Talk: Tuesday 10 October 2017 Clive Chatters:Saltmarshes

Saltmarsh:Clive Chatters

With saltmarshes on their doorstep, members of the society were delighted to hear Clive Chatters' talk, and the subject of his latest book, on this topic. Clive is well known as a botanist and a former chairman of the National Park and Hampshire and Isle of Wight Wildlife Trust.

Saltmarshes are created when salt, water and vegetation combine. There are differing types of saltmarsh according to variations in these elements. In estuaries peat bogs can be formed when tides hold back the flow of fresh water and debris build up. The marshes at Kentra in Argyll in a sheltered bay are created from seawater strength salinity, while the marsh at Ainort on the Isle of Skye becomes less saline at times of heavy rainfall.

The salinity creates a tough habitat for vegetation, and plants need to be able to adapt to extreme conditions. Plants like the glassworts have adapted superbly, rather like desert plants, reducing flowers and leaves to simple scales. Annual and perennial plants can survive in saltmarshes. In areas of lower salinity trees like Alder and willow can survive but they die if the salinity increases. In the Lymington reedbeds there is evidence of the willows dying as a result of rising tides. Once a peat bog has formed, caused by the build up of land debris held back by the tide, the soil will become less saline and other species will be able to move in. Peat bogs were once a very common feature but now only exist in places like the Somerset Levels and Norfolk Broads. In fact London was built on a former saltmarsh.

Saltmarshes have long been used as grazing land. There is evidence of Auroch, Elk and deer grazing on the marshes after the Ice Age and this grazing is important to the quality and character of salt marshes. The quality of the grass is much better than much grazing land and the lack of parasites is an advantage to animals. The Lymington marshes are grazed to this day.

There is evidence for a salt industry as far back as Roman times. The pan evaporation technique is familiar from Lymington but saltmarshes are not confined to the coast. There is a notable inland one at Pasturefields, Staffordshire, which is a nature reserve, where water flows over salt deposits underground, and there is even a salt lake at Neumanns Flash at Northwich, where the land appears white.

One of the most abundant plants of the saltmarsh is Carex maritima but others include Sea Plantain, Sea Milkworts, Sea Heath and many varieties of sea lavender. The dominant grass in the Lymington marsh is Spartina anglica, a grass that didn't exist 200 years ago. It is a hybrid of Spartina alternifolia and S. maritima and in around 1840 it became a superweed and colonised the shores of the Solent. Because of its ability to raise the surface of mudflats it was exported all over the world, especially to China, to create more land for agriculture. However, it is not stable, it can grow fast but soon loses vigour.

Saltmarshes are always on the move. At Lymington it is reckoned that 10m a year is disappearing due to changing sea levels and urban pressures but the saltmarsh in the River Test estuary is increasing by 1.4m per lunar month, and in the more contained Langstone Harbour, where originally Eelgrass was replaced by Spartina, Eelgrass is now returning as the sea level rises and land becomes submerged again. The sea wall at Selsey has been abandoned and saltmarsh is returning, doing the sea defence job naturally and for free.

Charles Darwin, on his voyage on the Beagle, travelled to see flamingos and the salt works in the Andes and noticed the flamingos' food, the Brine Shrimp, living in waters of incredible salinity. He observed the ability of creatures to inhabit almost any part of the universe. However, unknown to Darwin, another species of brine shrimp (now extinct) was already at work in Lymington. They were used in the salt industry to clean ponds as part of the manufacturing process and were known as clearer worms. The sea salt industry collapsed in the 1860s as it became cheaper to mine salt and the Lymington saltmarshes became obsolete. Their importance was recognised and the land was purchased by Hampshire County Council between 1973 and 2006 and is now an important nature reserve. (AM)

Indoor meetings of the Society take place at the Lymington Centre throughout the winter months and field meetings take place all year round. See for details. Visitors are always welcome.