Flanders Moss NNR: Explore colourful ‘shaking’ bogs

Flanders Moss is a fabulously colourful and wild lowland raised bog, a surprising place that holds the secrets of 8000 years of environmental history beneath your feet

1. Flanders Moss National Nature Reserve is best seen from above. Image: © Scottish Natural Heritage

Flanders Moss is Britain’s largest lowland raised bog comprising four linked domes of peat. If you jump on the ground you’ll find it’s not like any normal solid earth! The ground really shakes beneath your feet because it holds so much water. In some areas, the peat is a remarkable 7 metres deep! It has been formed by the accumulation and preservation of dead bog mosses being laid down, layer after layer, in the saturated ground, growing peat at a rate of about 1 millimetre per year. It is not surprising that it has taken over 8000 years to form the raised domes of Flanders Moss. The rain-fed peat domes hold the water table close to the surface of the bog, and it is in this wet ground that the carbon from the dead plants is preserved, playing an important role as a natural carbon store.

During the last glaciation, around 22,000 years ago, sea level was lower than today and an ice sheet covered Scotland, pushing the land downwards. As the climate warmed up and the glaciers melted around 15,000 years ago, the sea rose faster than the land and it flooded into the Carse of Stirling. Eventually, as the land rebounded, the sea retreated, and left a layer of beach sands and silty estuarine muds. Plants and then mosses colonised the land surface, forming a layer of peat on the poorly drained ground. Between about 12,900 and 11,500 years ago, the climate became severely cold again and glaciers formed once more in the Highlands; an event known as the ‘Loch Lomond Re-advance’. One of these glaciers extended into the upper Forth Valley, forming a prominent end moraine that extends from Menteith to Buchlyvie.

Later, around 9000 years ago, the sea again flooded inland and the Carse of Stirling once more became an extension of the Forth Estuary. The earlier land surface and most of the peat bogs were buried by new mudflats comprising silty clays. However, near West Moss-side farm, the bog grew so fast that it remained above the level of the encroaching sea, forming one of several peat islands in the estuary. It is hard to imagine today, but whales swam in the estuary at this time – their skeletons have been found buried in the carse deposits in several places west of Stirling. Around 7500 years ago a series of submarine landslides off the coast of Norway, known as the Storegga slides, caused tsunamis to flood the east coast of the British Isles, leaving behind a distinctive sandy layer covering the low-lying land. These flood deposits have been found at Flanders. The sea finally retreated 7000 years ago, and peat accumulated again, forming a network of bogs that stretched across the Carse of Stirling. Today, scientists can take cores down through the sediments at Flanders Moss and adjacent areas to discover much about the changing climate and sea levels of those past times.

It is not just the record of geological events that Flanders keeps stored below its surface. At a depth of 7 metres, the domes of peat themselves are a time capsule of historical information. Heavy metals, flowering plant pollen, moss spores and unicellular creatures are preserved in the peat, and provide us with clues to local environmental changes that have taken place in the area since the bog formed.
Many of the Carse bogs have been damaged or entirely removed over the years and Flanders Moss now sits almost completely surrounded by managed farmland. Flanders Moss National Nature Reserve (NNR) remains as a mere speck of a once wild and ancient landscape.

Text contributed by Dave Pickett and Ness Kirkbride

Find out more
D.E. Smith (1993) Western Forth Valley, p456-464 in Geological Conservation Review- Quaternary of Scotland eds Gordon J.E and Sutherland D.G.
Flanders Moss NNR web site lists details of events, guided walks, volunteering and bog restoration work, as well as links to leaflets and field guides: nature.scot/flanders-moss
Flanders Moss NNR Blog https://2bogsaswampandsomeislands.wordpress.com/

Harrison, J.G. (2003). A historical background of Flanders Moss. Scottish Natural Heritage Commissioned Report No. 002 (ROAME No. F02LG22)

3. Flanders Moss National Nature Reserve. Image: Lorne Gill © SNH.

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