All of it starts with a road. Except for a handful of federal and state highways—including the east-west Trans-Amazon Highway and the controversial BR-163, the "soy highway," which splits the heart of the Amazon along 1,100 miles from southern Mato Grosso north to Santarém in Pará—nearly every road in the Amazon is unauthorized. There are more than 105,000 miles of these roads, most made illegally by loggers to reach mahogany and other hardwoods for the lucrative export market.

In Brazil, the events set in motion by logging are almost always more destructive than the logging itself. Once the trees are extracted and the loggers have moved on, the roads serve as conduits for an explosive mix of squatters, speculators, ranchers, farmers, and, invariably, hired gunmen. The land sharks follow the roads deep into previously impenetrable forest, then destroy tracts to make it look as if they own them. Land thievery is committed through corruption, strong-arm tactics, and fraudulent titles and is so widespread that Brazilians have a name for it: grilagem, from the Portuguese word grilo, or cricket. Grileiros, the practitioners, have been known to age phony land titles in a drawer full of hungry crickets. When Brazil's agrarian reform agency, Instituto Nacional de Colonização e Reforma Agrária, reviewed Amazonian land ownership records over the past three years, it voided more than 62,000 claims that appeared to be fraudulent.

Guarantã do Norte, a city of 32,000 at the northern extremity of the paved section of BR-163, is the regional headquarters of Brazil's environmental protection agency, Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA). With only a handful of inspectors to monitor thousands of square miles of territory, Márcio da Costa, the IBAMA chief, is overwhelmed. He works from a makeshift office behind the charred wreckage of the former headquarters, which was torched by an angry mob in 2004 after IBAMA agents and police broke a ring of timber traffickers, shutting down illegal sawmills and issuing millions of dollars in fines to loggers in the nearby town of Alta Floresta. The inquest into the arson failed to produce a single suspect.

A sputtering air conditioner barely churned the soupy air as da Costa showed me a 2004 logging certificate, along with a carbon copy. The copy, signed by an export inspector 1,500 miles away in southern Brazil, listed thousands of cubic feet of wood nowhere to be found on the original document—all contraband. "Yesterday, we seized five trucks loaded with timber coming out of the same area," da Costa said.

In 2005, after gunmen hired by grileiros murdered Sister Dorothy Stang, an American-born nun and environmental activist, the Brazilian government accelerated a crackdown, suspending logging permits throughout the Amazon—most of which had been falsified to launder illegal timber. Federal police and IBAMA intensified their investigation into irregularities in the timber business. Waves of troops were dispatched to Mato Grosso and Pará. They seized truckload after truckload of contraband timber. Of the more than 300 people arrested, about 100 turned out to be IBAMA officials involved in a far-reaching conspiracy to sell millions of cubic feet of endangered hardwoods to the U.S., Europe, and Asia.

To reduce fraud, Brazil will soon introduce electronic logging certificates. Meanwhile, to aid in policing the sprawling Amazon hinterland, government agents are turning to satellite technology and remote sensing to alert them to the work of grileiros. Yet even when officials spot a desmatamento, or illegal clearing, they are usually hamstrung by a lack of manpower or equipment. And when the police do react, the resources they manage to scrape together can be modest.