Kamishima Island is a small, uninhabited island located in Tanabe Bay, Tanabe City, Wakayama Prefecture. Covering approximately three hectares, the island consists of two small peaks known as Oyama and Koyama.
The entire island is covered in dense evergreen forest. For centuries, Kamishima has been regarded as a sacred island where the gods reside, and its natural environment has been carefully protected by the local community.
Its exceptional natural and academic value led to its designation as a National Natural Monument of Japan. In 2015, it was also designated as a Place of Scenic Beauty as part of the “Landscape of the Minakata Mandala,” recognizing its importance in the life and thought of the renowned naturalist Minakata Kumagusu.
Kumagusu, one of Japan’s most remarkable scholars of natural history, spent decades studying the island and campaigning for its protection. His work helped establish Kamishima as an internationally significant example of the relationship between biodiversity, local culture, and nature conservation.
Today, landing on Kamishima is generally prohibited in order to protect its fragile natural environment. Nevertheless, the island can be admired from the surrounding coast and waters. Its thick green forest rising from the blue waters of Tanabe Bay creates an especially mysterious and beautiful landscape.
Kamishima has long been revered as a sacred island associated with the protection of people at sea. Its name literally means “Island of the Gods,” reflecting the spiritual significance it has held since ancient times.
At the highest point of the island stands a small shrine associated with Kamishima Shrine. Local fishermen traditionally prayed here for safe voyages and abundant catches.
The forest covering the island was considered a shinrin, or sacred forest, where cutting trees was prohibited. As a result, human intervention remained extremely limited, allowing the original vegetation to survive for generations.
The island’s forest was also valued by local fishermen as a “fish-attracting forest.” In traditional Japanese coastal communities, people understood that healthy forests could contribute to healthy marine ecosystems.
Leaves and organic material carried from forests into the sea provide nutrients that support coastal ecosystems, while the forest itself helps protect the shoreline and surrounding waters. This traditional understanding reflects an important principle that is now widely recognized in modern environmental science: healthy forests and healthy oceans are closely connected.
For the people of Tanabe, protecting Kamishima’s forest was therefore not only an act of religious devotion but also an important part of protecting their livelihoods.
Kamishima also has a connection with the long history of Kumano pilgrimage. From the Heian period through the Kamakura period, pilgrims from across Japan traveled along pilgrimage routes toward the three sacred shrines known collectively as the Kumano Sanzan.
A plant known as Hakamakazura, which grew naturally on Kamishima, was particularly valued during this period. Its seeds could be used to make prayer beads, which were treasured by pilgrims traveling toward Kumano.
Because these beads were made from a plant growing on a sacred island, they were regarded as having special significance and were associated with protection during the journey and protection from misfortune.
In this way, Kamishima became part of the wider spiritual landscape of Kumano. Even today, the island remains an important symbol when telling the story of the region’s connection between nature, pilgrimage, and religious culture.
No discussion of Kamishima would be complete without Minakata Kumagusu, the pioneering Japanese naturalist, biologist, and folklorist born in Wakayama.
Kumagusu first visited Kamishima in 1902 and continued studying the island for approximately four decades. He investigated fungi, slime molds, flowering and other higher plants, and numerous other forms of life.
He described Kamishima as a “treasure house of living things” and recognized that an extraordinary diversity of organisms existed within this very small area.
The island was particularly important for the study of warm-climate plants and rare slime molds. Kumagusu believed that Kamishima demonstrated how an exceptionally rich natural environment could exist within a remarkably small area.
His research on the island contributed to a broader understanding of the biodiversity of southern Japan and established Kamishima as an important site for natural history research.
During the late Meiji period, a government policy promoting the consolidation of Shinto shrines placed Kamishima’s natural environment at risk.
There were plans to merge Kamishima Shrine with another shrine and sell the island’s forest, with the proceeds potentially being used for projects such as school construction. If the forest had been cut down, the island’s unique ecosystem could have been permanently damaged.
Minakata Kumagusu strongly opposed the plan.
He argued that Kamishima was extraordinarily valuable from a scientific perspective and emphasized its importance to local fisheries, traditional culture, and the natural environment. Working with local residents and other researchers, he launched a campaign to protect the island.
His efforts helped lead to Kamishima being designated as a protected forest in 1912 and subsequently as a National Natural Monument in 1935.
Kumagusu’s determination played a major role in preserving the forest that visitors can still see today. His activities also represent an important early example of modern-style nature conservation in Japan.
Kamishima is also associated with a memorable visit by Emperor Shōwa.
In 1929, Emperor Shōwa visited Tanabe Bay and received an explanation of the area’s natural history from Minakata Kumagusu. Kumagusu reportedly showed the emperor specimens of slime molds and marine organisms while explaining the scientific importance of Kamishima.
After the visit, Emperor Shōwa composed a waka poem about the island and Kumagusu:
“Seeing Kamishima veiled in rain, I think of Minakata Kumagusu, born in the land of Kii.”
It is unusual for an individual’s personal name to appear in a poem composed by Emperor Shōwa. The poem illustrates the strong impression that Kamishima and Kumagusu made on the emperor during the visit.
The most striking feature of Kamishima is its dense evergreen forest, which covers almost the entire island.
The vegetation includes trees characteristic of warm regions of Japan, such as holly olive, camphor trees, Japanese camellias, tabunoki evergreen trees, and Japanese umbrella pine.
The island is also rich in climbing plants such as hakamakazura and teikakazura. Their tangled growth contributes to the impression of a lush, almost subtropical forest.
Rare plants can also be found on the forest floor, including species such as Kinokuni sedge. Despite its small size, Kamishima supports an unusually diverse plant community.
Kamishima is important not only for its plants but also for its many animal and microscopic organisms.
Research into terrestrial mollusks and soil organisms has resulted in the discovery of species for which Kamishima became a type locality, meaning the place associated with the original scientific description of a species.
The island is also particularly important for the study of slime molds, a group of organisms that fascinated Kumagusu throughout his career.
The remarkable biodiversity of Kamishima can be attributed in large part to the fact that its environment has remained relatively undisturbed for such a long period.
Although Kamishima has been protected for generations, its ecosystem is not completely immune to environmental change.
Since the 1990s, large numbers of Japanese cormorants and great cormorants have begun gathering on the island. Their droppings have damaged some of the trees, and sections of the forest have experienced increasing tree death.
Other environmental issues, including increases in rats and changes in vegetation, have also emerged. These changes have created new challenges for researchers and conservation authorities.
Today, efforts continue to determine how the island’s ecosystem can best be restored and protected for future generations.
The challenges facing Kamishima demonstrate that nature conservation is not simply about protecting an environment from human development. It also requires continuous observation and management as ecosystems respond to changing environmental conditions.
Because of its exceptional ecological and cultural value, landing on Kamishima is currently prohibited for ordinary visitors.
This restriction is intended to protect the island’s fragile ecosystem and preserve its scientific and cultural heritage for future generations.
Although visitors cannot normally walk on the island, Kamishima can be viewed from the surrounding coastline and from boats operating in the waters of Tanabe Bay. From the sea, the dense green forest rising from the small island creates a striking and mysterious silhouette.
Visitors interested in the story of Kamishima can also explore other places associated with Minakata Kumagusu in and around Tanabe. Combining these sites with a visit to the island’s surroundings offers a deeper understanding of Kumagusu’s scientific work and his pioneering ideas about nature conservation.
Kamishima is much more than an uninhabited island.
Its forests preserve the history of Kumano faith, the island’s name reflects centuries of reverence for nature, and its ecosystem demonstrates the close relationship between forests and the sea. At the same time, the island’s history is inseparable from the life and conservation efforts of Minakata Kumagusu.
Within an area of only a few hectares, Kamishima brings together religion, biodiversity, scientific research, local fishing culture, literature, and environmental conservation.
Looking across Tanabe Bay toward the quiet green island, visitors can appreciate not only its beauty but also the generations of people who worked to preserve it.
Kamishima offers a powerful reminder that some of Japan’s most important natural treasures are not simply places to visit, but places to respect and protect. Its forests, legends, and scientific heritage continue to tell the story of the deep relationship between the people of Kumano and the natural world that surrounds them.