Why Is That Beach Turning Into a Meadow? Shell Sand and Wind

The sand of an ordinary beach is mostly ground-up rock and is slightly acidic or neutral, but on certain exposed north-western coasts the seabed is so rich in shellfish that the sand is largely crushed shell instead, which is calcium carbonate. Strong prevailing winds drive that shell sand inland over low-lying ground behind the beach, where it settles and mixes with the peaty soil already there. The result is a flat sandy plain that is strongly alkaline where everything around it is acid peat, which is a chemical reversal of the surrounding landscape and is the whole reason the place is unusual.

The features that define it are all consequences of that origin:

• •Shell sand rather than rock sand, giving lime-rich alkaline soil
• •A flat plain a metre or two above sea level, not high dunes
• •Very shallow soil over sand, so drought comes quickly in summer
• •A water table close to the surface, with wet hollows in winter
• •Low nutrient levels, since sand holds little
• •Exposure to salt spray, which restricts what can grow

A visitor in July sees a solid carpet of flowers across whole fields, with counts of forty or more species in a square metre, and that richness has an unromantic explanation. Low nutrient levels prevent any vigorous grass dominating and shading the rest out, which is the usual reason improved grassland has few species. The lime-rich soil suits plants that cannot grow on the surrounding acid peat. Traditional management maintains it precisely, with small-scale cultivation of oats and rye using seaweed as fertiliser, fallow periods, and cattle grazing in late summer after the flowers have set seed. Remove any part of that management and the display disappears within a few years, which has happened wherever farming intensified or stopped.

The plain supports wildlife that has declined severely elsewhere, which is the other reason it attracts attention. Ground-nesting waders breed there in densities far above anything else in Britain, since the damp hollows provide feeding and the open sward provides nesting, and lapwing, dunlin, redshank and ringed plover all occur together. The corncrake, now almost gone from the rest of the country, survives in the tall vegetation of the field margins and depends on cutting being delayed until the chicks can run. Great yellow bumblebees and several other rare insects feed on the flowers. Each of those depends on the same traditional farming rather than on the landscape alone.

This landscape occurs in quantity only along the western coasts and islands of Scotland and Ireland, which makes it internationally rare and gives those countries a disproportionate share of the responsibility for it. The threats are specific. Abandonment allows rank grass to take over, since without grazing and cultivation the sward closes up. Intensification with artificial fertiliser raises nutrient levels and destroys the diversity directly. The surface is held together only by plant roots, so vehicles, rabbits or overgrazing can break through and start a blowout that the wind then enlarges rapidly. And it sits barely above sea level on an exposed coast, so rising seas and stronger storms threaten the whole formation.

Wind drives crushed shell sand inland over peaty ground, producing a flat lime-rich plain in the middle of an acid landscape. Low nutrients stop any grass dominating, so forty or more flowering species can share a square metre. Traditional small-scale cultivation with seaweed and late grazing maintains that, and the display vanishes within a few years if farming intensifies or stops.