Imminent Extinction Crisis Among the Endemic Species of the Forests of Yanbaru, Okinawa, Japan

Oryx Vol 34 No 4 October 2000 Imminent extinction crisis among the endemic species of the forests of Yanbaru, Okinawa, Japan Yosiaki ltd, Kuniharu Miyagi and Hidetoshi Ota Abstract The natural forest in Yanbaru, the northern Although an area in Yanbaru occupied by the US part of the main island of Okinawa (Okinawa Honto), Marine Corps has, to date, preserved good natural is an important area for nature conservation, because it forest, a new plan to establish seven military helipads has a large number of endemic animals and plants. in this area is now being examined. Possible outcomes First, we explain the status of the most important of such a development are evaluated. In addition, re- endemic animals of Yanbaru, stressing that most of quests by Japanese biologists for the Defence Facilities them are endangered and near extinction. Second, we Administration Agency, Japan to consider alternate show especially high species diversity of trees, insects sites for the helipads are described. and mites in the Yanbaru forest. However, the integrity of the Yanbaru forest is seriously threatened by clear- Keywords Endangered species, endemism, Japan, Oki- cutting and complete removal of forest undergrowth. nawan forests, species diversity, Yanbaru. of the Yanbaru forest dominated by C. sieboldii trees Introduction older than 30 years as natural forests, and to those Yanbaru, the northern montane part of Okinawa including some pine trees Pinus luchuensis as secondary Honto, the largest island (1202 sq km) of the Ryukyu forests (pine trees cannot survive in the climax forest of Archipelago of Japan is an important area from both Okinawa) (Tsuchiya & Miyagi, 1991; see also Yokota, ecological and aesthetic points of view, because it sup- 1994 for English explanation). ports a number of specialized endemic animals and Most of the characteristic Okinawan wildlife, includ- plants (see Appendix). ing mammals and birds endemic to this island, can The climax vegetation of Yanbaru (300 sq km in area) breed only in natural forests. However, except for the is subtropical rain forest, dominated by the evergreen forests located in the US Marine Corps Northern Train- oak or chinquapin Castanopsis sieboldii with other ever- ing Area (NTA, hereafter), which occupies c. 25 per cent green broadleaf trees such as Distylium racemosum and of the Yanbaru on the eastern slope of the central Schefflera octopln/lla (Plate 1). Although the true virgin montane area (Fig. 1), the natural forests of Yanbaru are forest is restricted to a few small areas because a large now being destroyed by clear-cutting and complete part of the forest is subjected to thinning or clear-cut- removal of undergrowth by national and prefectural ting, forest sections that were thinned or cut 40- governments. Thus, extensive areas of natural forest 50 years ago (chiefly for the reconstruction of houses now remain in the NTA only (Fig. 1). burned completely or destroyed during the war) have A new problem, however, arose in 1999. In response recovered the basic features of the climax community. to a request from the Marine Corps, the Defence Facili- Following the definition by the Nature Conservation ties Administration Agency (DFAA) of Japan is now Society of Japan (Anonymous, 1995), we refer to parts planning to establish seven helipads within two of the best preserved natural forest areas in the NTA (see Fig. 1). One of the main reasons for the publication of this Yosiaki ltd (corresponding author) 2908, Kaguyama 2-chome, article is to highlight the biodiversity of the sites that Nisshin, Aichi 470-0134, Japan. Tel. & fax: +81 52 805 0437; are planned for development. e-mail: [email protected] Kuniharu Miyagi Faculty of Arts and Sciences, Okinawa Endangered animal species International University, Ginowan, Okinawa 901 -2701, Japan. Tel. & fax: +81 98 892 1111; e-mail: [email protected] The Appendix shows a list of species and subspecies of Hidetoshi Ota Faculty of Science, University of the Ryukyus, terrestrial vertebrates living on Okinawa Honto, includ- Nishihara, Okinawa 903-0213, Japan. Tel: +81 98 895 8937; ing their distribution characteristics and status accord- fax: + 81 98 895 8576; e-mail: [email protected] ing to the revised Red Lists of the Environmental Agency of Japan (Anon., 1997, 1998). Although Revised manuscript accepted for publication 5 June 2000 i 2000 FFI, Oryx, 34(4), 305-316 305 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.42, on 27 Sep 2021 at 07:16:51, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.2000.00136.x 306 Y. Ito et al. there are some endangered species in the sea around area of Japan). For example, Yanbaru has 2 Yanbaru (e.g. Dugong dugong), we discuss hereafter (16.7 per cent) of 12 CE species and 4 (20 per cent) of 20 terrestrial vertebrates only. High proportions of species E species of mammals living in Japan. or subspecies that are endemic to Okinawa Honto (in- In addition, it is worth noting that 5 of the 11 CE and cluding some species which are endemic to Yanbaru) or E species of 4 tetrapod classes, shown in the Appendix, endemic to the Amami Islands and Okinawa Islands are endemic to Yanbaru only, and the other 6 species (N-MR) are notable (69 per cent of mammals, are endemic to the Ryukyu Archipelago. Even for the 74 per cent of reptiles and 75 per cent of amphibians). latter, extinction of the Yanbaru population may induce Migratory species, stragglers, and species belonging to a high risk of complete extinction of these species from groups that live on the seashore, around rivers or the earth, because populations living in the other is- ponds, crags and buildings were omitted from the list lands (especially Amami-Oshima Islands and of birds. Nevertheless, of the 22 species found in the Tokunoshima Islands) seem to be smaller than those in forests of Yanbaru, two species and one subspecies are Yanbaru. unique to Yanbaru, and 17 are subspecies that are In the revised Red Lists of Japan, only a part of endemic to the Ryukyu Archipelago. which have been published to date, the Environmental Table 1 shows the numbers of Critically Endangered Agency is using three subcategories of the category (CE), Endangered (E) and Vulnerable (V) species of 'Threatened', namely CE, E and V (see explanation in terrestrial vertebrates living in Yanbaru, as compared Anon., 1997, 1998), similar to the new IUCN Red with the numbers in the whole of Japan. Yanbaru has a Lists (IUCN, 1999). However, due to the lack of good notably large proportion of threatened vertebrate spe- quantitative data on the current population size and cies, despite its small area (c. 0.08 per cent of the total rate of recent population declines in many species, the 128° E * J * i Secondary forests Forests of C. sieboldii • of > 30 yr old Special conservation area of mammals and birds Nature conservation area Fig- 1 MaP of Yanbaru< showing natural forests, US Marine Corps Northern Training Area (NTA) and areas proposed for '• US. Marine Corps Area establishment of Marine Corps helipads (A 10 km and B). i 2000 FFI, Oryx, 34(4), 305-316 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.42, on 27 Sep 2021 at 07:16:51, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1046/j.1365-3008.2000.00136.x Extinction crisis of endemic species in Yanbaru, Okinawa 307 Table 1 Number of Critically Category Area Mammals Birds Reptiles Amphibians Endangered and Endangered species, living in the whole of Whole of Japan 12 17 2 1 Japan and Yanbaru, described Critically Endangered in the new Red Lists of the Yanbaru 2 1 0 0 5 Environmental Agency of Endangered Whole of Japan 20 25 4 Japan (Anon., 1997, 1998) Yanbaru 4 2 0 1 Vulnerable Whole of Japan 16 48 11 9 Yanbaru 0 2 2 4 categorical designations in the Japanese Red Lists are have been found in the last 5 years. Thus, the mean not sufficient to satisfy the conditions necessary to numbers of individuals of these two species in recent define the status of a species according to the IUCN years are believed to be fewer than 1000. Although categories. In addition, the Environmental Agency uses quantitative data are not available, numbers of living subspecies in the Red List of Japan. For example, individuals of other E species in Yanbaru, such as the Tokudaia osimensis osimensis from Amami-Oshima and Okinawan rail Gallirallus okinawae (Plate 3), are not Tokunoshima Islands and T. o. mueninki from Yanbaru believed to exceed 10,000. are listed as two independent Threatened species (al- As far as invertebrates are concerned, the giant long- though some Japanese mammalogists consider that the armed scarab beetle Cheirotonus jambar (Plate 3) is at Yanbaru population belongs to a separate species, T. risk because it may be close to extinction. Its larvae can mueninki, different from T. osimensis: Abe et ah, 1994). grow only by feeding on the humus that accumulates in Nevertheless, at least for the mammals and birds of large holes on large trees (i.e. stem diameter of breast Yanbaru, the CE and E categories of the new Red Lists height, DBH, > 40 cm: Azuma et ah, 1985, 1986; of Japan are almost equivalent to those of the IUCN. As Azuma, 1994), but a few large trees only remain in discussed below, the numbers of living individuals of areas outside the NTA due to clear-cutting, and these three CE species listed in the Appendix are believed to trees are often checked by poachers who sell beetles be fewer than 1000 and those of six E species of illegally; the giant long-armed scarab beetle is a special mammals and birds are fewer than 3000 (of which two national emblem of Japan.

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