2023-11-04 20:08:00
Sand is the most exploited natural resource in the world following water. Each year, between four and eight billion tonnes of sand and sediment are extracted from marine and coastal environments. “Every year, we extract enough sea sand to build a wall 10 m high by 10 m wide that would go around the Earth. It’s not sustainable,” asserts Pascal Peduzzi, expert from the United Nations Environment Program.
These approximately 8 billion tonnes are in fact “dangerously close” to the reconstitution rate and the 10 to 16 billion tonnes of sediments annually that must arrive in the oceans to maintain coastal and marine ecosystems, according to Unep. “Furthermore, because of the construction of dams and direct extraction in rivers, less and less of this sediment is reaching the oceans, which poses a problem for the replenishment of sand to our coasts and beaches. And half of the sediments that arrive from rivers into our oceans are then extracted and transported by the sand industry,” explains Pascal Peduzzi, who believes that the marine environment must therefore be given time to recover.
The UN warns of a possible “sand crisis”
The Mekong is collapsing
For Unep, the finding is “particularly worrying” for regions where dredging is more intense and where extraction already considerably exceeds the sediment supply from the land to the sea. In the Mekong Delta, for example, the Sand is extracted in such large quantities that the delta is sinking, causing erosion in this fertile place, a source of food for the population. In America, from Texas to Maine, beaches must be regularly re-fertilized to prevent erosion. New infrastructures in West Africa that consume a lot of sand are also very visible on the Marine Sand Watch platform that Unep has just launched and which monitors dredging activities using artificial intelligence and data signals. security issued by ships.
Report along the Mekong, this treasure of biodiversity threatened from all sides
The South China Sea, the North Sea and the East Coast of the United States are among the areas where the greatest number of dredging has taken place, indicates Unep. “The North Sea is overexploited,” warns Belgian Arnaud Vander Velpen, specialist in the sand industry and data analysis at UNEP. We extract much more sand from the North Sea than comes in. On our platform’s map of the North Sea, we can see that the amount of sand used and the number of projects underway are staggering. And with sand, the main impacts are often not those of a single local project, but all the surrounding projects. The impact of sand mining on the very small Belgian coast may be limited, but the cumulative impact of all projects in the North Sea must be taken into account.”
Strategic resources
The Belgian part of the North Sea is characterized by the presence of numerous sandbanks where extraction is technically possible. Marine sands have chemical and physical characteristics which allow their use in various industrial applications including construction. And the extraction of marine sand in the North Sea meets the economic needs of the densely populated regions which border it…
Our country is, however, among the few to have studied their sand reserves and according to Unep, if we continued to exploit at the same pace, the sand reserves in the Belgian part of the North Sea will be exhausted in 80 years (read opposite). And if other countries took the trouble to carry out the same analysis, they might arrive at the same worrying figures, warns Arnaud Vander Velpen. A situation which complicates the fight once morest climate change (see opposite) but which is also a “strategic” question. “We must manage this resource intelligently for years to come. Until now, we consider sand to be a common material and of which we think that we have a lot of it, underlines Pascal Peduzzi. It’s true that we have a lot of sand, but accessibility to sand is a question of the ratio between what is available and what we use. And at some point, if we use a lot of sand, it exceeds the capacity of the system to provide sand and it becomes more scarce. Sand must be considered as a strategic material. Your schools, your hospitals, your roads, your hydroelectric dams, wind turbines (75% of wind turbines are concrete), solar panels and computer chips (silicate sand), glass… Our entire society depends on sand as a material of construction. Beyond that, sand also has a role in the environment: for our aquifers in particular because sand and gravel are the place where we pump our water… It is a substrate for fish populations and the biodiversity… Its role must be recognized.”
Why sand, like oil, is a limited resource… but increasingly coveted
Sterilization of the seabed
And the impacts of marine sand extraction on the environment are major, he continues, referring to these enormous boats resembling a “giant vacuum cleaner”. Large ships “sterilize the sea floor by extracting the sand and crushing all the micro-organisms that feed the fish, which means there is an impact on biodiversity and fish stocks”. The turbidity of the water is also disturbed because the extraction of sand, by rejecting particles that are too small, creates plumes of particles. While sand that is too “large” and rejected accumulates on marine organisms. Not to mention the noise of the machines or the risk of coastal erosion if extraction takes place too close to the coast.
International dredging requires a minimum standard, adds Arnaud Vander Velpen. “The dredging industry has just published best practices and it is a step in the right direction but, to this day on a global scale, it still happens that the cheapest solution is implemented and not the most sustainable: on a global scale, we really need to improve our practices.” A red line (well respected in Belgium): the over-extraction of sand in the “active system” of the beach (which does not end where the water stops but which in fact extends strongly into the sea).
Industry reaction
In any case, it was Belgians who were the linchpins of these guidelines recently published, salutes Arnaud Vander Velpen. Experts from Belgian dredging companies Jan De Nul and Deme, as well as other international heavyweights, are calling, with concrete examples, to “reduce the quantity of sand extracted from marine resources by using alternative sources, such as sediments extracted during investment and maintenance dredging works” and emphasize that “dredging in or near sensitive sites of high natural or cultural value is only feasible with thorough monitoring, compliance with strict limits and adequate supervision”. The quantity and quality of sand and the functions of the ecosystem must be taken into account during the design of the project and the biodiversity inventoried so that “the sand extraction area with the lowest impact can be selected and mitigation, compensation and restoration measures can be taken”.
Sand, the yellow gold that must be preserved and developed in Walloon Brabant
Industry experts also recommend the use of modeling of the hydrological dynamics of the coastal zone in the case of projects, because this (intensity of waves and currents, etc.) can be disrupted by sand extraction. The industry generally recognizes that “there are concerns regarding the increasing quantities (of sand) extracted and their impacts on the environment and society. The dredging industry has an important role to play in addressing these concerns”.
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