As he squatted down to examine an orchid on the Kitulo Plateau of this east African nation, Saidi Mwile's face lit up.

But his delight was not in the brilliant red flower. He was imagining the delicious taste of its root.

"When it's cooked, it tastes very nice, a lot like liver," Mwile said, carefully slicing off the tuber, which resembles a tiny potato.

For generations, people on this high, chilly plateau known as the "Serengeti of Flowers" have been harvesting the tubers of terrestrial orchids. Then they dry, pound and boil the resulting flour with wood ash to prepare "kinaka," an orchidean sausage that is a prized local delicacy.

But a burgeoning -- and illegal -- export trade in tubers to gourmets in neighboring Zambia is threatening the plateau's remarkable orchid population.

Between 2.2 million and 4.1 million tubers of dozens of species of terrestrial orchids are harvested every year for export to Zambia, said Tim Davenport, a field biologist with the Wildlife Conservation Society.

The society has set up the Southern Highlands Conservation Program in Mbeya, 420 miles southwest of the capital, Dar es Salaam, to protect important upland habitats and species in southwestern Tanzania.

"The problem is growing -- the demand in Zambia seems to be so high that people are now willing to move anywhere. . . . conservation is now very difficult," Davenport said.

The Kitulo Plateau is not just home to orchids. For six months of the year it is covered with other spectacular wildflowers as well, and is home to many species of birds, including the blue sparrow.

One solution would be to make the 52-square-mile area a national park, the first in tropical Africa aimed specifically at protecting endangered flora.

Davenport and Henry Ndangalasi, a botanist at the University of Dar es Salaam, have been studying the orchids for the past two years, and they warn that orchid collecting is growing too fast to be sustained.

Orchids are protected under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, CITES, which requires certification of plants taken across international borders.

But Mwile, a 41-year-old farm worker, has never heard of CITES and doesn't know orchids are protected. Like others on the plateau, he looks to the harvest, which gets underway about this time of year.

Solomon Mtwebe, who works with the Wildlife Conservation Society to inform locals about the dangers of over-harvesting, said collectors now burn off the plateau grass so that the orchids shoot up quickly and can be easily harvested.

"They dig them up and sell to me," said Eliath Sangah, a middleman who packs the tubers in 220-pound sacks and transports them to the border town of Tunduma 75 miles away.

He buys 44-pound plastic buckets full of tubers for about $1.50 apiece, then sells them in Tunduma for about $5 to $6.

"It's a better business than selling potatoes," said the 30-year-old Sangah.

"It's not true that orchids are getting finished," he said. "There are many other buyers who started trading in 1983 -- when exports began -- and who are still in business."

But the harvesters know there is a problem. These days it takes them three days to fill a bucket; two years ago it took a day.

"It is now a very tough job. I do it because I need money," said Pascal Kiondu. "We don't have to buy the tubers, and it's better to be digging up orchids than to be idle or stealing."

A year ago, President Benjamin Mkapa declared the Kitulo Plateau -- which the WCS says hosts "a staggering diversity of orchids" -- would become a national park. But the nation's parliament has not yet approved the declaration.

Farmers prepare a field to plant potatoes on the Kitulo Plateau in southwestern Tanzania, above, where endangered terrestrial orchids normally grow. The farmers also dig up orchid tubers for sale as delicacies to neighboring Zambia, but the orchids don't reproduce as quickly as potatoes do. Left, Solomon Mtwebe works with New York-based Wildlife Conservation Society to inform locals about the dangers of over-harvesting.