Windscapes

Regular readers of the blog, or indeed anyone who has had power off for several days,  will know that wind has been a bit of a feature of our lives lately. Power cuts, a huge amount of damage to trees and a massive clear-up operation have been left in the wake of three big storms this winter. But, in truth, wind is always a feature of our lives at Forvie and you only need to look at the landscape to see this.

Aerial picture of dunes (C) Ron Macdonald

It’s most obvious at the estuary end of the reserve. Forvie actually has the 5th largest sand dune system in the UK and there’s times it looks more like a desert landscape. It certainly feels like it when you’re trudging through soft sand and maybe a better title for this blog would have been ‘sandscapes’. The wind is a great part of what shapes these dunes and, this winter, with a series of gales, we can see the landscape reformed on almost a daily basis.

Drifting sand and marram grass on the dunes at Sands of Forvie NNR.
©Lorne Gill
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It is part of the wonder and challenge of Forvie. The mobility of the landscape is what makes it special and it’s easy for us, with a human outlook, to view anything that changes like this as a bad thing. It’s too easy to see the negatives – the buried village, our endless battles to keep the tern fences standing and clear of sand – but we should perhaps focus on the fact that this wild, dynamic landscape still exists in world of intensive land use and increasing human population. So much of our coastline has been built on, farmed or generally stabilised that places like Forvie have become increasingly rare.

Ythan estuary

So, how does sand move? Well, it gets delivered to Forvie by the tides, the eroded remains of land and mountain washed down rivers to the sea. Once washed up above high water mark, it is at the mercy of the wind. Normally, in this part of the world, our prevailing wind direction is from the south-west, so the sand tends to move north-east. It does this is three main ways: suspension, saltation and creep.

Sand eroded around tiny pebbles leave them stood on a mini pillar of sand

Suspension is the dramatic one. This is sand which has been picked up by the wind and is being blown along. Think of a really rough day at the beach, when the sand stings your skin, gets in your eyes and is generally unpleasant. The sort of day that fills every nook and cranny of your clothes with sand and when you shake, a shower of sand goes all over your newly-hoovered carpet. A sand-blasted, wind-scoured, battered-by-the-weather day. But only 1% of sand moves like this. Most moves by a process called saltation, which is where sand grains bounce along the ground. The wind is strong enough to move it, but not pick it up and blow it it for any great height or distance. And the final way sand moves is creep, where bouncing sand grains knock into other ones and move them.

Sand blow

Sand movement can sometimes be fast and dramatic. You can see how much sand has buried an earlier snow shower here.

Sand and snow

You can usually tell which way the wind as been blowing when you look at a dune. On the side where the wind is coming from, a dune will usually have a long, shallow slope. But, on the sheltered, leeward side, it will usually have a steep slope.

Leeward side of dune

As you move inland, our dunes become more stable as they become covered with marram grass. Now, the reserve staff find this a fairly unlovable plant, as its waxy, rolled, water-retaining leaves come to a needle point that will cheerfully stab you and/or break off in your skin. Walk through marram all day, even in fairly thick trousers, and your legs will look like you have a rash, with lots of itchy, pinpoint pricks. But it is the plant that it most resilient to the harsh, salty, free-draining sandy conditions and its amazing root system is what starts to stabilise the open dunes. It soon becomes the dominant plant on the dunes.

Marram roots

Yet further inland, the marram gradually starts to disappear as it gets outcompeted by other plants. By now, there is more humus in the soil and it retains more water, so other plants can get a foothold. To the north of Forvie, heather, crowberry and creeping willow cover the now stable dunes, while, in the dune ‘slacks’ (wet hollows), plants like bird’s foot trefoil thrive and bloom.

Bird’s foot trefoil

In spite of the prevailing wind here being south-westerly, this winter, we have seen a series of north-westerly and westerly gales. Remember Arwen? And Mailk, and Corrie? You can see their effect if you look across the river from Newburgh. The ‘big dune’ has been flattened and tonnes of sand have been moved to the south east. This has led to big changes on the edge of the ternery, where a lot of the shingle has been buried by sand. It’ll be interesting to see what this means for the terns, as little terns like nesting in shingle and this is now under sand. It’s all part of the natural process of the site but is an example of the challenges of living in a dynamic landscape. Many years ago, this wouldn’t have posed a problem for the birds but now there is virtually no undisturbed-by-people coastline for them to move onto. Let hope the wind shifts back to the south-west and scours clear some shingle before they arrive back in April. And it’s not often you’ll hear the reserve staff wish for more wind!

Blown sand burying marram grass

Big dune