Peat is produced by decomposing organic matter, of mainly plant origin, in a place with little oxygen but saturated with water. In the Somme Valley, it has formed very slowly to between 0.5 and 10 metres thick, over several thousand years, at the rate of 0.2 to 1 mm per year. Peat has long been used as fuel, with the first evidence of its use in Glisy dating back to 1476, in a document that mentions peat-cutting rights granted to Jehan, Lord of Glisy (1), who lived locally. As the population increased in the 18th century, wood became rare and an alternative was needed. The use of peat developed in the 19th, then declined with the introduction of another, more efficient fuel: coal. The last application to dragonfly for peat-cutting rights dates back to 1915. In places where peat was cut, ponds formed. These peatland ponds are called "chés' entailles" in the local dialect, Picard. Looking at the pond just opposite, the straight bank on the other side is where peat-cutters lined up their planks for the last time, perhaps in 1916. They used to hold on to planks while pulling the peat out using a large shovel. (1) He served in the armies of kings Charles VII and Louis XI, and distinguished himself in several wars to become a Knight of the King's Order.
A rich and fragile area You are opposite a low-lying zone, origin unknown. It generally floods during the winter and spring and is connected to the network of ditches draining the grasslands and to the former arm of the Somme behind you. This wetland, with its ditch, fosters the development of herbaceous vegetation growing in waterlogged or even flooded land. These are megaphorbia (vegetable formations dominated by tall grasses) and sedgeland (plant formations made up of shorter plants, mainly sedge). They are the habitat of several endangered species. Endangered plants include pennywort, liver fluke, cyperus sedge, the marsh bedstraw, yellow meadow-rue and a type of blackcurrant, and endangered birds include the Bluethroat.
An environment in constant evolution This half-hectare area must originally have been deeper and certainly more often in water. Over the years it has gradually filled with accumulating plant matter (stems and dead leaves). Thus, aquatic plants and helophytes (aerial plants with their roots in water) have given way to shrubs, mainly willows that have invaded the area. They are cut back regularly. Otherwise, they would have already covered the whole area, culminating in a grove.
Much-needed conservation work Natural plant dynamics climax with bushes and trees growing over the wetlands, ultimately drying them out. This phenomenon is becoming increasingly widespread throughout the Somme Valley, with the abandonment of activities using reeds, shrubs and trees. As a result, the flora and fauna typical of open environments (reedbeds, sedgeland and prairies) are far less common, with some species now threatened with extinction. However, work can be undertaken to ensure their preservation, clearing wetlands and ditches, or stripping away topsoil to improve moisture levels). You have a good example right here. Glisy council is committed to the preservation of biodiversity. Several low-lying areas and marsh ponds are undergoing extensive work.
A target species The Greater Spearwort is a beautiful buttercup that flowers from June to August around the stream. It is legally protected and therefore cannot be picked or damaged. It is one of the treasures of Glisy Marsh. Preserving it is a real challenge because it needs water, mud and shade in very precise proportions.
MARSHLAND KID
Ech'marister
"Our teacher is a botanist. I like this word, it sounds really scientific! So he said he could recognize most plants. He’s drawn up a list of those in the marsh. It is a book with a picture of each plant that grows in the region. He let me borrow this book and, with Rémy, I have had fun trying to find each species. If you take the trouble like us to look around carefully, you will be able to see all sorts of flowers, plants and small animals while out for a walk. Let’s have a look at this one. Hum, it’s a pretty plant, small white flowers. It smells of carrot when you crumple its leaves. I know what it is! It’s a wild carrot.
Green-veined white - Pieris napi
Tadpole-Treated Willows - Salix
Wild carrot - Daucus carota
Greater Spearwort - Ranunculus lingua
White-legged Damselfly- Platycnemis pennipes (Zygoptera)
Marsh Sedge - Carex acuformis
Bluethroat - Luscinia svecica
Grass snake - Natrix natrix
Brown Hawker - Aeshna grandis (Anisoptera)
Hemp-agrimony - Eupatorium cannabinum
EVOLUTION OF WET DEPRESSION 1945 1985 2015 Unless we carry out conservation work: 2035