The sea rises sideways

Early in my career, I studied farmers along the Batinah Plain, and some of them were thinking about raising fish because the sea had come in under their gates and into their wells. My work with them was to explore this idea by introducing recirculating aquaculture, where fish are raised in tanks and the water is filtered and reused again and again. It was built around the farmers’ response to the salt; where salinated water wells were costing them their crops, the question in front of them was whether the same farm could raise something else.
Beneath that coast, fresh groundwater and seawater meet along a boundary nobody can see, and the boundary moves. From the late 1980s, the Batinah aquifer was pumped faster than rain could refill it, and by the early 1990s seawater was advancing into the areas drawn on hardest; wells and farms near the shore have since been abandoned as the salt spread. Cyclone Gonu sent a surge of 2 to 3 metres along the Batinah and Muscat coastlines in 2007, some years before my research, and much of the salt those farmers were answering was older than the storm, pulled inland through the ground by what we had taken out of it.
If you have driven up the coast from Muscat towards Suhar, you have crossed the Batinah Plain and know how gently it rises from the sea. A Sultan Qaboos University study of that plain, home to about 28 per cent of Oman’s population, estimated that a rise in sea level of 1 metre could move the shoreline back by as much as 3.4 kilometres, and Oman’s Directorate-General of Meteorology explains the height of storm surges along this coast by its shallow, slowly deepening seabed.
Today, heads of state and ministers are gathering at the UN General Assembly in New York for a day devoted to sea level rise, and the declaration they are expected to adopt by consensus affirms a presumption that a state continues whatever the water takes, together with its sovereignty and its seat at the United Nations. Last year, the International Court of Justice came to a similar view, finding that a state does not necessarily cease to exist when an element that makes it a state disappears, and that countries need not redraw maritime baselines once they have been properly established. Island states have pressed for this for years; some sit only a few metres above the sea, and for them the question is literal: whether a nation can outlive its territory.
The farmers I studied were facing a smaller version of that question. Some looked to fish, hoping to keep farming by changing what they produced, and a farm raising fish where its tomatoes once grew holds ingenuity and loss in the same place. The declaration in New York does something those farmers would recognise: keeping a country in existence by agreeing that the country can go on without the ground it was built on. A state continuing in law has to find somewhere for its people to live.
No presumption agreed today will reach the boundary under Al Batinah, and the sea pressing on continues rising at about 4.7 millimetres a year, up from 2.1 when satellites began tracking in the 1990s. Somewhere beneath the plain, the line between fresh water and salt is moving as you read this, pushed by the sea from the coast and drawn by our wells from inland, and each farm it passes beneath will meet the choice those farmers faced, whether to hold on or to become something else.