Environment

Fears for Okinawa's unique ecosystem

by Mick Corliss

Okinawa Prefecture punctuates the Japanese archipelago as the period on its southern border. Stretching westward like an island path leading to Taiwan, the island group, though small, is teeming with a diverse abundance of plant and animal life.

Uniquely located where two distinctly different climates intersect, Okinawa is the southern and northern limit for a host of plant and animal species. Its subtropical climate, combined with its position between the tropics of Southeast Asia and the more temperate Japanese mainland, have turned the island into a biological melting pot.

The Okinawa group of islands is geographically part of the Nansei Islands encompassing a broad arc 1,200 km southwest of Kyushu. In common Japanese parlance, however, Okinawa is the main element of the Ryukyu islands, which group smaller islands southwest into a unit Japan calls Okinawa Prefecture.

Okinawa accounts for a meager 0.6 percent of Japan’s soil but is host to an unusual amount of its flora and fauna, including many endemic species found nowhere else.

While its beaches, coral reefs and nature have achieved notoriety, the island is also becoming a popular destination for tourism, especially ecotourism.

However, experts are worried about the prefecture’s environmental prospects. Coral experts say they have seen most of Okinawa’s reefs disappear in the past 25 years and are striving to protect those that remain. Naturalists and conservation groups say the Yambaru area, home to many unique species, is also in need of protection.

Also nationally unique and at risk for Okinawa is the dugong. This mysterious seaside denizen is a gentle, elongated sea mammal related to the manatee. Dugongs live in shallow waters and feed on sea grass.

Okinawa is struggling to achieve economic strength on par with the mainland, but the pressures of increased tourism are taking a toll on the Yambaru forests, coral reefs and the dugongs. Logging and development in Yambaru, construction projects along the coasts and military facilities and fishing nets are all posing various threats.

Ryukyu species in danger

The Ryukyu Islands’ biodiversity has earned it the local nickname “Galapagos of the East.” The Ryukyus are home to a quarter of the nation’s mammal species, half of its fowl and more than a third of its plants.

After the islands split from continental Asia, some species marooned on Okinawa survived nicely while their mainland counterparts disappeared. Other animals took advantage of the island to diversify, blazing new evolutionary paths uncharted elsewhere.

This gave rise to an ecosystem of living fossils and undiscovered species that thrived under the protection of the broad-evergreen forests of northern Okinawa Island.

Locally known as Yambaru, this forested area is only a small chunk of the prefecture and a thousand times smaller than the nation’s total land mass. But what it lacks in area is made up for by its estimated 192 endemic species.

Devoid of major predators, Yambaru helped evolve such species as the Okinawa Rail, a flightless bird officially discovered in 1981 but known to locals since at least the 1970s. Estimates of the bird come to between 5,000 and 10,000.

But the introduction of nonindigenous animals — cats, dogs and especially mongooses — have trimmed their numbers.

The Okinawa Woodpecker is in danger of disappearing. Although about 500 of the birds are estimated to exist, they nest in the hollows of Yambaru’s dying broadleaf trees. As the trees disappear, so do the woodpecker’s chances for survival.

Aside from numerous birds, the dense forest is also a haven for rodents. Japan’s largest rat, the Ryukyu Longtailed Giant Rat, and the Spinous Country Rat are unique to Yambaru. Likewise, the nation’s largest beetle, the Jambar Long-armed Scarab Beetle, dwells beneath Yambaru’s lush canopy. Like the birds, each creature has an ecological niche and occupies one or more of the forests’ three to four levels of vegetation.

But the biggest threats to Yambaru are, according to nature groups, dams, logging and the invasion of foreign species. Access by new species is being facilitated by a network of timber roads that are nearly complete.

Yambaru’s mountainous terrain keeps farmers in the flatter, southern half of the island, but development is slowly creeping northward.

Today the most well-preserved areas of Yambaru are located within the U.S. military’s jungle training area. Roughly half is scheduled to be returned by 2002, and the Environment Agency is pushing to turn it into a park. If successful, the move could mark a shift from the area’s piecemeal species-by-species preservation policy to something more holistic.

Shiraho coral

Coral could well be considered Yambaru’s marine counterpart. Like the forest, coral nurtures and protects a fantastic multitude of animal life and once existed in abundance beneath the shimmering blue surface of Okinawa’s waters.

But land reclamation, development and soil runoff have ravaged most of the aquatic organism, with liberal estimates putting the death toll at 90 percent.

Today, the most renowned reef is located off the village of Shiraho. This reef is home to huge clusters of coral and more than 200 species, rivaling Australia’s Great Barrier Reef.

After years of working to protect the reef, the World Wide Fund for Nature Japan set up its first domestic research facility in Shiraho last April.

Construction for a new Ishigaki Airport, originally proposed in 1979 and slated to be built on top of the reef, brought vigorous resistance from locals.

Alternative sites were proposed, and a year of intermittent talks has resulted in the selection of a hill overlooking the reef.

But stripped of its protective vegetation cover, Okinawa’s fine red soil erodes easily into the sea, where it clouds the water, starving light-dependent organisms that make up the coral’s food source.

Questions about the environmental effects of construction still remain.

Dugong threat is human

Like many species in Yambaru and others throughout Okinawa, the dugong is also living at the edge of its habitat — the northern edge. Dugong live in areas ranging from east Africa to Australia, and experts estimate there are more than 100,000 of the mammals.

In Japan, experts say their number has sunk to double digits. Famous for being mistaken for mermaids, the dugong is now only seen around Okinawa’s main island, and principally along the east coast.

Most sightings have centered on the Henoko district of Nago, the spot slated for construction of a new civilian-military airport. Conservationists worry the airport will split the dugong’s habitat in half and reduce its food supply.

On June 17, a dugong appeared on the west side of the island in Motobu Port and has been lingering in the area ever since. Some reports say it has a swollen belly, and some experts speculate it is pregnant. Others fear it is sick.

The incoming airport is one of the major perceived threats to the animal. The other is fishing nets.

Roughly one dugong a year gets entangled and drowns in the nets, and nongovernmental groups in the area are calling on the prefecture and the central government to conduct surveys to gain a more complete understanding of dugong behavior. The groups plans further calls for action during the G-8 summit.

Impact of development

Since the return of Okinawa from the United States to Japan in 1972, the island group has struggled to develop its economy and accommodate the U.S. military while maintaining its unique, delicate environment. This struggle promises to continue.

But the future of Okinawa’s natural environment is three-pronged: economic development, military imperatives and nature preservation. While all are pressing, the kinds of choices that need to be made and their effect on this abundant environmental treasure-trove of lush forests and thriving coral can only be determined by time, and cautious consideration.

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