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Number 62 • December 2008
In Practice
Bulletin of the Institute of Ecology and Environmental Management
Mitigation
INFORMATION
In Practice No. 62, Dec 2008. ISSN 1754-4882 Institute of Ecology and Environmental Management
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EDITORIAL AND CONTENTS
Editorial Contents
Information 2
B y the time you read this editorial the Institute will have
had a thorough discussion about mitigation at its annual
conference in Glasgow. This issue of In Practice concentrates on
Editorial and Contents
Mitigation Banking: Securing No Net
Loss for Biodiversity?
3
4-6
the subject, which should be at the heart of our work as ecologists William Latimer CEnv MIEEM and David
and environmental managers. The conference will have had the Hill CEnv FIEEM
benefit of reviewing a number of case studies, and discussing their Large Scale Mitigation: A Case Study 7 - 10
outcomes. I have to anticipate what the outcomes may be, as I write Using Water Voles
Helen Markwell CEnv MIEEM
this editorial, the day before the Conference starts.
Site Mitigation for Invertebrates 11 - 12
I think we may hear calls for change in the way we go about mitigation and the way that Alex Ramsay MIEEM
decision makers and project managers alike rely on mitigation. I use ‘mitigation’ here in
Mitigating Urban Pressures on Natura 13 - 16
the broader sense, commonly used in environmental assessment, to cover avoidance, 2000 Heathlands in Dorset
cancellation and reduction measures, rather than the narrower meaning of ‘mitigation’, only Heather Tidball MIEEM and Phil Sterling
as the action of reducing the severity or seriousness of something. I argue that we should
take these measures into account at every stage of the decision making process. However, Can Non-Intrusive Geo-Physical 17 - 20
Techniques Assist in Mapping Setts of
we should distinguish between them and ‘compensatory measures’, which should be the Eurasian Badger
considered only after the decision in principle has been taken to proceed with a damaging P O’Donoghue CEnv MIEEM, L Dolan, P D
change. Dansie MIEEM and I Sharkey
I am advocating a more structured approach to mitigation and compensatory actions, Understanding the Habitats Directive: 21 - 23
following a sequence, down a ladder of counter-acting measures; where we give priority Appropriate Assessment - What is it and
to avoidance, then cancellation, then reduction measures, before considering seven types what is ‘appropriate’?
Roger Morris CEnv FIEEM
of compensatory measures. These are, again in the order I suggest they should normally
be prioritised: in situ repair; like-for-like habitat or species restoration; like-for-like habitat Survey Guidance for Assessing Bat 24 - 27
creation; alternative habitat or species restoration; alternative habitat creation; new Activity at Proposed On-Shore Wind
protection measures and translocation. All of the measures are not, of course, available in Farms
James Cook MIEEM, Andrew McCarthy
every case, and are not mutually exclusive. They should be used individually or in various CEnv MIEEM, Stephen Holloway CEnv
permutations to deliver the most reliable and most complete recompense for the adverse MIEEM and Gary Oliver CEnv MIEEM
effects in the longest term.
Neglected Biodiversity: Mosses, 28 - 31
Requiring mitigation is routine, but compensatory measures are more difficult to secure Liverworts and Ecological Impact
in most regulatory regimes. Furthermore, although government policy (e.g. PPS9) urges Assessment
the spatial planning system to conserve and enhance biodiversity resources, development Des A Callaghan MIEEM
management and other regulatory processes are not well designed to deliver net benefits. Restoration Network Ireland 32
There is scope for a bigger contribution, through regional and local spatial planning, to the Catherine A Farell MIEEM
planning and delivery of both compensatory measures and net benefits, at greater-than-
Autumn Conference Report 33
project- level scale. I also think that there is a positive role for ‘habitat banking’ as a form of
mitigation, or more often, a compensatory measure, when done with care and integrity and The IEEM Medal: Citation for Professor 34
when properly accounted for. Charles Gimingham
Pat Rae CEnv MIEEM and Una Urquhart
I think we should also place more weight on the need for, and value of, monitoring. All too CEnv FIEEM
often projects offer mitigation or compensation measures, decision makers accept them, or Best Practice Awards 2008 35 - 36
impose alternative measures, the project is implemented and we all assume the measures
were properly applied and fully effective. There are some good examples of diligent Ecological Skills Gap Project 37 - 38
monitoring and adjustment of measures in response to actual, as opposed to predicted, IUCN World Conservation Congress 39
effects. These should become the norm not the exception. A monitoring and review
procedure should be imposed as a requirement (by way of enforceable conditions) in every New Fellows 40
case where EIA has been undertaken, and potential harm identified. Tony Bradshaw Obituary 41
David Parker CEnv MIEEM
David Tyldesley MIEEM Institute News 42
Principal, David Tyldesley and Associates
Geographic Section News 43 - 45
Partnership News 46
Correction In the Journals 47 - 50
In the EcIA Questions and Answers article, in In Practice 61, the third last Recent Publications 51
paragragh on page 27 should make reference to the ‘NERC Act Section 41 list’ News in Brief 52 - 53
rather than to the ‘CRoW Act Section 74 list’. This correction was made by the
author, but unfortunately was not included in the final print version. IEEM would like Tauro-Scatology 54
to apologise for any inconvenience caused. New and Prospective Members 55
Diary 56
Cover image: Professor Charles Gimingham
Merry Christmas and Happy New Year! (right) receives the IEEM Medal from Mr Michael
Russell MSP, Environment Minister, Scottish
Everyone here at IEEM would like to wish you a Government
wonderful Christmas and a prosperous New Year!
Artwork on the cover will normally illustrate an
article in, or the theme of, the current issue. The
Editor would be pleased to consider any such
material from authors.
MITIGATION BANKING
Mitigation Banking: Securing No
Net Loss for Biodiversity?
William Latimer CEnv MIEEM and David Hill CEnv FIEEM**
* Associate Director, Faber Maunsell
** Chairman, The Environment Bank Ltd
Introduction habitat creation and management. Credits
for land set aside for mitigation banking
planning authorities in its Planning Policy
Statement No. 9 takes this principle
E nvironmental advisors and can increase in value as the ecosystem further, stating (para. 1.vi) ‘Where a
develops or populations increase to a planning decision would result in significant
planners are frequently
stable and self-sustaining level. In the USA, harm to biodiversity and geological
confronted with uncertainties the scheme now encompasses broader interests which cannot be prevented or
over ecological mitigation, habitat and species banks with around adequately mitigated against, appropriate
whether the proposed 150 institutions administering the banks compensation measures should be
compensation is adequate and or providing ecological and conservation sought. If that significant harm cannot be
how it will function over time. expertise. prevented, adequately mitigated against, or
The advantages of acquiring and compensated for, then planning permission
Mitigation banks have inverted conservation
should be refused’.
retaining land in advance for values: where wildlife conservation in
ecological mitigation required the development context was formerly The focus is therefore shifting from
by subsequent development has regarded as a financial drain and a site-based conservation of habitats and
been demonstrated primarily in liability, the mitigation banking system species, to the maintenance of biodiversity
has transformed protected species and and functioning ecosystems as emphasised
the USA where such Mitigation habitats into assets. in the Government’s 2005 Sustainable
Banking (or Biodiversity Development Strategy (Ch. 5) which
Offsets, ten Kate, Bishop and The results of mitigation banking from
recognises the importance of biodiversity
Bayon 2004), pioneered for the the US experience appear to be broadly
to self-maintaining natural systems and
positive as a large number of successful
conservation of wetlands over 20 conservation schemes have been achieved.
“ecosystem services”. While the converging
years ago (Crooks and Ledoux policies on biodiversity and sustainability
There have been some failures attributed
2000), is now established in the might be considered fairly straightforward,
principally to the lack of regulatory
there remain considerable risks to
regulatory framework. supervision, highlighting the need for
sustainable development under the current
effective enforcement and monitoring.
Essentially, the mitigation bank is planning system.
established by acquiring land for
the creation, or enhancement and Mitigation Banking: its Section 106 ‘Agreements’ of the 1990
Town and Country Planning Act allow
management, of habitats or ecosystems
for a particular wildlife or environmental
Application in the UK the applicant to enter into legally binding
agreements to secure mechanisms to
resource. The asset is valued in terms The Legislative and Planning offset adverse environmental effects.
of credits and the better the condition
Framework While this adds power and flexibility to the
of the land in terms of its environmental
planning process there are a number of
objectives, the greater its value. Credits The Habitats Directive, enacted in the notable disadvantages:
may be purchased, held, and traded in a UK by the 1994 Conservation (Natural
process analogous to carbon trading. Habitats, &c.) Regulations (Habitats • agreements with the local authority
Regulations), requires the protection, usually predicate that the works
Land may be acquired by financial
at a ‘favourable conservation status’ of or mitigation feature operate at a
institutions, businesses, land-owners or
habitats and species deemed to be rare local level, often adjacent to the
investors and managed to maximise its
or vulnerable at an international level. This development, which may not be an
biodiversity or environmental capital.
principle of no-net-loss applies certainly to optimal strategy;
Credits may then be sold as the land comes
the network of European protected sites
into appropriate and stable condition • mitigation is often initiated at the same
but also to qualifying species that may
for which the asset was purchased. The time or even after the development
obtain resources, at least occasionally,
purchase of credits does not in any way has taken place leading to a temporal
outside protected sites. Examples of the
obviate adherence to existing legislation loss of ecological resources;
latter might include birds from a protected
regarding environmental protection, natural
estuary or marshland that may also roost • timescales for ecological succession
resource or wildlife conservation, but may
or graze outside a Special Protection leading to habitat stability are
be used where impacts are deemed to be
Area (SPA) or bats from a Special Area therefore often too short; and
unavoidable. Along with the reduction in
of Conservation (SAC) that forage along
ecological risk that comes to the developer • overarching mitigation for combined
adjacent hedgerows. Where developments
with the acquisition of credits also comes developments, which may be
outside protected sites may affect the
a reduction in financial risk: credits for temporally as well as spatially
interest within, the statutory regulator will
species or a functioning ecological system separated is rarely sought, unless
require an ‘appropriate assessment’ to be
can be more accurately costed. part of an appropriate assessment
undertaken and, if needed, mitigation to
ensure no net loss. under Para. 48(1) of the Habitats
The monetary value of the credits is
Regulations.
related to the costs of land acquisition,
Recent UK government guidance to
4 In Practice December 2008
MITIGATION BANKING
In addition, there can be a substantial gap Location habitats undergo the correct development
between what is promised by developers period are therefore:
It is often appropriate to re-create
through planning obligations and what
habitats in the same ecological area • the longer the period of development,
is delivered, due to the inadequacy of
(e.g. English Nature’s Natural Areas or the greater the likelihood that some
subsequent monitoring and enforcement.
Joint Character Areas) to obtain the measure of habitat stability is
Statutory Requirements and best like-for-like replacement. It may achieved, though this is often reliant
Ecological Principles also be necessary to make even finer on the correct management regime;
discriminations based on microclimatic
Like-for-Like Mitigation • with appropriate monitoring, and
factors or soil types. Adjacent
remedial action where needed, the risk
The no-net-loss principle dictates that compensation for housing or employment
of failure declines over time;
where mitigation is obtained by means of developments provides a visible
credits, these should have parity with the and accessible amenity and a public • the habitat is therefore better able to
losses due to development, both in keeping perception of replacement of valued fulfil its intended biodiversity function;
with the scale of loss and the nature of the natural resources. and
loss. The financial analogy would be that However, in some cases, the success • the value of the credits for the habitat
the credits are of the appropriate currency of mitigation may be compromised by increase over time, in keeping with
and monetary value. Thus a pond with siting the area in close proximity to greater stability, habitat quality and
protected great crested newts necessarily the development. These would include the assurance that the habitat will fulfil
lost to development would require mitigation areas for species that are its objectives.
replacement habitats for that species, sensitive to anthropogenic disturbances
chalk grassland re-created in mitigation such as visual disturbance from walkers, The ability to produce mature and stable
for losses to development should be of a noise, fires, disturbance or predation habitats is perhaps the key advantage of
similar plant community. from domestic pets. The degradation the mitigation banking system, as long
of lowland heaths as an apparent result as the bank is correctly regulated and
Critical Natural Capital or Non- monitored.
Replaceable Habitats of proximate housing developments is
well documented (Liley and Clarke 2002, Mitigation for Habitats and
Mitigation banks are limited to those Underhill-Day 2005) and has led to the
habitats that can be created or manipulated
Species without Statutory
development of local spatial planning
to increase their conservation value in policies (English Nature 2005). On-site
Protection
terms of their ecological function, habitats, or adjacent mitigation may also not be For habitats and species without direct
or species. The system cannot deal with appropriate for busy transport corridors statutory protection, there is an increasing
losses to habitats that are deemed, in with high levels of noise, collision risk, or emphasis on similar compensation being
realistic timescales, to be irreplaceable. poor air quality. In such cases it would be provided for any losses of biodiversity
Such critical natural capital (e.g. ancient necessary to seek alternative sites well due to development (PPS9). Species and
woodlands and raised mires) cannot be beyond the range of expected impact. habitats requiring conservation action are
traded, along with other habitats that may Climate change adds a challenging new listed under Section 74 of the 2000 CRoW
be very difficult to replicate because of dimension to this debate. The value Act (reinforced by Section 40 of the NERC
environmental complexity (e.g. habitat of habitat banking is that it provides Act) and are generally subjects of the UK
mosaics on complex geology) or intricate a mechanism for the delivery of this Biodiversity Action Plans (BAP). In addition
relationships between physical and resource and this principle can be to BAP and Section 74 habitats and
biological factors (e.g. hibernation caves extended to the provision of the core species, the Red and Amber lists of bird
for bats). sites and green corridors comprising species (JNCC 2002) and Red Data books
Spatial Relationships between ecological networks. point to additional species for conservation
Development Areas and Mitigation action.
Timescales for Habitat Development
Sites and Ecological Succession While mitigation banks could be developed
Size to permit compensation for BAP species
Where the mitigation bank can be created
and habitats lost to development, it would
The creation of large reserve areas well in advance of its requirement in
clearly be inappropriate for gains within the
for wildlife is often more successful in compensation for losses to development,
banks to be counted as progress towards
producing stable and self sustaining the uncertainty as to the success of
BAP targets for key habitats or species
populations of the target species and mitigation is reduced as the process of
and the development of mitigation banks
habitats than small isolated sites, ecological succession, and management
should not, in any way, reduce the effort
vulnerable to random catastrophic factors as needed, render the habitat better
to promote the favourable conservation
or the deleterious effects of inbreeding. suited for its purpose. Timescales for
status of these species. Nevertheless,
Small sites can require a disproportionate habitat creation vary according to the
in some cases the presence of core
effort of management in order to maintain type of habitat. Ponds may be available
populations within the banks, developed
their ecological interest, e.g. the control for colonisation by protected amphibian
to compensate for losses elsewhere, may
of invasive species on small heathland or aquatic insect populations within one
make a temporal, local contribution to
patches, and mitigation costs for separate or two years; species-rich grasslands
species recovery outside the banks where
developments can also be higher where may take 4-5 years, with appropriate
favourable habitats exist.
administration and management are management, to stabilise, while woodlands
replicated both spatially and over time for will clearly take many decades to mature. Development in Farmland, a Case in
the same target habitat or species. The principle that newly created habitats Point
should be in place in appropriate condition
There is therefore now considerable for their compensatory purpose is noted With increasing development on greenfield
interest in developing large ‘reserves’ at a in Paragraph 30 of the UK Government’s sites, pressures continue on communities
landscape scale, e.g. the various initiatives Circular on Biodiversity and Geological of the mosaic of farmland habitats,
for the restoration of extensive reedbeds Conservation, but this can be difficult to already much depleted by intensive
in the Fens, habitats or biotopes sized to achieve under the current planning regime. farming. The concern over the loss of
support sustainable populations of key, species characteristic of arable farmland
‘flagship’ species. The important advantages in ensuring that is highlighted in plans within the UK BAPs
In Practice December 2008 5
MITIGATION BANKING
and summarized in chapter 4 of the comprising sustainable rural communities biodiversity. Journal of Applied Ecology 44:
Government’s Biodiversity Strategy for where economic, social and environmental 6-12.
England (Defra 2002a). In view of this, issues are all taken into account. Where
Crooks S and Ledoux L (2000) Mitigation
the statutory conservation agencies compensation for the loss of farmland
banking: potential applications in the UK.
and planning authorities are likely, in biodiversity is required, mitigation banking
Environmental and Waste Management 3(4):
accordance with the requirements of PPS could transfer some of this commitment,
1-8.
9, to seek appropriate mitigation for such currently funded from the public purse
losses due to development. The advance through piecemeal Environmental Defra (2002a) Working with the Grain of
acquisition of biodiversity credits in species Stewardships, to the developer. Nature: A Biodiversity Strategy for England.
and habitats characteristic of farmland
The system would benefit extensive Defra (2002b) Strategy for Sustainable
habitats appears to be increasingly tenable
landscape initiatives where progress and Farming and Food - Facing the Future.
given current concerns over landscape
sustainable management may be limited www.defra.gov.uk/farm/policy/sustain/
conservation, intensive agriculture, food
by the uncertainties and unpredictability newstrategy/strategy/strategy.pdf
quality and the rural economy.
of piecemeal funding (Wall 2006). As
Whole Landscape Conservation noted above, such initiatives could also be Defra (2004) The Rural Strategy. www.defra.
spatially designed to deliver the ecological gov.uk/rural/strategy/default.htm
By supporting a farming system geared
networks needed to enable the dispersion Ecosystem Marketplace. See:
towards conserving declining animal
of species across the wider landscape, ecosystemmarketplace.com/index.php
and plant species of increasingly rare
from local, through regional, even to
farming landscapes, other gains, in English Nature. Natural Areas. www.english-
national dimensions, providing one of the
addition to enhanced biodiversity, may nature.org.uk/science/natural/NA_search.
pre-requisites for mitigating the effects of
arise. There is some evidence that asp
climate change.
extensive and organic farming methods
not only produce increasingly sought- English Nature (2005) Thames Basin Heaths.
Delivery of the Mitigation Banking
after products with a high market value Pulling together for access, conservation and
System development. A new approach to housing
but also support a landscape that offers
sustainable production (Bullock et al. With no formal system in place for a allocations and nature conservation (see:
2007) with a higher biodiversity than nationwide approach to mitigation banking, www.english-nature.org.uk/about/teams/
modern conventional intensive farming the approach at present would rely on team_photo/Thames1.pdf). English Nature
(New Scientist 2004). Organic farming partnerships between financial institutions Thames and Chilterns Team.
is now seen as a viable sector of the UK and land management or conservation Liley D and Clarke R T (2002) Urban
agriculture industry with acknowledged agencies. There is, however, nothing development adjacent to heathland sites
benefits for sustainability, biodiversity and to prevent developers from acquiring in Dorset: the effect on the density and
the rural economy (Defra 2002b, 2004) additional land and managing this in order settlement patterns of Annex I bird species.
though without farm diversification, the to provide for future mitigation needs. English Nature Research Report No. 463.
economics can, at present, be borderline. However, we believe such acquisition, or Natural England, Peterborough, UK.
establishment of land is more appropriately
Payments for biodiversity credits held by done through a third party working New Scientist (2004) Organic Farming
landowners who conserved ecological independently of the developer and boosts Biodiversity. 11 October. www.
assets upon their land could assist in relieving him from the specialist work of newscientist.com/article.ns?id=dn6496
keeping land-owners or tenant farmers ecological mitigation design, construction
and their employees working on the land, ten Kate K, Bishop J and Bayon R (2004)
and management.
thereby assisting the rural economy. Biodiversity offsets: Views, experience and
Management for sustainable food Regulatory supervision, as with the the business case. IUCN, Gland, Switzerland
production and biodiversity often requires carbon trading scheme administered by and Cambridge, UK and Insight Investment,
a higher level of skilled application whether the Environment Agency, would be most London, UK. www.iucn.org/themes/
applied to the management of rotational properly undertaken by the appropriate business/Biodiversity%20Offsets/ten%20ka
farming, sound and sympathetic animal statutory conservation agencies, though te%20et%20al%20paper.pdf
husbandry, or the management of habitats it is highly likely, and clearly desirable both
Underhill-Day J C (2005) A literature review
and ecosystems. for the regulators and the development
of urban effects on lowland heaths and their
industry, that these agencies would require
Landscapes farmed in part for biodiversity wildlife. English Nature Research Report No.
that managers of mitigation banks and
objectives have a higher visual appeal 623. Natural England, Peterborough, UK.
developer seeking credits should obtain the
than those under intensive agriculture assistance of professional ecologists. The UK Government (2005) Sustainable
which often result in rather forbidding and Development Strategy; Securing the Future.
constrained environments for ready public There is a real opportunity to obtain
Defra (see: www.sustainable-development.
access. Bio-diverse landscapes would much greater gains for biodiversity and
gov.uk/publications/uk-strategy/index.htm)
have an enhanced high value for public ecosystem function, at varying landscape
enjoyment and, linked to public goods and scales through the implementation of a Wall T (2006) Inching towards conservation
services, enhancements of ecological mechanism based on mitigation banking. at the landscape scale. Conservation Land
patches and networks on farmland, The required investment in land and skills Management 4: 2, 4-7. English Nature.
delivered through mitigation banking, could should find favour in the current economic
also provide more areas for people to visit, climate and the re-visiting of Keynesian
alleviating pressure on vulnerable protected economics. We propose that such a This article is based on Mitigation Banking:
sites, assisting in progress towards mechanism is enshrined within the planning Securing No Net Loss to Biodiversity? A UK
government targets for restoring the Sites process in the UK. Perspective by William Latimer and David
of Special Scientific Interest (SSSI) network Hill in Planning, Practice & Research, Vol.
to favourable condition. References 22, No. 2, pp. 155–175, May 2007.
The Rural Strategy (Defra 2004) presents Bullock J M, Pywell R F and Walker K Correspondence:
a government vision of a living, working, J (2007) Long-term enhancement of william.latimer@fabermaunsell.com
protected and vibrant countryside agricultural production by restoration of dhill@davidhillecology.com
6 In Practice December 2008
WATER VOLE MITIGATION
Large Scale Mitigation: A Case
Study Using Water Voles
Helen Markwell CEnv MIEEM
Senior Environmental Scientist, Halcrow Group Ltd
Summary the protection
afforded by Map of rivers in the BFAP project area
L arge scale development projects can pose the Project’s
flood
significant challenges when implementing
defences.
protected species mitigation, but also provide
opportunities for developing novel solutions and In order to
best practice methodologies. A prime example deliver the
works, a large
is the issue of water vole mitigation required team of civil
for the Broadland Flood Alleviation Project engineers,
(BFAP). Achievements to date have included the environmental
development of an effective mitigation technique, scientists,
using water draw down as a displacement tool, and project
and a rapid assessment survey methodology. managers
Post works monitoring indicates mitigation is a are employed
by the client,
success and Broadland continues to provide a UK design
stronghold for the species. consultant
and works
Project Background contractor,
operating from
The BFAP is a long-term project providing a range of flood a single main
defence improvements, maintenance and emergency response office base.
services within the tidal areas of the Rivers Yare, Bure, Waveney An extensive
and their tributaries. The contract for the Public Private network of
Partnership Programme was awarded in 2001, and the 20 site personnel
year programme of works is being delivered on behalf of, and implement the construction works. All baseline ecological
in partnership with, the Environment Agency (EA). The project surveys are either undertaken in-house or are sub-contracted
is the first of its kind to provide flood defences on this scale; to relevant specialists. Impact assessments, mitigation
more than 240 km of floodbanks protect in excess of 21,000 prescription, on-site environmental (clerk of works) supervision
hectares of Broadland. and strategic post-works monitoring are all undertaken by
Situated in East Anglia, Broadland is one of the finest areas members of the Project’s Environment Team.
of wetland in Britain. It includes open water, the Broads
themselves, and the low-lying marshland surrounding the tidal Nature of Works
river reaches. The rivers reach the sea at Great Yarmouth, and
together with the Broads comprise a major inland navigation. Under the BFAP contract the main flood defence improvement
works are to be completed by 2012. As a result many tens of
The Broads, a unique and environmentally sensitive area, has kilometres of floodbanks may be worked each year. The works
a status equivalent to a National Park, and is home to plants are based on the use of sustainable techniques, and utilise
and animals found in few other places in Britain, many of which locally sourced material for building new and strengthening/
are protected under UK and European law. The Project area crest raising existing floodbanks wherever possible.
contains 28 Sites of Special Scientific Interest (SSSI), amounting
to more than 7,000 hectares in total, the majority of which The zones and habitats directly affected within the works
benefit from protection under European law either as Special corridor comprise the rond (area of reed/saltmarsh located
Protection Areas (SPAs) or Special Areas of Conservation between the main river and the floodbank); the floodbank itself;
(SACs). Two Ramsar sites are also located within the Project the folding (area of land between the floodbank and the soke
boundary. Conservation bodies own or manage some of dyke); and the soke dyke. The soke dyke runs parallel to the
the sites, but most of Broadland is productive farmland and floodbank and is the traditional source of local material for
much of the land is now used for traditional summer livestock building and maintaining the flood embankments.
grazing. Many of the biodiversity features of the area rely on The construction works involve removal of vegetation and large-
Habitats schematic of works corridor
In Practice December 2008 7
WATER VOLE MITIGATION
scale earthworks, of displacement techniques, whereby habitat in the working
including the need corridor is rendered ‘unsuitable’ for water voles, to encourage
to in-fill sections them to move to nearby alternatives. Prior to 2007, vegetation
of redundant dyke. cutting comprised the main method of habitat manipulation
Furthermore the used. Because of concerns about the effectiveness of
timing of works (April vegetation cutting alone as a displacement technique (e.g. Dean
to October to benefit 2003), trapping was used as an additional method to ensure
from suitable ground animals had left the area subject to mitigation, whether fresh
conditions) means that field signs were recorded in the area or not.
Example of pre works soke dyke habitat impacts on habitat
Due to the scale of the mitigation required, certain aspects of
and associated plant
recommended ‘best practice’ (Strachan and Moorhouse 2006)
and animal life can
are not routinely implemented as part of the BFAP:
be considerable, indeed unacceptable, without appropriate
mitigation being taken to avoid or reduce them. • Individual burrow entrances are not marked. Capture of
animals post cutting indicates burrow entrances are not
Water Voles generally blocked.
• Vegetation is neither strimmed off to bare earth nor raked
The catastrophic decline of the UK water vole Arvicola terrestris
and removed, but mainly cut using excavator mounted
population during the 1980s and 1990s is well documented
flails.
(e.g. Strachan and Moorhouse 2006). Populations have suffered
primarily as a result of habitat loss and fragmentation, and • ‘Soft release’ methods are not used for relocated animals.
predation by feral American mink Mustela vison. Measures
to address this decline culminated in April 2008 when the • Fencing is not used due to cost, maintenance and waste
species was afforded full legal protection under the Wildlife issues.
and Countryside Act, 1981 (as amended). One of the main • Mitigation is undertaken from spring through to early
consequences for development works resulting from the update autumn.
to the legislation is that trapping of animals as part of mitigation
now requires a license from Natural England. In 2006, the first year when large scale mitigation was required
as part of the BFAP, more than 470 animals were captured
Within the UK East Anglia is considered a stronghold for water from more than 13 km of soke dyke habitat despite vegetation
vole, and increased recording effort since 1999 indicates that cutting being implemented and maintained. Animals were
they remain widespread in Norfolk, with density in the Broadland relocated to alternative suitable nearby dyke habitats.
area being the highest or one of the highest in Britain (Henson
2001). Habitats in Broadland which support large, apparently The significant number of animals caught during 2006
robust populations include reedbeds, the extensive grazing prompted an internal review of mitigation. Concerns included
marsh dyke systems, and in the upper stretches of tidal rivers the effectiveness of vegetation removal alone in achieving
reeded ronds. As part of the wider grazing marsh dyke system displacement as part of large scale mitigation, and potential
soke dykes often provide important water vole habitat. welfare implications for the high numbers of animals caught.
The review resulted in a modification of the approach to
mitigation, most notably a concerted effort was applied to
Mitigation of Impacts achieve maintained water draw down in combination with
Whilst the improvement works require major earthworks, vegetation removal. Draw down is achieved by bunding discrete
including the in-filling of lengths of soke dyke used by water sections of dyke and using diesel pumps to remove the water.
voles, they are fundamentally important for the protection This technique was applied to more than 16 km of dyke in 2007.
of the wildlife value of the wider marshes from inundation by During 2007 an undergraduate research project used radio
river water that is brackish and/or eutrophic. The floodbank collars and Passive Integrated Transponder (PIT) tracking to
corridor habitat (including the soke dyke) is always re-instated monitor the reaction of individual water voles to mitigation
as part of the works, and scheme implementation provides implementation. Mitigation comprised vegetation cutting,
the opportunity to improve habitats otherwise undergoing repeated on an as required basis, and at least two weeks
succession. maintained water draw down. The project was undertaken by
As one of many protected species present within the Project Ben Raybould, a student from the University of East Anglia, with
area, water voles are a material consideration for design and assistance in the use of PIT tags and radio collars provided by
construction. Whilst they have always been present within the Merryl Gelling, a WildCRU researcher from the University of
BFAP since its commencement in 2001, the numbers found Oxford. The research was funded by the Project and the EA,
within the working corridor in 2006 and 2007 were exceptional, and was based on a SSSI owned and managed by the Royal
with more than 30 km of soke dyke subject to mitigation for Society for the Protection of Birds (RSPB) adjacent to the River
water voles in those two years alone. Baseline surveys indicate Yare. The marshes of the site are subject to moderate intensity
this will continue to be the case for the remaining works. grazing, and have an extensive water vole population present
across parts of the site. As such the site provides a comparable
The large scale and longevity of the Project, together with a standard for much of the BFAP project area.
Project dedicated Environment Team, affords opportunities with
regard to research and development of survey and mitigation Although based on a small sample size, the research
techniques. The main outcomes related to water voles are demonstrated that
summarised below. a proportion of
Water vole mitigation: vegetation removal
the resident water
and dewatering of soke dyke
vole population
Displacement: Vegetation Cutting was displaced to
and Water Draw Down nearby alternative
habitat (Raybould
Because of the extensive dyke system adjacent to the works 2008). Of the 30
corridor, mitigation for water voles mainly comprises the use PIT tagged animals
8 In Practice December 2008
WATER VOLE MITIGATION
Water vole awaiting radio-
collaring Example of soke dyke habitat one year after
monitored along a 1700 m length Monitoring works completion
of soke dyke, 10 of which were indicates that,
radio collared, nine animals were in order to be
confirmed to have dispersed to considered
nearby dykes through radio tracking successful, the
and recaptures. Two animals were mitigation methods
trapped and actively relocated to must include:
alternative nearby habitat within
• thorough
the marshes, one of which was
vegetation
subsequently recaptured at the
cutting,
release site a few months later. Two
repeated on
animals were known to have died
an as required
prior to mitigation commencing,
basis;
found by their radio collars. The fate of the remaining animals
was unknown, although at least one radio collar was presumed • maintained water draw down, in conjunction with vegetation
to have been removed from the site by a predator, as its signal removal, for a period of at least two weeks; and
was lost entirely during the monitoring.
• the presence/provision of suitable alternative habitat for
Animals recorded as dispersing generally moved only relatively animals within proximity of the works corridor.
short distances to nearby marsh dykes i.e. up to 300 m
but mainly less than 150 m. More males than females were Tool Box Talks, Mitigation Practice Notes, Environmental Issue
displaced, possibly reflecting population demographics, Posters and the regular presence of environmental staff on site
territoriality and/or seasonality factors. Males generally moved to monitor works are all approaches used to ensure mitigation
greater distances than females. Monitoring indicated that is successfully implemented. As it is believed that the methods
animals largely remained in situ when vegetation cutting alone developed are the best available techniques suitable for use
was implemented and, only when subsequent water draw down, on the BFAP, trapping is no longer used as a routine method of
commenced and was maintained, did animals respond through water vole mitigation.
permanent relocation.
At other sites worked during 2007, more than 14 km of soke
Water Vole Habitat Suitability
dyke was subject to mitigation which included trapping as a final Assessments
measure, after vegetation cutting and water draw down were
maintained for at least two weeks. The exception was one small A Water Vole Habitat Suitability (WVHS) assessment was
length of 330 m where asbestos removal resulted in the cutting developed for use as a survey tool for the BFAP during 2007.
short of water draw down. In total, 33 animals were caught. The assessment is based on a method developed by Jane Harris
Seventeen of these were from the 330 m length where water of Kepwick Ecological Services, a local sub-consultant regularly
draw down was not maintained for the full two week period. employed by the Project. It is designed to enable a rapid
assessment of habitat suitability over extensive lengths, which
Field observations indicated the density of animals present can then be validated using searches for field signs at a number
in 2007 was comparable to 2006. This allows comparison of sub-locations.
between years of the effectiveness of displacement based on
vegetation cutting alone vs. vegetation cutting and water draw The assessment considers eight separate site characteristics,
down, using the number of animals trapped as a measure of based on cover, food source, burrow and nesting opportunities,
animal persistence: and freedom from disturbance. Sites receive a score of 1 to 8,
which relate to ‘unsuitable’, ‘sub-optimal’ and ‘optimal’ habitat
Comparison of trapping numbers from water vole types.
mitigation undertaken in 2006 and 2007
The main benefit of
Year Length of No. of animals Animals per the use of habitat
mitigation (m) caught km equivalent assessments relates Example of works corridor one year after
2006 17,280 476 27.55 to the recognition completion (new double soke dyke to left
that baseline surveys of photo)
2007 14,075 33 2.34
for field signs only
2007* 13,743 16 1.16 provide a snapshot
evaluation of animal
(*excluding data from 330 m length where water draw down not
presence at any one
maintained)
time, and can quickly
The data indicate the number of animals caught is reduced by (within a breeding
an order of magnitude when water drawn down is implemented season) become out
in addition to vegetation cutting alone. When the 330 m of date. However,
length where water draw down was not fully implemented is if a habitat is
removed from the assessment, a greater than 95% reduction considered suitable
in the number of animals caught over standardised lengths is for supporting
apparent. water voles, it will generally remain suitable from one season to
another i.e. a precautionary approach can be taken. Validation
Whilst predation pressure will almost certainly be a factor checks can then be used to confirm the presence of field signs.
affecting displaced voles, the data gained using the radio Where habitats are assessed as unsuitable, thorough checks
tracking study and results from animal trapping in 2007 indicate for field signs are required prior to works commencement to
a proportion of resident water voles are successfully displaced confirm animals are absent. The method can also be used to
from habitats subject to development works, to establish assess habitat suitability of adjacent marsh dykes for displaced
territories nearby. Such operations are likely to be considerably animals, and in post-works surveys to assess the success of
less stressful for animals than trapping and forced relocation. habitat re-instatement.
In Practice December 2008 9
WATER VOLE MITIGATION
to develop best practice, and a pro-active workforce who
enabled the mitigation to be implemented successfully over a
huge scale on the ground.
It is believed that the methods developed are the best available
for implementation on the BFAP. The data indicate water draw
down is an
effective
displacement
tool and
post works
monitoring
demonstrates
no long term
negative
impacts upon
water vole
distribution at
Example of pre and post works monitoring data (Strumpshaw and the Broadland
Buckenham Marshes, River Yare) scale. Indeed
an increase
Experience gained using the WVHS method in 2007 and 2008
in distribution
indicates habitat assessed with a score 5 or better is routinely
is apparent in
found to support water voles, based on validation checks for
recent years.
field signs. Furthermore, the method was applied to 423 sample
The works
points during the undergraduate research project (Raybould
to date have
2008). Logistic regression analysis demonstrated a significant
generated a
positive relationship between habitat suitability scores and the
huge dataset
probability of the presence of water vole (PINVERTEBRATE MITIGATION
Site Mitigation for Invertebrates
Alex Ramsay MIEEM
Senior Invertebrate Ecologist, RSK Carter Ecological
Which Invertebrates on a series of habitat patches
which can extend over several
are Likely to Require kilometres, and if the core
habitat area is lost to a
Mitigation? proposed development, this
O
will have a significant bearing
ver 30, 000 invertebrate on whether the development
species have been actually goes ahead.
recorded from the UK and it is
clear that not all species can UK BAP Species
be mitigated for during site
The recent review of BAP
development. Mitigation plans
species (Anon 2007) led to
usually focus on species with the inclusion of 411 species. Floral diversity is key to retaining good bee faunas on
statutory protection, currently Some of these are well-known mitigation sites
71 species. Biodiversity Action and include charismatic Photo: Alex Ramsay
Plan (BAP) species are also now species such as the stag
a material consideration in the beetle and a third of all British
butterflies, to more obscure species of scarce and threatened species are
planning process, currently an invaluable resource for the ecology
such as the lacebug Physatocheila
411 species (Anon 2007). Rare and distribution of rare invertebrate
smreczynskii, which is found only in old
species identified in the Red orchards. Generally speaking, good species and can provide a useful
Data Books (Shirt 1987, Bratton invertebrate sites will include a number starting point for developing a mitigation
1991) may also be considered of BAP species and in such cases rare scheme. Kirby (2001) and Fry and
(some of which are likely to also species are also likely to be present. Lonsdale (1991) provide habitat-based
management principles which can be
be protected or BAP species),
used in conjunction with specific ecology
particularly on sites where Rare Species for target species.
there is an assemblage of rare
Defined as species which occur in less A decision needs to be taken regarding
species that could be nationally than fifteen 10 km squares in Great best practice - ideally mitigation areas
significant. Britain (Shirt 1987), the criteria for such are retained within the development,
species are gradually being upgraded but if this is not possible then suitable
Protected Species to IUCN threat categories which are sites for translocation will need to
based on level of threat to the species in be identified. However, it should be
Most protected invertebrates only Britain rather than simply on rarity. The stressed that retention of habitat within
occur at one or two sites and hence advantage of this system is that it allows the development is usually the best
are rarely likely to feature in the status to be assessed internationally. option. Mitigation for mammals and
planning process or be affected by Recent status assessments of many other groups can require large
development. However, a few species invertebrates which use the IUCN criteria areas, but for invertebrates small areas
are extremely widespread but very include Foster (in press) for the water of habitat can support populations for
rare and could occur wherever the beetles and Falk and Chandler (2005) for many years, although the likelihood of
habitat is suitable. This includes the Nematoceran flies. success can be enhanced by connecting
fairy shrimp, mole cricket and marsh areas of suitable habitat within the site.
fritillary The former two species are
found in flood plains, where a number
What Form is the For more mobile species, maintaining a
series of habitat patches within the site
of housing developments have been Mitigation Likely to may be a minimum requirement.
sited in recent years. For more mobile
invertebrate species such as the marsh Take? Mitigation Timing
fritillary, mitigation needs to cover a
larger area as the species is dependent This is largely dependent upon what
is known about the ecology of the Creation of new habitat for invertebrates
species or assemblage present. In is not an instant process, and ideally
The mole cricket can potentially occur in a mitigation site should be set up at
floodplain development areas some cases the ecology is extremely
well-known, but in others very little least a year before animals are moved
Photo: Alex Ramsay to maximise natural colonisation.
is known. Where notable species are
found, repeat site surveys to study the Careful consideration should be given
ecology of poorly-known species will to the location of mitigation areas,
certainly add to the known information. particularly as aspect and levels of
Background literature including British shading are crucial - there is little point
Red Data Books for Insects (Shirt 1987) in moving insect species from flower-rich
and Invertebrates other than Insects grassland on a sunny, south-facing bank
(Bratton 1991), and the JNCC reviews to a shaded north-facing bank because
In Practice December 2008 11INVERTEBRATE MITIGATION
kill subterranean insect larvae). and donating it to a conservation body
Ideally, such areas should be to preserve a similar assemblage off
monitored post-construction site. Ideally this should include a sum for
to assess the species future upkeep of the site.
present. If compensatory
habitat is created, then it
can be prepared at this
Monitoring
stage which would maximise Almost always regarded as an
the chances of colonisation afterthought, the post-construction
before existing habitat is monitoring of any invertebrate mitigation
lost. This is most likely to be is crucial to determining the success of
successful if mitigation areas the mitigation technique used, be that
are immediately adjacent to the retention of key breeding areas for rare
proposed development area so invertebrates or colonisation success of
Mitigation for stag beetles could require provision of that species loss is minimised. re-created habitat. There is unfortunately
partially buried logs for larvae If this is not possible then steps very little published or readily accessible
Photo: Alex Ramsay should be taken to ensure that material on success (or otherwise) of
plants and soil present on the invertebrate mitigation schemes due
inevitably they are unlikely to survive. proposed development site are to lack of adequate post-mitigation
Consideration should also be given to carefully removed to the mitigation site monitoring. This is a situation that needs
when the translocation is carried out prior to construction. to be urgently addressed so that future
and to the life-stage of the species being schemes can be improved or refined. At
moved - in some cases eggs or larvae Medium-Term the very least a post-construction survey
may be appropriate, in other cases would enable the target species to be
the adult stages of the target species Mitigation identified as still present, and allow for
will be more appropriate. If adults are slight changes in management if these
It is crucial that appropriate are required to boost populations.
moved, this should ideally be early in
management is implemented for
their emergence period to ensure that
the mitigation site to ensure the
eggs are laid in the mitigation site,
translocated species continue to thrive.
References
although there are always exceptions
Such measures could include phased Anon (2007) New UK BAP Species 2007.
- female stag beetles lay a single batch
planting of host plants for plant-feeding www.ukbap.org.uk/newprioritylist.aspx
of eggs towards the end of the breeding
species, or nectar plants for bees and
season and so a later translocation may
wasps. Soil disturbance in some areas Bratton J H (ed) (1991) British Red
be more appropriate for this species.
would provide basking and hunting sites Data Books 3: Invertebrates other than
For certain species a mid-successional
for a variety of species and ensures that insects. Joint Nature Conservation
habitat is crucial and mitigation might
parts of the sward are open to provide Committee, Peterborough.
involve creation of several habitat
potential future breeding habitat through Falk S J and Chandler P (2005) A review
patches which will vegetate at different
natural succession. The implementation of the scarce and threatened flies of
rates, thereby providing a continuity of
of appropriate management is necessary Great Britain. Part 2: Nematocera and
future habitat.
to maintain and enhance invertebrate Achiza not dealt with by Falk (1991).
populations on the mitigation site. Early
Moving Entire successional habitats such as grassland
JNCC Species Status Report, No.2.
Joint Nature Conservation Committee,
Assemblages may benefit from occasional surface soil
disturbance to maintain optimum habitat
Peterborough.
This will usually involve a more broad- conditions. Late successional habitats Fry R and Lonsdale D (1991) Habitat
brush approach so that any newly- such as woodland may benefit from Conservation for Invertebrates
created habitat will be suitable for enhancement of the dead-wood resource - a neglected green issue. Amateur
the widest range of species possible. by provision of log piles. Entomologist’s Society, Middlesex.
Specific host plants may be selectively Foster G N (in press) A review of the
planted, and if swards can be moved Long-Term Mitigation scarce and threatened Coleoptera of
then careful removal and replacement Great Britain, part 3. Aquatic Coleoptera.
will provide a seed bank of hostplants Veteran parkland trees retained
JNCC Species Status Report, No.1.
and may contain eggs and larvae of in a development are of particular
Joint Nature Conservation Committee,
invertebrates. Particular care should be importance for saproxylic beetles
Peterborough.
taken to ensure that the sward is not and flies. Long-term mitigation for
inverted during removal and replacement these species is crucial to maintaining Kirby P (2001) Habitat Management for
on the mitigation site, as this would bury the fauna, and this will involve an Invertebrates: a practical handbook (2nd
eggs and prevent development. assessment of the local age structure edition). RSPB, Sandy.
of trees present and identifying gaps in
Shirt D B (ed) (1987) British Red
Short-Term Mitigation recruitment ages of the trees. Where
these are identified then further planting
Data Books 2: Insects. Joint Nature
Conservation Committee, Peterborough.
This usually involves careful selection of of trees to fill identified gaps will help
key areas for invertebrates which can to ensure long term survival of the
be retained during development. They saproxylic fauna present.
Correspondence:
must be adequately protected from A potential mitigation mechanism which ARamsay@rskcarterecological.co.uk
construction processes including night has been only rarely applied in the UK
lighting (a particular problem for moths), context (although in widespread use
excessive dust (which can kill insect host in the USA) is the concept of buying
plants) and soil compaction (which can areas of pristine invertebrate habitat
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