“Like sand on the beach” – nothing of the sort!

Sand as far as you can see, millions of square metres, flat or piled up in impressive dunes:  The gigantic sand mountains of the Sahara are up to 100 metres high, can add up to more than one-million tonnes of sand and shine yellow, beige, light grey and orange. In other regions of the Earth, sand is snow-white, dark-grey, speckled of even blood-red – in innumerable shades of colour that the naked eye can hardly appreciate, depending on which stones were involved in the formation of the sand thousands of years ago.

But sand has more than just an aesthetic attraction: Along the coasts and on the seabed, it serves as a playground for thousands of living creatures. And it’s a bulwark against the lashing waves, weakens their unrelenting force, thus protecting the coastal inhabitants. But it is precisely this ecosystem that is endangered in many places: The sand is disappearing – it is being exploited in huge quantities. For concrete, glass, computer chips, paper, cleaning agents, toothpaste, cosmetics and many other things – it is an indispensable component. According to statements made by the United Nations Environment Programme (UNEP), no other resources, only with the exception of water, is being consumed in such large quantities. “Sand, rarer than one thinks” was hence the title for a dossier released by the Programme in 2014. Due to the enormous demand, costs for sand have increased explosively in recent years – and it has become a subject of research for scientists who are searching for alternatives.

In Saudi Arabia, an entire coral reef is dying; in other regions algae and seaweed are suffocating 

The consequences of sand mining for the ecosystem are often times devastating: the suction nozzles stir up the sediment along with its inhabitants and leave behind huge holes in the seabed.  And the oceans react sensitively to changes: The dredges disturb a complex sequence of layers – from the water surface down to the sediment.

“Even the procedure of suctioning up sand represents a disruptive factor; sand-dust trails spread out for kilometres around the mining site, the sediment is re-deposited at other locations where it really doesn’t even belong, and where it changes the composition of the sediment or buries the ground organisms living there,” says Martin Wahl. He is a marine biologist at GEOMAR Helmholtz Centre for Ocean Research Kiel, and a member of the excellence cluster “Future Ocean” that is based there. In Saudi Arabia Wahl observed how an entire reef is dying, because foreign sediment is covering and suffocating the coral due to sand mining. In other regions, algae and seaweed are being covered with sand and suffocating.  In his area of research – marine ecology – Wahl also busies himself with stress factors in the ecosystem. “Algae and seaweed are essential for the ocean’s hygiene. They bond carbon dioxide (CO2) and produce oxygen. If an area of ten square metres is suctioned up, that does not represent a problem – but if it is ten square kilometres, that becomes a big problem.”    

When beaches are dredged until empty, there is no more sand to be washed back into the ocean; regeneration is hardly possible

Animals that live on the seabed – snails, worms, echinoderms or small crabs – take their nutrition from the upper layers (flooded with light) of the ocean. This so-called Bentho-pelagic coupling – the intake and discharge of nutrients at the interface between sediment and water – is an important process in the global carbon cycle. In this manner, thus, the carbon dioxide on the ocean’s surface bonded by photosynthesis is transported into the sediments on the seabed. If the living conditions for the animals in the sediment deteriorate, they will migrate. This initiates a chain reaction: “Because the smaller living organisms comprise the nutrition for larger fish, they migrate from the area as well. And so on. At the end of the chain we have the fishermen, who can no longer catch anything in their traditional territories,” says Wahl.

In the Baltic Sea and North Sea as well, Klaus Schwarzer examined excavation holes in the context of several research projects a few years ago. “Off Fischland on the West Pomeranian Baltic Sea coast, relatively fast regeneration occurred; conversely, in Tromper Wiek off the coast of Rügen, we could still see traces of excavations, after 15 years, from the GDR era.”

And in the North Sea off the coast of Sylt, it is apparently taking even longer – “In the holes where sand had been suctioned off for landfills, there was more or less no regeneration to be seen after a number of years,” says Schwarzer.

About half of the sand replenishment driven by rivers never reaches the sea, due to reservoirs and the straightening of watercourses

“It is a dangerous mistake to believe that sand is a quickly-renewed resource. This is not true,” warns the geologist Kay-Christian Emeis,  Institute Director at the Helmholtz Zentrum Geesthacht – Centre for Materials and Coastal Research. “Sand is basically nothing more than a crushed product from geologically older stones that arises through erosion. But this process takes tens of thousands of years,” explains Emeis. “Sand is crushed by glaciers and transported by rivers into our lowland plains, onto the coasts and into the ocean. Through physical effects – the energy of the flowing water, the friction on the ground in the river bed – sand gets its typical granular size and shape."

The disappearance of sand and the shrinking of beaches are not related exclusively to dredging and sand suction devices; rather, it also has to do with artificial interventions into nature, says Emeis. Dams for example that intercept sand on its way to the sea, or river straightening and concrete walls that are built as protective walls along the coasts influence the natural transport of sand. For this reason, about 50 percent of the sand replenishment driven by rivers never reaches the sea, according to estimations by experts.