In spite of efforts to limit deforestation and encourage "sustainable development," the assault on the Amazon basin continues in Brazil.

The Amazon basin, which is larger than all of Europe and extends over nine countries, accounts for more than half of what remains of the world's tropical forests. But in spite of heightened efforts in recent years to limit deforestation and encourage "sustainable development," the assault on its resources continues, with Brazil in the lead. On Monday, the United Nations' World Summit on Sustainable Development is to begin in Johannesburg. That conference comes 10 years after an Earth Summit in Rio de Janeiro was attended by more than 100 nations, who signed a series of ambitious agreements aimed at protecting forests, oceans, the atmosphere and wildlife. As the host country, Brazil was one of the sponsors of those accords. Within three years, however, the annual deforestation rate in the Amazon, which accounts for nearly 60 percent of Brazil's territory, had doubled, to nearly 12,000 square miles, an area the size of Maryland.

Since then, the rate of destruction has slowed and the government has begun numerous initiatives aimed at further curbing the cutting and burning of the forest. Just this week, the government announced the creation of the world's largest tropical national park, in the northern state of Amapá near the border with French Guyana.

But the Brazilian jungle is still disappearing at a rate of more than 6,000 square miles a year, an area the size of Connecticut. What is more, the deforestation is likely to accelerate, environmentalists warn, as the government moves ahead with an ambitious $43 billion eight-year infrastructure program known as Brazil Advances, aimed at improving the livelihoods of the 17 million people in the Amazon.

Over the last 30 years, most destruction in the Amazon has been in a 2,000-mile-long "arc of deforestation" along the southern and eastern fringe of the jungle. But now the government is moving to turn the Cuiabá-Santarém road, which slices through the heart of the forest, into a paved, all-weather highway so that farmers to the south can more easily transport soybeans and other products to the Amazon River and then to Europe.

Soybean production has begun to play a big role in the destruction of the jungle. Both the deforestation here and the growing pressure to finish paving the highway are to a large extent driven by economic developments half a world away, in China. Rising incomes there have created a huge and expanding middle class whose appetite for soybeans is growing rapidly.

As recently as 1993, the year after the Rio conference, China was still a soybean exporter. Now it is the world's biggest importer of soy oil, meal and beans. Brazil, the largest exporter of soy products after the United States, is rushing to meet that demand.

The potential environmental impact of asphalting the 1,100-mile-long road is enormous. About 80 percent of deforestation in the Amazon occurs in a 31-mile corridor on either side of highways and roads, and when these are paved "deforestation goes up tremendously," said Philip Fearnside, a researcher at the National Institute for Amazon Research in Manaus, known as INPA.

A paved section of the highway ends barely 12 miles from here, putting this remote and dusty town of 14,000 on the front line of the agricultural frontier. Dozens of sawmills now operate along the road where just a handful existed five years ago, and at night, after government inspectors have gone home, trucks carrying illegal loads of valuable hardwoods rattle down side roads that lead deep into the jungle.

"The sensation is that of being on a battlefield and not having the weapons to defend ourselves," said the Rev. Anselmo Ferreira Melo, the parish priest here.

Trairão, founded in 1993, is named for a game fish that has traditionally been plentiful throughout the Amazon. But the new lumber yards here are dumping so much sawdust into local streams that the fish population has dropped sharply.

No one knows exactly the quantity of greenhouse gases Brazil is already pumping into the atmosphere as a result of such efforts to tame its vast jungle. Though a national inventory of carbon emissions was supposed to have been announced three years ago, it still has not been made public.

But scientists at INPA estimate that Brazil's carbon emissions may have risen as much as 50 percent since 1990. They calculate that "land use changes," most of which occur in the Amazon, now pour about 400 million tons of greenhouse gases into the air each year, dwarfing the 90 million tons annually from fossil fuel use in Brazil and making it one of the 10 top polluters in the world.

Part of the recent decline in deforestation rates is attributable to the Brazilian economy, whose rapid growth was responsible for the spike of the mid-1990's but has since cooled, or simply to weather patterns. But scientists also credit specific Brazilian government steps for the improved performance.

One symbolically important step with practical consequences has been the demarcation of indigenous lands. According to government statistics, more than 385,000 square miles, or 12 percent of Brazil's territory, an area larger than England and France combined, has been formally transferred to Indian control.

As a result, tribes with a warrior tradition, like the Kayapó, Wamiri-Atroari and Mundurucú, have rushed to defend the reserves set aside for them and become aggressive defenders of the forest.

"If you put together satellite images of all the fires burning in the Amazon, you can see the outline of the indigenous areas just from that," said Stephan Schwartzman, senior scientist at Environmental Defense in Washington. "Where Indian land starts is where the fires stop."

In some areas of the Amazon, the Brazilian government's environmental protection agency, known as Ibama, has also played a leading role in deterring deforestation. An environmental crimes law passed in 1998 gave the agency, founded in 1989, new enforcement powers, which it has used, albeit selectively, in raids aimed at arresting and fining the most blatant violators of the law.

"Ibama is full of problems and underfunded, but they are still making progress, thanks especially to these blitzes," said Daniel Nepstad of the Amazon Environmental Research Institute in Belém. "The cost of doing business as a logger has increased and the profit margins have gone down, and the sense of impunity that existed just a few years ago has diminished."

But the initiative that the Brazilian government sees as most promising is in the southern Amazon state of Mato Grosso, where deforestation is licensed and monitored by satellite. Though the state's name means "thick jungle" in Portuguese, huge deforestation began in the 1970's and accelerated with the soybean boom of the 1990's.

Since the program went into effect late in 1999, deforestation in Mato Grosso, which has had the fastest growing economy of any Brazilian state, has declined by more than half, to about 4,600 square miles over the two-year period that ended on Jan 1.

Large ranchers and farmers can clear no more than 20 percent of their land, and those who exceed that limit are punished with fines and prison sentences.

"The truth is that nobody ever controlled this, and that you can't control properties one by one even if you have an entire army of men," said Federico Muller, director of the state's environmental protection agency. "But now the satellite does it for us. It's like Big Brother, an all-seeing eye in the jungle."

But the neighboring states of Pará and Rondônia, where deforestation has been equally intense, have yet to adopt the initiative. As a result, loggers, sawmill operators, cattle ranchers, land speculators and other adventurers have simply moved northward up the Cuiabá-Santarém highway, deeper into the heart of the jungle, to areas like this one.

Armed with guns and global positioning satellite locators, loggers are also pushing into the Tapajós National Park west of Trairão and other nature reserves. Peasant settlers here say that they have complaimed to the police and to the environmental protection agency but that nothing has been done.

"Everything functions on the basis of bribes or threats, and so Ibama does not act," said José Rodrigues do Nascimento, who farms 250 acres. "These loggers tell us they have the authorization to go in there, but they never show any papers, and because they have gunman, you don't dare to contradict them."

José Carlos Carvalho, the environment minister, acknowledged problems but promised improvements by next year's dry season, saying that the states of Pará and Rondônia were now installing the same monitoring system as Mato Grosso. In addition, he said, the environmental protection agency is to double the number of its agents, to 2,000.

"We recognize that the predatory occupation of the jungle doesn't work and has to give way to a system of sustainable development, and we are moving in that direction," he said.