Marram Grass as a Natural Sea Defence

Marram Grass, Ammophila arenaria, at sunset in summer on Burnham-on-Sea’s beach
© Karen Netto (Andrews)

My winter walk on Burnham-on-Sea beach this weekend showed how well sand dunes can stand up to a week of high winds and heavy rains. It gave me an opportunity to contrast my plant finds with those of the summer in the same area. Marram Grass, Ammophila arenaria (Poaceae), is a plant that binds sand together and makes it possible for other coastal plants to colonise dunes. It dominates mobile dunes.

You could tell that the Marram Grass, Ammophila arenaria, had defeated the high tide by the irregular channel that ran along the base of the dunes. I was surprised at the heavy pieces of driftwood discarded so high up the beach by the sea. Sometimes they were large, long branches. They conveyed the power of the sea and tides to me.

A channel ran irregularly along the base of the dunes with heavy pieces of discarded driftwood
© Karen Netto (Andrews)

A tight network of Marram Grass roots was exposed where the sand had occasionally given way. The Marram Grass was already recovering with fresh green shoots. The next winds to blow up the beach will soon cover the roots over again.

No roots were exposed back in the summer.

There was stronger evidence of storm action near the sea wall. Debris had been thrown over the sea wall at both Brean and Burnham. The Burnham wall was just shorter than my standing height. (You can see pictures of the Brean sea wall in my previous ShoreSearch at Brean blog).

Vegetation Succession

There are a lot of different levels and vegetation stages in the sand dunes at Burnham-on-Sea. The variation in plant cover closest to the sea did not appear as great as in the summer. Some plants showed signs of burning by the salt spray. No doubt, many of these coastal plants will return in calmer weather next year.

Expanse of vegetation over water on walkway to the golf course in summer
© Karen Netto (Andrews)

Second Line of Defence

Sea Buckthorn, Hippophae rhamnoides (Eleagnaceae) offers the second line of defence against the sea’s incursions. It forms a tough, impenetrable thicket.

Other Coastal Plants

Euphorbia paralias, Sea Spurge (Euphorbiaceae) was another plant that had weathered the storm in patches protected by Marram Grass, Ammophila arenaria. It showed signs of burning from the salt spray, where it was not protected.

I found one bedraggled specimen of Sea Radish, Raphanus raphanistrum ssp. maritimus (Brassicaceae) during my walk at Brean. The fruits have previously confirmed the local subspecies. There was not any visible Sea Rocket, Cakile maritima (Brassicaceae).

I didn’t see any of the local Salsola kali, Prickly Saltwort either. It will no doubt reappear from the sand in time. It is well-adapted to the salty, sandy environment.

Salsola kali, Prickly Saltwort. © Karen Netto (Andrews)

After my post-storm walk, I returned home with extra admiration for the resilience of Marram Grass compared to man-made, concrete sea walls.

© Karen Netto (Andrews)

References and Further Reading (2018): Met Office issues warning for 70mph winds in Burnham area today. 8 December 2019. Last accessed 8 December 2019. (2018): Burnham-on-Sea, Berrow and Brean see damage in storms. 5 January 2018. Last accessed 8 December 2019

Field Studies Council (2016): Sand Dunes Succession. FSC Biology Fieldwork. A Level. Last accessed 8 December 2019.

Streeter, David et al (2016): Collins Wild Flower Guide. 2nd Edition.

Wildlife Trusts, The (?): Sand Dunes. Last accessed 8 December 2019

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