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Peat Project


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									                                                              Broads Forum
                                                              7 October 2010
                                                              Agenda Item No 9

                         Broads Authority Peat Project
             Report by Conservation Officer and Head of Conservation

Summary:     This report sets out the ever increasing value of peatlands for wildlife
             conservation and climate change mitigation. It highlights the
             fundamental role of the Broads peat resource in supporting and
             conserving key habitats and species, as well as providing additional
             services as a greenhouse gas store. In addition the report represents
             the key role the Authority has undertaken to set out the framework for
             understanding and restoring degraded peat habitats in the Broads,
             feeding into national peat studies and raising awareness through local
             school peat projects.

1     Background

1.1   Globally peatlands form only 3% of the land area yet contribute 30% to the
      global soil carbon. These peatlands are capable of storing double that stored
      in the global forest biomass.

1.2   Peatlands are England’s most important carbon store. The Broads when
      under good wetland management enhance wetland ecosystems and
      biodiversity which in turn retains significant stores of carbon. If degraded, by
      poor management practice such as drainage or intensive agricultural
      management, the potential of this type of lowland peat to release CO 2 is
      significant. Natural England reports that England’s degraded lowland fens
      could release between 2.8 and 5.8 million tonnes of CO2 each year, resulting
      in them acting as a net source of emissions, even after accounting for
      sequestration from forestry. (Natural England - Browse Catalogue: Climate

1.3   An ecosystems approach has valued carbon stored in the Broads wetland to
      be over £240,000 per year. (Broads Restoration - Broads Authority - see Lake
      Restoration Strategy and Ecosystem Services Appendix 6).

2     Framework for Peat Work in the Broads

2.1   Given the value of mitigating environmental damage through storage of CO 2
      the Broads Authority is currently working within the following framework:

      A. Keep the peat resource in good condition
           o understand where the peat is and what its quality is.
      B. Add to the existing peat resource
           o wetland creation and enhancement projects;
           o advice to land managers.

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      C. Raise awareness of the importance and value of peat
            o Develop information for schools;
            o Develop information for land managers.

3     Broads Carbon Landscape: Delivery Stages:

3.1   What do we know: Collating existing evidence

3.1.1 Collating historical peat studies and peat core records in the Broads.

3.1.2 Undertaking peat surveys at selected sites in the Ant, Thurne, Bure
      and Waveney valleys.

3.1.3 Reporting on survey findings and proposing site recommendations for
      appropriate management of peat soils.

3.1.4 GIS mapping of existing and present day peat cores detailing depth and peat
      types. This will provide a more detailed peat map for the Broads, feeding into
      national studies on peat quality, extent and carbon storage.

3.2   Implementing actions: Land Management Projects

3.2.1 Undertaking Broads restoration projects with key partners to restore peat soils
      and wildlife habitats such as those currently being undertaken at South Fen,
      Oulton Marshes, Hickling and Brograve.

3.3   Sharing the knowledge: Provision of management and advice

3.3.1 Providing practical advice to willing landowners on the appropriate
      management of peat soils.

3.3.2 Undertaking appropriate management of important peat habitats at How Hill

3.4   Collecting evidence and educating: School Peat Project ‘For Peat Sake’

3.4.1 Establishing a schools peat project ‘For Peat Sake’ in the Broads. The project
      will enable local schools to visit and undertake practical peat studies at key
      fen sites. The children can understand firsthand the role peat played in the
      formation of the Broads, its value for wildlife conservation and climate change

Appendices:   APPENDIX 1 – Extract from Broads Authority Peat Resource Contract 2010

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                                                                          APPENDIX 1

          Extract from Broads Authority Peat Resource Contract 2010

                                   4. CONCLUSIONS

4.1 Summary of peat conditions

The survey of peat bodies located within the 16 land parcels demonstrated the
variability of peat conditions at sites within the Ant, Bure, Thurne and Waveney
valleys. Areas of peat were found to be in good conditions in each valley, but some
parts of peat bodies, most noticeably adjacent to arterial drains and watercourses,
were assessed to be in poor condition.

The survey demonstrates the need for site scale assessments of the condition of
Broadland peats, and provides a useful means by which to inform landowners and
agri-environment advisors of the potential for peat restoration, and reasonable
targets for success.

Table 8 gives a summary of the condition of the peat body in each surveyed land
parcel. In several cases, the peat body shows differing condition features in different
parts of the land parcel, which are graded accordingly. The comments in Table 8
summarise the location or issues governing the stated condition of the peat.

At a number of sites, such as the Waveney survey area north of the railway line at
Covehall Farm, North Cove, the peat remains in good condition, with hemic peats
that retain visible plant remains close to the surface. Groundwater flows near the
surface are also present in some valley margin peats, such as at Dilham Hall, Dilham
and the southern margins of the Manor House Farm, Ingham survey area.

However, it is noted that none of the surveyed sites contained examples of peats in
‘Excellent’ condition. This is to be expected as such peats are largely restricted to
undrained areas of the main valley floors.

Notwithstanding, peat bodies are also assessed to be in fair, or even poor, condition.
These typically result from the exclusion of groundwater upper layers by lowering of
water levels in the surrounding drains or watercourses.

Where low watertables are long-standing, and particularly where arable cultivation
has taken place, the peat topsoil may have lost its cohesive character and be very
prone to compaction or wind erosion. This peat can be difficult to distinguish from
mineral soil and is said to be fully ‘earthy’. Such topsoils do not absorb water, and
tend to revert to an unmanageable slurry when wet.

Peats next to main drains or rivers typically exhibit signs of degradation at depth,
where fluctuating water levels allow the penetration of atmospheric oxygen into sub-
surface peats leading to the progressive breakdown of the organic materials and
migration of sulphur and iron-bearing solutions.

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Away from arterial drainage, watertables may still be lower than optimal conditions
for peat preservation. The surveys were undertaken in late winter and early spring,
and on many sites, even those reverted to grassland, the watertable was more than
30 cm below the ground surface. These sub-optimal levels are likely to drop during
the growing season, leaving great thicknesses of the surface peats vulnerable to

4.2 Options for management

4.2.1 Target conditions
It is possible to specify three broadly defined target conditions relating to carbon
storage. In some situations, a reasonable target is to minimise carbon loss, by
reducing erosion of the degraded surface peats and by minimising the time that sub-
surface peats are exposed to biochemical breakdown.

Targets can also be set for re-instating a neutral carbon balance, or creating a
positive carbon balance. In these cases, land management practices are restricted
and may be dependent upon isolating sites from the surrounding drainage systems.

Target 1. Minimising carbon loss
Once the processes of peat degradation are initiated, they cannot be reversed.
Revegetating and rewetting peats will not improve the condition of the existing peat,
much of which is thousands of years old. In common with drained regions
throughout lowland Europe, the top layer of ‘earthy’ peat forms the current upper
surface of a peat body that may have been raised much higher in the past, but has
been completely degraded and lost by erosion, or been extracted for fuel. The
boundary of the base of this layer with the less decomposed hemic peat beneath is
largely determined by the height of the watertable.

  Target 1a. Reducing loss of the surface ‘earthy’ peats
  Clearly, a primary target is to minimise the loss of the degraded surface peat. As
  the peat dries out it is prone to wind or water erosion, and its loss lowers the
  ground surface thus encouraging deeper drainage. Typically, as is the case on all
  survey areas, loss of carbon from the degraded surface peats is reduced by
  putting fields down to grass. This acts both to bind the ‘earthy’ peat, reducing
  wind and water erosion, and also to stimulate the development of carbon-fixing

  Target 1b. Preserving the subsoil peats
  If the existing boundary between the ‘earthy’ and hemic peat shows the general
  state of the peat body’s hydrology, the presumption is that the longer the height of
  the watertable remains above this boundary, the less degradation of the ‘good’
  peat. The target is therefore to maintain the watertable height above the hemic
  peat subsoil for as much of the year as is possible. In the field, some peat bodies
  show a marked black ‘gritty’ layer where the watertable has been lowered into the
  upper part of the hemic peat by enhanced drainage (see Table 4). Where the
  watertable has recently been raised, this gritty layer is preserved as a ‘marker’
  showing the zone of degraded peat.

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  When the watertable lies within the ‘earthy’ peat layer, the rate of oxidation of the
  peat is also reduced. However, the trafficability of the peat is then frequently poor,
  and plant growth is affected. It is therefore unlikely that arable cultivation, with its
  associated deep drainage, will be able to accommodate subsoil peat preservation.

Target 2. Re-instating a neutral carbon balance
In situations where year-round watertables have been maintained near the ground
surface, there may be only a thin earthy layer (less than 10 cm thick). The peat body
is otherwise in good condition. Here, groundwater flows may rise up to near the
surface and, with rainfall, may act to preserve sufficient dead plant material each
year to make up for the breakdown of peat during the growing season. Similar
amounts of carbon are being assimilated into the soil to match losses by oxidation.

The target is therefore to maintain the watertable within 10 cm of the ground
surface all year round. This target is attainable within sites where fields are isolated
from arterial drains and watercourses, and where groundwater flows are still
functioning. Such areas often retain low-intensity summer grazing, and are typically
associated with rough shooting and fen meadows.

Target 3. Creating a positive carbon balance
Positive carbon balances tend to be restricted to two types of location:

Where the watertable within areas of the valley floor is within 10 cm of the ground
surface all year round, but is frequently above the ground level for extended
periods. Usually, such sites have long been recognised as of little value to
agriculture, and have histories as wet woodland or reed fen. Where groundwater can
be maintained at these high levels, the accumulation of organic matter can exceed
peat breakdown year-on-year, leading to peat growth.

On the margins of the peat body, especially where peat is known to have formed in
the past, positive carbon storage can be established on mineral soils by
establishing permanent grassland. Although carbon levels may initially be low,
compared to peatland, a body of scientific evidence is developing that demonstrates
the significance of mineral soils in acting as a carbon store.

4.2.2 Importance of grassland reversion in carbon storage
There has been considerable recent interest in the role of biologically active
grassland soils in sequestering atmospheric carbon.

Recent research undertaken by Professor Mark Adams, Dean of the Faculty of
Agriculture at Sydney University (Cawood, 2009), indicated that one hectare of
pasture land could sequester as much methane as emitted by around 162 head of
cattle in an entire year. This is due to the activity of methanotrophic bacteria in
biologically active soil, which utilise methane as their sole energy source (Dunfield,
2007). Soil methanotrophs have the opposite function to methanogens, the bacteria
that produce methane in order to prevent acidosis in the rumen.

Methane emitted from livestock has a very short cycle, that is, it is generally recycled
rather than moving to the upper atmosphere. Appropriately managed rotationally

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grazed perennial grasslands, where atmospheric carbon is sequestered in soil as
stable humus, result in more carbon sequestered than emitted, easily compensating
for the methane produced by livestock.

A recent report by FAO (Neely et al., 2009) asserts that grasslands have vast
untapped potential to mitigate climate change by absorbing and storing CO 2.

New research is being carried out by scientists from the Lancaster Environment
Centre, Lancaster University, to work out how much carbon is being stored in UK
grasslands and find out if it could potentially store even more.

The DEFRA funded study is intended to improve understanding of how grassland
can be managed to protect carbon stored in soil, while performing other key roles
such as biodiversity conservation and the maintenance of viable agricultural

4.2.3 Management opportunities

The principal mechanism by which landowners can re-wet peat bodies and their skirt
soils and establish permanent grassland is through Natural England’s Environmental
Stewardship programme.

Key considerations include:

      Raising the watertable to achieve one of the targets specified in section 4.2.1
      requires control over the quantify and quality of water. In many cases, this
      control is only partial and may affect or be affected by, surrounding

      Limits to water control by individual landowners are frequently affected by the
      duties and arrangements undertaken by the Environment Agency and Internal
      Drainage Boards.

      Re-wetting peatlands has a number of potential effects on the balance of
      greenhouse gas storage and release. Recent research is reviewed in Natural
      England (2010).

      Where peatlands are in good condition they tend to support, or may
      potentially support, valuable types of vegetation, such as BAP Habitats, or
      assemblages of other biotic groups. Such sites may be worthy of local
      biodiversity designations or be prioritised for funding assistance.

In developing opportunities to manage the peat resource, The Broads Authority has
a key role to play in working with landowners, farm environment advisors and land
management organisations.

In particular, the Authority’s Broad Peat Resource project may develop its role in:

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       Providing an assessment of the characterics of the peat resource, and
       identifying peat bodies that may hold potential for restoration through agri-
       environment schemes undertaken by land managers and administered by
       Natural England.

       Providing a framework within which opportunities to restore peat bodies under
       more than one ownership can be assessed, and by which common issues
       relating to water control affecting several land parcels can be explored.

       Promoting positive management of peat soils, by identifying and developing
       opportunities for sustainable forms of peatland management, including
       concepts such as ‘carbon credits’.

Table 3. General field characters of geological materials

Material            Field characters
Peat                Peat is defined by the British Geological Survey (BGS) as
                    partially decomposed masses of semi-carbonized vegetation
                    which has grown under waterlogged, anaerobic conditions.
                    The general locations of peat bodies are mapped by BGS within
                    the Broads river floodplains, and are typically degrading as a
                    result of drainage, leading to a reduction in extent and changes
                    in their character. Field evidence for these changes is described
                    in Table 4.
Silty clay          This material is typically grey, varying from light to dark
                    according to their degree of oxidation and chemical composition.
                    This fine, alluvial material is found either within or below peats in
                    the survey areas or as a mantling layer in the River Waveney
                    survey area.
Clay loam           Clay loam is found within the valley floors as a surficial material
                    overlying clay alluvium or peat. It may be derived by the
                    development of soils in floodplain clay alluvium following
                    drainage and cultivation or more locally as hillwash or stream
                    wash materials near valley floor margins.
Silty loam          Silty loam topsoils are often developed by marked and long-term
                    drainage and cultivation of peat topsoils. As fen peats develop,
                    they accumulate silts and fine sands blown onto them; the
                    oxidation of peat topsoils by drainage tends to concentrate these
                    deposits and the topsoil becomes increasingly composed of
                    mineral rather than organic materials.
Sandy loam          This is a typical substrate on valley slopes, derived from sandy
                    sediments that have accumulated finer particles, often by wind
                    deposition. The material may also occur overlying peats near the
                    valley margin, or form accumulations within the valley sediments
                    following hillwash.
Silt                Silt sediments are water-borne mineral deposits that have
                    typically accumulated in floodplain situations where water flow
                    has slowed. They tends to be composed largely of similar-sized
                    particles (fine, medium and coarse) and are commonly found at
                    the base of floodplain peat bodies.

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Sand                 Like silts, sand layers are separated into fine, medium and
                     coarse grades according to their typical grain size. Sands are
                     similar to silts in their mode of deposition, but are found in
                     deposition environments formerly characterised by higher water
                     energy. In the survey areas, beds of sands are typically located
                     beneath the peat bodies; coarse sand was frequently regarded
                     as the ‘basement’ of this survey.

In natural fen situations, the height above Ordnance Datum of the peat surface will
be in direct relation to the seasonal height of the groundwater table. In theory, a
balance is achieved between the addition of dead plant remains and their rate of
decomposition and/or preservation as peat. Unless raised bog development is
initiated using rainwater, rather than groundwater to preserve plant remains, the
upper surface of the peat will consist of freshly added plant litter overlying fibric and
hemic peat layers, as defined in Table 4.

Table 4. Terms used to describe peat condition

Fibric     This type of peat is typically composed of visible fragments of fen
peat       mosses, plants and pieces of wood suspended in a straw-coloured
           liquid. Rarely encountered in the survey and only at depth. Its presence
           indicates part of the peat body that has remained virtually anaerobic
           since its formation.
Hemic      This type of peat has been partially decomposed so that much of the
peat       softer plant remains are no longer more than ‘fossil’ traces left in a
           watery mid-brown paste that also suspends fragments of wood and other
           harder plant remains.In this survey, hemic peat was initially recognised
           by its colour. Secondary forms of recognition are by squeezing a sample
           (confirming a watery paste) and by locating plant fragments.
Woody      In many cases, the hemic peat was largely derived from the remains of
inclusions fen woodlands. Where wood fragments occurred within hemic peat in a
           core, this was recorded.
Liquid     Many cores, encountering hemic peat, recorded a sudden change in
peat       consistency as the semi-solid hemic peat became a mid-brown coloured
           ‘slop’. This liquid peat indicates the build-up of groundwater within the
           peat body. Although the auger cannot retrieve this watery material, it was
           usually possible to locate the mineral surface below it.
Earthy     Found above the hemic peat, and usually forming the ground surface of
peat       the peat body, earthy peat is the very dark brown to black-coloured form
           of peat exposed to the atmosphere. Called ‘earthy’ peat to signify the
           ripening, or maturing, of the peat near the ground surface, the material is
           dust-like when dry. As the dust cannot return to the gel-like consistency
           when wet, it typically ponds rainwater after a shower. Moisture held in
           the peat topsoils therefore becomes increasingly different from the
           groundwater. In fen peats, this is reflected in the vegetation that
           develops. For example, Hard rush Juncus inflexus tends to colonise
           drains side influenced by calcareous groundwater while soft rush J.
           effusus colonises the normal ground surface, reflecting the influence of
           the more acidic rainwater.
Silty loam The topsoils of several drained peats in the survey areas can be defined

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            as silty loams.Here, oxidation and dispersal of the organic matter has
            increased the proportion of silt and fine sand particles either entrained
            during peat formation or subsequently blown in from surrounding mineral
            soils. The development of this kind of peat topsoil may be hastened by
            cultivation, as this increases the loss of organic matter by oxidation, or
            simply be a feature of the original peat-forming environment.
Gritty      This distinctive material is associated with fluctuating watertable levels in
peat        drained peatlands. It is caused by the effects of the periodic wetting and
            drying on the chemistry of that part of the peat body defined by the high
            and low watertable levels. Typically, gritty peat marks the boundary
            between earthy and hemic peat layers in susceptible types of peat. The
            material indeed has a granular texture, and is dark grey to black in
            colour, depending on the chemistry of the type of peat in which it forms,
            and the intensity and duration of the process.
            Once formed, a layer of gritty peat will remain even if changes in
            watertable level means that it is no longer subject to wetting and drying.
Sapric      Sapric is a generic term to describe well-decomposed peats where
peat        fibrous plant remains are no longer evident. The peat surveys identified
            several bodies of sapric peat, which is very dark grey in colour, beneath
            hemic peat. The locations of sapric peat in this situation are probably
            correlated with the drawdown zones of fluctuating waterbodies. These
            include drains linked to rivers and to rivers themselves. At the time of
            survey, these peats were beneath the watertable but were readily
            extracted by the auger as they were relatively dense in structure. It is
            possible they have shrunk during low flow periods, and have failed to re-
            wet and attain their original volume.
Sapric      Within hemic peat bodies, pockets of sapric peat were found at some
elements    sites within the arisings of cores.

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