivity.
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Key modifications to the Defra Metric: Position in network
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Post-development multiplier
• As per pre-development table with one addition
Areas of habitat creation or expansion within the aims of a specified Nature
Improvement Area (NIA) or Biodiversity Opportunity Area (BOA) scheme also
score multiplier of 3;
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Conclusions and lessons learnt (so far….)
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Metric
• HS2 modifications represent a natural progression to
Defra metric
Opportunities for on-going improvement (e.g. condition
scoring)
• Consideration of position in the network can be built
into the metric
Particularly relevant to linear infrastructure schemes, but
can be incorporated for all developments
Better acknowledges full impact of losses and focuses
minds on providing mitigation in locations that achieve
best ecological outcomes
Can help achieve progress towards policy goals.
• Important to place limits/caps within the metric that
temper compensation targets to that which is realistic
to achieve.
IMAGE TO BE
INSERTED (TBC)
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Conclusions and lessons learnt (so far….)
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Undertaking no net loss calculation
• Vital to get your habitat mapping correct
Habitat maps need to clearly differentiate
habitats of principal importance
Phase 1 vs Integrated Habitat System (IHS)
• Resource intensive
Use GIS to automate the process
Difficult to predict all eventualities at this
scale
Expect to undertake multiple iterations to
reach your final answer
• Condition scoring guidance needs to be further
developed to allow it to set management goals
• Potential to use the calculation throughout the
project lifecycle
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Acknowledgements
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• Jo Hughes (URS)
• Ecology leads at Arup (Oliver Barnett), Atkins (Kat Stanhope/Kate
Vincent), The Ecology Consultancy (Jon Riley/Tom McArthur/Matt
Wainhouse) and ETM (Beth Costes/Naomi Shepherd)
• All other consultants involved in undertaking the calculations, associated
GIS work and wider HS2 field work.
• Natural England (Adrian Jowett), Defra (Richard Plant, John Kilner) the
Major Infrastructure and Environment Unit (MIEU) (Will Armitage), and
all other stakeholders who provided comments on our draft
methodologies.
• Natalie Hall (HS2 Ecology advisor), Mike White (HS2 Environment GIS
manager)
Comparing losses and gains in biodiversity: Lessons learnt from HS2 Phase One
Further information and contact details
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• Technical Note: Methodology for demonstrating no net loss in
biodiversity is an appendix to the Scope and Methodology report
addendum. Available @
https://www.gov.uk/government/uploads/system/uploads/attachment_dat
a/file/260153/Vol5_Scope_and_methodology_report_addendum_CT-
001-000.2.pdf
• Email contact - [email protected]