Solimar Ferreira dos Anjos felt a sense of connection one morning last month as he made his way along a stream in the Brazilian Amazon rainforest, clambering over tree trunks, branches and rocks. “It’s a great privilege for me,” said the 49-year-old. “I’m sure that my father, when he was young, travelled along these paths when he was tapping for rubber. He always wanted to bring me here and finally I’m doing it.”

Solimar is among a group of about 40 people marking out the boundaries of the 550-square-kilometre (212-sq-mile) community of Montanha-Mangabal that they and other residents inhabit here in the state of Pará, beside the Tapajós River. The community, formed over a century ago by European- and African-descended rubber tappers who intermarried with members of local indigenous groups, won the right in 2013 to become an Agro-Extractive Settlement after an protracted political and bureaucratic struggle. That status gives community members exclusive rights to the land and to its forest products provided they collect this produce—Brazil nuts and hearts of palm, for instance—in an environmentally sound manner and do not sell any of the land.

By law, such designations must be followed by a formal demarcation of the land by Brazil’s National Institute for Colonization and Agrarian Reform (Incra). This did not happen, prompting Montanha-Mangabal to call on the agency repeatedly to act. Meanwhile, outsiders were entering the community’s territory without permission to engage in unlawful logging, gold mining and other destructive activity. In August, Ageu Pereira, president of the Association of the Communities of Montanha-Mangabal, an umbrella organization representing the community’s villages, made the 600-kilometer (370-mile) journey to deliver Incra officials in Santarém a letter in which local inhabitants demanded redress. Pereira complained in the letter and in person that he and other leaders frequently were threatened by outsiders claiming to be “owners” of the land, even though private ownership of Montanha-Mangabalis community lands is not permitted.

The appeal failed to have an effect, so in early September the inhabitants took the initiative. They organized a five-day expedition to start marking out the borders of their land themselves—a process they have called “autodemarcação,” or self-demarcation. Remarkably, they received the support of indigenous groups, who for many decades were their sworn enemies as the river dwellers and indigenous groups battled over territory. A second such expedition, this one lasting six days, was held in November to continue the demarcation, which is now about half complete.

Juarez Saw Munduruku, the cacique, or leader, of the nearby Sawré-Muybu indigenous community, says his people now have common cause with non-indigenous riverbank dwellers such as those of Montanha Mangabal. Sawré-Myubu, just across the Tapajós River from Montanha-Mangabal, is one of a number of groupings of the Munduruku Indians, who inhabit the Tapajós River Valley. Says Saw Munduruku: “We are threatened in the same way by the government’s projects, gold miners and loggers, so we’ve made this alliance.”

Ageu Pereira and Francisco Firmino da Silva, a community leader in Montanha-Mangabal, helped the Munduruku self-demarcate the Indigenous Territory of Sawré Muybu in 2014. As a result of this action, the Munduruku were able in 2016 to kick-start the process of getting their land the official indigenous-territory designation they had been seeking for many years. Their new status was a factor in the August 2016 decision by Ibama, the enforcement arm of Brazil’s Environment Ministry, to refuse a license for a large hydroelectric dam known as São Luiz do Tapajós, at a downstream site on the Tapajós River. That’s because the dam’s reservoir would have flooded part of the indigenous territory and thus required relocation of the Indians, which the Brazilian constitution forbids. The project remains suspended.

“Now it is our time to help, and I brought 24 warriors, men and women, with me,” Saw Munduruku explained while taking part in the initial demarcation in September.

The Sateré-Mawé Indians, whose land spans the states of Pará and Amazonas, also have sent warriors to help. In September, indigenous and non-indigenous participants marked out just over 18 kilometers (11 miles) of the boundary, which measures about 70 kilometers (43 miles) in all. Along the way, they discovered that in an area just over a mile from the Trans-Amazonian Highway, palms and other trees had been felled. While the community harvests the berries from wild palms without harming the trees, the outsiders had destroyed the trees to extract heart-of-palm, a valuable commodity. Moreover, in a clear sign that the trespassers intended to return, members of the demarcation crew encountered five rough tracks hacked out of the forest to link the area with the Trans-Amazonian Highway.

It is this kind of activity that worries the community. During the expedition, Firmino da Silva—a highly respected leader of Montanha-Mangabal who is widely known as Chico Caititu—explains why in addition to marking the boundaries, he and other crew members were putting up notices telling outsiders to keep out. “We’re making it clear what is their land and what is ours,” he says. “In the past people have said: ‘I don’t know what is my land.’ I think that from today everyone who arrives from the road will know where our land is and understand that they can’t come onto it.” But the outsiders didn’t take kindly to the notices. On returning and seeing them, they began threatening Montanha-Mangabal families.

Unable to get Incra’s attention, the families turned to the Federal Public Ministry (MPF), an independent body of federal prosecutors. At the end of October, the ministry came through for the community, issuing a statement declaring self-demarcation “a legitimate right” and instructing gold miners, loggers and those seeking heart of palm to stop all activity within the settlement. Federal Police displayed the notice in bars, hotels and stores along the Trans-Amazonian highway.

Pressured by the MPF and press reports, Mário Sérgio da Silva Costa, superintendent of Incra’s Santarém office, visited the community on Nov. 17 in the company of four other Incra officials, meeting with inhabitants and Paulo de Tarso Oliveira, a prosecutor with the MPF. Says Oliveira: “The Brazilian state is weakened, finances are very bad, the political orientation from the government isn’t geared to social rights, but even so it is important to believe in the institutions and to demand that they carry out their constitutional and institutional role.”

Costa encouraged families to keep up the pressure: “It’s important that you denounce what is going on … that the MPF snaps at our heels.”

Incra agreed to take over the demarcation, making its own measurements and posting its own notices, but it only sent three employees to establish the 71-kilometer (43-mile) boundary through the hilly and thickly forested terrain. Community leaders concluded that with such a small crew, Incra would take months and outsiders would have too much time to continue their incursions, so they decided to carry out the second “self-demarcation.”

The 18 kilometers (11 miles) they marked out during the expedition that took place during Nov. 22-28 brought the demarcation total to 36 kilometers (22 miles), with 35 kilometers (21 miles) now remaining. Among the indigenous groups taking part were the Munduruku, the Sateré-Mawé as well as five other indigenous groups from the Trombetas River Valley. This time they unexpectedly encountered a group of gold miners. Most of the miners stopped work once demarcation crew members showed them the notices that they were nailing to trees. But one miner became angry, saying: “So we’ll see who is powerful down here! … All this land belongs to Jesus. He is the only true owner! And now you come and say it’s yours!”

Though the tension brought on by such incidents remains, Montanha-Mangabal residents are feeling more optimistic. An elderly inhabitant, Dona Maria de Nazaré Oliveira, says residents are regaining the determination they showed 15 years ago, when they mobilized the community and went to court to prevent a real estate company from taking over their territory using forged land titles. “We were very united then,” Oliveira says. With many more outsiders moving into the region, she adds, the community once again must take action: “Today it’s very good that we are marking out our land, because it will give us security.”

Solimar Ferreira dos Anjos agrees: “It’s already a victory to be here today and I’m sure we’re going to be more united than ever in the future”.

During the September demarcation, old and young worked side by side. A 17-year-old Munduruku Indian, Nelison Saw Munduruku, used his GPS device to mark out the boundaries while Chico Caititu, aged 68, drew on knowledge he had acquired through his many years of roaming the forest. “My GPS is in my head,” he said. So is knowledge of tricks for rainforest travel, such as using creepers as a rough compass. Says Caititu: “Creepers only climb around trees from the side of the rising sun to the setting sun.”

As the demarcation crews advanced through the forest, younger members hunted wild animals to provide them with food. On the first expedition, the oldest indigenous warrior, cacique Chico Índio, helped Munduruku women each night to build a rustic stove made of wood and straw. Using water from nearby streams, they cooked a stew of meat from peccaries, caimans, the razor-billed curassow (Pauxi tuberosa) bird and other game caught by young people on the expedition.

At night, the Montanha-Mangabal inhabitants and the Indians recalled the early days when they could wander at will in the forest. Though the two groups at different historical moments have rejected the territorial restraints imposed on them, they share memories of the inroads being made into their region and agree that marking their boundaries is now the best means of protecting their lands.

This new collaboration between indigenous and non-indigenous communities may spawn further such initiatives. One might involve the Sateré-Mawé people of the Andirá-Marau Indigenous Territory, which is located on the border of Pará and Amazonas states, between the Tapajós and Madeira Rivers. The Sateré Mawé say that much of their traditional land lies outside their recognized territory and want the reserve expanded. Bernardino Mikilis dos Santos, their elderly cacique, made a ten-hour boat trip with another member of his community in September to join those taking part in the initial demarcation work. “The union here between the Sateré, our Munduruku relatives and riverine communities gives us strength,” he said. “I suffered during the long trip but I’m very happy to be with you. It is the first time that the Sateré took part in a self-demarcation. And now I want to do the same thing on our land.”

All participants seemed excited by their alliance. “I don’t know how to thank enough the Munduruku and the other Indians,” said Ezequiel Lobo, a Montanha-Mangabal community leader in charge of organizing the expeditions needed to complete the demarcation. “We’re going to demarcate and we’re going to struggle. We’re going to be with the Indians until the end.”

Soon people from Montanha-Mangabal will be helping the Munduruku once again, this time to clear the rough paths cut during the self-demarcation of the Sawré Muybu Indigenous Territory. Few doubt that difficult days lie ahead. The Tapajós River Valley has become an important export route for Brazil’s agricultural exports, particularly soybeans. The BR-163 highway, which is in the process of being paved, is already congested during harvest. The government is trying to press ahead with construction of a 1,142-kilometer (710-mile) railway, called Ferrogrão, or Grainrail, to run parallel with the road. Big investment, particularly Chinese, is pouring into a new port complex, Miritituba, on the east bank of the Tapajós. There also are plans for a dredged barge route along the Tapajós and its two “legs”—the Teles Pires and Juruena Rivers. If that project goes forward, it will involve dynamiting numerous rapids on these rivers, disrupting fish populations and the lives of river communities that depend on them.

This rapid opening, while cheered by business interests, has drawn criticism from scientists and others concerned that the development projects will cause future rounds of forest clearing, thereby accelerating habitat loss and climate change. The soybeans Brazil exports are used as animal fodder in Europe and Asia. China, self-sufficient in soy until 1995, increased its imports from 56 million tons in 2011 to 102 million tons in 2017. By 2024 it plans to import 180 million tons, much of which is expected from Brazil. Yet experts say Brazil cannot produce such a quantity of soy without extending the agricultural frontier deeper into the Amazon and the Cerrado, the country’s enormous tropical savannah.

The need for corrective action is beginning to take hold in the business world—including the livestock industry, which is estimated to account for 15% of all greenhouse-gas output. A new analysis from the Farm Animal Investment Risk and Return (FAIRR), an investor initiative that is boosting awareness of the risks of factory farming, says that a tax on meat is “inevitable” within five to 10 years, as the world struggles to curb the greenhouse-gas emissions that spur climate change.

Such action might eventually quench demand for Brazilian soy and beef, but it is unclear whether this would occur soon enough for communities in the Tapajós River valley. Meanwhile, those communities vow to mark off and defend their boundaries as best they can. Cacique Juarez Saw Munduruku, for one, is determined to collaborate to that end with indigenous and non-indigenous neighbors alike: “That’s what my life is about now: helping these people mark out their land, because this will help them and future generations.”