Japan's Environment Minister, Yoriko Kawaguchi, recently told Mick Corliss of The Japan Times that she would like to incorporate an "environmental perspective" into public-works projects. If she is serious, there could be no better place to begin than Mount Takao.

Mount Takao is less than an hour west of Shinjuku by train and stands a modest 599 meters high, yet it is as gracious and elegant a mountain as you will find. It also lies in the path of a planned expressway, the Ken'odo, and is slated to have two major tunnels drilled through its core.

Every year, more than 2 million people visit Mount Takao to hike, visit shrines and temples and eat at restaurants and stalls. Nature is the main attraction, but few visitors realize they are witnessing one of Japan's most diverse ecosystems.

The forests of Mount Takao shelter 1321 varieties of plants; 137 species of birds; 30 different mammals, including fox, wild pigs, badgers, raccoons and Japanese mink; 12 species of reptiles, including eight kinds of snakes; 10 kinds of frogs; and thousands of species of insects, including 88 species of butterflies and 55 of dragonflies. This unusual biological diversity results from Takao's location at the confluence of the Kanto Plain and the central mountains of Honshu, where the warm Pacific and temperate zones meet.

The mountain is often mentioned as a potential UNESCO World Heritage site.

Not surprisingly, construction authorities have kept a low profile on the project. If built, the Ken'odo ring road will circle through four prefectures and western Tokyo. On some highway maps, the projected route veers harmlessly around Mount Takao. PR materials distributed by the construction authorities show tunnels, but no mountain.

The Ministry of Land, Infrastructure and Transport plans to carve out two tunnels and two major interchanges, one on either side of the mountain. The junctions will require cutting numerous access roads into the surrounding hills and forests.

Opponents argue that no comprehensive environmental-impact assessment was done for the tunnels, nor for the Ken'odo project as a whole. They say the assessments that were done were unscientific and merely intended to rubberstamp the project.

When the Ken'odo plan was formulated 20 years ago, Japan had no national environmental-assessment law. The present law came into effect in 1998. As a result, the impacts of the expressway were considered piecemeal, using different laws and guidelines in Tokyo and each of the four prefectures. Raising further concerns, the Tokyo leg of the project (a 22.7-km section through Ome and Hachioji), was divided into two parts for assessment, and access roads were assessed as separate entities.

Local residents have brought suit against the Public Highway Construction Corporation and the national government. Since Mount Takao is no ordinary mountain, the legal action too is extraordinary: 144 lawyers from across the nation have joined the plaintiffs.

The lawyers hope to save Takao, and at the same time highlight several shortcomings in Japan's public-works culture: first, the lack of citizen participation in formulating public-works projects; second, the environmental destructiveness of such projects; and third, the threat posed to endangered species and the nation's biodiversity. The plaintiffs include 1061 individuals and six conservation groups.

But Takao is more than just a popular recreation spot known for its natural beauty and wildlife. It is also a site of unique historical, religious and cultural significance. The first temple was constructed on Takao in 744, and for over 1200 years the mountain has been protected, originally as a temple forest, later as a burial forest, and now as a quasi-national park.

In January I spoke with Shushin Nagashima, the deputy abbot of Takao-san Yakuouin Temple, which sits atop Mount Takao. He chose his words carefully, explaining, "We have to stay neutral because people supporting this temple are on both sides. Some are working for construction companies and some are not, so the wisest thing is to stay neutral."

Nevertheless, he said, Mount Takao is unique. "In the Kanto area, there are a few so-called sacred mountains, but historically this mountain has the strongest and longest history as a religious site."

When was his temple first notified of the project? "We have not been contacted," replied Nagashima. "Nothing has been officially reported to the temple office. We heard it as a rumor. No plan has been shown, no explanation has been given."

Nagashima agreed that this was discourteous, but repeated that he could not take an official stance on either side. After a moment's thought he added, "Even though we cannot make a public statement, our real feeling from the bottom of our hearts is that this is a sacred place and its nature should not be touched."

Nature, however, is not high on the list of concerns for public-works bureaucrats. As Noriko Hama, chief economist at the Mitsubishi Research Institute, told BBC radio recently, the government still has a post-war mentality. "They are thinking that a lot of infrastructure building needs to be done to prop up the economy."

But times have changed, says Hama. "Public works are no longer effective economically. If anything, the money that goes into these projects, had it been used in the private sector, would probably have stimulated the economy much, much more."

Nature-protection laws have changed too. According to a Takao resident, if you felled a tree in the 16th century, you lost your head. "One tree, one head," she said. "A very strong protection rule."

Certainly one that would give public-works bureaucrats pause for thought.