EL MIRADOR, Guatemala — Great sweeps of Guatemalan rain forest, once the cradle of one of the world’s great civilizations, are being razed to clear land for cattle-ranching drug barons.

Other parts of the Maya Biosphere Reserve, Central America’s largest protected area, have been burned down by small cities of squatters.

Looters and poachers, kept at bay when guerrilla armies roamed the region during the country’s 36-year civil war, ply their trades freely.

“There’s traffickers, cattle ranchers, loggers, poachers and looters,” said Richard D. Hansen, an American archaeologist who is leading the excavation of the earliest and largest Mayan city-state, El Mirador, in the northern tip of the reserve. “All the bad guys are lined up to destroy the reserve. You can’t imagine the devastation that is happening.”

President Álvaro Colom has grand plans to turn the region into a major eco-tourism destination, but if he hopes to bring tourists, officials say, he will have to bring the law here first.

The reserve, about the size of New Jersey, accounts for nearly two-thirds of the Petén region, a vast, jungly no man’s land that juts north into Mexico and borders Belize to the east. Spanning a fifth of Guatemala and including four national parks, the reserve houses diverse ecosystems with niches for jaguars, spider monkeys and scarlet macaws.

Pre-Colombian inhabitants mined limestone quarries here 2,600 years ago to build the earliest Mayan temples. The temples would tower above the jungle canopy before the cities were abandoned as Mayan civilization mysteriously collapsed around the ninth century A.D.

Some sites generate robust tourism. The spectacular Maya city Tikal, which draws up to 350,000 visitors a year, is a relatively well-protected oasis. Only about 3,000 visit El Mirador, which contains what may be the world’s largest ancient pyramid structure.

The threats to the reserve are many and interlocking, legal and illegal. Claudia Mariela López, the Petén director for the national parks agency, said about 37,000 acres of the reserve was deforested annually by poachers, squatters and ranchers.

The squatters are mainly peasants who have come in search of farmland. But the population of Petén has grown to more than 500,000 from 25,000 in the 1970s, according to a Unesco report. Not all of the residents are illegal, and many seek no more than subsistence.

Willingly or not, they often become pawns of the drug lords. The squatters are numerous, frequently armed and difficult to evict. In some cases, they function as an advance guard for the drug dealers, preventing the authorities from entering, warning of intrusions and clearing land that the drug gangs ultimately take over.

A recent State Department report said that “entire regions of Guatemala are now essentially under the control” of drug trafficking organizations, mainly the Mexico-based Zetas. Those groups enjoy a “prevailing environment of impunity” in “the northern and eastern rural areas” of Guatemala, the report said.

The Biosphere Reserve is about the size of New Jersey.

The drug organizations have bought vast cattle ranches in the Petén to launder drug profits, as well as to conceal a trafficking hub, including remote, jungle-shrouded landing strips. Cattle ranching in the Petén has quadrupled since 1995, with herds totaling 2.5 million cattle, according to Rudel Álvarez, the region’s governor.

“Organized crime and drug traffickers have usurped large swaths of protected land amid a vacuum left by the state, and are creating de facto ranching areas,” Mr. Álvarez said. “We must get rid of them to really have conservation.”

Deforestation has led to soil erosion at Yaxchilán, a Mayan city across the border in Mexico, which in turn has swollen rivers that erode limestone temples, said Norma Barbacci, regional director for the World Monument Fund. Ash from the squatters’ burns to clear fields for planting cause acid rain that wears at temples.

Fires, tree poaching and ranchers are encroaching in parts of the Laguna del Tigre national park in the western part of the reserve, threatening a sanctuary for 250 endangered scarlet macaws, the country’s last, said Roan McNab, country director for the Wildlife Conservation Society. Jaguars, crocodiles, river turtles and monkeys are also losing their habitat, he said.

The road to El Mirador, a five-day mule trek from the town of Carmelita that involves occasional bushwhacking with a machete, passes countless ditches where looters have ripped out Mayan graves. A wild toucan rockets down and then disappears off into the canopy. The remote dirt road that leads to the reserve is lined with newly razed cattle ranches, and the persistent buzz from a logging company drowns out the rain forest’s more subtle cacophony.

A local trail guide, galumphing along ancient limestone freeways buried beneath the forest, chain-smokes marijuana cigarettes rolled in notebook paper.

This rapidly deforesting mini-narco-state is a far cry from President Colom’s vision of a lush Mayan-themed vacationland.

His ambitious Cuatro Balam plan, named for the four main figures in the Mayan creation myth, would divide the reserve into an archaeological park in the north and an agricultural zone in the south. It was ostensibly intended to stem the northward migration of farmers and ranchers. Through a combination of public and private financing, he hopes to build an $8 million electric minitrain to shuttle tourists through the reserve and a Maya studies center for scholars.

The goal is to attract one million tourists a year to the reserve by 2023.

Guatemalan authorities have made some progress. Soldiers have blasted craters in secret landing strips and kicked squatters off protected lands. The government says it has retaken 269,000 acres of protected land in the Petén.

But the government remains hopelessly outgunned. The entire Petén, nearly 14,000 square miles, is patrolled by 600 soldiers, police officers and park guards, Mr. Álvarez said. Isolated and underpaid, the security officials are also susceptible to corruption.

Governor Álvarez himself is under investigation for money-laundering, charges he says are false and intended to intimidate him for supporting Mr. Colom’s crackdown on squatters and traffickers.

The park guards at El Mirador are expected to monitor up to 12,000 acres of jungle each.

“We have nothing,” said one guard, who asked to remain anonymous so as not to antagonize drug lords. “How are we supposed to stop drug gangs trying to run this place?”

To Mr. Hansen, an Idaho State professor of archaeology, the risks of not protecting the region are obvious in every stone he unearths. The Maya, he said, largely sealed their fate through deforestation and erosion.

“The Maya destroyed their environment,” he said. “They cut down their jungle” and it ruined them forever. “And we’re doing the same thing today.”

Daniel LeClair/Reuters

Richard D. Hansen, an American archaeologist, leads the excavation of the earliest and largest Mayan city-state, El Mirador, in the northern tip of the Maya Biosphere Reserve in Guatemala.

New York Times