General Pizarro, a one-telephone town in the northern province of Salta, gained some notoriety last month when environmentalists chained up bulldozers to protest the sale of a nearby nature reserve.

Plans to raze forests have sparked wider fears that a push north by Argentina's farming frontier could sacrifice the environment to economic growth.

A boom in easy-to-grow, genetically modified soybeans in Argentina, the world's No. 3 soy producer, has brought farming to plots never before seeded. After a surge in prices, soybeans are now grown on half of all farmland here, and northern provinces represent 16 percent of that acreage, up from 9 percent a decade ago.

Some see the expansion as a godsend for such backwater areas as General Pizarro, a dusty, depressed town of 3,000 people 1,000 miles northwest of Buenos Aires.

But environmental groups say that clearing trees for big farms or ranches will bring few jobs and do great ecological harm, undermining long-term growth.

"People complain that landowners want to convert their property into farmland, but no one offers economically viable alternatives," said Carlos Suarez, an agricultural engineer and forestry specialist from Salta province.

"There's got to be a balance between environmental, social and economic factors," he said. "If not, there will always be conflicts."

Greenpeace, which staged last month's demonstration in General Pizarro, is seeking a two-year, nationwide ban on tree clearings to assess and protect forested areas. In June, environmentalists won a six-month halt to deforestations in neighboring Santiago del Estero province.

"The main threat to Argentina's remaining native forests is the advance of the farming frontier, especially to make way for genetically modified soybeans," said Emiliano Ezcurra of Greenpeace Argentina.

This year, Salta's government stripped the Pizarro reserve of its protected status and divided 39,500 acres among three private companies -- one of which focuses on soybean production. Provincial officials argued that the reserve was highly degraded and would be better put to productive use.

"What good do butterflies in the woods do me when people are dying of starvation and don't reach their 40th birthday?" said Salta's labor minister, Victor Manuel Brizuela.

Farms have spread north to arid areas where soils are fragile because land is cheaper, no-till planting techniques conserve moisture and cyclical climate changes have brought more rain.

About 60,500 acres a year were razed in Salta's Chaco woodlands from 1997 to 2001, at least quadrupling the world rate, a federal government study showed.

When Salta's government sold the former reserve for 10 million pesos ($3.3 million), about 40 families were living or raising animals there. The state wants to relocate them and to assist a community of Wichi Indians, who survive by collecting firewood, honey and plants.

This approach contrasts with the government's past inaction. Nearly everyone, from Salta officials to local townspeople, agrees that the state never protected these lands, even after designating the area a reserve in 1995.

"My intention is just to keep living here," said Ramon Rodriguez, 69, a subsistence rancher who has lived in the former reserve for 20 years. "I don't have anywhere to go or anywhere to take my animals."

Brizuela said revenue from the sale will go toward improving local roads, communications and the power delivery system.

Some local residents worry that the companies will monopolize water, pollute the environment and provide few jobs -- especially if they dedicate their land to highly mechanized soybean production.

"It's the enrichment of one person and the impoverishment of 3,000," local activist Carlos Ordonez said.

In the Chaco woodlands of Argentina's Salta province, the site of a protest last month, about 60,500 acres a year were razed from 1997 to 2001. Greenpeace activists walk through an area that was deforested to make room for farms in Argentina's Santiago del Estero province. Greenpeace protesters known as "Jaguares," or jaguars, ride dirt bikes in front of a bulldozer in a wooded area of Salta province that had been set aflame as part of the land-clearing process.