Nepal, March 8 -- Tehran is moving to restrict-or effectively close-the Strait of Hormuz to shipping, as part of the latest escalation in the war involving Iran.

Markets have reacted to the global impact of closing this incredibly busy shipping channel, focusing on the risk to oil and gas flows, the prospect of higher crude prices and the inflationary pressures that would follow.

That concern is justified. But it captures only part of the story. A sustained disruption of traffic through Hormuz would not simply constitute an energy crisis. It would also represent a fertiliser shock (where prices go up dramatically and supply goes down)-and, by extension, a direct risk to global food security.

Modern agriculture runs not only on sunlight...