Despite being an economic success, prawn farms built in Brazil's mangroves have displaced natural ecosystems and the coastal communities which rely on them, says Kennedy Warne in an exclusive extract from 'Let Them Eat Shrimp'

A flat-bottomed punt with an ancient outboard motor ferries me across the Rio Jaguaribe. Golden light gleams on fishing boats catching the afternoon breeze in their sails. Laughing children dive like sprites in the river while a man fishes for crabs from a rickety pier. A straggle of mangroves lines the river's edge. Their looping, spidery prop roots make the trees look as if they have strolled out of the sea, found the place to their liking, and settled in. Who could blame them? The name of this place is Porto do Céu, the gates of paradise.

Two residents lead the way along a dirt track to show me their new neighbor, a shrimp farm.