Lateglacial vegetaion

Holocene vegetation


Streetmap extract

Cyclotella antiqua


Huperzia selago

Aith Meadows

Significance: this site holds one of the most detailed records of environmental change on Shetland over the last 13,000 years

Aith Meadows is a SSSI for its wet-meadow flora. Hidden below the turf is up to 9 m of peat, silt and clay which has yielded an environmental record spanning the last 13,000 years after much detailed study (Birnie, 1981, 1993, 2000, 2005).

Diatoms indicates that all of the sediment column was laid down under fresh water. As at other low-lying sites, such as Loch of Spiggie, it is clear that sea level has not been higher than the present during the Holocene.

The base of the deepest core in the basin showed up to 30 cm of grey clay, barren of pollen and diatoms, deposited soon after deglaciation. This is overlain by 0.5 m of brown organic clay, with much more abundant organic remains. A diverse and prolific diatom community including Cyclotella indicates the presence of a shallow, clear water lake, possibly with seasonal ice cover. Pollen includes that of the aquatic Myriophyllum. Dwarf willow grew amidst a tundra vegetation on the surrounding slopes, with Oxyria on stream margins. The base of the grey clay has yielded an adjusted radiocarbon age of 12,950 yr BP, indicating that these organic sediments belong to the Windermere Interstadial warm stage.

The succeeding grey clay shows a reversion to cold conditions during the Loch Lomond Stadial. Diatom concentrations are very low and there have been some reworking of pollen from older sediments. Cyperacaeae and Salix pollen predominate.

The overlying Holocene sediments show the development of a grassland with Huperzia selago (fir clubmoss) before the re-establishment of birch woodland in the surroundings. The birch woodland is lost as a lake forms again in the Meadows, with Isoetes. Shallowing brought an invasion of sedges, grasses and the tall herb, Filipendula.

The first signs of human impact appear after 5000 yr BP. Occasional pollen grains of cereal size suggest cultivation of the surrounding slopes. Plantago lanceolata also appears, regarded as a marker for Neolithic farming. The latest peat layers show a reduction of tall herbs and ferns in a wet grassland landscapes, suggesting use as hay meadows.

Sea level rise now threatens this lowland and the margins of the peat bog are being eroded. The storm of 1900 swept away the Mill of Blosta and left boulders strewn over the Meadows. An earlier storm around 1680 also appears to have submerged parts of the Meadows (Birnie, 2005)