A maritime world: shipping lines and trade
Sea transport is the cheapest way to move heavy goods over long distances. About 80% of world trade by volume travels by ship: oil, grain, ore, coal, cars and manufactured goods in containers (standard steel boxes, 20 or 40 feet long).
Shipping lines are fixed regular routes between large ports, like bus routes for goods. Big ships carry thousands of containers, so costs per box are low. This is why factories can be far from the buyers, one of the key engines of globalisation.
The maritime economy includes shipping, shipbuilding, ports and logistics, fishing, offshore energy (oil, gas, wind), cruise tourism and the jobs around them.
Ports, axes and coasts that gather people
A port is where sea and land transport meet: ships, cranes, storage yards, trains and trucks. The biggest ports are called hubs: ships bring goods there and smaller ships spread them to nearer ports.
The main sea axes (major routes) join the busiest regions of the world: East Asia, South Asia, the Middle East, Europe and North America. They run east-west through the northern oceans, with branches to Africa, South America and Oceania.
Coasts attract people and work: ports, factories, fish, flat land, tourism. Many of the world's largest cities are on coasts. This crowding brings risks too: pollution, loss of wetlands, and floods when sea level rises.
Straits, canals and chokepoints
A strait is a natural narrow sea passage between two lands; a canal is a man-made one. Because they are narrow, they are chokepoints: a lot of traffic passes through a small gap. Well-known examples are the Strait of Malacca, the Suez Canal, the Panama Canal and the Strait of Hormuz.
Chokepoints make ships faster (a short cut avoids a long trip around a continent) but also make trade fragile: an accident, a conflict or a storm can delay goods across the world. Countries therefore invest in alternative routes and safe passage.
Submarine cables: the internet under the sea
Submarine cables are fibre-optic cables, as thick as a garden hose, laid on the sea floor. They carry almost all the internet, calls and bank messages between continents; satellites carry only a small share. Cables land at coastal landing stations. Ship anchors and fishing nets, earthquakes and landslides can cut them, so there are several routes for safety.
Who owns the sea? Territorial sea, EEZ and freedom of navigation
The United Nations Convention on the Law of the Sea (UNCLOS) splits the sea by distance from the coast (1 nautical mile = 1.852 km):
- Territorial sea: up to 12 nm (about 22 km). The coastal state has authority, but foreign ships have the right of innocent passage.
- Exclusive economic zone (EEZ): up to 200 nm (about 370 km) from the coast. The coastal state alone may use the fish, oil, gas, wind and minerals. Ships and cables of all states may still pass.
- High seas: beyond the EEZs. Open to all (freedom of navigation), but with rules against piracy and pollution.
A country with a long coastline, islands far from the mainland or strong ports, a big navy and merchant fleet is called a maritime power. An EEZ can be much bigger than the land of the state: islands can give a state a huge EEZ.
Oceans as climate regulators, resources and fragile seas
The ocean stores huge amounts of heat and absorbs about a quarter of the carbon dioxide we release. Currents move warm water towards the poles and cold water to the tropics, so the ocean regulates climate and weather.
Resources: fish (a main food for over a billion people), oil and gas, offshore wind, sand, salt and minerals on the sea floor.
Fragility: overfishing, plastic, oil spills, warm water that bleaches corals, and noise. Conservation tools: fishing quotas, marine protected areas where fishing is limited so fish can breed, cleaner ships, rules against dumping, and treaties for the high seas.
Key formulas and definitions
- 1 nautical mile (nm) = 1.852 km
- Territorial sea: up to 12 nm = about 22 km
- Exclusive economic zone: up to 200 nm = about 370 km
- About 80% of world trade by volume goes by sea; ocean cover = about 71% of Earth
Worked examples
1. Convert the 12 nm territorial sea to kilometres.
12 x 1.852 = 22.2 km, about 22 km.
2. Convert the 200 nm EEZ to kilometres.
200 x 1.852 = 370.4 km, about 370 km.
3. A ship sails 740 km along a lane at 20 km/h. How long does it take?
Time = distance / speed = 740 / 20 = 37 hours.
4. A ship is 150 km from a coast. In which zone is it?
12 nm = 22 km and 200 nm = 370 km. 150 km lies between them, so it is in the EEZ.
5. A ship sails from port A to port B around a continent: 21,000 km. A canal makes it 12,000 km. How much distance does it save, in percent?
Saved = 9,000 km. 9,000 / 21,000 = 42.9% shorter.
6. Why do countries accept that foreign ships pass through their EEZ and territorial sea?
Because the law of the sea gives innocent passage in the territorial sea and freedom of navigation in the EEZ. All states depend on it for their own trade.
Common mistakes
- Thinking the EEZ is the same as national territory. In the EEZ the state owns the resources, but ships of all states can still pass.
- Mixing nautical miles and kilometres. 1 nm = 1.852 km, not 1 km.
- Saying satellites carry most of the internet. Most data between continents goes through seabed cables.
- Thinking a chokepoint is only a danger. It is also a useful shortcut that makes shipping cheaper.