KAWAI, K., TERADA, R. and KUWAHARA, S. (eds): The Islands of Kagoshima Kagoshima University Research Center for the Pacific Islands, 15 March 2013 Chapter 22 Biodiversity in the Islands of Kagoshima Takahiro OKANO 1. Introduction ference in temperature. The average temperature he plane leaves from Kagoshima Airport head- in Isa City (average value from 1981 to 2010, the Ting south, with Mt. Sakura-jima smoldering same shall apply hereinafter) is 15.3 ˚C, 18.6 ˚C below. Yakushima Is. comes into view. Also known in Kagoshima City, 21.6 ˚C in Amami City Naze, as a “Floating Alps,” the mountains of Yakushima and 22.4 ˚C in Okinoerabujima Is. Furthermore, the Is. rise almost 2,000 m out of the ocean surrounded annual average temperature of Yoronjima Is. to the by the Kuroshio Current. Yakushima Is. is a world south was 22.8 ˚C from 2001 to 2010. The tempera- heritage site famous for its Japanese cedar, some of ture difference of lowland north to south is 7 ˚C, which are more than 1,000 years old. To the side, and is classified as warm-temperate and subtropical long and flat Tanegashima Is., with its rocket base, climate zones. can be seen. While gazing at the chain of Tokara The highest mountain of Kagoshima Prefecture, as Islands, the plane begins to descend. Welcomed by well as all of Kyushu, is Mt. Miyauranodake (1,936 m). coral reefs, white sandy beaches, and the beautiful Also in mainland Kyushu, Mt. Karakunidake of blue ocean, the plane lands in Amami-Oshima Is. Kirishima mountains soars 1,700 m high. As eleva- As you get off the plane, you notice the difference tion increases, temperature decreases. In winter, air in temperature. Depending on the season, there can temperature near the mountain top drops below zero even be a 10 ˚C difference. Amami-Oshima Is. is and snow can be seen, and the area belongs to the a semitropical island. Even the appearance of its cool-temperature zone. forest differs from that of mainland Kyushu. In the Due to the world's largest warm current, dense subtropical evergreen forests of the Amami Kuroshio, rainfall in Kagoshima Prefecture is abun- Islands, many plants and animals are found which dant. Rainfall is especially heavy during the rainy do not exist anywhere else on earth, such as the en- and typhoon seasons. Average rainfall in Isa City demic Amami rabbit. (average value from 1981 to 2010, the same shall Kagoshima Prefecture, with its chain of unique apply hereinafter) is 2,057 mm, 2,265.7 mm in islands stretched out 600 km north to south, is a Kagoshima City, 2,837.7 mm in Amami City Naze, prefecture rich in biodiversity. This biodiversity is 1,836 mm in Okinoerabujima Is., and 1,740.9 mm supported by the wide diversity of the environment. in Yoronjima Is. Especially Yakushima Is. is known This article introduces the characteristics of the var- for its abundant rain. Average rainfall in the seaside ious environments and their biodiversity, and major areas is 4,477.2 mm, and 8,000-10,000 mm falls in species of the islands. the mountainous areas. 2. Environmental diversity 2.2. Two biogeographic areas 2.1. Three climate zones and abundant rainfall Kagoshima Prefecture stretches across two biogeo- eographically, Kagoshima Prefecture stretch- graphic areas, reflecting long north to south geo- Ges over 600 km north to south, with a latitude graphic characteristics, and island formations of the width of five degrees, from Shishijima Is. rising Ryukyu arc from southern Kyushu to Taiwan. from Yatsushiro Bay at 32˚ N to Yoronjima at 27˚ A biogeographic area divides the earth into N. This difference in latitude is reflected in the dif- geographical distribution patterns of plants and 136 The Islands of Kagoshima animals. Geographical distribution is determined by animals is assumed to have been blocked, and thus terrain which blocks migration, such as an ocean or formed a border line. For instance, Habu, a poison- mountain chain, history of connection and separa- ous snake, does not live north of the Tokara Straits. tion of the continent and island, etc. Based on this, Looking at the seafloor topography of the the earth is largely divided to six zoogeographic Ryukyu arc, there is another 1,000 m + deep trench. provinces and six floristic kingdoms. Kagoshima This is the Kerama Straits, located south of the Prefecture is classified in the Palearctic and Oriental Kerama Islands. This is also a borderline for land an- zoogeographic provinces and in the Boreal and imals. Regarding Habu snakes, Habu are distributed Paleotropical floristic kingdoms. Kagoshima Pre- north of the Kerama Strait, but the Sakishima habu fecture is the only prefecture in Japan which is in- is distributed south of Kerama Strait. Hence, when cluded in two geographical regions. considering biodiversity of the Ryukyu Islands, the The border line between the Palearctic region area north of the Tokara Strait is referred to as North and the Oriental region for land animals such as Ryukyu, and the area between the Tokara Straits and mammals, terrestrial reptiles, and amphibians, is the the Kerama Straits as Middle Ryukyu, and the area Tokara Straits located between Akusekijima Is. and south of Kerama Straits as South Ryukyu. Kodakarajima Is. of the Tokara Islands. This border In contrast, the straits between Yakushima Is. and line is called the “Watase line” (Fig. 1). mainland Kyushu, as well as between Tanegashima During the glacial period, water was stored in Is. and mainland Kyushu, are no deeper than 100 m. the continental glaciers as the earth cooled, and Consequently, these areas are assumed to have been ocean water levels are estimated to be more than connected to mainland Kyushu with the 120-140 m 100 m lower. However, the Tokara Straits still ex- drop in sea level during the latest glacial period about isted as water straits because the water depth was 20,000 years ago, allowing land animals such as more than 1,000 m. As a result, migration of land deer and monkeys macaques migrated freely be- Fig. 1. Map of the island-chain of Kagoshima and Okinawa Prefectures, southern Japan, showing Satsunan and Ryukyu Islands. 137 Kagoshima University Research Center for the Pacific Islands tween. As a result, the biota of Yakushima Is. is very 3. Characteristics of biodiversity in Kago- close to that of mainland Japan, including Kyushu. shima Prefecture Yakushima Is. is the southern limit of the distribu- 3.1. Various forest types tion of the Japanese macaque. lants have optimal conditions and limit values Distribution of flora has consistently changed Pin which to survive, and the areas in which they due to the influence of the Kuroshio Current which live are limited by temperature, sunlight, and arid- flows northward. The Satsunan Islands are a transi- ity. Since Kagoshima Prefecture has abundant rain- tional zone between the Holarctic floristic kingdom fall, forests have developed to adapt to three climate and the Paleotropical floristic kingdom. zones. An evergreen broadleaf forest developed on 2.3. 605 Islands Osumi Peninsula, which is a warm-temperate zone. Kagoshima Prefecture has 605 islands, second only This kind of forest is mainly comprised of evergreen to Nagasaki Prefecture. However, according to the broad leaf trees, such as white oak, Chinquapin total area of the isolated islands is about 2,500 km2, (Castanopsis), laurels such as Japanese machilus and Kagoshima is the largest. camphor trees, theaceaes such as “Sakaki” (Cleyera Island structure also varies. Some islands were japonica) and camellias. This type of forest is also formed as the continent tore apart due to crustal called a “glossy leaved forest” because the plants movement. Others were formed volcanic eruption, have small, thick leaves which can withstand cold elevated coral reefs, or elevated seabed sediment on and dry conditions, and the surface cuticle layer of the seabed. Still others were formed by the elevated the leaves reflects the sunlight. Amami-Oshima and rocks. The environments of the islands also greatly Tokunoshima Is., which belong to the subtropical vary depending on the constitution of the islands. zone, have subtropical evergreen broadleaf forests Furthermore, because of the many islands, the comprised of Chinquapin (Castanopsis siebol- total extension of the coastline is 2,643 km, and dii known colloquially as “Sudajii”), “Okinawa- is the third longest of all the prefectures in Japan. urajirogashi” (Quercus miyagii), Japanese machi- Coastlines also vary between rock reef, coral reef, lus, Distylium racemosum. For a humid forest to pebble beach, sandy beach, and tidelands. Within develop at this latitude is unusual in the world. the sandy beaches, the sandy beaches on Yakushima The high elevations of Kirishima Mountains Is. are comprised of shaved granite and those on and Takakuma Mountains are cool-temperature Yoronjima Is. by the coral pieces. Large-scale zones of summer-green forests consisting of de- mangrove forests are established at the mouth of ciduous broadleaf trees. Takakuma Mountains is the Sumiyou River on the Amami-Oshima Is. southernmost limit for Japanese beech and Japanese oak, which are the dominant species of the cool- 2.4. Complex topography temperate zone. Kagoshima Prefecture is one of the prefectures which have many volcanoes in Japan. There are 3.2. Rich diversity of species four massive calderas, Kakutou, Aira, Ata, and Because Kagoshima Prefecture has three climate Kikai, and 11 active volcanoes. The activities of the zones and two zoological regions, Kagoshima earth have created a complex topography, and vari- Prefecture has a rich diversity of species, including ous environments. The activities of active volcanoes 49 mammals, 419 birds, 48 reptiles, and 26 amphib- have influenced the creatures living nearby, at times ians.