Over 60 percent of rare plant species, including endangered ones, that were transplanted due to the construction of U.S. military helicopter landing and takeoff sites in Okinawa have died, documents showed Sunday.
Construction of the landing zones for Osprey tilt-rotor aircraft is under way in the U.S. military's Northern Training Area on northern Okinawa Island.
The construction commenced in 2007 under a U.S.-Japan agreement on the return of part of the land used for the training area in exchange for the new helicopter zones. The government's Okinawa Defense Bureau plans to build 75-meter-diameter helipads at six locations in four districts of the training area.
According to bureau reports obtained under the freedom of information law, in one of the four districts, the bureau transplanted 11 plants of rare species in July 2007 but by September 2011, seven of them, or 64 percent, had died.
Of 41 plants transplanted to a different location between 2007 and 2008, only one had died as of November 2011, but the number in good condition had declined to 12 from 26 as of last June.
The names of the plants involved were not disclosed in the documents, but according to prefectural officials briefed by the bureau, the dead plants included endangered species. The bureau said the transplanted plants may have died due to typhoons or soil erosion from rain.