Japan is crowded because one plot of land fed three harvests¿Por qué Japón está tan poblado a pesar de tener tan poco territorio?

Japan is a mountainous island where only 12% of the land can be farmed, yet for centuries it was among the most densely populated places on earth. Why?

Start with dinner

In the ancient world the ceiling on people was the ceiling on food. Japan gets plenty of rain, and water running off all those mountains carries sediment that makes river valleys fertile.

In the first millennium BC, the Yayoi arrived from Korea with paddy rice and iron tools. Rice yields more calories per acre than almost any other crop.

Where the warm current reaches, so do the rice fields

A warm current from the Philippines and Taiwan heats Japan's coasts. It meets a cold current coming down near northern Honshu. That cold water carries nutrients and fish, but it also draws the northern limit of rice.

So the east-west islands of southern Japan share a climate, and rice and a way of life spread across them. Where Honshu bends north, temperatures drop fast, and Hokkaido and Sakhalin further north stay empty.

Not fighting is also a form of productivity

Japan sits 200 km off the mainland and acted as China's natural buffer; the Mongols invaded only twice and both times ran into typhoons. The three main islands were under one government by around 1100. Wars were far fewer than elsewhere.

When the good land ran out, population stalled; from the 12th to 18th centuries double cropping and irrigation pushed yields up again. But denser people spread smallpox and measles, which put a second brake on growth.

So sushi is the answer

Rice from the south, fish from the cold current in the north: put the two together and you have Japan. The whole story of an island's population is written in that one bite.