Las Coloradas is a factory, and it never pretends otherwise. Seawater is drawn out of the Ría Lagartos estuary on the north coast of Mexico's Yucatán and pushed through a chain of shallow ponds; the pans have been producing since the 1940s. A bank of packed salt runs out between them and the sea, wide enough to walk, with brine and the open Gulf a few metres apart on either side of you. Everything on that causeway tells you it is a workplace: the air smells of minerals and low tide, trucks grind along the far banks, and white hills of harvested salt sit along the edges. When the crystallisers are worked, machines and men move down into water the colour of raw meat and drag the salt out in slabs. Pond colour here is an instrument rather than a decoration. It reads salinity, and it climbs a ladder as you follow the causeway in the working direction. The young basins run green and amber, then rose, then the deep fuchsia of the ones nearest the refinery.
Salt has been the point of this coast for far longer than the factory. The Maya beds at Emal, on the same shore, were the richest on the peninsula, ringed with fortifications and shrines. The same brine feeds the birds. Caribbean flamingos filter the shrimp that graze these shallows, and launches leave the fishing town of Río Lagartos, threading the mangrove channels of the reserve out to the flats where they work. Up to forty thousand cross from Celestún each spring to nest in the remotest parts of it. When something spooks a flock it goes up as a single sheet of pink and black, the black only showing once they are over you. What they take out of the water is pigment: the algae are loaded with it, the shrimp eat the algae, and the flamingo reworks it into feathers, skin and bill. Every chick here hatches grey, and it is two or three years on the same diet before one of them flushes fully pink.