A.Okinotorishima Islands is the southernmost island in Japan, located at N 20°25 E 136°04, about 1,700 km from Tokyo and about 900 km away from Chichijima Island of the Ogasawara Islands. This island is a table reef with an 11 km perimeter, spanning about 4.5 km from east to west and about 1.7 km from north to south. It's extremely important in preserving the national land as it serves as the basis for exclusive economic zones totaling around 400,000 km2, larger than Japan's land area (around 380,000 km2). Only two islets within it remain above the sea level at high tide: Kitakojima and Higashikojima. Conservation work was started in 1987 to build seawalls, etc. because these two islets were at risk of submersion due to erosion. Severe weather and maritime conditions could also damage the islets, however, so protective structures made of titanium wire mesh and other preservation measures were also put in place. The Ministry of Land, Infrastructure, Transport and Tourism (the Ministry of Construction, at that time) has been directly maintaining and controlling Okinotorishima Island's shores at the country's expense since 1999, ensuring its conservation as an extremely important island in preserving the national land. The Low-Tide Line Preservation Act was enacted in 2010 and included setting up 14 low-tide line preservation areas, making control of Okinotorishima Islands even more important. In 2020, the observation base facilities that had been built 30 years prior and had deteriorated due to typhoon damage and corrosion from salt damage were renovated.Okinotorishima Islands is the southernmost island in Japan, located at N 20°25 E 136°04, about 1,700 km from Tokyo and about 900 km away from Chichijima Island of the Ogasawara Islands. This island is a table reef with an 11 km perimeter, spanning about 4.5 km from east to west and about 1.7 km from north to south. It's extremely important in preserving the national land as it serves as the basis for exclusive economic zones totaling around 400,000 km2, larger than Japan's land area (around 380,000 km2). Only two islets within it remain above the sea level at high tide: Kitakojima and Higashikojima. Conservation work was started in 1987 to build seawalls, etc. because these two islets were at risk of submersion due to erosion. Severe weather and maritime conditions could also damage the islets, however, so protective structures made of titanium wire mesh and other preservation measures were also put in place. The Ministry of Land, Infrastructure, Transport and Tourism (the Ministry of Construction, at that time) has been directly maintaining and controlling Okinotorishima Island's shores at the country's expense since 1999, ensuring its conservation as an extremely important island in preserving the national land. The Low-Tide Line Preservation Act was enacted in 2010 and included setting up 14 low-tide line preservation areas, making control of Okinotorishima Islands even more important. In 2020, the observation base facilities that had been built 30 years prior and had deteriorated due to typhoon damage and corrosion from salt damage were renovated.
A.Okinotorishima Islands is the only island in Japan with a tropical rainforest climate; its islets are protected from that climate's severe weather and maritime conditions by tetrapods and concrete.
A.enovating those facilities will allow those on the island to continually and reliably observe its weather and ocean data.
A.(1) Inspecting and repairing concrete seawalls
Higashikojima and Kitakojima are both protected by concrete seawalls. Okinotorishima Islands is the only island in Japan with a tropical rainforest climate; high temperatures, humidity, and ebbs and flows can cause separation and cracks on the concrete's surface due to sudden temperature changes, the impact from waves, etc. Thus, we're investigating and inspecting damage to the concrete seawalls, along with repairing and removing broken pieces from the cracked areas.
(2) Maintenance on meteorological and marine observation equipment, etc.
Meteorological and marine observation equipment is installed at the observation base facilities. The weather and ocean data obtained through them is used when considering conservation measures, etc. for Okinotorishima Islands. We're also working with the Japan Coast Guard to strengthen the surveillance systems here and detect unfamiliar ships using radar and CCTV cameras. We properly maintain these instruments to ensure that observations and surveillance are carried out.
(3) Environmental studies on coral, etc.
Okinotorishima Islands is made up of coral, so we are doing the studies, observations, and aquaculture tests on coral species' habitats that are necessary to maintain their wave absorption abilities (atolls and reef crests), which preserve the islets.
(4) Low-tide line patrol
We go out on boats to patrol the waters around the low-tide line, which forms the basis of the exclusive economic zones, etc.
A.Those facilities are powered by installed solar panels.
A.Employees go to Okinotorishima Islands every year to maintain and control seawalls, etc. and conduct environmental studies. In fact, some are there now.
A.They eat and sleep on the workboat while there. Life onboard the ship is different than everyday life: TVs and mobile phones don't work there. They also have to keep heat stroke and other issues in mind while working as they're working in an area with severe weather and maritime conditions and no shade.
A.The Keihin River Office is the only division in the entirety of the Kanto Regional Development Bureau in the Ministry of Land, Infrastructure, Transport and Tourism that has a Coastal Division within it. The Coastal Division currently has six employees, who are responsible for controlling and preserving Okinotorishima Islands and for implementing coastal conservation measures at Kanagawa Prefecture's Seisho Coast.
A.Many people know the name Okinotorishima Islands. Many people may think of Kitakojima and Higashikojima as small, round islands because they're often introduced as such in textbooks and elsewhere. However, Okinotorishima Islands is a long, elliptical coral-made island that spans about 11 km, and it's extremely important in preserving the national land as it serves as the basis for exclusive economic zones totaling around 400,000 km2. The citizens of Tokyo and Japan need to understand the importance of Okinotorishima Islands and the conservation work, etc. that Keihin River Office does on the island.
The official website of the Tokyo Metropolitan Government