The Okinawa dugong's days could be numbered. At most 10 of the marine mammals remain in Japan's southernmost prefecture, according to the Nature Conservation Society of Japan (NACS-J). Now, land reclamation needed for a new U.S. Marine Corps air base threatens two of the region's few remaining major beds of seagrass, which dugong depend on, says NACS-J, which has petitioned U.S. Ambassador to Japan Caroline Kennedy for permission to conduct a survey.

Dugong inhabit coastal zones in tropical and semitropical waters of the Indian and Pacific oceans. Populations have been decimated by hunting, habitat loss due to coastal development, and fishing by-catching. The International Union for Conservation of Nature lists the dugong as vulnerable to extinction worldwide. Japan's environment ministry considers the Okinawa dugong, the northernmost population of the species, critically endangered.

The new base offshore of the Henoko district of Nago city in Oura Bay could be the death knell for the Okinawa dugong. One seagrass bed will be covered by the construction, and another will be dredged for sand. In mid-July, the Okinawa Defense Bureau, which is overseeing construction, restricted access to the site to start a drilling survey needed to finalize reclamation plans. NACS-J had planned to have two foreign experts last month examine recently sighted feeding trails, the characteristic paths through seagrass beds dugong create as they uproot and eat the vegetation. But the U.S. Marine Corps denied access to the construction zone, citing safety concerns. So last week NACS-J appealed to Kennedy, emphasizing the scientific nature of their intended survey and asking for her "special attention to and reconsideration on this profound problem."

NACS-J acknowledges that its aim is to stop construction of the base. "It will be very, very hard for the dugong to survive if this project goes on," says Mariko Abe, head of conservation for NACS-J.

The controversy over the new base is just the latest twist in a protracted dispute over the U.S. military presence on Okinawa. Responding to concerns about noise, air pollution, and safety, in 1996 the U.S. and Japanese governments agreed to relocate the current U.S. Marine Corps air base, called Futenma, to the Henoko–Oura Bay site in northern Okinawa. Environmental groups have long opposed the plan, as the construction would destroy a coral reef as well as the two major seagrass beds. Twice in the past month, thousands of demonstrators have marched to the shore near the site demanding construction be halted, and sympathizers in Tokyo staged a protest rally this past Saturday. On 3 September, the Okinawa prefectural assembly adopted a resolution calling for an immediate halt to the drilling survey. The current governor was elected in 2010 on a platform calling for the base to be moved out of Okinawa Prefecture entirely. But late last year he changed his mind and gave the go-ahead for reclamation work. He now faces an antibase rival in a 16 November election.

The U.S. Marine Corps apparently feels that environmental concerns have already been dealt with. In a letter to NACS-J denying the request to enter the restricted waters, C. B. Snyder, deputy commander of the Marine Corps Installation Pacific, wrote: “Our understanding is that Japan studied the potential impacts of the current construction activity under Japanese Environmental Impact Assessment law.” The U.S. embassy press office could not immediately confirm whether Kennedy had received the 16 September NACS-J letter. In the meantime, the Center for Biological Diversity and other U.S. and Japanese environmental groups filed a lawsuit on 31 July in U.S. district court in San Francisco, California, seeking to force the U.S Department of Defense to halt construction.

Okinawa’s dugong may be doomed no matter what. Even if the seagrass beds are preserved, "it's hard to imagine that a population this small is viable, as it is also isolated and at the extreme of its range," says Ellen Hines, who specializes in marine and coastal conservation at San Francisco State University. Nevertheless, she says, "it is against both U.S. and moral conventions for the U.S. military to degrade habitat for this critically endangered species and accelerate its extirpation."

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