M alé is one of the world’s most overcrowded cities, but it faces double pressure. As well as a growing population, the capital of the Maldives is also threatened by rising sea levels. Owing to climate breakdown, its living space is shrinking.

So the justification for a land reclamation project seemed clear. Take sand from elsewhere in the archipelago and use it to build up the land available for Malé’s people. What could go wrong? After all, it’s only sand, right?

Around the world, urban development and industry is using sand at a rate of 50bn tonnes a year, a figure that is expected to grow.…