This is a guest blog by Rodrigo Leitão, environmental lawyer and member of Coletivo Pororoka, and Alexandre Anderson, of Rede Ahomar — a nationwide organization representing fishermen and fishing communities in the Guanabara Bay region, in the state of Rio de Janeiro, and throughout the country. On October 7 2026, Brazil’s National Petroleum Agency (ANP) is set to hold its next oil block auction — including further expansion of exploration areas in the Foz do Amazonas basin. The confirmed discovery of oil off the coast of Oiapoque, at the mouth of the Amazon in northern Brazil — an area known as the Foz do Amazonas basin, puts the region on a slippery path that fishers in Guanabara Bay already know well. A path that, once travelled, leaves marks impossible to erase. Rodrigo Leitão is an environmental Lawyer; member the Amazonian organization Pororoka and Representative of the Brazilian Institute of Environmental Law (IBDA). Photo: AHOMAR Guanabara Bay, in the Brazilian state of Rio de Janeiro, knows what it looks like when the oil industry arrives. The story began in 1954, when the Manguinhos Refinery started operating. In 1961 came the Duque de Caxias Refinery, known as REDUC. After that came the pipelines, the terminals, the petrochemical plants, the support structures for the offshore industry, the vessels and the new facilities. Decade after decade, the industry took up more of the Bay, competing for space with the people who already lived there. Separate licences, accumulated impacts In Guanabara Bay, the destruction caused by oil didn’t happen all at once — it built up slowly, one project at a time. Each new project was licensed on its own, so no one ever assessed the full, combined impact. By the time the damage became visible, a great deal had already been lost. In January 2000, a ruptured of a pipeline spilled around 1.3 million litres of oil, roughly 340,000 gallons, into Guanabara Bay. Mangroves, beaches, fish, birds and thousands of fishers were hit. But the violence against small-scale fishing did not begin at that moment. It had already been under way for years: in the shrinking fishing grounds, the exclusion zones, the traffic of large vessels, the dredging, the pollution and the steady transformation of the territory. A participatory mapping carried out with small-scale fishers in Guanabara Bay showed the scale of that loss. The study by Carla Ramôa Chaves, developed at the Federal University of Rio de Janeiro (UFRJ), found that only 12% to 25% of the bay remained free of restrictions on fishing. The oil industry stood out as the largest single user of the water surface. Territory and life Losing a fishing territory is not simply losing an area on a map. Territory means income, food, knowledge and spirituality. Even the definition used by Brazil’s Federal Government recognizes that life in these communities is organized around the waters and their cycles. It took many generations to learn the right time to take from nature what nature offers. And for that, fishers depend on mangroves, rivers, estuaries and seas that are still alive. So when a fishing territory disappears, what disappears is far more than an economic activity that could easily be swapped for another source of income, as many people assume. It is a form of violence, because it wipes out a way of life handed down from parent to child, built in community and in respect for nature. It is violence because it destroys what people learned to love and to value, in the name of a development that never arrived and never will. It is impossible to look at this history and not think about the mouth of the Amazon. Fishing industry leaders from Rio de Janeiro join forces with leaders from the Amazon against well drilling at the mouth of the Amazon River. Photo: AHOMAR Block 59 is only the first On August 14 2026, Petrobras confirmed that it had found oil in the main well of Block FZA-M-59 – the first confirmed discovery of oil in the mouth of the Amazon River. As soon as the news broke, several foreign oil companies applied for permission to drill in the area. The block, with four wells planned, can be presented as an isolated business venture 175 kilometres (about 109 miles) off the coast of Amapá. But we are not talking about a single project. In 2025, contracts were signed for 19 new blocks in the Foz do Amazonas basin, at the mouth of the Amazon River. In June 2026, Brazil’s National Petroleum Agency (ANP) listed another 36 blocks in the same basin for study, with a view to including them in future auctions. What these facts show is the opening of Foz do Amazonas basin as a new frontier for oil exploration. Once production begins, what comes with it are support vessels, shuttle tankers, helicopters, subsea structures, safety zones, logistics bases, port facilities, fuel, waste, workers, storage, pipelines and terminals. That is how the occupation of Guanabara grew, little by little, until it stopped being a set of separate projects and became a permanent dispute over territory. Fishers in the Foz do Amazonas basin do not need to wait twenty or thirty years to find out what fishers in Guanabara learned over the course of their own lives: oil does not only occupy the seabed. It moves into living territories and destroys them. A mangrove that wraps around the planet Unlike the generations before us, our greatest challenge is no longer to control nature. It is to join it, if we want any chance of surviving climate change. In the delicate balance of the world, mangroves play a key role. They are important sinks for carbon dioxide, one of the gases responsible for global warming. At the mouth of the Amazon lies the largest mangrove belt on the planet and most of Brazil’s mangroves, stretching across the states of Amapá, Pará and Maranhão – a huge carbon sink. Mangroves are also fundamental to local life. They are nurseries for countless marine species that provide food and income for traditional communities, something already recognized by Brazil’s Ministry of the Environment. IBAMA, the federal environmental agency, has classified the region as extremely sensitive in social and environmental terms, pointing to Indigenous Lands and protected areas that shelter Indigenous villages, threatened species and one of the greatest concentrations of biodiversity known. IBAMA has also warned that assessing a project in isolation, as in the case of Block 59, does not answer the question of whether the region is suited to receiving the entire oil production chain. ‘May the wind blow strong in Guanabara Bay’ That is the motto of the Association of Men and Women of the Sea of Guanabara Bay (AHOMAR), a kind of omen that comes before a great victory. AHOMAR, founded in 2007, today brings together 11 associations and around four thousand fisherpeople who are fighting for formal recognition of their community territories and against the steady loss of fishing grounds in Guanabara Bay. The group stands up to chronic pollution, to the pressures created by REDUC’s operations and by the logistics expansion linked to COMPERJ, the Rio de Janeiro Petrochemical Complex project, in a context of serious socio-environmental conflict and threats against fishers. The experience of Guanabara can help strengthen a wide alliance of small-scale fishing in the Foz do Amazonas basin: to map fishing territories, to record traditional fishing spots and routes, to track changes in the quantity and quality of the catch, to monitor impacts, to produce information through the communities themselves, and to fight so that these peoples have a voice before decisions are taken and not only after the damage is done. To fight so that an economy that may last a few decades does not destroy a socio-bioeconomy that has sustained generations and could sustain many more. Alexandre Anderson de Souza is a fisherman and president of the Association of Men and Women of the Sea (AHOMAR). Photo: AHOMAR May the wind blow strong in Guanabara Bay, and may it reach the peoples of the mouth of the Amazon. The post Oil Exploration at the Mouth of the Amazon: a Warning from the Guanabara Bay appeared first on 350.