SCARLET MACAWS ARC through the sky like flaming arrows.

"I count six, seven," says Greg Sho, training his binoculars on an 80-foot quamwood tree.

"Four more in the tree west of them," says Sharon Matola, standing knee-deep in the Macal River, jotting notes as a rare Morelet's crocodile sunbathes on a boulder nearby.

Matola, the 48-year-old director of the Belize Zoo and an expert on scarlet macaws and tapirs, and Sho, 43, a stocky naturalist who moonlights as a guide for the British Army special forces units that train in Belize's "back-a-boosh," have come to the western divide of the Maya Mountains to observe the macaws' daily commute. Each morning these birds, a rare subspecies known as Ara macao cyanoptera, or the northern Central American scarlet macaw, fly over the spine of the Mayas to feed on the eastern slope, then return in the afternoon. Their home, high up in the leafy canopy that lines the Macal as it rolls down from the highlands into Guatemala, nurtures one of the greatest pockets of biodiversity north of the Amazon basin. During the rainy season, from June to November, the river swells, the succulent plants explode, and the animals—sleepy iguanas, darting oropendolas, packs of collared peccaries—belly up to nature's salad bar. But that may soon change. "Once the dam comes," says Matola, "everything you see here will be underwater. For good." The dam is a proposed $30 million, 160-foot-high concrete cork called the Chalillo Project. It would turn 12 miles of the Macal, and six miles of its tributary the Raspaculo, into a big bathtub, drowning 2,800 acres of pristine tropical forest and with it the riparian habitat that supports the macaws, along with jaguars, Baird's tapirs, ocelots, and spider monkeys.

An American expat who settled in Belize 20 years ago after a hitch in the U.S. Air Force and a stint as a lion tamer in a Mexican circus, Matola has been fighting the Chalillo Project since it was first announced by Prime Minister Said Musa in 1999. It's been an uphill battle, with banana-republic overtones and a clown car of competing parties facing off in the center ring.

The cast includes the Belizean government, which never saw a development project it didn't like; Belize Electricity Ltd. (BEL), which desperately wants the dam's 7.3 megawatts to drag the browned-out country into the 21st century; Fortis Inc., the Newfoundland-based energy conglomerate that owns BEL and wants to make some money; the Natural Resources Defense Council (NRDC), Probe International in Canada, and the Belize Alliance of Conservation Non-Governmental Organizations (BACONGO), which have sicced their enviro lawyers and mailing lists on BEL and Fortis; Matola, who wants to save the scarlet macaws and spare the fecund Macal Valley; a Cambridge-educated judge from Sierra Leone; a lone-wolf geologist; and a cadre of bulldozer-driving Mennonites.

Matola is an ace at maneuvering through the fiery hoops that pass for politics as usual in Belize and has rallied some handsome eco-celebs to her side. Harrison Ford, who filmed The Mosquito Coast here in 1985, slammed the project in a September 2001 op-ed piece in Toronto's Globe and Mail, and NRDC senior attorney Robert F. Kennedy Jr. denounced it as "one of the most harebrained, reckless schemes that I have seen in 20 years of environmental advocacy." Even Steve Irwin, a.k.a. the Crocodile Hunter, paid a visit to Matola's zoo this past February and shot an episode of his show on the Macal to bring attention to the birds' plight. But none of this has stopped Fortis, BEL, and the government from moving ahead with their plan. Which raises a thornier question that stretches beyond Belizean borders: How do you stop an underdeveloped nation from selling its environmental heritage to a multinational corporation?

Tough one. Especially for the northern Central American scarlet macaws. Only 60 survive in Belize; Matola and Sho know this because they've counted them. The rest—an estimated population of 3,000, ranging from southern Mexico to Nicaragua—are already considered endangered by the World Parrot Trust. If the dam goes up, Belize's flock could very well disappear. "The birds want a clean tree with open sight lines to see predators, which is why they nest in trees on the river," says Sho. "They don't nest in the jungle. The trees are too close together."