Asia Pacific Bat News

JAPAN

The effect of the new Ishigaki Airport on bats

Dr Sumiko Matsamura. Posted: 14 August 2008

In 2006 we formed the “Kara Karst Scientific Investigation Committee” to survey the cave fauna and to monitor the impact of airport construction work. We secured funding to make four investigations of bats, cave insects and hydrology. The locations of bat species found, and the types of roost, are shown in Pic. 2. “A-Cave” is very important for bat populations. Within it we found maternity colonies of two species (Hipposideros turpis and Rhinolophus perditus). In addition, during our investigation in July 2006 (the maternity season), over 1,000 individuals of Miniopterus fuscus emerged from the cave, and 90 in 2007. We caught a lactating female in the vicinity of the cave in 2007, but we were prohibited by the construction office from netting for bats at the cave entrance or within it. We concluded that A Cave is also occupied by a maternity colony of M. fuscus, the only one that has been found on Ishigaki Island, but the Okinawan government refuses to accept this as a breeding site for this species based on our records. Nevertheless, our conclusion is that A Cave is the most important of all known sites for bats on Ishigaki, with breeding colonies of all three resident species.

In a report the Okinawan government maintained that, “because A and D Caves are to be preserved, the influence [of airport construction] on bats is negligible.” But our surveys before and after the construction work commenced indicate that this view is mistaken, as there has been a clear decrease in bats in A and D Caves. Before the construction, the total number of bats of all three species roosting in the caves was about 8,000 through the year, but now it has decreased to 1,000 or less. We published a report informing the government of Okinawa Prefecture (New Ishigaki Airport Construction Section) of this serious situation, but they ignored our opinion and told us “evidence of a decrease was not given in reports by the assessment company (NPO ABRI, Chief is Dr. K. Maeda) whom we contracted” and “We are consulting the bat specialist (Dr. K. Maeda) at every stage.” In the Environmental Assessment Reports of this project, Okinawa Prefecture said “if a significant negative influence on bats is identified, construction work will be halted, advice sought from experts, and the situation re-examined.” But this has not been done. We did an assessment recently, supported by WWF Japan and Pro Natura Foundation- Japan, and found that the bat numbers had decreased even further. Moreover, a new cave was exposed by construction work while constructing a pond for precipitation of red clay (Pic.3).

In order to mitigate the loss of cave roosts, Okinawa prefecture has constructed an artificial cave system to the east of the airport. Conservationists involved in the construction of artificial caves will however be familiar with the long delays before they are occupied by bats.

Pic. 1 Location of planned airport over golf course and arable fields with caves shown in orange. The blue lines on the right of centre is a newly constructed artificial cave system.

Pic. 2 Location of caves and bat roosts in relation to the airport construction area (shown by broken line)

Pic. 3 Cave exposed by construction work

Ishigaki is one of the subtropical Yaeyama islands at the south western end of the Japanese archipelago, and is administratively part of the Okinawa prefecture. The construction site for the airport overlaps the Kara Karst, an area of karst limestone of about 1 km²(Pic. 1). It is estimated that more than 8,000 bats roost in caves in this area, which is around 40~50% of the total bat population of Ishigaki Island.