Saltmarsh and mudflats
What is it?
In coastal areas sheltered from waves, slow-moving tides gently lap over a flat expanse of fine mud. Covered at high tide and exposed during low tide, mudflats support a wealth of life; bristle worms, bivalves and mud snails - all food for flocks of wading birds.
Towards land, in the absence of manmade structures, mudflats become saltmarshes - first vegetated with succulent samphire and then with cord-grasses, sea purslane, sea aster and sea lavender as the mud becomes drier. Creeks fan out through the saltmarsh, channelling the water up to flood the lower marsh at high tide and draining away rapidly as the tide drops.
Why is it like this?
Mudflats form within the shelter of estuaries or natural harbours, where fine silt and clay sediments settle. The mud is very fertile thanks to its high content of organic material, making mudflats ideal for hosts of filter-feeding and scavenging invertebrates.
When the accumulating mud rises above the water surface saltmarsh plants can colonise. These capture more sediment and allow the marsh to keep building for as long as it is still low enough to be flooded by the higher tides.
Distribution in the UK
Found in sheltered estuaries and natural harbours around the UK.
What to look for
Visit southern saltmarshes in late July and August to see lilac-tinged expanses of flowering sea lavender – look out also for the pretty, soft leaves and delicate pink flowers of the scarce marsh-mallow at the very top of the saltmarsh. On the grassier, grazed saltmarshes of north-west England and Galloway, huge flocks of wintering wildfowl can be spectacular - visit the east coasts in late autumn and winter to see tens of thousands of wintering waders pushed by the rising tide onto the saltmarshes to roost.