Onkruidenier projects

Can a soil still contain traces of a flood after 100 years?

The flood of Waterland, 1916

Commemorative year 2016 marks exactly 100 years since a major dike breach in Amsterdam North flooded the peat landscape of Waterland. The 1916 flood was an unnamed storm surge until a few years back, but has been renamed Waterland Flood in the 2016 commemorative year. The Zuiderzee burst at the seams, leaving a trail of destruction in its wake. For months, pastures were under water. To tangibly reclaim the memory of this breach in the Waterland landscape, the Onkruidenier began a search for the salt of the flood. Can we still find the Zuiderzee salt from 100 years ago? And which salt-loving plants indicate the salt in the landscape? In order to find salt-loving plant species, we went on an expedition with scientist and biologist Claud Biemans along the Durgerdammerdijk in Amsterdam Noord and got in touch with ecologist Ed Buijs, working for the municipality of Amsterdam.

Claud has done counts of plant species in this area for Floron in the past and was happy to take us on a tour. During the explorations with Claud, we encountered the true heemst near Durgerdammerdijk 114. How does this lost and lonely heemst get salt? And does the plant know how to hold its own in a tight green slope of mowed grass? The location of our find gave rise to more questions than answers.

The heemst plant became an important stop during expeditions on bicycles in Waterland. The resident of the house at 114 Durgerdammerdijk became curious as to why we kept stopping at ‘her’ plant. We got talking to the lady, who is almost a hundred years old and has been taking care of the marshmallow plant for as long as she could remember. She knows exactly when the council’s mowing machine is coming by and has been making sure the plant is not mowed away for years. Because of this bond between the heemst and this lady, we can still find the plant among the grass in the dike.

The salty influence of the sea reaches much further than we assume. In the transition between water and land, freshwater and saltwater systems meet. Here it is brackish. The perfect habitat for heemst, which loves to grow in brackish reed marshes. These brackish water systems are becoming extinct in the Dutch landscape; a mix where the influence of the sea with its tides has been reduced to hard boundaries in the form of dykes, dams or flood defences.

Looking at the distribution of heemst in the Netherlands, many sightings are noted in Zeeland and along the coast. Heather, also known as marshmallow in English, is an indicator of salt in the soil. After the flood in Waterland, specimens of heemst have also been found in Waterland. Especially along the old sea dyke in Durgerdam and on the side of the North Holland Canal, many specimens have been found. Completely captivated by the English name of heemst, a search for the marshmallow’s origin began. This took us back to the times of the Egyptians, who collected the roots of the holly along the salty Nile banks. The juice from the roots of the heemst was extracted by pounding them. This heemst root juice was then mixed with egg whites and honey.

An exploration in the peat meadow landscape of Waterland with ecologist Ed Buis led to a long-standing fascination with cattail. The wonder began during a conversation about the contradictions we found in Waterland’s landscape in relation to the artificially low water table in the polder. When the water table is kept low, it has benefits for grasslands and cattle breeding. However, a lower groundwater level causes the faster degradation of the peat package, resulting in land subsidence and CO2 emissions. Local residents often tell us they live on thick water, referring to the soft and black watery peat pack on which they live. A landscape that faces limited sustainability due to its current use. How long can this agricultural landscape sustain itself?
When water levels are kept higher, the composition and use of the grasslands changes. Water and plants that love it, such as the cattail, are promising defining building blocks for the future of this landscape, says Ed Buijs.

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