ATLANTIC MACKEREL, A fatty schooling fish, for years has been caught by fleets in parts of Europe and sold around the world—where it gets pickled, grilled, smoked, and fried. It is among the United Kingdom’s key exports.
But a decade ago, warming temperatures began driving this popular fish north, into seas controlled by Iceland. Almost overnight, this seafood gold began shredding relations between some of the world’s most stable governments. It led to unsustainable fishing, trade embargoes, and boat blockades. It even helped convince Iceland to drop its bid to join the EU. And that was among friendly nations.