16/12/2020

What are peatlands?

“Appearance blinds, whereas words reveal” - what are peatlands?

Oscar Wilde’s maxim is particularly relevant to our peatlands. Many commentators casually or deliberately interchange terms such as moorlands, peatlands and blanket bog. But just because these habitats look superficially similar, they are not the same.

And a lack of clarity comes with a risk. Catch-all use of the term ‘peatland’ in prescriptive legislation relating to its management could lead to unintended impacts on a range of habitats, biodiversity, impacting international obligations and associated ecosystems. Her Majesty’s Government needs policy that encourages and supports Natural England’s advisors and private land managers to co-create adaptive, site-specific plans that reflect the granularity of our peatland, their management, and a range of environmental outcomes.

Let’s clarify the peatland lexicon.

International Union for the Conservation of Nature (IUCN) definition

“Peatlands are a type of wetlands … covering 3% of the global land surface. The term ‘peatland’ refers to the peat soil and the wetland habitat growing on its surface. Peatland landscapes are varied – from blanket bog landscapes … to swamp forests ….” It goes on to state that in the UK: “There is no single formal definition of ‘peat’ and ‘peatland’, differing interest groups having differing definitions.” The UK is a signatory to the IUCN but management of peatlands is devolved, affecting both the definitions of deep peat (see Deep peat protection below) and regulations that define their management. However, much of its regulation in England (and Wales and some in Scotland) relates to protection as SSSIs, which stems from Wildlife & Countryside Act 1981 as amended.

Why are we interested and what should legislators be aware of as pitfalls in this lack of clarity?

Carbonis the key component of peat. Plants accumulate it through photosynthesis. Its release, through decay, is slowed or stopped by the (anaerobic) waterlogged conditions. This accumulation (sequestration) and limited release (storage) is significant in action against climate change because of the huge amounts of carbon stored in UK peat. Good regulation for ‘peatland’ protection and restoration would recognise not just the organic content of the underlying soil, but the height of the water table and the amount of peat-forming vegetation growing. To achieve most carbon protection and, potentially, more carbon sequestration, national policy should focus on deep peat, as it presents the greatest areal proportion of peat in England.

Peat-forming vegetation in the UK’s climates is mostly made up of mosses, grasses, sedges and shrubs. Sphagnum mosses are an important component of an active peat-forming system and often one of the elements used to define a mire or blanket bog system. Importantly, although some claim otherwise, there is no clear relationship between Sphagnum abundance and peat formation. It is the hydrological and environmental conditions that determine peat formation rather than particular species. As peat has formed over millennia, peatland can exist as just the underlying soils without the accompanying peat-forming vegetation.

Sphagnum (or bog moss) is considered important as it contains a chemical that inhibits the microbial activity that causes decomposition and has been estimated to hold up to 20 times its weight in water. These characteristics may support peat formation where conditions are sub-optimal.

Peat is a soil with an organic content greater than 35%. The high organic content results from dead vegetation only partially decaying due to the waterlogged conditions (see peat-forming vegetation). Peat accumulates where the production of organic matter exceeds its decomposition.

Mires are all types of currently active peat-forming systems – ensuring these function as well as possible should be legislation’s primary focus. Bogs are rain-fed mires as opposed to fens, which are predominantly ground-water fed mires – the mineral content of fen soils is greater.

Blanket bogs are extensive areas of peat-forming vegetation on saturated peat-rich soils. Blanket bogs are an administrative artefact – they have more than 40cm of peat in England and more than 50cm in Scotland; these are both deep peats. Blanket peat is a large, consistent extent of peat of these depths, but this does not say whether more peat is being made on top. Most blanket bogs are flat, rain-fed areas in the uplands or far north of Scotland.

Deep peat protection (more than 40cm of peat in England) comes in two approaches – (a) preventing peat loss to wind and rain by re-profiling and vegetating exposed peat surfaces, or (b) restoringdeep peat function through re-wetting to raise the water table and encourage active mire formation. Counter-intuitively, cool, managed burns can be used to remove the woody canopy and allow the underlying bog-forming species to grow. And managed fires never set out to, and incredibly rarely do, ‘burn peat’ – this is a deliberate obfuscation.

Shallow peat (i.e. less than 40cms of peat in England) is, given the impacts of climate change, likely to be more difficult to recover to accumulating peat function but is still a carbon store, and forestry planting is not allowed on peat of >30cm. However, banning burning on habitats growing on shallower peats could have a significant negative effect on remaining heathland flora and fauna (see heathlands below).

Moorland is an oft-used term which is mistakenly interchanged with peatland. Moorland embraces upland heathland, blanket bog, upland grassland, bracken, scrub, native woodland and exposed rock and is a landscape rather than a key component.

Heathlands do not refer to the soil, but to the vegetation such as heather, bilberry, crowberry, cross-leaved heath and purple moor-grass. The soils can be drier deep peats or on wet, acidic, impoverished, shallow organic soils. Heaths are typical where there is limited peat formation; perhaps the climate has dried over thousands of years or because of drainage or fire. It is not clear at any site which process may have led to the peat not growing. Heathland is an internationally important resource that is of high conservation priority given the suite of flora and fauna it supports. Heather management through managed burning creates a mosaic of heather ages that has been proven to benefit a number of species that are in severe decline such as curlew, as well as to limit the impacts of wildfire.

Grouse moors are projected as the doomsday scenario for peat. But theyare located in moorland ‘landscapes’. The exact area of peatland managed for grouse is unknown. In our Peatland Report we estimated the area as being between 4 and 41% of the total peatland area in England. The higher figure uses Moorland Association data.

What then are peatlands?

Peatland, then, is only broadly descriptive at best. If used there should be recognition that it encompasses a granular mosaic of management; different surface flora (and fauna); variable qualities of organic ‘peat’ soils; dry to saturated soil (the hydrology); and different approaches to preventing damage and enhancing function. It has been estimated that England has 14,185km2 of peatland with 34% of that classified as deep peat and 25% blanket bog. In England deep peat and blanket bog are not synonymous – almost all blanket bog is deep peat, but there are large areas of deep peat that are fens (often badly degraded).  

Peatland Uk

George Orwell said, “The great enemy of clear language is insincerity.” However, in getting the most from our peatlands, sincere but deliberately inaccurate language is just as much of a threat.

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Comments

Blanket Bog Definition ?

at 11:58 on 21/12/2020 by Geoff Eyre

This now needs a far more detailed hydrological study given the depth initially was 1m then 600mm now 400mm purely defined by a quango group , we even have this bog definition for a possible plough depth on free draining land often sloping, at last a great article but just needs agricultural type definitions for various peat depths as many will never be satrurated peat (just rain fed) in the Peak District.

Peat

at 12:18 on 18/12/2020 by Suzanne Wynn

The research conducted by GWCT is invaluable, and particularly so regarding peat. I wish everyone would refer to it as the start point for their own discourse.

Peat

at 12:42 on 17/12/2020 by John Riley

At last it's all set out in plain English. Most interesting I hear so much rubbish being talked about peat how refreshing to see it described correctly. Kind regards to the team John Riley. Life Member.

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