Consider a map of the whole world, at night, from a satellite. Lights pick out the coasts. 8/10 of the largest cities in the world are coastal cities – Tokyo, Mumbai, Lagos, Shanghai, New York, LA – and the population density in coastal areas is predicted to rise over the foreseeable future, as our population grows.
Coasts have been kind to us. Transport, trade, and money flows in and out of ports. Another level of exchange is taking place between fresh and salt waters. Places like estuaries and mangroves are rich in nutrients; all sorts of species revel in these, going up the food chain. Coasts are naturally rich in biodiversity. It’s the ultimate “edge effect”, between land and sea.
Agonisingly, perhaps unsurprisingly, a consequence of the intense human habitation in these areas and the flow of rivers out to the sea, is that there is a darker version of the familiar map.