Natural influences

‘In winter, and even until the middle of May, the western division or machair, is almost a desolate waste of sand’

James Macdonald (1811)

Over the last 8,000 years or so, sand blow has been vital in maintaining the machair landscape and many of its characteristic plants. Blowouts and severe erosion can, however, occasionally be catastrophic and Skara Brae vividly demonstrates how dynamic the landscape can be. Even in recent times changes in sea level and climate, or inappropriate land use, can damage the plants that bind the machair, triggering further sand movement.

In the winter months large areas of the machair can be flooded, protecting it from wind erosion and also providing good feeding grounds for wildfowl. The machair lochs are rich in nutrients and support an interesting range of water plants (including the rare slender naiad), many invertebrates and large numbers of wintering and breeding waterfowl.

Most machair has formed where it is exposed to the full force of Atlantic storms. Just offshore, dense forests of the seaweed, kelp or Laminaria help break up the force of the waves. Every winter huge quantities of battered and broken kelp (often referred to as tangle) are thrown up by the waves and form a natural sea wall along the dune edge. The soft, sandy machair shorelines therefore gain essential protection from this stout leathery seaweed – both living and dead.

Sand and storms

On 19th February 1749, the Reverend John Walker recorded how a hurricane from the northwest, coinciding with high tides, breached an isthmus in Barra, undoubtedly Eoligarry where the airport building now stands. It nearly happened again in 1816.

In 1756 the houses of Baleshare in North Uist were buried in sand up to their roofs. Indeed the name ‘Baile sear’ means the eastern town, which implies that there would have been a western town ‘Baile siar’. The village of Hussaboste is mentioned in a document dated 1389 and was said to have been washed away in the 15th century. It is remembered locally as an offshore reef just west of Baleshare called Sgeir Husabost, while local tradition maintains how it was once possible to journey across to Heisgeir (the Monach Isles) by horse and cart.

Human influences

It must not be imagined that this Hebridean sand is on a barren soil, it being destitute of vegetation only when drifting loose. When in some degree fixed by moisture, or the interspersion of pebbles and shells, it affords excellent crops of barley, when manured with sea-weeds, and its natural pastures are by far the best.

William Macgillivray (1830)

The rich machair grassland behind the dunes appealed to prehistoric settlers. The inhabitants of Skara Brae were Neolithic farmers; sheep and cattle bones have been unearthed from their middens along with the remains of barley. The light sandy soils were easily tilled and ploughmarks have been uncovered in machair, such as near a Neolithic settlement in Westray. These early ploughs would have scratched the surface rather than turn a furrow and it is likely that these early farmers used seaweed as fertiliser.

The machair is still farmed to this day and although agricultural methods have obviously progressed considerably, seaweed is still a vital component. The application of cast tangle before ploughing adds important organic matter to machair soil that not only enriches it but helps to bind it together, hold moisture and resist wind erosion. It is also vital to the long-term stability of the machair pastures. In much the same way, dung from stock, especially cattle, being wintered out on the open machair, helps humus to form.

The kelp boom

The harvesting and collection of seaweed occurred extensively during the late eighteenth – early nineteenth centuries. The seaweed was burnt to produce a high quality soda ash that could then be used in the manufacture of glass, soap, bleaching agents and gunpowder. During the Napoleonic wars prices peaked at around £25 a ton. Where Clanranald earned only £5,297 per annum in rent from his South Uist tenants, he was making nearly twice that from his kelping enterprise.

Crofters spent more time processing kelp than tending their fields, diverting seaweed from the land to maximise their income. The population of South Uist increased by 200% during the kelp boom, and in Tiree rose from 1509 to 4391!

In 1811 James Macdonald reported how ‘the Uists have in many places lost up to one quarter of a mile in breadth by sand drift and sea encroachment’. Exploitation of kelp was exposing the machair to excessive erosion.