ON THE BORDER OF THE TAMBOPATA RESERVE, Peru — The raid began at dawn. In four small wooden boats, the forest rangers and Peruvian marines, checking and rechecking their automatic weapons, headed silently downriver toward the illegal gold miners.

They didn’t have to go far. Around the first bend was a ramshackle mining settlement, tarps stretched over tree poles. Soon, the marines were firing into the air, the miners and their families were on the run, and the rangers were moving in with machetes.

They speared bags of rice and plastic barrels of drinking water, kicked aside toys and smashed tools before setting everything on fire. High above the Amazon rain forest, home to , heavy plumes of black smoke spiraled toward the clouds.

Trying to protect one of the most biologically diverse places on earth from an army of that has carved a toxic path through the rain forest, the Peruvian government is setting up outposts and stepping up raids along the Malinowski River in the .

But some experts wonder whether it is far too little too late.

To get here, a remote front line in Latin America’s battle against illegal mining, I hiked nine and a half hours through the jungle, at times in water up to my armpits. But any sense of being in a pristine wilderness was lost at the river’s edge. Already, the miners had done that the water ran the color of milky coffee. The landscape was worthy of a “Mad Max” movie. Huge sandy craters, mounds of pebbles and poisoned waterways were everywhere. Garbage — rags, plastic bags, plastic foam food containers — clung to the freshly cut tree branches piled up in the river’s nooks and crannies.

With the price of gold high for years, illegal mining has blossomed in many parts of Latin America, not just in . But in this country, one of the world’s major gold producers, the problem has gotten particularly bad.

The amount of gold collected by unlicensed miners is far larger than elsewhere in Latin America. And it is ballooning so quickly that environmentalists fear that even a remote reserve like this one — home to thousands of species of plants and animals, some perhaps not even identified by humans — has little chance of survival.

For all the environmental damage done by corporate mining, illegal miners are far more destructive, experts say. While mining companies tend to concentrate on areas with rich underground veins of gold, illegal miners move swiftly across vast amounts of territory. They cut down broad swaths of jungle, sifting through perhaps 200 tons of topsoil to find enough flecks of gold for a single wedding ring.

Without help, some experts say, the areas they leave behind — robbed of all topsoil and loaded with mercury — could take 500 years to recover.

The miners use so much mercury to process the gold that the government declared a health emergency in much of the Madre de Dios region in May. Tests in 97 villages found that more than 40 percent of the people had absorbed dangerous levels of the heavy metal. Mercury poisoning affects people in many ways, from chronic headaches to kidney damage, but it is most harmful to children, who are likely to suffer permanent brain damage.

“The next generations will pay for what we are doing now,” said Manuel Pulgar-Vidal, who heads the Peruvian Ministry of the Environment.

Statistics undercount the amount of illegal mining. But Víctor Torres Cuzcano, an economist with the Universidad Nacional Mayor de San Marcos, calculated that unregistered and informal mining increased by 540 percent between 2006 and 2015, while production from legal mining, which brings in tax revenue, fell by 28.5 percent.

“I fear that illegal mining is crowding out the legal activities,” said Guillermo Arbe Carbonel, an economist with Scotiabank. “You see social protests against the legal mining all the time. But the illegal is growing, and it is the worst kind of mining when it comes to the environment.”

Deforestation from gold mining accelerated from 5,350 acres per year before 2008 to 15,180 acres each year after the 2008 global financial crisis that rocketed gold prices.

Less than a year ago, the Tambopata reserve, a roadless area about the size of Rhode Island, part forest and part savanna, was untouched. Now satellite photographs show telltale patches of wasteland in the reserve, and so much mining that the river on its edge — the Malinowski, named after a Polish explorer — has been pushed off its course, made wider and more shallow. In areas where the miners work, the rangers say, the water is so polluted that the fish are all gone.

Some advocates say the reserve is all but lost. Early indications suggest that it is rich with gold, especially compared with other parts of this remote state, including the area officially reserved for artisanal mining and the “buffer zone” bordering the Tambopata reserve.

“They are getting about 12 to 18 grams a day in the official mining corridor,” said Victor Hugo Macedo, who oversees the reserve. “They are getting 60 to 80 grams in the buffer zone, and they are getting 150 to 200 in the reserve. The miners care more about that than what happens to Tambopata.”

The government has tried varied policies to contain illegal mining, including controls on the amount of fuel coming into the region, Mr. Pulgar-Vidal said. But he conceded that these efforts had had little success. The Peruvian tax authority recently estimated that more than $1 billion worth of gold had been smuggled out of the country just between February and October 2014.

In recent years, the authorities have sometimes swooped in by helicopter from the capital, Lima. But prosecutors said the miners often seemed to have been warned and were back in business within days. Corruption and , they said, helped drive illegal mining, and many of the mining camps were essentially lawless communities where slave labor and sex trafficking flourished.

Mr. Pulgar-Vidal hopes that the constant presence of armed marines and a stream of raids will persuade the miners to leave the reserve alone.

Critics are skeptical. Some suggest that the government may not really be interested in stopping illegal miners. Some Peruvian politicians openly argue that the miners, many of them from indigenous communities, should be allowed to earn a living, a popular stance in a country where half the population is under the poverty level.

Up close, the raids look doomed to failure. The marines and rangers are outmanned and underequipped. Even getting to their outposts is a challenge. The best routes are controlled by the miners and considered too dangerous, even for armed soldiers. So on a rainy day, we walked down a narrow path from daybreak through afternoon, but the soldiers had no radios to call for help when it quickly became flooded for vast stretches.

In rushing water full of debris, we all took baby steps looking for solid footing as the rain forest suddenly turned into a turbid lake. Weighed down by backpacks filled with water, the soldiers carried their weapons over their heads and tried to keep from going under, not always successfully.

The prosecutor who accompanies them on raids had gone ahead on the back of a dirt bike. But that was a luxury. The rangers have only four motorcycles — for about 100 men stationed at the two outposts along the river.

Yet there are at least 5,000 illegal miners in the area, and perhaps as many as 10,000. After a few raids, the marines were out of dynamite and resorted to a less sophisticated tactic: using mallets to smash the truck engines that miners use to power their derricks.

The boats used in the raids aren’t any faster than the ones the miners have, and they stalled often. While there has been no violence so far, a sense of menace was in the air. At times, the miners stood on the river’s edge, arms folded, as the marines and rangers sailed by.

Carlos Moscoso Garces, a marine, said it was a matter of time before trouble broke out. The miners shrugged off the occasional raid, but what happens once the cost of replacing destroyed mining equipment begins mounting?

“Then,” he said, “who knows what they will do.”

At one small encampment, a woman implored the soldiers not to destroy her home. She told the men she was just a single mother trying to make a living, so they put some food aside for her before setting everything else on fire.

Downriver, as soldiers made a bonfire of several motorcycles they had found, one young man tried to grab his. Forced to his knees, he told the soldiers he was only visiting friends, a story that no one believed. But there was no thought of arresting him, or anyone else. Miles from the nearest paved road and with no facilities for holding prisoners, the logistics made that impossible. Like everyone else encountered, he had no identification and was released without so much as a summons.

The marines are realistic. When they passed a giant tent city, with satellite dishes poking up and poles for many more dwellings under construction, they sailed on in search of a more manageable target.

By day’s end, the raiders had destroyed two dozen encampments and 15 mining derricks, and invaded mining camps far better equipped than their own. Along the way, the soldiers helped themselves, taking home a freezer, a satellite dish, a VCR, a television set, a soccer ball, a black-and-white puppy and a young pig for dinner.

At night, you could hear the sounds of the mining derricks starting up again.