5. Get the fundamentals right first

This section covers the fundamentals:

• 5.1 Definitions
• 5.2 Extent
• 5.3 Condition
• 5.4 Restoration
• 5.5 Emissions

5.1 Definitions

Statistics on peatlands are very sensitive to definitions. This can make fair comparisons between data sources difficult and cause confusion.

There is no international definition of peatlands which has been consistently applied. Technical definitions of peatlands often reference:

• Soil depth (profile)
• Soil organic matter (SOM) or soil organic carbon (SOC)
• Surface vegetation

These terms can be combined in different ways, leading to multiple definitions of peatlands. Notably, there isn’t a consistent definition across the UK. Reviews by the James Hutton Institute (JHI) and International Union for Conservation of Nature (IUCN) Peatland Programme explain the reasons for these differences in more detail. In summary:

• In Scotland, the conventional 50 cm depth threshold originates from the suitability of peat for industrial extraction. It also has practical relevance for peat and soil surveys.
• Northern Ireland also uses a 50 cm depth threshold.
• In England and Wales, the 30 to 40 cm depth threshold originates from the estimated maximum ploughing depth in agriculture. In England, there are proposals to revise this down to 30 cm.

Even within Scotland, definitions vary. The Wildlife Management and Muirburn (Scotland) Act 2024 defines peat as soil with an organic content of more than 60%, and peatland as “land where the soil has a layer of peat with a thickness of more than 40 centimetres”. On the other hand, a 50 cm depth threshold is used by National soil map of Scotland classification system, the National Planning Framework 4 and reporting of emissions from Scotland’s peatlands to the UK GHG inventory. A 50 cm depth threshold is also used by the Good Agricultural and Environmental Conditions (GAEC) 6 - Maintenance of soil organic matter, but note that GAEC 6 has an additional requirement for semi-natural vegetation.

For official statistics, we have to be precise in how we use specific terms, so that users are clear what we are referring to. Importantly, we do not intend to recommend how others use peatland definitions, which may have particular legal or contextual requirements. For use in official statistics, the following definitions are proposed, in line with the most commonly applied Scottish definitions, such as the National Planning Framework 4 and Soil Survey of Scotland:

• Peat refers to a type of soil deposit with a SOM above 60%.
• Peat soils refer to areas where the peat depth is at least 50 cm (often termed organic soils).
• Peaty soils (often termed organo-mineral soils) refer to areas where the peat depth is less than 50 cm.
• In line with the National Planning Framework 4, peatland is “defined by the presence of peat soil or peaty soil types. This means that ‘peat-forming; vegetation is growing and actively forming peat or it has been grown and formed peat at some point in the past.”

Since these definitions are soil based, they aren’t affected by the type of surface cover: areas of woodland, arable fields or buildings which sit on top of peat of at least 50 cm depth are still classed as areas of peat soils, and are counted as such in the UK GHG inventory. When we are referring to peatland habitats specifically, we will make this clear, for example, “blanket bog”, “bog woodland” and so forth.

In an attempt to balance consistency with flexibility, a practical approach for official statistics on Scotland’s peatlands would be to:

• Use the broadly conventional definition of peat soils for most headline figures (at least 50 cm depth and at least 60% SOM).
  • This would provide a clear and consistent narrative for general users.
• Where possible, provide additional figures for alternative peat depths (30 and 40 cm).
  • This would help users to make reasonable comparisons when figures for alternative peat depths are required.

This approach will help show how assumptions and definitions influence the statistics.

We welcome views on our approach to definitions and terminology for the purposes of the statistics.

In this document, we use the term peatland restored for ease of communication, but it is worth bearing in mind some important caveats. In using this term, we are referring to areas of peatland where restoration work has been undertaken to improve the peatland condition. However, it can take a long time for these improvements to occur and there may be situations where improvements are unsuccessful. A useful analogy is the use of the term ‘woodland created’ in Forestry Statistics and Forestry Facts & Figures.

5.2 Extent

Since our definitions are soil based, field surveys are the gold standard method to determine the location of peat. This technique is best suited for smaller areas where accurate, detailed or repeated mapping is required, for instance, in peatland restoration or infrastructure development. The main disadvantage of field surveys is that they are labour intensive. National scale surveys have not been undertaken for some time – field work for the last Soil Survey of Scotland primarily took place between 1947 and 1981, and was used to create maps which are still useful today.

To overcome the burden of field surveys for large regions, the extent of peat can be predicted by computer modelling, rather than by direct ground measurement alone. These models use a variety of inputs to make predictions, such as climate, vegetation and gradient. However, these models are currently limited by a lack of sufficiently large and representative training datasets.

Consequently, recent estimates of the extent of peat soils in Scotland have varied widely, from around 1.2 to 2.4 million hectares. For headline figures in the statistics, we would use the same map of peat soils as the UK GHG inventory, which gives a national estimate of peat soils of around 2 million hectares, to ensure consistency with data used in high profile GHG statistics.

However, we will provide additional figures, summarised from a range of sources and depth thresholds, to help illustrate uncertainty. This approach is shown in the example table, below:

Table 1: Example for peat extent

Region	Area as per UK GHG Inventory	Multiple sources: 50 cm	Multiple sources: 40 cm	Multiple sources: 30 cm
Scotland	2 mha	~ 1.2 to 2.4 mha	~ 1.6 to 2.8 mha	~ 2 to 3.4 mha
Etc…	…	…	…	…

Efforts are under way to improve the training datasets for computer models by undertaking further field surveys. It is hopeful that these uncertainties will reduce over the next few years.

We are unable to provide spatial data for the UK GHG inventory basemap to download, due to licensing restrictions on proprietary data from the British Geological Society. However, we will aim to make available estimates of peat extent from a range of other sources. We will overlap these in a single map to show areas of agreement and disagreement.

5.3 Condition

Peatland condition is a vital part of the statistics. We can use it to infer the ability of peatlands to provide a range of services, even when we cannot measure these services directly. For instance, we would expect, in general, near-natural peatlands to be associated with good water quality, and for degraded peatlands to be associated with poorer water quality. Once again, field surveys are the gold standard for assessing peatland condition, but this is impractical for large regions. Instead, peatland condition is estimated. The most important classification system is that used by the UK GHG inventory, which uses 18 categories, broadly according to land cover. Land use is closely related to condition, with categories such as “near natural bog”, “cropland”, “forestry” and “intensive grassland” amongst others.

Scotland's peat base map in the UK GHG inventory takes a reasonably simple approach whereby the Land Cover Map for Scotland 1988 (LCS88) is used to allocate condition categories. However, there are known innaccuracies, especially for grasslands. In addition, this map was designed for Scotland-level estimates, and some condition categories e.g. eroding modified bog, don’t have a specific spatial location.

To improve peatland condition mapping in Scotland, the JHI developed an improved method which uses additional land use or land cover datasets and machine learning techniques. This is a very useful resource which can better reflect the current state of peatlands, and these techniques will improve with time. A notable advantage is that drainage and erosion features are mapped.

In line with the peat extent section, for headline figures, we would propose using the conventional UK GHG inventory classification methods. However, additional figures would consider alternative sources of peat extent and depth thresholds, as shown in the example table, below:

Table 2: example for peatland condition

GHG inventory condition category	Year	Area as per UK GHG inventory	Multiple extent sources, 50 cm threshold	And so forth for 40 and 30 cm depth thresholds
Forest	2023	359 kha	Range X to Y	Range X to Y
Etc…	…	…	…	…

Peatland ACTION surveys and the Peatland Code use alternative condition categories. These don’t always directly correspond to the 18 GHG inventory categories, but are often quite closely related.

We will provide the detailed GHG inventory figures in data tables. However, for ease of communication, we would also propose simplifying the 18 categories from the GHG inventory further. Note that these simple categories won’t be used for calculations of GHG emissions – their purpose is to simplify communication.

At the highest level, three simple categories would be proposed:

• Near-natural
• Degraded
• Restored

This makes is easier to make statements such as “X% of Scotland’s peatlands are degraded”.

The degraded peatland and restored peatland categories would each be split further into ‘moderately degraded’ and ‘severely degraded’ categories. The ‘severely degraded’ category would include actively eroding peatland, together with forest land, cropland, settlements and peat extraction sites. Modified bog which is not actively eroding would be considered ‘moderately degraded’. This would give five categories:

• Near natural peatland
• Moderately degraded peatland
• Severely degraded peatland
• Restored peatland (previously moderately degraded)
• Restored peatland (previously severely degraded)

This makes it easier to make statements such as “X hectares of peatland have been restored since 1990. Of this, Y hectares were considered moderately degraded and Z hectares were severely degraded prior to restoration.”

It should be noted that there are alternative peatland classification systems, for example:

• “Bog breathing” classification methods look at peatland surface motion from remote sensing, with three classes: degrading, stiff and good.
• The National Vegetation Classification (NVC) scheme divides peatland into classes according to patterns in vegetation communities.

Alternative classification systems are unlikely to feature in the official statistics initially, but may be included in the future, subject to further development and data availability. Remote methods in particular may be useful for monitoring maintenance on restored sites, subject to further development. The Scottish Land LiDAR Programme has strong potential to drive innovation in remote assessment and monitoring of peatland condition.

5.4 Restoration

Where peatlands are degraded, peatland restoration aims to put these areas on a path towards a more natural state. This can reduce GHG emissions and preserve the huge amount of carbon that these peatlands store, alongside multiple co-benefits such as improved water quality and biodiversity. The majority of peatland restoration in Scotland has been delivered by Peatland ACTION.

Restoration data is one of the few areas where we have direct measurements, rather than estimates. In addition, we can use the area restored as a proxy for expected improvements to ecosystem services, even when these services cannot be measured directly.

Once again, the gold standard would be to take repeated field measurements, such as water table depth or vegetation cover, and monitor changes over time. However, this is generally impractical. Instead, we calculate a “restoration footprint” based on restoration features, e.g. blocked drains or peat dams.  These restoration features are mapped out, and a buffer is often applied (30 to 50 m radius to date – it has not been fully standardised). The area inside this buffer is classified as ‘re-wetted’.

For older projects, sometimes a restoration footprint is not available, and instead the mapped area restored is estimated by using a circular buffer around a project centroid (a point location). Data for these older projects is often poor, with substantial uncertainty.

There are several sources of restoration data to consider for peatland statistics:

• Peatland ACTION (PA) is our primary data source, and captures the majority of restoration work in Scotland from 2012-13 onwards. There have been some differences in the recording of peatland restoration footprints between peatland restoration projects and over time, but this has shown improvement in recent years with the introduction of a spatial template from the 2019/20 financial year onwards.
• Restoration data from 1990 to 2012 is very limited with considerable uncertainty. It is likely that these initial estimates of 21,326 hectares will be revised after quality assurance.
• The Peatland Code (PC) is a voluntary carbon market standard, whereby carbon credits are issued as a means to encourage private investment in peatland restoration. Most PC projects in Scotland are also registered with PA, and so provide no additional information on hectares of peatland restored. Restoration is recorded differently between the PC and PA: the PC tends to have stricter requirements for classifying areas as restored, such as depth requirements, due to the need to generate carbon credits of a guaranteed standard.
• Other restoration efforts take place, whether through alternative grant-funded means, such as the Agri-Environment Climate Scheme (AECS) or MERLIN, or privately funded means. There are some significant challenges such as avoiding double counting and suitable handling of offsetting (restoration to compensate for degradation elsewhere).

Another important consideration is time. Restoration projects often take place over several years. Each year, around May or June, figures are released for PA restoration efforts of the previous financial year (i.e. up to April). This sometimes includes ‘interim hectares’ for projects in progress but not completed. As such, decisions will need to be reached on when to release new figures and how up to date to make them. The more up to date they are, the more likely it is that figures will be revised slightly each year.

In the statistics, we propose presenting two main time series of restoration data:

• Hectares restored, using definitions used to report towards restoration targets. This normally uses a larger buffer of 50 metres, but there have been some differences in how restoration footprints are recorded. We expect that this will also include other restoration efforts in the future, alongside PA data and pre-2012 restoration activity, subject to suitable data quality standards. We suggest that these will be the headline figures.
• Hectares restored as reported to the GHG inventory. This uses a smaller buffer of 30 metres and, to date, only includes PA data plus pre-2012 restoration activity. We suggest that these will be used as additional figures.

In addition to these aggregated figures, we would also provide a project-level dataset. The main distinguishing features of this dataset, compared to existing sources, would be:

• This dataset will include restoration projects funded by sources other than PA
• This dataset will provide additional information on pre-restoration condition, depth and GHG emissions

We aim to align this dataset with developing Peatland Metadata Standards, and to provide information for each project under the following themes:

• Administration and funding: to include a unique identifier, location, main funding sources, grant ID(s), project start and end dates, and so on.
• Site characteristics: to include information on hectares restored, pre-restoration depth, condition, GHG emissions and any other relevant metrics.
• Long-term maintenance and monitoring: to include information from field-based surveys and remote sensing (subject to future development).
• Project linkages: to provide references to closely related projects, for instance, Peatland Code projects.
• Spatial data: to provide a project centroid at a minimum, and a full restoration footprint where available.
• Quality assurance: to provide information on data quality, for example, whether a restoration footprint is available, and whether the footprint area matches the reported hectares of peatland restored.

We would also summarise basic information from the Peatland Code. This would be done in a very similar way to the presentation of Woodland Carbon Code projects in Forestry Statistics:

• Counts of projects according to status (under development, plan validated, restoration validated, verified)
• Project area according to status
• Projected carbon sequestration according to status

It is important to mention a few further caveats and limitations of restoration data:

• Peatland ACTION requires that, in general, most of the peat within a project area must be 50 cm deep. However, some areas of peat will be shallower than this. This is expected, to a degree, since peat depth can vary considerably across a short distance.
• The area of peat restored is measured at a relatively high resolution, but national estimates of the extent and condition of peat soils use coarser resolution.
• There can be associations between several peatland ACTION projects or subsites, and several Peatland Code projects. This means that it is not always possible to match these projects or subsites as simple one-to-one pairs.

Restoration data helps us to understand how peatlands are changing over time, but this isn’t the complete picture - we also need to consider new peatland degradation. However, acquiring and analysing relevant data is challenging due to lack of a centralised data source and standardised methods of recording peatland degradation.

5.5 GHG emissions

Of all the ecosystem services associated with peatlands, GHG regulation has had the greatest focus. GHG emissions from peatlands can be considerable. In the Devolved Administration GHG Inventories 1990-2023, net emissions from peatlands were estimated at 6.2 MtCO2e (million tonnes of carbon dioxide equivalent) in 2023 in Scotland. To give a sense of persepective, GHG emissions from domestic transport were 11.4 MtCO2e in Scotland in 2023.

As far a possible, we will align GHG emissions estimates in the statistics with those of the The UK National Atmospheric Emissions Inventory (NAEI) reports. For national, Local Authority and National Park estimates, we can use figures from the inventory directly. Note that it is expected that there will generally be a two-year lag between the year of publication and year of reporting for GHG emissions estimates. An example table is shown below:

Table 3: example for GHG emissions estimates

Region	Year	Emissions as per GHG inventory (MtCO2e)
Scotland	2023		6.2
Etc.	…		…

It is important to bear in mind that GHG emissions estimates are dependent on estimates of peat soil condition, and in turn, peat soil extent. Any uncertainties in peat soil extent and condition feed through into the uncertainties for GHG emissions estimates, leading to a relatively high level of overall uncertainty. These uncertainties can become even greater when national level estimates are broken down for smaller regions. We will aim to provide some indication of this uncertainty quantitatively.