Forestry

It is estimated that around 18% (439,410 hectares) of UK peatlands are under forestry¹, including areas of the Flow Country of Caithness and Sutherland, the Border Mires of Cumbria and Northumberland, and the mires of the Scottish Southern Uplands. Whilst it is difficult to know how deep the peat layer is in these areas, it is thought that most of these plantations occur on deeper peat (>30-50 cm) that has been drained². It is likely that large areas of shallower peat have also been afforested, but the extent of this is unknown.   

There have been small net reductions in the extent of forestry on peat in England and Wales from 1990 to 2013, but in Scotland and Northern Ireland (and despite recent large forest-to-bog restoration projects) there were net increases, leading to an overall increase in UK peat under forestry of 24,000 ha during this period³.  

The conditions that make peatlands ecologically valuable - their wet, acidic, and nutrient-poor soils - also make them unsuitable for productive forestry. Many plantations on deep peat have underperformed, with stunted tree growth and low timber quality, making the long-term economic viability of such land use questionable. Moreover, some of these sites have been abandoned without harvesting the timber. 

Over time, the environmental consequences of commercial forestry on peatlands have become increasingly clear, as the associated drainage, fertiliser application and tree growth has led to a range of adverse and long-lasting impacts: 

• Hydrological disruption: peatlands rely on high water tables to maintain their structure and function. Forestry operations typically involve extensive drainage, which lowers the water table and dries out the peat. This not only accelerates decomposition but also increases the risk of peat erosion, flooding downstream, and water quality issues due to sediment and nutrient runoff. Drainage can have further impacts on adjacent and associated peat bodies.
• Biodiversity decline: healthy peatlands support a rich array of wildlife, including specialist birds, insects, and plant species. The dry and shaded environment of dense conifer plantations is inhospitable to these species, leading to a dramatic loss of biodiversity and reduced connectivity though fragmentation and ‘islandisation’ of peatlands. For example, plantations can displace peatland bird species directly through habitat loss and through ‘edge effects’ where changes in population or community structures occur at the boundary of two or more habitats – for example, when birds are essentially displaced from adjacent peatland areas⁴. Dunlin populations have suffered where forestry has been planted on peatlands, possibly be due to dense conifer stands enabling predators such as hooded crows and foxes to live close to dunlin breeding grounds.
• Carbon loss and impact on climate: peatlands store more carbon per hectare than any other terrestrial ecosystem. When drained for forestry, the peat begins to oxidise, releasing large amounts of carbon dioxide into the atmosphere. Instead of acting as a carbon sink, these areas become significant sources of greenhouse gases, undermining climate change mitigation efforts.  

The IUCN UK Peatland Programme’s Position Statement: Peatlands and Trees discusses the impact of plantation forestry on peatlands and the positive effects of the removal of commercial plantations on peatland function. 

Governments, private land managers and NGOs have recognised that commercial forestry practices damage the ecology of peatlands and are now working to reverse this trend through forest-to-bog restoration. In the period since the Commission of Inquiry on Peatlands (2011) there has been a significant increase in the amount of this type of restoration (also see the Commission of Inquiry update: Peatlands and forestry that considers the evidence for good practice forest-to-bog restoration).  

Forest to bog restoration involves: 

• Removing non-native trees and stopping further afforestation on deep peat soils
• Blocking drainage ditches to rewet the peat
• Reintroducing bog vegetation, particularly peat-forming Sphagnum mosses  

Whilst the techniques used to restore these areas are beginning to develop, the delivery of this work has, to an extent, relied on trial of emerging techniques and follow-up monitoring to estimate success. These restoration efforts are already showing success across the UK, with improved biodiversity, reduced carbon emissions, and enhanced water regulation. These projects are often supported by public funding, private investment, and community engagement, reflecting a growing recognition of peatlands as vital natural assets. 

The Peatland Code recognises that tree removal is an important peatland restoration opportunity but is awaiting reliable estimates of carbon impacts before it can be formally included in the scheme. This lack of consensus prevents potential funding from private investors through the Code and may prevent the aspiration of restoring afforested peatlands from being fully realised.  

Whilst tree planting schemes aim to help sequester carbon, guidelines in the UK restrict planting on peat. Whilst it may seem attractive to plant on degraded peatlands, it can be counterintuitive, as more carbon can be released from peat than the planted trees take up. There is a need for sustainable management and enhancement of both peatlands and woodlands in the UK, but without compromising one for the other. To protect the functioning of peatlands, the UK Forestry Standard (UKFS) prohibits the planting of new forests on deep peat soils (deeper than 50 cm) and sites that would compromise the hydrology of adjacent bog or wetland habitats⁵. 

In England, a decision support framework for peatland protection and the establishment of new woodland is in place to provide guidance. The framework states that woodland creation will not be approved on areas of soil organic matter content of more than 30%, or peat greater than 30 cm deep and hydrologically linked surrounding areas. Scotland, Wales and Northern Ireland follow the UKFS definition of >50 cm peat depth for new tree planting;⁵ however, medium and high disturbance soil cultivation techniques are prohibited on peat deeper than 10 cm in Scotland⁶. 

Opportunities remain for expansion and management of woodlands within peatland landscapes on non-peat soils, given that it does not compromise the restoration of adjacent degraded peatland habitat. There are also limited opportunities for woodland regeneration on peatland soils in some specific situations, such as fen carr woodland adjacent to lowland raised bogs or the natural regeneration of native woodland expanse on shallow peat in both upland and lowland settings.

However, the figures used for peat depth classification are arbitrary when informing climate-based decisions about land use, and the distinction between deep and shallow peat in forestry policy should be reassessed, as shallow peats are also significant for carbon storage. A thin peat layer of 30 cm has a carbon store equivalent to tropical rainforests⁷ (hectare for hectare). 

To effectively meet international obligations to 2050 Net Zero targets, we need to carefully consider the potential impact of future afforestation of thin peat soils, and the biodiversity implications of planting on other habitats supported by thin peat soils (e.g. wet heath). National land use planning should be developed and used as a tool to guide decisions so that benefits can be achieved in the most sustainable way rather than simply addressing conflicts at the single site scale. 

The optimum solution for carbon and biodiversity is to restore and maintain non-afforested peatlands, restore forested peatland to open habitat and secure new tree cover on suitable non-peat soils or areas of benefit to peatlands. 

1. Artz R, Evans C, Crosher I, Hancock M, Scott-Campbell M, Pilkington M, et al. The State of UK Peatlands: an update. IUCN UK Peatland Programme; 2019. Available from: https://www.iucn-uk-peatlandprogramme.org/sites/default/files/2019-11/COI%20State_of_UK_Peatlands.pdf  

    

2. Evans C, Artz R, Moxley J, Smyth MA, Taylor E, Archer N, et al. Implementation of an emissions inventory for UK peatlands. Centre for Ecology and Hydrology; 2017. Available from: Implementation of an Emissions Inventory for UK Peatlands 

    

3. Artz R, Evans C, Crosher I, Hancock M, Scott-Campbell M, Pilkington M, et al. The State of UK Peatlands: an update. IUCN UK Peatland Programme; 2019. Available from: https://www.iucn-uk-peatlandprogramme.org/sites/default/files/2019-11/COI%20State_of_UK_Peatlands.pdf  

    

4. Wilson JD, Anderson R, Bailey S, Chetcuti J, Cowie NR, Hancock MH, et al. Modelling edge effects of mature forest plantations on peatland waders informs landscape-scale conservation. J Appl Ecol. 2014;51(1):204–13. Available from: https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2664.12173  

    

5. Woodland Trust. Trees and peat in the nature and climate crises: Position Statement. 2023. Available from: https://www.woodlandtrust.org.uk/publications/2023/09/trees-and-peat-position-statement/  

    

6. Scottish Forestry. Cultivation for upland productive woodland creation sites – Applicant’s Guidance. 2021. Available from: https://www.forestry.gov.scot/publications/forests-and-the-environment/protecting-and-managing-soil-in-forests/1032-cultivation-for-upland-productive-woodland-creation-sites-applicant-s-guidance  

    

7. Lindsay R, Ifo A, Cole L, Montanarella L, Nuutinen M. Peatlands: the challenge of mapping the world’s invisible stores of carbon and water. Unasylva. 2019;70(1):46–57. Available from: https://repository.uel.ac.uk/download/5406a696f749d690ef6047d1845349033cbe4545807f9e3dd21143a387be5bde/1231427/ca6842en.pdf