The salt meadows in the Wadden Sea

Marco Brodde, Fiskeri- og Søfartsmuseet & Bent Jacobsen, NaturKulturVarde

tide & laNdScape

translation: Nanna Mercer, Sirius translationpage 1 of 4

The salt meadows and their plant life can be studied from May to October, with most species blooming in July.

tHe Salt MeadOWS iN tHe WaddeN Sea aN eteRNal StRUGGle aGaiNSt tHe Salt

The salt meadows are one of the characteristic types of landscape in the Wadden Sea and an example of the fascinating interplay between plants, insects, birds, landscape and the doings of man.

The term salt meadow reveals that this nature type is found close to a coast. The term, meadow, is ac-tually connected to man’s use of the area in que-stion. A meadow will only remain as one such when the vegetation is kept down by either grazing or hay harvesting. When a meadow is not being used it will develop into a bog, a swamp or a thicket.

A salt meadow is often affected by the salt from sea flooding or from the air. In the Wadden Sea, the ef-fect of the salt is greater than in the salt meadows on the eastern Danish coasts, and there is generally a greater dynamic. The tide and the storms are instru-mental in the creation of new salt meadows, while others erode at a speed not seen at other places in this country.

The daily deposits of fine-grained material that oc-curs when the tide rolls across the wadden ensure that the sea floor, so to speak, is raised slowly close to the coastline. When the level is sufficiently eleva-ted, the first plants start showing up on the new land. The more plants that take root in this zone between sea and land, the more sediment can be retained

from the water. The dance has started, the level is raised further and other plants join the line for a chance with their dance cards and a new piece of salt meadow has been created.

Grazing animals have several functionsIn the outer zone of the salt meadow, the one closest to the coast, the effect of the salt is greatest and ge-nerally decreases higher up in the terrain and yet, it is not that simple. Hollows in the upper part of the salt meadow, can turn out to be much more affected by the salt, when a flooding has left a small and iso-lated lake, a so-called salt pan, where the water eva-porates, but leaves the salt.

The effects of the salt in the meadow, stops many plant species from immigrating. Thus, taller bushes are kept at bay and the vegetation will consists of only the characteristic salt meadow plants. Howe-

ExpEriEncE thE salt mEadows in ...

AUTUMN WINTERSUMMERSPRING


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ver, reeds can immigrate and change the meadow to a so-called reed swamp, a nature type which is of great importance to reed forest birds such as the reedling or the marsh harrier, but far more species-poor than the light filled salt meadow.

Grazing or simply the mere appearance of livestock furthers the biological diversity on the meadow. For one thing, grazing secures light for a long list of plants and insects, and for another animals tramping around creates small recesses in the soil, where specialized species can find room to grow. As well, the animals inadvertently move plant seeds around and in this way ensure propagation. The presence of sufficient amounts of light on the cropped pastures leaves the meadow rich in insects that attract typical marshland birds such as the lapwing and the oyster catcher.

impressive adaptabilityPlants adapt in different ways to life on the salt mea-dows.

The beautiful sea starwort collects the salt in older leaves that then die and wither, while plants like sea lavender and rice grass try to get rid of the salt through glands on the underside of their leaves. This can be both seen and tasted by moving a finger over, or rather underneath, a leaf on a summer day when the evaporation of water from the glands is greatest

and the need to secrete salt on the rise.

Other plants like the annual glasswort dilute the salt simply by growing, since the plant tissue contains watery cells. After only one season the glasswort must give up. Success is sure, for the plant has run to seed that will be spread effectively by the tide.

Paradoxically enough, the plants in the salt mea-dows must be able to retain a larger concentration of salt in their cells than what is present in the sur-rounding soil. If they could not, water from the plants would simply wander into the soil to maintain the salt balance. The plants must therefore be able to regu-late the salt concentration, for a concentration that is too low means a lot of water while a concentration that is too high means salt poisoning. Life on the salt meadow is not easy.

Add to that the fact that the plants must be able to stand, knee-deep, so to speak, in water or even at some point, be completely flooded. Not only are the

Rice grass try to get rid of the salt through glands on the underside of their leaves.

The insects on the salt meadows or the Wadden living with flooding and an oxygen-poor environment are smaller than the average insect. Thus, they have a low metabolism and a shorter oxygen transport time. The insects can also carry an oxygen depot, for example under their wings.

small crittErs


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oxygen conditions poor in water, but the flooding re-duces the amount of light which leaves photosynthe-sis almost on standby. Flooding also wears on the plants, which makes it a challenge to hold on to the soil that erodes by the continual movement of the water.

The plants compensate for the lack of oxygen in the waterlogged environment by developing many ex-tra small roots with the primary function of weaving through the topmost layer of soil, where the greatest amount of oxygen is found. Some plants are even more subtle in their ability to send oxygen from the above-ground parts of the plant down to the under-water roots. This ability requires a certain type of air tissue that is characteristic for swamp or salt mea-dow plants such as the common reed.

The physical wear and tear caused by repeated flooding result in different strategies. When tiny frag-ments of the salt meadow grass are spread, say, by cattle tramping around, each individual piece of grass will take root and quickly send runners out across the soil.

dikes and designed environmentsThe Wadden Sea contains some of the most valua-ble salt meadows in Denmark. It is almost impos-sible to imagine the incredibly large meadow areas that were spread across the region up until the 20th century. By diking the marsh on the mainland, large areas of tide-dependent salt meadows from Esbjerg to Højer lost their connection to the sea. Today, salt meadows are found exclusively on the islands or in front of the dikes. In Margrethe Kog, the natural pro-cesses have been imitated by pumping saltwater on the otherwise diked, fresh-water hinterland, where it is still possible to find salt-tolerant plants and the inter-reliant bird life.

After only one season the glasswort must give up.

Many of the insects on the salt meadows carry an inter-nal tide table. Even when in a laboratory far from the coast, they know when the tide rises and falls, which is rather remarkable considering that the tide table shifts every day. Some insects have even managed to synchronize their egg laying with the spring tide that happens every two weeks.

insEcts and thEir intErnal tidE tablE


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Some of the vaster salt meadow areas in the Wadden Sea are found on Skallingen and on Grønningen on Fanø. In both places it is pos-sible to experience, in the best way possible, the different plant zones from the elevated dunes to the low salt affected meadows. Be considerate of the grazing animals, for they have an impor-tant function out here. The salt meadows and their plant life can be studied from May to Octo-ber, with most species blooming in July.

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NaturKulturVarde Gl. Skovfogedbolig Roustvej 111 DK-6800 VardeT: +45 75 22 22 50E: [email protected] W: www.naturkulturvarde.dk

VadehavscentretOkholmvej 5 Vester Vedsted DK-6760 RibeT: +45 75 44 61 61E: [email protected] W: www.vadehavscentret.dk

Naturcentret TønnisgårdHavnebyvej 30 DK-6792 RømøT: +45 74 75 52 57E: [email protected] W: www.tonnisgaard.dk

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The salt meadows in the Wadden Sea