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Identifying suitable sites for paludiculture

As part of any assessment of the suitability of a site for paludiculture a number of factors need to be considered. The aim is to find out whether an area is suitable for paludiculture, which crops are suitable for the site, which areas may be preferable and how implementation can be successful. These pre-requisites can be divided into three categories: site characteristics, availability of land and legal factors. These prerequisites should all be met.

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There may be a number of aims linked to the implementation of paludiculture systems, these may include:

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  • Climate protection: reducing greenhouse gas emissions

  • Production: Production of raw materials for the bioeconomy

  • Nature and species conservation targets

  • Water protection, climate adaptation, flood protection

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The extent to which these objectives compete with each other should be checked carefully, establishing if there are synergies or conflicts. The main driver for land use change is likely to be the need to reduce greenhouse gas (GHG) emissions from the fossil carbon held within the peat soil, but which is lost steadily from drained soils. Harvest of raw materials is often only a secondary objective or it may be required to achieve a certain vegetation structure (maintenance utilisation) for nature conservation reasons.

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Once sites that have potential for paludiculture are identified, then it is important to consider which paludiculture crops are most appropriate. Given the early market development for paludiculture crops, processing and marketing should also be considered at the earliest stages. Ideally, conversion of land to paludiculture should be thought through, developed and implemented in parallel with development of the processing steps. This will require cooperative approaches along value chains.

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Site characteristics

Site Characteristics

Organic soil:

A pre-requisite for establishment of paludiculture is that the area under consideration is entirely, or at least largely, peatland or an associated soil from within the peatland succession (organic soil). The terms moor, mire and bog commonly describe the landscape units within which peat soils and soils with peaty surface horizons (organo-mineral soils) occur.

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Peat forms in the lowlands where vegetable matter is only able to decompose partially due to waterlogged conditions leading to oxygen deficiency. However, the definition of peat and peat soils (by soil carbon content and the minimum thickness) in soil classification systems varies between countries. For example, according to the U.S. Department of Agriculture Soil Classification, peat is an organic soil (Histosol) that contains a minimum of 20% organic matter ( = 12% organic carbon content) increasing to 30% if as much as 60% of the mineral matter is clay. The soils are then classified according to the amount of decomposition that has occurred. The surface organic layer of peat soils that are most decomposed and humified (known as Saprists) have plant remains difficult or impossible to identify. In contrast, thicker peat soils contain less decomposed organic matter in which the remains of the different kinds of plants can be identified (these are known as Fibrists and Hemists). In some countries, maps of soil types may be available to help identify regions and subregions where peat soils occur.

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In England, peat soils are defined as those with more than 40 cm of organic material in the upper 80 cm or with more than 30 cm of organic material over bedrock or very stony rock rubble. The main lowland peat soils classified as soil series in England and Wales include Adventurers, Altcar, Crowdy, Longmoss, Mendham and Turbary Moor series. Often these soils are found in association with a range of organo-mineral soils characterised by organic surface horizons over a range of parent materials (clays, silts, sands and limestone). While the main peatland regions are well known in England, there is no currently reliable sub-regional map to show the occurrence of peat soils on a field-by-field basis in England -Peaty Soils Location (England).

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Peatland type:

Care is needed in taking information from different locations as different countries classify their peatlands differently, but peatlands are referred commonly by names such as bogs, fens, and mires. The term mire is usually used when the system is actively forming peat.

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Groundwater-fed (geogenous) peatlands, i.e. fens, are nutrient-rich (minerotrophic). Fens commonly have neutral pH all year, and are characterised by abundance of base cations, e.g. Ca and Mg. In the lowlands if the peat surface is able to rise above the groundwater level (usually as a result of moss colonisation) then the peat receives water from precipitation only (ombrogenous), and an acid and nutrient-poor peatland will form over time (lowland raised bog). Lowland raised bogs represent the successional zenith where rainfall inputs are high enough to support sphagnum moss growth.

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Knowledge of the hydrological factors that determined peatland formation in the past, together with the peatland type can be used to assess water and nutrient availability (Table 1). This can also be used as information to help assess wettability as it also gives information about the water supply before drainage. Peatlands may form in small pockets, such as kettle holes in glacial outwash plains, or occupy large areas in the freshwater fringe of estuaries.

Table 1: Suitability of different peatland types found in lowlands for paludiculture.

+++ = very good, ++ = good, + = moderate, ~ = limited, - = not suitable or high levels of technical input required

Basin fens
Ombrotrophic (raised) bog
Floodplain bogs/fens
Sloping fen
Watershed bogs
Location
Lowland
Lowland
Lowland
Upland fringe
Usually upland
Water source
Groundwater
Rainfall
Surface water
Groundwater springs
Rainfall and surface water
Water supply (before drainage)
(Mostly) continuous
Mostly continuous
Periodic
Continuous
Periodic/ continuous
Slope
None
Slight; dome of peat forms
None/ moderate
Moderate - extreme
None
Capacity for water storage (before drainage)
Mostly large
Large
Small
Small
Moderate - large
Wettability
+++
+++
+++
~
++
Suitability for paludiculture
++
+++
++
-
-

Wettability:

For paludiculture, the peatlands can either already be wet or it must be possible in principle to raise the water level. For paludiculture, water levels where the annual average water table 10 - 30 cm below the surface and a summer water level <10 cm below the surface should be the aim to enable peat preservation. Where climate protection is a key aim, then the highest achievable maximum summer water level should be the target for any site in each case.

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For any individual site, whether the water level can be raised will need to be determined during the detailed planning process, using the indicators of water availability (climatic water balance, total runoff), water demand, nutrient supply, terrain model (relief) and drainage system to check feasibility. This detailed hydrological analysis or feasibility study may need to be commissioned from a specialist. At this point, further examination can take place to see if, and indeed which measures should be used to ensure that the target water levels can be achieved and maintained through the year.

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If an initial assessment suggests that it is not possible to achieve high water levels for a site, then the first question should be whether broader actions could be taken at catchment scale. For example, are there other water sources available? The introduction of external water or construction of storage reservoirs should not be dismissed. An additional supply of surface water may be necessary to actively supply water in summer to maintain high water levels consistently. If no summer irrigation is possible then the water deficit in summer can only be minimised by retaining winter precipitation by means of overflow storage and management. These landscape-scale changes may affect communities and wildlife and hence should be planned carefully.​

Land ownership and management structures

Land Ownership

Implementation of paludiculture, especially when it includes rewetting, can cause concerns for landowners with regard to property rights and value. This is due to the assumption in many financial management systems (banking, accounting etc) that only drained peatlands can be utilised and produce profitable yields.

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Land management change that includes rewetting is likely to require consent from owners. In many areas, there are also active land and water management governance systems in place; these stakeholders will need to be identified and engaged at an early stage. The organisation or individual considering implementing a paludiculture system will therefore need to consider a range of issues and questions at the outset.

Preliminary considerations for paludiculture projects

  • Who needs to take an active role in the planning and implementation process?

  • How can they be engaged at an early stage?

  • Are there options/ opportunities to involve others in collaboration as partners?

  • What skills and interests are present locally to support implementation as partners or sub-contractors?

  • What changes are likely to occur because of implementation?

  • What impacts might these have on the business or the property?

  • Does the land-owner agree with this?

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If yes:

  • Is a framework agreement needed to cover compensation for possible damage?

  • Are rent reductions possible in any transition phase?

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If no:​

  • Can early notice be given on any lease?

  • Are there opportunities to buy or swap land?

Can the project only be delivered in co-operation with the owner's of neighbouring land?

If yes:

  • Is a collaborative project possible?

  • Are there opportunities to buy or swap land?

In some areas, there may be complicated ownership structures combining public and private land ownership or with a large number of private owners across the drained catchment. Where this is the case, it can delay or hinder implementation. Use rights, e.g. grazing leases or access rights, are also important, in addition to the land ownership structure. A change of use may be more difficult if owners or leaseholders are financially dependent on current management. For example, it may not be possible to implement paludiculture if the farmed peatland accounts for a high proportion of the land-based value added. Pressure on land can also arise from long-term supply contracts, e.g. with biogas plants, or long-term investments and loans, e.g. for livestock housing or vegetable processing, which are linked to existing drainage-based management. A farm may be able to re-allocate production to other soil types or lease further non-peat soils, or land exchanges may be able to be arrange between farms, but the availability of these options will vary greatly from region to region, depending on the pressure on the land. Framework agreements between the users and the overall project lead organisation can also help to facilitate consent, e.g. through specific regulations on damage compensation in the event of project-related moisture damage on private land.

Legal Prerequisites

Legal pre-requisites

In each region, several legal frameworks are likely to operate that may limit the options for use of any site or restrict the suitability of an area for paludiculture. In general: the fewer restrictions there are, the easier it will be to achieve a project.

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Firstly, in some regions, it is essential that the land is formally recognised for agricultural use. This is usually the case if the area has already been used for agriculture or if it is located in a priority or reserved area for agriculture. Where these restrictions occur, then the desired paludiculture system also must be recognised as agriculture. In the European Union, new opportunities have emerged since the recognition of paludiculture under the CAP from 2023; this enables the landowner to access agricultural support payments as appropriate.

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The choice of the paludiculture crop or system must not conflict with already stated and legally binding nature conservation interests. Where the implementation of paludiculture is planned to be on or adjacent to protected sites (such as Sites of Special Scientific Interest), then early engagement with the local reserves manager or other conservation specialist is essential. However, a change in use to paludiculture can also contribute to an improvement of the protected area e.g. where wet meadow paludiculture displaces a cultivated system.

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If protected species have colonised a site as a result of drainage, replacement habitats may have to be created in the immediate vicinity of the impact site.  Nature conservation surveys are likely to be required together with cooperation with the local nature conservation authority responsible. Implementation of possible conditions can be costly, but at the same time the presence of certain species or habitats also offers potential synergies that can be used to finance the project. Both climate protection and nature conservation goals might be part of paludiculture projects: this can be both synergistic and a source of conflict. In principle, however, an improvement for typical peatland species can be expected by raising the water level and switching to paludiculture on deeply drained and managed peatlands. Therefore, meaning the potential impacts on biodiversity are likely to be considered positively in most cases.

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If there are protected features, such as cultural monuments or archaeological sites in the project area, opinions must be obtained from the specialist authorities and external expert opinions may be required.

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Incompatible or competing infrastructure or land use of public interest, such as underground pipelines, overhead lines, railway embankments, public roads, may be affected by water level changes. Technical solutions may have to be considered to ensure compatibility for the different land uses, or it may be necessary to recognised that the area may not be suitable (as a whole) for the establishment of paludiculture at this point in time. For example, areas that have been prioritised for raw material extraction (and possibly adjacent areas) would not be suitable for paludiculture during the extraction phase. Local and neighbourhood plans may also compete with the establishment of paludiculture. However, early engagement with local communities and authorities can mean that such plans can also directly reflect the "paludiculture capacity" of the site. More work is needed in the UK to build links with the relevant authorities and specialist planners to ensure that relevant public concerns that may limit rewetting can be considered appropriately.

Other important factors that can determine success

Other

Once the basic requirements described in previous sections have been met, a number of other desirable characteristics of the site and surrounding area should be considered. These can highlight opportunities and help to clarify the specific priorities or identify possible synergies within a project. Here we describe these characteristics but without any prioritisation; individual project objectives will determine the factors that are most important locally.

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Areas where water levels can be raised with little technical and financial effort are particularly favourable for implementation. This is the case if:

  • the site is already hydrologically delimited, e.g. by embankments or ditches;

  • the site is lower than its surroundings;

  • the project area is identical to the catchment area of a pumping station;

  • no adjacent areas belonging

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Ideally active water regulation should also be possible. Sufficient water will need to be available to input to maintain water levels, e.g. as irrigation, especially during low rainfall and/or high evaporation periods. Sufficient freeboard should also remain after rewetting to allow the site to deal with extreme rainfall and mitigate flood risk elsewhere. Active monitoring of water levels together with an additional active supply of surface water in summer are often necessary, and even essential for some paludiculture crops (e.g. sphagnum cultivation).

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Economic success will depend on size of the area available for cultivation and the presence of supporting logistical infrastructure for processing, as well as market access. The appropriate size depends above all on the individual farm situation (machinery, labour, land area, other crops/ enterprises), the harvesting, transport and storage logistics required as well as existing regional processing capability and wider market demand. Collaborations (e.g. machinery rings, producer groups, cooperatives) can have a positive impact on start-up viability and overall profitability. For most paludiculture crops, a site should be at least ~ 10 ha in size in order to be economically viable. In most cases, at the outset, overall land requirements are much greater so that sufficient biomass can be produced to support the development of a suitable processing chain (exceptions may be pharmaceutical or flavouring crops, such as sundew). Logistical infrastructure at, and close to, the site plays an important role in supporting effective land management with higher water tables. Existing access roads, (possibly raised) embankments and ditch crossings, biomass handling sites at the edge of the area, storage and (covered) drying capacities all favour implementation of paludiculture.

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Co-operation at a catchment scale is usually required so that the water storage in the near-surface groundwater can be optimised for all land users. It is often the case that the initial investment on smaller areas needed to raise the water level, for water management and for infrastructure is more complex and costly (on a per hectare basis) where the surrounding areas continue to be drained. Although such isolated solutions are costly, they may be the only way to raise water levels and specifically manage them to meet crop requirements. In many cases, subdivision of a drained catchment is necessary due to the infrastructure required (e.g. road embankments, water control to deal with elevation changes. Hydrological subdivision can be problematic in the case of shallow bogs with sandy sub-surface materials.  

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Wider interest from the community, local authorities or other private interests in exploiting synergies between climate protection, nature conservation and water protection goals can be helpful so that even complex projects can be financed and implemented quickly. Synergies with the implementation of paludiculture can also include:

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  • Flood protection

  • Nutrient removal

  • Stabilisation of the landscape water balance

  • Localised evaporative cooling

  • Education and recreation

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There are increasing options to value and valorising these additional services of paludiculture, e.g. via certificates.

Site requirements of different paludiculture crops

Site requirements

Both the main water source (groundwater, surface water, rainfall) and the water quality (nutrient content, other contaminants) are important for an assessment of whether site is suitable for a particular paludiculture crop. The current condition of the site also has an impact.

 

If drainage is relatively recent, and the original peatland vegetation and the former natural site conditions are known then this may enable near-natural land preparation with use of regenerating wetland plants as wet grassland. Near-natural peatlands have a wide range of site conditions, and these can be categorised using ecological peatland types defined by the vegetation present. The near-natural peatland vegetation can also provide an indicator of the nutrient content and acidity (pH value) of the site. Nutrient content is also roughly categorised according to the C/N value of the litter materials into nutrient-poor (oligotrophic, C/N 33 - 50), moderately nutrient-poor (mesotrophic, C/N: 20 - 33) and nutrient-rich (eutrophic, C/N: 10 – 20).

Peatland type
Natural vegetation
Trophic status
pH
Raised bog
Prostrate shrub - cotton grass - sphagnum
Very low (oligotrophic)
Acidic pH<4.8
Acidic transition bog
Sphagnum - sedge meadows
Moderate (mesotrophic)
Acidic pH>4.8
Alkaline (base rich) percolation or spring-fed transition fen
Brown moss (e.g. Campylium stellatum) and sedge meadows
Moderate (mesotrophic)
Near neutral pH 4.8 - 6.4
Calcareous (limestone) percolation or spring-fed fen
Saw sedge (cladium mariscus) or bottle sedge (carex rostrata) in fens that are less alkaline, with brown mosses
Moderate (mesotrophic)
Alkaline pH 4.8 - 6.4
Basin fens
Reed beds, sedge meadows, alder swamps
Nutrient rich (eutrophic)
Usually alkaline/ near neutral

Where drainage, land use and fertilisation have changed the characteristics of the site, often over decades or centuries, then vegetation can no longer serve as an indicator. The changes that have occurred  in the soil after drainage-based agriculture depends on the type of peatland, the intensity of use as well as the duration of drainage. In general, degraded peatland soils have a greatly altered structure, which reduces water storage capacity and water permeability compared with natural peatlands. In drained peatland areas, the main aim of paludiculture is to reduce GHG emissions as much as possible and to permanently preserve the peat body of the peatland as a basis for production ("peat-preserving "). In order to maintain the peat, water levels close to ground level are necessary with a target water table depth of 10 cm during the growing season, when the peat is warm and hence potentially microbially active. Where average summer water levels fall to 30 cm below ground level, these sites will continue to consume peat and produce significant carbon dioxide (CO2) emissions (together with nitrous oxide (N2O) emissions). Higher CO2 emissions mean higher peat depletion. Where the drained water level is much lower than 50 cm, raising the water levels from will lead to a significant reduction in GHG emissions. Like natural peatlands, peatlands growing paludiculture crops can emit methane (CH4) and a small quantity of CO2. Particularly in the first few years after rewetting, while the vegetation adapts to the new water level or before full groundcover is established, CH4 emissions can rise sharply. The reduction potential of the site's GHG emissions thus varies depending on the level of GHGs in the initial state and in the intended form of paludiculture. In fact, the changes in GHG emissions with water table depths are continuous, but these boundaries help to practical implementation and so were introduced for pragmatic reasons based on the currently available GHG emission balances. New findings may emerge that may change the target water table depths in the future.

Management
Average water level within the peatland
Emission ranges (tonnes of CO2 eq per ha per year)
Climate impact
Peat-depleting Strong
Deep-drained peatland: summer water level more than 50 cm below ground level
~20 - 50
High to very high GHG emissions (especially CO2)
Peat-depleting Weak
Summer water level: approx. 30 to 50 cm below ground level
~5 - 20
CO2 and N2O emissions were reduced compared with deep-drained sites, low CH4 emissions.
Peat-preserving
Water levels just below ground level, slight water level fluctuations possible, inundation possible. Summer water level not more than 10 cm below ground level
~0 - 8
Maximum possible climate protection: minimum CO2 emissions or CO2 sink; CH4 emissions may increase where there is standing water in summer

Different paludiculture crops and management systems can lead to different site emissions, depending on site characteristics. However, current data show that paludiculture systems have lower GHG emissions largely due to the increased water levels. If the products of paludiculture are used within the bioeconomy replacing fossil fuel-based raw materials or as durable long-term materials (e.g. in construction) then further GHG mitigation benefits result. If this low carbon footprint were considered as part of the product, this would lead to a market advantage and could raise demand for paludiculture raw materials.

Paludiculture crop
Global Warming Potential (GWP) CO2 eq. per ha per year
Reed
~ 0 - 7
Typha (bullrush / cattail)
~ 6 - 7
Large Sedge
~ 3 - 10
Sphagnum (peat mosses)
~ 3
Wet pasture with water buffaloes
~ 8 - 12
For reference
Grassland (on average)
31.7
Arable production (on average)
40.4

In drained, agricultural peatlands, the nutrient balance also will have been greatly altered by fertilisation, liming and peat mineralisation. When they are rewetted, raised bog sites that have been intensively managed as grassland or arable or horticultural land will initially have conditions that favour nutrient-loving species. Regular harvesting of paludiculture crops will result in nutrient offtake. In addition, nutrient supply from mineralisation of peat is interrupted and nutrients for crop growth will mainly be supplied by the water. The nutrient content and quality of the water therefore plays an important role in nutrient management of site. It is important to note that there very little long-term experience in maintaining and managing yields for paludiculture crops. There is still a need for research on long-term management approaches, especially for former raised bog sites.

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Paludiculture plants can grow under a wide range of conditions and nutrient levels, but the best productivity is achieved under nutrient-rich conditions and with a balanced nutrient supply. This does not apply if species adapted to a low nutrient supply are chosen, such as certain sphagnum species. Thatching reed may also have better quality with low-moderate nutrient inputs. Unfortunately, there is still limited experience on how peatland type and location may interact with management to affect the quality aspects of the paludiculture products. We have summarised what is currently known in the following table:

Table 5: Site requirements for various paludiculture crops.

Crop
Peatland type
Water levels and water management
Nutrient requirements
Requirement for surface homogeneity (relief, slope, etc.)
Reeds
Fens
Permanent water levels below the surface, some salinity and waterlogging tolerated
Medium-high*: Nutrient replenishment requirements depend on utilisation, lower if harvested in winter
Small-scale differences in relief are tolerated
Typha (Cattail)
Nutrient-rich fens
Permanent high water levels at or above the surface, salinity and waterlogging tolerated
High: Constant replenishment required
Surfaces should be homogeneous, and the water should be able to flow evenly over the surface
Wet meadow (sedge)
Fens
Water levels at or just below surface, short-term waterlogging or lower water levels tolerated
Medium: Low requirement for regular replenishment
Small-scale differences in relief are tolerated
Reed canary grass
Alkaline-rich fens with good nutrient supply
Alternating moist to wet, oxygen-rich water; permanent waterlogging is not tolerated
High: Regular supply of nutrient- and oxygen-rich water via flooding necessary
Small-scale differences in relief are tolerated
Sphagnum
Raised bog
Water levels always uniform at surface (rising with the growth of the peat mosses)
Low: Natural replenishment sufficient
Surfaces should ideally be levelled; slight differences in relief (c. 20 cm) are tolerated
Black alder
Alkaline-rich fens
Moist to very moist locations with moving soil water; crop sensitive to prolonged flooding
High to very high: Regular replenishment of alkaline-rich water
Small-scale differences in relief are tolerated

* There are no uniform standards for thatching reeds. Individual quality assessments by reed cutters are often based on intergenerational experience.

This information is taken from a translation of the Leitfaden Fur Die Umsetzung Von Paludikultur, originally produced in German in 2022.

Nordt, A., Abel, S., Hirschelmann, S., Lechtape, C. & Neubert, J. (2022) Leitfaden für die Umsetzung von Paludikultur. Greifswald Moor Centrum-Schriftenreihe 05/2022 (Selbstverlag, ISSN 2627–910X), 144 S.

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With thanks to the Greifswald Moor Centrum and to funding from the Paludiculture Engagement Fund (within the Nature for Climate Fund).

Greifswald Moor Centrum.jpg

Implementation of paludiculture is currently still very much in the pilot stage. Many farmers are aware of the significant climate impact of their peatlands, but they lack specific practical knowledge for conversion alongside specific economic prospects and commercial exploitation partners. Some pioneering farms are already implementing cultivation at high water levels and paludiculture crops are being further developed and tested in research projects. However, large-scale realisation of paludiculture systems in practice is still in its infancy.

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We therefore expect this guide to grow and develop as farmers and researchers provide new information to update it. If you spot errors or want to add material, please contact us at: paludiculture@niab.com.

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