The coastlines I trace resemble logos and luxury icons: palms, crescents, pixelated grids, surreal ornaments etched into shallow seas. The cartography is striking. The environmental consequences are very concerning.

There is an urgent need to evaluate the negative effects and risks associated with these artificial structures around the world, especially as climate change makes sea-level rise more extreme.

For ten years, I have been tracking changing coastlines and trying to map the spread of artificial coastal developments. But this is difficult for two reasons.

First, it’s tricky to define what counts as reclamation and what doesn’t. Does a polder (a piece of low-lying land reclaimed from the sea) belong in the same category as a luxury island? Do sea walls belong in the same category as “dredge-and-fill peninsulas” (land created by digging sand from a seabed or river banks that is used to fill an area of water).

Second, at a global scale, constantly updating maps with rapidly changing unnatural boundary designs is a never-ending task, which involves extracting data from satellite images.

The geometry of reclaimed sites and artificial shorelines can seem bizarre – ranging from the leafed fronds of Ocean Flower Island in Hainan, China, to perfect crescents in Durrat Al Bahrain in the Persian Gulf, and straight-edged lattices in Lagos, Nigeria. In most cases, they are designed to look appealing........

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