Tidal flats - Soil of the Year 2020

Also every year the patronage of the World Soil Day changes between the federal states, this year the Free and Hanseatic City of Hamburg takes over and presents the tidal flats soil in the state representation in Berlin. It is important to portray soils and their function in the balance of nature and thus to approach people in order to achieve sustainable use and hence protection of this natural and vital resource. Characteristics, origin, relevance for humans, endangerment, occurrence - these are all aspects which should be illuminated.

Tidal flats can be found on all continents and in every climate zone. In the international soil classification, tidal flats are classified as Tidalic Gleysols. They are not only found on coasts, but also in river tidal flats. The geologically young soils are constantly changing, depending on the current and sedimentation process, mudflats or firm sandy soils (with the typical ripple marks) can develop.

In the tidal flats of sea coasts, up to about 35 grams of salts per litre of soil water occur. This makes the soil appear rather hostile to life. However, the tidal flats are very rich in species and forms and provide a habitat for a large number of species - be it seals and harbour seals, tidal flat and resting birds up to the smallest in the area - the lugworm, cockle, sand flea, mussels or the tidal flat snail.

Due to periodic flooding, sediment shifting and wave loads, the soil of the year presents itself as a priority area for nature and species protection. With every flood, mineral material (sand, silt and clay) and organic material (plankton, unicellular algae, plant and animal remains) are deposited. Mudflats are threshold floors that connect underwater ocean floors and land floors. They are therefore mediators between the anoxic and oxic life worlds, the different groups of organisms in this habitat survive high demands. As a transition zone between land and water, many rare and often highly specialised plants and animals can be found here. Thus the mudflats act as an ecological niche.

A tidal flat soil develops into raw marshes if increasingly dense plants such as the upright glasswort or the cordgrass gradually grow in the border area between sea and land soils (siltation zone). These stocks act as sedimentation traps for marine sediments, which are washed up during high tide and deposited as mudflats. Gradually, the area grows out of the daily flooding, and other saltwater tolerant plant species such as beach aster, beach lilac and andelgrass settle. A raw marsh soil develops.

The largest contiguous mudflat area is located on the southern North Sea coast (approx. 3,500 km²). The sensitive ecosystem is increasingly being disturbed due to various pressures such as pollution, high nutrient inputs, oil spills and intensive tourism. An important step was the announcement of a UNESCO World Heritage Site. In this case the countries Germany, Denmark and the Netherlands have committed themselves to the protection, development and nature education. In addition, the establishment of versatile nature reserves and mudflat national parks to protect the habitat tidal flats as a sensitive location and to ensure careful use.