- Brazil’s environmental agency approved oil drilling off the mouth of the Amazon River, even though oil company Petrobras considers it “unfeasible” to rescue large animals like manatees in the event of an oil spill.
- Potential oil spills threaten a unique hybrid manatee population perfectly suited to live in the Amazon River mouth area.
- A simulation testing Petrobras’s wildlife rescue plan showed lack of basic supplies and boat accidents.
- The project is part of a massive new oil frontier in the Equatorial Margin estimated to hold 10 billion barrels of oil.
In October 2025, Brazilian state oil company Petrobras began drilling in the seabed where the Amazon River empties into the Atlantic Ocean, following a long, controversial environmental licensing process. At the center of the debate were concerns about the unique wildlife living here, on the shores of the states of Amapá and Pará, and about the company’s capacity to rescue these animals in the event of an oil spill.
The potential victims range from marine birds and turtles to the recently discovered Amazon reef system. One endangered marine mammal, however, has prompted particular concern because of the extra challenges to rescuing it in the event of a disaster: the West Indian manatee (Trichechus manatus), a species that grows to a length of around 3.5 meters (11.5 feet) and weighs an average of 700 kilograms (more than 1,500 pounds); some individuals reach up to 1,600 kg (more than 3,500 lbs).
“Handling and transporting animals of this size requires complex logistics and large-scale equipment,” said marine biologist Fábia de Oliveira Luna, coordinator at the National Center for Research and Conservation of Aquatic Mammals (CMA), which is part of Brazil’s environmental ministry. With a population estimated at only 1,047 individuals in Brazil and a reproduction rate of one calf every four years, “every individual removed undermines the survival of the population,” Luna told Mongabay.
According to scientists, the oil project also jeopardizes a unique genetic code shared only by animals from this region, a result of the interbreeding between the marine manatee and its freshwater relative, the Amazonian manatee (Trichechus inunguis).
The West Indian manatee is found throughout the Caribbean and is categorized as vulnerable to extinction on the IUCN Red List. The subspecies Trichechus manatus manatus, which inhabits the coastal zone from the Bahamas to Brazil, has its IUCN classification increased to “endangered.”
In Brazil, its shrinking population reflects a poaching culture that persists in the country’s northern region. More recently, animals have also been displaced from their coastal retreats by the real estate industry, according to researcher and veterinarian João Carlos Gomes Borges, who said he was captivated by the manatee’s helpless look 35 years ago.
“Although it’s a seemingly large animal, whenever I look at a manatee, it always seems like it needs care,” said Borges, who works with the rescue and rehabilitation of the species in Brazil’s northeastern states.
Petrobras’s drilling is focused in the so-called Morpho well, located 179 kilometers (111 miles) from the Amapá coast and around 500 km (310 miles) from the mouth of the Amazon.
The well is part of the Amazon River mouth’s sedimentary basin, one of several basins that make up the Equatorial Margin. This new oil exploration frontier extends deeper into the Atlantic, where Petrobras says it expects to find 10 billion oil barrels. If confirmed, these reserves may boost Brazil as a new oil power and open the whole Equatorial Margin to oil exploration. In April, Brazil approved plans for companies eager to explore 19 other blocks in the area, and Petrobras requested approval from the federal environmental agency, IBAMA, to drill three new wells in the region.
IBAMA, however, has warned that this area “bears no resemblance to any other producing basin in the country in terms of natural resources and socio-environmental sensitivity.” As such, “the emergency response and wildlife rescue plan in the event of an oil spill must also be unprecedented,” the agency’s experts wrote in a technical note in 2025.
Petrobras’s wildlife protection plan, which details how the company will manage an oil spill, was rejected five times by IBAMA. Its sixth and final version was also deemed insufficient by the agency’s experts. However, it was approved by IBAMA’s then-president, Rodrigo Agostinho, amid strong pressure from President Luiz Inácio Lula da Silva, who openly defended Petrobras’s plans.
“The Individual Emergency Plan [which includes the wildlife protection plan] submitted by Petrobras was deemed unsatisfactory by all the technical committees that reviewed it,” said federal prosecutors from Amapá, who are seeking the revocation of Petrobras’s environmental licensing alongside their colleagues in Pará. Environmental groups have also slammed Agostinho’s decision.
In an email to Mongabay, Petrobras said it “met all the requirements established by IBAMA, fully complying with the environmental licensing process, which led to the issuance of the license for activities at the Morpho well in the Equatorial Margin.”
IBAMA experts, however, pointed to several flaws in Petrobras’s wildlife rescue plan. The West Indian manatee would be especially vulnerable since the company considers it “unfeasible” to rescue manatees and sea turtles weighing more than 50 kg (110 lbs).
According to Petrobras, rescuing such animals in stranded situations or in the water would require at least eight people, posing risks to both the animal and the team. “The animal may strike out with its powerful caudal fin — particularly with lateral movements — or with its head, in addition to the risk of self-injury when attempting to break free from improper restraint,” the wildlife protection plan says.
IBAMA’s technical body concluded that the plan “excludes a large portion of the local megafauna, condemning it to the harmful effects of oil contamination, which can lead to death.” In an email to Mongabay, however, the agency’s press office said Petrobras’s plan was “evaluated and deemed suitable.” In the case of animals heavier than 50 kg, protective actions would focus on “measures to prevent accidents and, should they occur, to scare these species away,” IBAMA wrote. (Read the agency’s full response here.)
Grounded boats and accidents
The Amazonian coast is the world’s new oil frontier, according to a report from Brazilian news outlet InfoAmazônia, holding nearly 20% of all recently discovered reserves. Guyana, Suriname and Venezuela have also been targets of the oil industry.
Most of the concerns about oil exploration in the area stem from the region’s maritime and weather conditions, since navigating along South America’s northern coast can be challenging. The area is known for frequent storms, persistent winds and ocean currents three times stronger than those observed in the continent’s southeast, where Petrobras does most of its offshore drilling.
Twice, the company found itself in trouble in the Amazon mouth area. In 2011, in a different well within the same region, crews had to abandon the ocean platform after a drill bit was swept away by the strong ocean currents. In January 2026, only three months after IBAMA’s green light for the Morpho well, 18,000 liters (nearly 4,800 gallons) of a toxic fluid leaked during a drilling operation.
As a final step to obtaining its license, Petrobras had to demonstrate how it would respond to an oil spill. A 70-hour simulation was conducted in August 2025, during which the company had to rescue 17 birds, two turtles, and one West Indian manatee calf, all represented by stuffed animals and inflatable floats.
In the fictional emergency scenario proposed by IBAMA, the Petrobras team had to respond to a synthetic fluid spill, where air rescue was not an option. The complex maritime operation included the transfer of animals from larger boats dedicated to offshore rescues, to smaller ones waiting in the Oiapoque River estuary, and then to the recovery center in Oiapoque, Amapá.
To comply with the 24-hour rescue deadline, the company failed to follow its own safety recommendation about transferring animals at night. Pilots in the Oiapoque River struggle to navigate around sandbars and rocky bottoms, and three accidents were recorded. One boat got tangled in a fishing net, while another grounded on a sandbank. In another incident, two boats collided. Nobody was hurt.
“The incidents reported during the river journey on the Oiapoque River underscore the importance of prioritizing safety criteria,” the IBAMA analysts wrote.
Although the company succeeded in rescuing the dummy animals within the allocated time, IBAMA noted that the weather conditions during the simulation were especially favorable. “It is well known, however, that this is not the reality in the region, which typically experiences more adverse weather and sea conditions.”
The agency also identified several flaws during the exercise, including the lack of basic supplies such as heating pads for the animals, which were improvised with surgical gloves filled with warm water. At some point, both boats designated to operate offshore were outside the accident area, preventing further rescues.
The simulation included the rescue of a dummy West Indian manatee calf, supposedly hit by a boat. IBAMA analysts praised the team’s technical expertise in treating the dummy, but complained about the time it took to transport it to the medical center.
“The situation highlighted communication breakdowns between the team at the accident site and the team responsible for allocating resources,” they wrote.
Vessel strikes are a major concern for large marine animals, since many boats are needed to support offshore oil operations. “In my view, vessel traffic is a much greater concern than the actual [oil] exploration activity itself,” said Borges, the veterinarian. Engine noise may also hinder communication between mother and calf manatees underwater. Once separated from their mothers, the calves could end up stranded on the coast.
A genetic treasure at risk
Petrobras stated in its wildlife protection plan that there’s a “zero” chance of an oil spill reaching the coast, the traditional haunt of West Indian manatees. “The [oil exploration] activity itself would take place in a very remote location, which is highly unlikely to be used by manatees,” said Borges, who coordinates a Petrobras-sponsored project to protect West Indian manatees in Brazil’s northeast.
Despite being marine mammals, these animals must remain near river estuaries to drink freshwater and give birth in calm waters. Evidence shows, however, that some individuals may explore areas far from the coast, as described by IBAMA experts in a technical note in 2024.
There is even an emblematic case of a manatee named Tico, who was released by a conservation project off the state of Ceará and swam 5,000 km (3,100 mi) to Venezuela.
The behavior of these marine mammals is even more unpredictable in the Pará and Amapá states, home to a unique population. Researchers found that manatees living in the area under the influence of the Amazon River mouth share a different genome, a mixture of the DNA of the marine (West Indian) manatee and the freshwater (Amazonian) manatee. This genetic variation has resulted in individuals adapted to live in an area strongly influenced by the Amazon River, the world’s largest river by water volume.
“It is a unique environment, with a unique salinity level, a different amount of sediment, and very different light conditions,” said biologist Camilla Savicius de Lima, who holds a Ph.D. in genetics and co-authored the study. “Hybrid individuals would be better adapted to these conditions than either of the other two, both the Amazonian and the marine species,” she told Mongabay.
These hybrid manatees tend to spend less time in estuary areas than their relatives from the Caribbean, Lima said. Deeper research, however, is needed to better understand these animals’ behavior and occupation areas. “Making changes to the environment before fully understanding it is very complicated. We don’t know what the potential impacts might be.”
It is also not possible to rule out eventual oil spills reaching the coast, as stated in a technical note by IBAMA. According to the agency, “significant amounts of oil” could “break up over time and drift for months, even washing up on coastal areas.” The agency cited the Deepwater Horizon disaster in 2010, when a gigantic offshore oil platform in the Gulf of Mexico spread oil up to 800 km (almost 500 mi), including up to the U.S. coast. Researchers estimate the disaster killed a million birds and up to 173,600 sea turtles.
In Brazil’s case, a spill reaching the coast around the mouth of the Amazon would hit the world’s largest mangrove belt, which is inaccessible by land and has complex coastal navigation, making any attempt to rescue manatees there much more challenging.
There’s also the phenomenon known as pororoca, when a high tide on the Atlantic coast sends waves up to 4 m (13 ft) high barreling upriver. “These are waves that enter the rivers and pose a significant obstacle to navigation,” Borges said.
According to Luna, the marine biologist, West Indian manatees would be directly exposed to the oil layer when they surface to breathe. The contamination may be transmitted from mother to calf. The oil may also hinder the animal’s swimming and navigation by blocking its vibrissae, the short hairs that cover its body and function as sensors. The seismic noise used in exploration activities could also affect other aquatic mammals.
As part of the environmental permitting requirement, Petrobras set up two wildlife care and rehabilitation centers in Pará’s capital, Belém, and in Oiapoque municipality, in Amapá, which, according to the company, are prepared to treat marine mammals. It also committed to supporting institutions already working on the rescue and rehabilitation of manatees in Pará.
Petrobras suspended work on the Morpho well for more than two months after the fluid accident in January 2026. The company says it expects to complete drilling the first well in the second quarter of this year, but additional drilling will be needed to confirm the oil reserves.
Banner image: Petrobras says in its emergency plan that it’s “unfeasible” to rescue animals weighing more than 50 kilos (110 pounds). Image courtesy of FMA collection.
UPDATE (6-10-2026): The story was updated to inform that the subspecies Trichechus manatus manatus, which inhabits the coastal zone from the Bahamas to Brazil, has its IUCN classification increased to “endangered.”
Seismic noise from oil companies threatens Amazon River Mouth marine life
Citations:
Moura, R. L., Amado-Filho, G. M., Moraes, F. C., Brasileiro, P. S., Salomon, P. S., Mahiques, M. M., … Thompson, F. L. (2016). An extensive reef system at the Amazon River mouth. Science Advances, 2(4), e1501252. doi:10.1126/sciadv.1501252
Vilaça, S. T., Lima, C. S., Mazzoni, C. J., Santos, F. R., & De Thoisy, B. (2019). Manatee genomics supports a special conservation area along the Guianas coastline under the influence of the Amazon River plume. Estuarine, Coastal and Shelf Science, 226, 106286. doi:10.1016/j.ecss.2019.106286
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