Are sand dunes a destructive or constructive force?
As seen from a human demographic side, they can be both destructive and constructive: In the African Sahara, sand dunes invade farmed land as they advance with the wind. In e.g. the coasts of Belgium, The Netherlands, Germany and Denmark, they make a natural barrier, protecting the inland fertile fields, called the Polders, from the the sea surge of winter storms. Last, sand dunes also fascinate mathematicians and statisticians because they consist of tiny sand corns, each an individual entity with no relation to the next one, yet they form – as seen from above – the same pattern of dunes, over hundred of miles.