Biro Island is located in Shibushi Bay and belongs administratively to Cho, Shibushi-cho, Shibushi City, Kagoshima Prefecture. This small island is known for its dense subtropical vegetation and distinctive natural environment.
The island’s name comes from the biro, or Chinese fan palm, which grows abundantly across the island and gives it a characteristic tropical appearance. Its plant communities have been preserved in an unusually natural state, making Biro Island an important site for the conservation of subtropical vegetation in Japan.
Biro Island lies approximately 4 kilometers offshore from Shibushi Port, near the center of Shibushi Bay.
The island’s geological foundation consists of sandstone and sandstone-shale formations dating from the early part of the Cenozoic Era.
The Chinese fan palm, known in Japanese as biro, grows thickly across the island and forms its most distinctive landscape feature.
Nearly 200 species of subtropical plants grow naturally on Biro Island. These include mokutachibana, shiratama-kazura, and kuwazuimo, a large-leaved plant related to taro. Together, they create a rich and diverse plant environment rarely found on the mainland of Japan.
The island’s vegetation has remained largely undisturbed for two main reasons. First, the island was not suitable for permanent settlement. Second, the forest was protected as the sacred woodland of Biro Shrine, and trees were not cut down. These circumstances helped preserve the vegetation in a natural condition.
On the southern slope of the island, old Chinese fan palms estimated to be 300 to 400 years old grow in dense clusters.
These plant communities are collectively known as the Biro Island Subtropical Plant Community. They were designated a National Natural Monument of Japan on March 3, 1921 (Taisho 10).
Later, on July 19, 1956 (Showa 31), the plant community was upgraded to the status of a Special Natural Monument under the Cultural Properties Protection Law. This designation recognizes the exceptional value of the island’s subtropical vegetation and the importance of protecting its natural environment.
On a hillside within the island stands Biro Shrine. According to tradition, the shrine was founded during the Wado era in the early 8th century.
It has long been worshipped as the guardian shrine of the island. The shrine’s sacred woodland also played an important role in preserving the island’s vegetation, as the trees were protected rather than harvested.
Near the end of World War II, the United States military planned an invasion of southern Kyushu as part of Operation Olympic. Shibushi Bay was among the areas considered for the landing operation.
The Japanese military became aware of the planned operation and constructed defensive positions in the region. Two 10-centimeter cannons and infantry units were stationed on Biro Island, where military training was also conducted.
Trenches built during this period still remain on the island today. They are reminders of the military preparations made in the final stages of the war and provide another layer to the island’s history beyond its natural environment and religious traditions.
Biro Island is a small island with a circumference of approximately 4 kilometers, yet it supports nearly 200 species of subtropical plants. Its dense Chinese fan palms, including trees estimated to be 300 to 400 years old, form a distinctive natural landscape.
The island’s plant community has been protected as a National Special Natural Monument since 1956. Its preservation is closely connected with the island’s history as an unsuitable place for permanent settlement and as the sacred woodland of Biro Shrine.
Visitors interested in nature and history will also find traces of the island’s past, from the shrine traditionally founded in the early 8th century to the defensive trenches constructed during World War II. Biro Island is a remarkable place where subtropical nature, religious heritage, and modern history meet.