Remote Ogasawaras harbor fragile ecosystems

The Yomiuri Shimbun

Ogi-ike cove formed into a unique shape through the erosion of limestone rocks. Snorkeling and swimming can be enjoyed in the area.

By Yukiko Furusawa / Yomiuri Shimbun Staff WriterOGASAWARA, Tokyo — The Ogasawara Islands were known by a variety of names during the Edo period (1603-1867), including “Munin-shima” (Uninhabited islands) — from which the English name The Bonin Islands derives.

The faraway islands were in those days stopover sites for whaling ships, and were first settled by Europeans, Americans and Hawaiians.

I boarded a boat in Chichijima island, home to the Ogasawara village government office, and set out for Minamijima island, about 1 kilometer away.

While gazing out at deep-blue waters that locals describe as “Bonin Blue,” I soon found myself in the presence of a school of spinner dolphins.

“They want to play with the waves forming off the bow,” said Fumio Takeuchi, 54, the boat’s skipper and a nature guide certified by the Tokyo metropolitan government.

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  • The Yomiuri Shimbun

    Minamijima island is a breeding ground for seabirds. Here a brown booby, right, and chick perch on a rocky outcrop.

As he spoke, the dolphins rode the waves alongside the boat, their back fins bobbing and weaving, or catapulted themselves into the air while twisting their bodies. I couldn’t help but shout with joy over their cute antics.

Minamijima has a rare geologic feature called “submerged karst” — limestone rocks that were eroded by winds and rains before sinking into the sea.

“Even on fine days, we can’t approach this island by boat if the waves are high,” Takeuchi said while carefully navigating through craggy, strange-shaped rocks.

Visitors to Minamijima must be accompanied by a guide and walk along designated routes to protect the island’s precious natural environment.

“The rules also cap the number of visitors at 100 per day, and limit the time you’re allowed to stay on the island to two hours,” Takeuchi said.

It was early October when I visited. Except for the year-end and New Year’s period, the island is off-limits from November to early February to protect its vegetation.

After climbing off the boat and up a steep rocky stretch, a huge arch-shaped wall of rock came into view. An emerald green cove called Ogi-ike (folding-fan pond) spread out before it. The cove’s water contrasted sharply with the bright-white sand surrounding it.

Countless number of partly fossilized shells of now-extinct snails were also strewn about, giving the place a mysterious, even fantastical look.

The uninhabited island is also a breeding ground for sea turtles and seabirds. Wedge-tailed shearwaters covered with gray feathers and the white chicks of brown boobies were seen relaxing on rocky outcrops.

Threat of alien species

The Ogasawara Islands have never been connected to a continental landmass, so they still contain a wide variety of indigenous animal and plant species, including land snails and ferns.

Chichijima and Hahajima islands have a number of well-maintained trekking routes that crisscross their precipitous topography, from which one can enjoy searching for birds and plants that can only be seen in the island chain.

Hikers must clean their shoes at washing areas at the starting points of trails in case planarian — an alien species similar to leech that preys on snails — is stuck to them.

Fences and traps for catching green anoles, an invasive species of lizard from the United States that preys on rare insect species, can also be spotted throughout the islands.

Ever since the Ogasawara Islands were registered as a UNESCO World Natural Heritage site in 2011, efforts have been made to conserve the environment and promote ecotourism, which seeks to leave a light footprint. As a result, there have been more sightings of endangered species such as red-headed wood pigeons in local communities.

Kosuke Kanno, 38, an official of the Ogasawara Ranger Office for Nature Conservation, said, “Although the impact on the environment from an increase in tourists has not been conspicuous, recovery becomes difficult once alien species are brought in.”

Creatures that live on the islands have evolved in a unique manner and are vulnerable to foreign enemies. The islands’ ecosystems are thus said to be “as fragile as glass.”

More than anywhere else, the islands inspire one to feel the immense importance of passing down irreplaceable natural environments to future generations.

Wartime relics

The Ogasawara Islands were hit by a U.S. air raid during World War II, and residents were forced to evacuate.

After the war, the islands were under the control of U.S. forces before being returned to Japan 50 years ago. Under the U.S. occupation, former residents who did not have roots in Western countries were forbidden to return home.

Wartime relics can still be spotted amid thick banyan forests on the mountainous islands, including gun batteries and trenches of the Imperial Japanese Army. Visitors can take guided tours to the relics.

Meanwhile, off the shores of Chichijima island is the rusting hulk of a ship sunk by a torpedo attack.


Chichijima island can be reached via a 24-hour boat ride from Takeshiba Pier in Tokyo aboard the Ogasawara Maru, a regular liner operating about once every six days. Accessing Hahajima island requires an additional two-hour trip aboard the Hahajima Maru.

For more information, call the Ogasawaramura Tourist Association at (04998) 2-2587 or Ogasawara Kaiun Co. at (03) 3451-5171.

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