The conflict in Iran has disrupted energy and commodity markets. Iran has effectively closed the narrow strait of Hormuz, a vital oil transit point, attacking more than a dozen ships over the past two weeks that have tried to sail through the waterway.

Donald Trump has been pressing US allies in Europe to help secure the strait, warning on March 15 that it will be “very bad for the future of Nato” if they do not support American efforts to reopen Hormuz. But Iran has vowed to keep the waterway closed.

The disruption to Gulf shipping has caused Brent crude oil prices to jump sharply from around US$70 (£53) a barrel before the crisis began to more than US$100. Global trade in a wide range of other goods – from consumer products to agricultural raw materials – is being affected too.

But the crisis has also highlighted a broader issue: that global trade depends on a surprisingly small number of narrow waterways, which are often called maritime “chokepoints”. Here is a guide to the chokepoints that matter most for global trade, and how vulnerable each one is to disruption.

Hormuz is the world’s most critical energy chokepoint. Connecting the Persian Gulf to the Arabian Sea, it carries around 39% of the seaborne crude oil trade and 19% of natural gas. Unlike most trade chokepoints, there is no viable alternative to Hormuz for Gulf states to export their energy.

Iran has periodically threatened to close the strait of Hormuz since the 1980s. But the disruption caused to shipping since late February, when the US and Israel........

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