Digitalisation, inclusion of lake and riverine islands and the 2011 Tohoku quake, all could be reasons
The Japanese archipelago, one of the world’s prominent island groups that lies just off the coast of Eurasia, now has 14,125 islands, according to the Japanese government.
This is double the 6,852 islands that was the official figure way back in 1987, the Kyodo news agency reported earlier this week.
The 6,852 figure was reached upon by the Japanese Coast Guard that “listed by hand islands with a circumference of 100 metres or greater shown on a map of Japan”.
In 2023 though, the Geospatial Information Authority of Japan counted the islands automatically. It used an electronic land map of Japan that it had come out with in 2022. It referenced this with various types of data.
“While the computer detected over 100,000 islands, only those with circumferences of 100 meters or greater were selected for the official list,” Kyodo noted.
The survey used the definition of ‘island’ as defined by the United Nations Convention on the Law of the Sea. It states that an island is a “naturally formed area of land, surrounded by water, which is above water at high tide.”
Japan is primarily made up of four islands known as the ‘Home Islands’ — Honshu, Hokkaido, Kyushu and Shikoku. In the north, Hokkaido is bounded by the Russian-administered Kuril islands while Kyushu is bordered by the Ryukyu group (Okinawa and other islands) that reach up to Taiwan.
According to the Japanese creation myth, the Shinto gods Izanagi and Izanami dipped a coral blade into the sea. When it came up, a few drops fell back and formed the Japanese archipelago.
While the country’s population is concentrated in the four ‘Home islands’, the sheer number of islands makes Japan the fourth-largest island nation globally.
But what could be the reason behind the increase in the number of islands?
According to noted seismologist Harsh Gupta, earth science could have an answer to this.
“Globally, there are about seven major tectonic plates, which keep on moving. They move away from each other, collide or slide past each other. The consequence of these movements can be the appearance or disappearance of islands,” Gupta told Down To Earth.
He stated that when the 2004 Sumatra Earthquake took place, the Andaman and Nicobar archipelago got almost a metre closer to India. The islands then drifted back but not to the same position.
“The counting of river and lake islands during the current recount could be one reason. The other could be the 2011 Tohoku Earthquake in Japan. It could have removed or added small islands,” he said.
According to Gupta, small pieces of land just above the waterline can show up as islands when one takes an electronic photograph from a satellite.
With sea levels going up, many islands will disappear in due course of time. “So if Japan were to do a recount some years down the line, the figure arrived at will be different,” Gupta said.
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