He and his allies have suffered defeats and may still lose the war. In April 1997 contractors finished a four-mile dike, an aggregation of 293 steel plates that effectively cut off a 7,400-acre portion of the Isahaya Bay wetlands from the sea. As a result, a lush marsh has turned to cracked earth, and the mudskippers forage for food in the isolated puddles that remain. Dumptrucks and excavators rumble through the dirt, preparing the foundation for a second dike. If the reclamation project continues across the wetlands, it could eventually wipe out as many as 300 species of birds, fish, amphibians and other animals.

But Yamashita, who works as a marine biologist at the Ariake Sea Fisheries Experiment, is in his strongest position ever to protect Isahaya Bay. The Japanese media now cover the issue after years of ignoring it, and the country's most popular opposition politician, Naoto Kan, made a much-publicized trip to the area. In April, Yamashita won a coveted Goldman Environmental Prize and used his $100,000 award to finance a TV documentary about the struggle to preserve the bay.

The biologist has already proved he'll never give up the fight. Over the years he has shrugged off a barrage of anonymous phone threats, and in 1982 he even turned an offer from the Ministry of Agriculture of $268,000 in "compensation" if he would drop his opposition to reclamation. Such obstinence infuriates his critics, who believe in the Japanese adage that any nail sticking up ought to be hammered down. "Yamashita may be an activist to preserve nature, but I've never understood what he's up to," says Shigeki Yamazaki, a local farmer. "He only associates with strange people in the nature movement, and he's not accepted by the community."

That kind of talk doesn't bother Japan's leading environmentalist. From his house above Isahaya, where the two microscopes in his tiny study are all but buried in a sea of books and research papers, Yamashita is busy enough fielding phone calls from journalists and politicians to feel confident that his campaign to save the bay is destined to be lifted by a big wave of support.