Beaches and strandlines
What is it?
A beach is a strip of land next to a big body of water made of loose sediment (typically sand or stone). Between tides, the sand is pummelled twice a day by waves, keeping the sand mostly bare, home only to a small range of invertebrates such as sand hoppers, cockles and lugworms. Waves carry debris including seaweed and driftwood, accumulating just above the limit of the highest tides; forming the strandline. Here, just beyond the normal reach of the waves, a few plants including oraches, prickly saltwort, sea rocket and sea sandwort can form a patchy ribbon of vegetation.
Above this high tide line on shingle beaches, large, deep-rooted perennial plants form an attractive display, typically including yellow-horned poppy and sea kale, with mats of sea campion, sea pea and sea mayweed. Further inland, more settled vegetation including lichen-rich grassland and heathland and even scrub and woodland develops on stabilised shingle. Sandy beaches play out a different story, where sand dunes can extend several hundred metres back from the beach with a constant supply of wind-blown sand and enough undeveloped space.
Why is it like this?
Waves battering against hard shorelines gradually erode them. The resulting sediment shifts with tides and currents, eventually washing up again onto the shore forming fringing beaches, spits, barriers or rounded forelands (known as nesses in East Anglia). Shingle beaches are only found on exposed coasts with the right sediment and the waves have enough energy to shift the shingle. The natural material accumulated at the strandline provides just enough nutrients and retained water for a few plants (whose seeds are also washed up) to gain a foothold for a while.
Sand and shingle beaches are dynamic places, constantly moving and reshaping as tides and storms shift the substrate about. On wider beaches, material accumulates in stable areas no longer reached by the sea, where good drainage supports healthy vegetation and eventually, stunted woodland (rare on shingle beaches). On sandy beaches, settled debris and plants capture blown sand; the first step in the creation of sand dunes.
The tide also brings flotsam and jetsam, including plastics: mostly packaging and production pellets (nurdles). It is estimated that there are over 5 trillion pieces of plastic floating in the world’s oceans – some lost overboard or blown and washed in from land, causing harm to wildlife and entering the human food chain.
Distribution in the UK
About one third of the UK coastline is fringed with sand or shingle beaches, although much is too mobile to support vegetation. The UK’s vegetated shingle beaches in particular are of global significance.
What to look for
Look for breeding ringed plover, oystercatcher, terns and gulls. On shingle in the north (including Northern Ireland) look for the pretty blue and pink flowers and silvery green leaves of oysterplant, while sea-pea is particularly characteristic of East Anglian shingle. Along the south coast, you might be lucky enough to find scaly cricket under debris, also likely to be home to a range of other invertebrates including springtails, woodlice, beetles and spiders and mites.
Committed beachcombers can find ambergris (a waxy substance formed in sperm whale intestines used in perfumes), amber, and ‘sea beans’ such as coconuts and sea hearts that may have travelled for months or years on the ocean currents. More common findings include mermaid’s purses (the egg capsules of sharks, skates and rays), the spongy pale masses of whelk egg cases, cuttlebones (the flat gas-filled ‘bone’ that cuttlefish use to control their buoyancy) and the moulted shells of crabs.
Over-stabilised by sea walls and groynes, and halted by development (including sea defences, industrial development, housing, and even golf courses or forestry plantations), sand and shingle beaches are often prevented from developing naturally - from mobile sand and shingle nearer the sea to fully vegetated communities inland. The mobility of beaches needs to be maintained to let this natural succession take place, and it is vital that we strategically approach the need to allow room for beaches to move inland with sea-level rise.
Beaches are of course much loved by visitors, and at popular sites recreational pressure needs sensitive management to ensure that the fragile vegetation is not destroyed, or prevented from developing, and that breeding birds are not disturbed by people and dogs. Cleaning is an important part of this, but mechanised beach-cleaning should be avoided as it removes the top layer of sand and the strandline, while compressing the beach, badly damaging important invertebrate populations.