What is a blanket bog?
Introduction
Blanket bogs have always fascinated me. The deep black peats, cut off sharply underneath by glacial gravels and solid rock, then crowned with a fragrant and undulating sea of floral colour, knee high and ever changing with the seasons. A hare’s ears here, a carnivorous plant lurking there, a mushroom you notice under the heather while sipping from a flask of tea. Blanket bogs are captivating. But how did they form? What do they look like? Why are they important? And where can you find them? Have a read to find out.
How blanket bogs form
There are three main types of peatlands in Ireland: fen, raised bog and blanket bog. Blanket bog is by far the most common type, accounting for 80% of the land area of all Irish peatland and is predominantly found on the west coast in places like the Iveragh peninsula in Kerry. For this reason, blanket bogs are the focus of this article.
While blanket bogs can form naturally without human intervention, the formation of vast areas of blanket bog in Ireland is closely associated with a changing climate and the expansion of agriculture some 4,000 years ago. The loss of old growth forests due to felling or ring barking created fields and exposed the deep soils - that had built up over millennia - to rain. As the rain percolated through the soil it carried nutrients such as iron from the upper layer downwards, creating a hard impermeable layer of nutrients known as a hard pan. This prevented water from draining away easily from the soil and thus, fields became more and more waterlogged over time. Finally, the plants that thrive in those damp conditions became dominant. When these plants die, they do not break down quickly because of the lack of oxygen in the waterlogged soils. This leads to a build-up of semi-decomposed plant material over time; that is to say, the blanket bog grows.
For a bog to grow, you need a consistently high and stable water level. This is why blanket bogs are found most commonly in the west of Ireland where precipitation exceeds the 1.25 meters per year required for blanket bog to form. This rainfall is also spread across the year, which keeps the land consistently damp. Compare this with Dublin’s annual precipitation of 0.6 meters and you can start to see why we have more blanket bogs in the west. The acidic sandstone bedrock of the Iveragh peninsula also aids in the formation of blanket bogs because it forms an impermeable layer underneath the wet soil.
Furthermore, there are two types of blanket bog: 1) Mountain blanket bog and 2) Lowland blanket bog (also known as Atlantic blanket bog due to its restriction to the Atlantic seaboard in Ireland). Mountain blanket bog occurs above 150 meter above sea level and lowland blanket bog below it. These two types of blanket bog are distinguished mainly by the slightly higher rainfall at higher altitudes and the slightly higher fertility at lower altitudes - due in part by enrichment from ocean mists coming in off the Atlantic. These factors result in a variation in the plant communities that are described in this article.
Cut-away showing where bog formed on gravel
The blanket bog landscape
When seen for a blurred second through a car window, blanket bogs can appear as flat, unchanging, and monotonous landscapes. But when you are in them you will quickly realise, they are not. Blanket bogs undulate across the landscape – like a blanket covering a bumpy surface – that is why they are called blanket bogs.
Did you know that blanket bogs features include waist high hillocks of vegetation to pools of questionable depths and everything in between, including the occasional jutting rock that creates its own biological microcosms.
Hillocks made up of mosses, grasses and heathers slope down to flatter planes of yet more mosses of varying hues, with bog myrtle and sedges, yellow bog asphodel and meshes of Cladonia lichens. Bog pools, each one a unique shape, form in depressions in the peat, and are filled with plant litter, bog bean, greater sundews, floating rafts of mosses and bladderwort and are fringed with snowy tufts of bog cotton. Metallic coloured dragonflies whish over these sunlit pools on the hunt for midges and other insects. This dynamic, living habitat that changes across the seasons is anything but monotonous.
The importance of blanket bogs
Blanket bogs are beautiful in their own right. They also serve many important functions for humans which can easily be forgotten.
They act as huge reservoirs of fresh water. Bogs can consist of over 90% water. They also contribute to flood defence by slowing water run-off.
They store millions of tonnes of carbon. Globally, peatlands store more carbon than all the living land plants on earth combined (IUCN, 2021). Ireland has 8% of the world’s blanket bogs. This is an astounding statistic and really highlights the importance of Irish peatlands in the fight against climate change.
They provide insight into what Ireland looked like thousands of years ago. As peat grows, it traps pollen. Deeper peat is older than peat closer to the surface and we can calculate its age using radio-carbon dating. Different plants produce different shaped pollen, and by looking at the changes in the different kinds of pollen at different depths in the peat, we can see what species grew at different periods in the past.
Blanket bogs store important artefacts from the past, such as field patterns, human dwellings and tools such as a middle bronze age axe that was found in the Emlaghlea blanket bog near Waterville.
Blanket bogs have strong potential to be marketed for tourism. Blanket bog is a globally rare habitat that is plentiful on the Iveragh peninsula. In Ireland we often overlook their beauty and intrigue, but many tourists have not seen blanket bog before or know anything about them.
Finally, blanket bogs are home to so many of our most colourful and rare native wildlife, the fascinating plants which can be read about in detail here.
Eroded blanket bog peat has exposed tree stump
Bogs in our culture
Blanket bogs are engrained in the cultural heritage of Iveragh. Many of Iveragh’s farms contain a significant proportion of blanket bog. Historically, there was a tradition of ‘booleying’ on Iveragh whereby people and their animals moved from the lowlands during winter to upland pastures - like blanket bog and heathland - during the summer. These peatlands are still often grazed during the summer. This benefits the farmer as they have additional forage for their animals, and it benefits the bog as it prevents trees establishing. Too much grazing, however, can lead to shifts in vegetation and peat erosion.
Blanket bog peat was traditionally cut as a fuel source to heat people's homes on Iveragh and most families would have had rights to cut turf on a specific patch of bog. The peat was cut with a two-sided spade known as a sleán. The Kerry bog pony, which is a recognised regional breed, is nimble footed and was used to haul dried turf off the blanket bog in baskets. You might still see these small ponies in fields today. Peat cutting is no longer advised as it drains the bog of freshwater, making it unsuitable for plants that contribute to bog growth, and causing the bog to release its stored carbon.
As so much of the land is blanket bog, the people of Iveragh created ‘lazy beds’ to grow crops on the damp, infertile and peaty soils. Lazy beds are cultivation ridges that were dug in downhill lines to channel the moisture and frost off the bog and allow potatoes or other crops to grow. They were enriched with seaweeds carried from the sea to boost fertility. These relics of past farming are still visible all around the peninsula.
Blanket bogs are a key focal point that help us understand the story of Iveragh’s cultural heritage.
Where to find them
Years ago, before I moved here to live, I visited the Iveragh peninsula regularly to hike sections of the Kerry way and other walking trails. I did so in different seasons and managed to see a great deal of the region. You soon realise how much blanket bog there is on Iveragh. Lots! I found that most walking trails pass through a blanket bog or at least have a vantage point where the topography of the land can be understood, and the mighty blanket bogs observed from afar.
A great place to start on your bog journey is with the network of short and long walking trails that span across Iveragh. The majority of these walks pass through blanket bog where you will encounter its special plants, animals and fungi. The LIVE project has covered a wide selection of these walks in detail. These digital guides also include useful information on other wildlife, historical structures, and practical amenities that are available on each walk.
Some blanket bog restoration projects can be visited at Coad bog near Castlecove and Dromalonhurt bog in Glencar. These projects that are run by the Irish Peat Conservation Council (IPCC) and Coillte, respectively, are examples of rewetting, where drainage ditches are blocked, and the water level allowed to rise again. This promotes the re-establishment of blanket bog flora that will again begin to accumulate peat and fix carbon over time, although this takes decades. These sites can be visited to see their progress. The Coillte site has a sign that can be read detailing the subject. See further reading section for links.
Blanket bog landscape showing bog pool
Caring for them
We are currently living through a biodiversity crisis. You can think of biodiversity as the variety of life in a particular area, and habitats as the home in which that life lives. We have many different habitats in Ireland and blanket bogs are one habitat that is facing rapid decline. I have already highlighted the benefits that peatlands provide above, and here I will pass on a few things here that you can do to minimise your impact while visiting the bog based on the ‘Leave no Trace’ principles that you can read more about here.
Consider the impact that your foot fall could have on the bog, as peat is not as durable as pavement. Consider sticking to the path or visiting the bog after a few dry days when the peat has firmed up a bit.
Avoid picking plants and interfering with wildlife. As mentioned above, many plants are rare or endangered and picking them might drive them closer to extinction. We can also avoid picking plants so that the next person to visit can have the same experience as we have had.
Take away any rubbish you have brought with you including fruit peels and other food.
Key to protecting our blanket bogs is to avoid cutting into them. Cutting into bogs drains the water out of them. This makes the bog unsuitable for many bog plants that are essential for the bog to grow and continue to sequester carbon. The drainage also starts the breakdown of the deep peats in the bog which releases carbon.
Conclusion
Blanket bogs tie together so much of Iveragh’s natural and cultural heritage. Humans were instrumental in their formation thousands of years ago and we have lived intimately with them ever since. Agriculture, including grazing and crop growing, as well as fuel supply have traditionally been linked to blanket bogs.
The blanket bogs of Iveragh have preserved human artefacts from dwelling places and field patterns all the way down to the tools used by the past people of Iveragh. They have also preserved the remains of ancient woodlands that grew many thousands of years ago. These have given us unique insights into how ancient Irish people lived and what their world was like. But we must now consider the impact we are having on these precious and rapidly declining habitats.
The next leg of the cultural relationship we have with our blanket bogs must be tied to seeing them for the rich biodiversity value, their gargantuan role as carbon sequestering ecosystems, and their valuable reserves of fresh drinking water.
Webinar
Watch the full webinar on blanket bogs here
Further reading
You can learn about the fascinating bog plants which live on Iveragh's unique Irish landscape here: Blanket Bog Plants.
Devoy, R., Cummins, V., Brunt, B., Bartlett, D., Kandrot, K. (2021) The Coastal Atlas of Ireland. Cork University Press, Cork.
Feehan, J., O’Donovan, G. (1996) The Bogs of Ireland. University College Dublin, The Environmental Institute.
Irish Peatland Conservation Council
