About the only time the world’s land-based public thinks about seaborne traffic and the globalised trade it underpins is when they look above the parapets of their sand castles and spy a ship on the distant horizon.

Or, when something happens, such as a war or a vital sea artery is blocked and prices creep up and super market shelves start to empty.

The latter is happening.

One of the world’s largest container ships – the Taiwanese-registered Evergreen – is blocking the Suez Canal. It is expected to take weeks to refloat it. Twelve percent of the world’s trade passes through the shortcut waterway linking Europe and Asia. So far 160 ships are parked at either end waiting for the salvage crews to free Evergreen. Every day that the ship is stuck it costs world trade $9.6 billion.

The blockage is already impacting oil prices which have so far jumped from $50 to $65 a barrel. But oil tankers are not the only ships affected. There also container ships and bulk carriers. They carry wheat, rice, coffee, textiles, steel, car parts, manufacturing components, computer parts, fruit, vegetables…

The owners of Evergreen refuse to divulge the contents of the ship’s cargo, but it is so big that if it is carrying bananas its containers would have enough to feed all of Europe for more than a year. All those hypothetical bananas would be spoilt and any other fresh produce on the ships idling in the Red and Mediterranean Seas.

The blockage will also hit production schedules right across the economy. Manufacturers, shopkeepers, processing plants, lorry drivers etcetera, have limited storage space. They rely on ships arriving on schedule to keep to their own tight programme. If they are late then lorry drivers and cargo trains have no goods to transport from the port to the shops or manufacturers. If a car assembly plant does not receive steel sheets from India or brake parts from China then it shuts down and the workers are laid off. No coffee from Kenya or tea from Sri Lanka means that those products simply disappear from supermarket shelves.

The ships can divert to sail the extra 3,500 miles around South Africa’s Cape of Good Hope. But this adds 12 days to the journey and – although shipping is the cheapest form of transport – it pushes up the cost to the ship owners which will inevitably be passed along to the consumers. And the extra 12 days fails to eliminate the problem of production bottlenecks.  It is, however, better than the several weeks which salvage experts are pessimistically projecting as a time scale for moving Evergreen which is why some ships are switching to the Cape route.

The Suez Canal is not the world’s only link waterway. Six percent of the world’s trade passes through the Panama Canal which joins the East and West coasts of America, the East coast to the Pacific Rim countries and the West coast to Europe and Africa.

There is also the Rhine-Main-Danube Canal which was completed in 1992 and connects Europe’s Rhine and Danube rivers and provides a continuous waterway from the North Sea to the Black Sea and then to the Eastern end of the Mediterranean. The ships are not as big as their ocean-going counterparts, but the route still manages to carry about seven billion tonnes of goods per day.

Canals are the most obvious watery chokepoints for maritime trade but not the only ones. The biggest is the English Channel through which 20 percent of the world’s trade passes. There is also the Danish Straights, The Straits of Hormuz, the Straits of Gibraltar, the Bosporus, the Cape of Good Hope, the Strait of Malacca and the South China and East China Seas. If climate change keeps melting the Arctic ice cap there will also be sea passages on the northern edge of Russia, Scandinavia, Canada and the US, the opening of which would draw traffic away from the Suez and Panama canals.

Eighty percent of the world’s trade travels by ship compared to ten percent by rail, nine percent by road and a meagre one percent by air. Traffic clogging Lorries are a constant part of our lives. Commuters use trains every day and planes are our chief passport to foreign parts.  For most of the world’s land-based public ships are out of sight and, thus, out of mind. The Suez blockage is very likely to change that – at least for a while.

* Tom Arms is foreign editor of Liberal Democrat Voice and author of “The Encyclopaedia of the Cold War” and “America Made in Britain". To subscribe to his email alerts on world affairs click here.