Intertidal flat soils are true natural treasures. In geological terms, tidal flats are young soils occurring in areas which are regularly flooded by high tides and lie exposed at low tide. Only a few pioneer plants colonise these soils.
Plants and soil organisms on the intertidal flats are subject to a constant rhythm of falling dry and flooding, erosion and deposition of sediments, fluctuations of the water and soil temperatures, and exposure to currents and waves. During low tide, they are impacted by sun, wind and rain. During high tide they drift with the water current. In addition, the salt content of the intertidal soil significantly determines colonisation by soil organisms and plants. The salt concentration in soils of marine intertidal flats is about 35 grammes per litre of soil water, compared to only up to 0.5 grammes per litre in the fluvial area. While these extreme conditions may seem hostile to life, intertidal flats are actually quite species-rich. Due to periodic inundations, constant redistributions of sediments and wave strains, intertidal flats are suited as priority areas for nature and species conservation. As the borderland between land and the sea, they provide an ecological niche and hence habitat for many rare and often highly specialised plant and animal species.
Tidal flats occur on all continents and in all climate zones. Climate change is a particular threat to these soils. Of all intertidal flats of the world, the Wadden Sea along the southern North Sea represents the largest continuous area, covering about 3,500 km². Because of the special plants, animals and microorganisms which live there a large area of the German Wadden Sea is protected (Wadden Sea National Park).
Scientific research has shown that climate change will have an impact along coastal areas in particular, flooding land and water in the tidal flats which will have to regenerate elsewhere.
This year's Soil of the Year is under the aegis of the Free and Hanseatic City of Hamburg. In international soil classification, intertidal mudflat soils belong to the Tidalic Gleysols.