Bog moss top trumps - Cors Fochno and its sphagnums

From time to time, our teams write a blog about the special places they look after. Here, Justin Lyons, Land Manager at Dyfi Ynyslas National Nature Reserve, talks about sphagnum mosses and why they’re so important.

Cors Fochno raised bog near Borth is part of the Dyfi National Nature Reserve. It is one of the best examples of a lowland raised bog habitat anywhere in the UK.

Raised bogs get their name because of their domed shape. They are areas of peat that have built up over periods as long as 12,000 years and can be as deep as 12 metres. Cors Fochno has peat up to eight metres in depth.

Raised bogs are one of Wales’ rarest and most important habitats and, because of their environmental interest and importance, they are designated Special Areas of Conservation (SACs), which means they are of European importance.

Cors Fochno is home to a wealth of wildlife over a large area. This includes many rare insects such as the rosy marsh moth and the bog bush-cricket, a host of wetland birds from waders such as snipe and redshank to numerous types of warblers and an impressive colourful display of flowers including the beautiful yellow spikes of bog asphodel and the lovely pink lantern shaped flowers of bog rosemary.

The importance of bog mosses

If you walk onto the squelchy surface of an undamaged raised bog, the most abundant plants to be seen are the wonderful sphagnum mosses.

They are famous for their amazing ability to hold water due to their morphology and cell structure. They can hold more than eight times their own weight in water and are made up of almost 95% water.

These, and other properties, make the sphagnum mosses the habitat engineers of raised bogs. As they grow upwards their old remains decompose very slowly under the waterlogged conditions and eventually form a dark brown soil called peat.

The partially and undecomposed plant material that peat is made of is a carbon store. Peatlands like Cors Fochno are one of the most effective carbon sponges on Earth.


There are many different species (types) of sphagnum moss. Hereon Cors Fochno there are 16 species and they are a multitude of colours including claret red, chestnut brown and golden yellow.

Each species prefers slightly different conditions, some grow in low hummocks, some high hummocks and some in lawns. One species called sphagnum cuspidatum likes to grow in pools and is often referred to as “wet kittens” as it resembles wet fur when it is removed from the water.

One of the most distinctive features in the central undamaged area of Cors Fochno is the presence of golden ‘lawns’ of the rare - but here plentiful - sphagnum pulchrum.

Its scientific name translates as ‘beautiful sphagnum’. These ‘lawns’ are the main home for another rarity in Wales, the impressive insect-eating plant, the great sundew.

Sundews ensnare their prey with a sticky substance on their leaf hairs. The sticky substance contains enzymes which digests the insect and enables the plant to absorb the nutrients it needs that are so lacking in this unusual habitat.

Effects of extreme weather

The recent extreme dry weather has put huge stress on the water holding capacity of Sphagnums, turning them to bleached crispy lawns and hummocks, as the water table is drawn down.

So, it was a real surprise during this drought to see one of the real rarities of the reserve, sphagnum beothuk, a hummock species perched well above the water table still looking and feeling hydrated. This was in complete contrast to all the other sphagnums around it (see pic).

Sphagnum beothuk during the recent dry weather

If you were playing moss top trumps, then you would definitely want sphagnum beothuk for its special powers for holding onto water!

Historic burning of the bog

Over Cors Fochno’s 4500-year history there will have been many events that will have affected its growth, such as drier periods where its growth will have been slowed, to wetter periods where the laying down of peat will have increased.

The most dramatic changes have been in the last 300 years as people have used the habitat for various purposes from conversion to pasture to digging peat for fuel. People often burnt the vegetation to help them in these activities.

There are many historical references to these fires and sometimes they would go out of control as described in a newspaper article (The Welshman) from June 10th, 1864. The article is a fascinating window into that period of the bog’s history. Here are a few snippets from the article:

“Borth Bog Ablaze – Miles of Country on Fire”

“Where the wild beauties of nature were formerly seen at their best, nothing now remains but a black, desolate expanse of country.”

“The principal sufferers undoubtedly are the peasants living on the outskirts of the bog. Several of these had just completed their peat harvest, and the fuel, which had been stacked on the bog to dry, was completely destroyed.”

“Another young person who was the support for her aged parents, after having many a weary day in digging the peat, has had her labours rendered useless by the fire.”

The call out of the fire brigade – “The distance of 10 mile to the scene of the fire was quickly covered, being performed in an hour and five minutes.”

Sphagnum Recovery

From the mid-20th century, Cors Fochno began to be recognised as a rare and special habitat by visiting scientists and those from the nearby Aberystwyth University.

They expressed concern about the damaging effects of the regular fires. The burning continued into the 1970s and a study from that time by Dr. FM Slater indicated that two of the rarer Sphagnums were expected to become extinct in the near future if the burning continued.

Thankfully the designation of Cors Fochno as part of the Dyfi National Nature Reserve helped reduce the number of fires and there have not been any major ones since 1985. The lack of fires, combined with the re-wetting of the site through projects such as LIFE are giving the reserve, with all its special wildlife including the Sphagnums, the best possible chance to thrive.

Roughly every 10 years, NRW has been monitoring the fortunes of these rare Sphagnums. We are currently in the middle of monitoring with the assistance of a moss specialist. The early indications are that Sphagnum beothuk is making a good recovery with many new colonies. Early indication for the other rarity Sphagnum austinii, although not increasing greatly is holding its own.

Cors Fochno is currently being restored as part of the EU and Welsh Government funded LIFE Welsh Raised Bogs Project.

There are seven sites being restored as part of the project and all are classed as SACs - Special Areas of Conservation. Only seven raised bog SACs exist in Wales, as almost 98% of the habitat has been lost.

To keep up to date with the LIFE Welsh Raised Bogs Project please follow us on Facebook @CyforgorsyddCymruWelshRaisedBogs or Twitter @Welshraisedbog

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