Flora and Fauna Living in Amami Oshima
- Flora and Fauna Living in Amami Oshima
The diverse habitats support abundant biodiversity
A variety of enviroments exist in Amami-Oshima, which is less than 0.5% of the area of Japan, due to the impact of topography and climate. A variety of creatures adapted to each enviroment where they nurture life.
creatures and plantsFlora and Fauna Living in Each Area
- The neighboring evergreen forests
- The aging forests
- The matured forests supported by large trees
- The Cloud Forest
- Mountain stream
01The neighboring evergreen forests
The growing forests are shimmering
Over 80% of Amami Oshima Island is covered in trees, most of which is secondary forest. After primeval forests were felled through forestry, castanopsis and other hardy plants sprouted, forming the forest as it is today. The forests surrounding the settlement, or shima, are bright, sunny forests that have grown over twenty years since the forest was felled. Old roads and charcoal kiln ruins remain in places, giving a glimpse into the relationship between humans and nature that has existed since antiquity. The castanopsis forests near human settlements are also teeming with plants and animals that take advantage of the sunlight here.
02The aging forests
A forest of luxuriant green leaves teeming with wildlife
Two to three decades after logging, secondary castanopsis forests reach their maximum height of roughly 15 meters, after which the trunk thickens and the lateral branches grow, the leaves luxuriating into a kind of umbrella. About thirty-five years after logging, the castanopsis leaves block the sunlight, making the forest dark and creating tiers containing many species, such as trees shorter than castanopsis, undergrowth, and the forest floor covered in fallen leaves.
03The matured forests supported by large trees
A forest that fosters myriad wildlife
20+ years after deforestation: In forests where more than fifty years have passed since deforestation, even larger castanopsis and other trees start to emerge. Its thick lateral branches branch even further, hollows form in the trunk, and great buttress roots develop as these trees take on new and various forms. It is thought that a forest takes more than one hundred years to return to a near pristine state after deforestation.
04The Cloud Forest
A Brisk Forest, Shrouded in Mist
Forests formed 500 meters above sea level in tropical and subtropical mountainous areas are called cloud forests, where fog and mist appear even on clear days, creating a humid environment with low sunlight. The Amami Oshima cloud forests are characterized short trees that can withstand the relatively low temperatures, strong winds, and poor nutritional conditions. With an abundance of ferns, orchids, mosses, and other species that thrive in damp environments, many plants endemic to Amami Oshima can be found growing on branches and rock walls here.
Life-nurturing, abundant water flow
On Amami Oshima, which has many steep terrains that stretch from the mountains to the sea, heavy rainfall has created numerous ridges and valleys by eroding the ground with water flow. In the upper and middle reaches of rivers that flow through these valleys, there are repeated fluctuations of water levels by 2-3 meters every time it rains. Plants have adapted to withstand the strong currents during floods and the dryness during droughts by having long and slender leaves or small leaves to reduce resistance against water flow, and by developing strong roots or rhizomes to cling to rocks or reducing hair on leaves to allow mud to dry more quickly. Additionally, Amami Oshima’s unique frogs and dragonflies can be seen around water sources.
Connecting Mountain Water to Abundant Oceans for an Environment Teeming With Life
Mangrove is the collective term for distinctive plants inhabiting brackish waters where fresh water and sea water come together, such as tropical and subtropical estuaries. One of the largest mangrove forests in Japan has developed near the estuary where the Yakugachi and Sumiyo Rivers meet, where nutrients and soil flow in from the vast subtropical rainforest. The main constituent species of this mangrove forest are Kandelia obovate and oriental mangrove, mixed with the looking-glass tree and Excoecaria agallocha.Mangrove forests also serve as breeding grounds for fish such as Ryukyu Ayu, as well as the larvae of crustaceans and mollusks. The muddy wetlands of the intertidal zone are home to a diverse range of creatures including Southern mudskipper, Southern fiddler crab, sesarmid crabs, Yamamoto butterflyfish, Okinawa anajakko, and many others.
The forest wildlife calendar
“The subtropical maritime climate of Amami Oshima Island is temperate throughout the four seasons. Here, we present flora and fauna adapted to each season of this temperate climate based on a seasonal almanac.”
The season when the leaves of the Castanopsis fall and the yellow flowers bloom. Insects attracted by the smell of flowers and birds that feed on them gather.
The rains increase the amount of water in streams and rivers. Water gets stored in fallen and composted leaves.
The forest protects the wildlife from strong sunlight and typhoons.
Acorns of the Castanopsis are an important source of food for the animals in the forest. Mammals enter the breeding season.
As the habu viper is less active, mammals enter the parenting season. Newborns grow up by eating acorns.。
A unique ecosystem topped by the hub viper
A lack of carnivores and large raptors in the ecosystems of Amami Oshima, Tokunoshima, and northern Okinawa Island in central Ryukyu has made the Ryukyu odd-tooth snake and the hub viper, which can grow as large as 2 meters in length, the largest snakes in their respective genera and the apex predators within the ecosystem.
The Amami rabbit (endemic to Amami Oshima and Tokunoshima) and three species of the spiny rat genus (endemic to Amami Oshima, Tokunoshima, and northern Okinawa Island) are nocturnal land creatures, meaning they are at high risk of predation by hub vipers; however, they have evolved behaviors to avoid this danger.