- The Madeira River, the largest tributary of the Amazon, has been losing water flow over the last 20 years while facing severe droughts.
- The water drop is worrying the local population, whose livelihoods depend on balanced water bodies for small-scale agriculture, wild fruit extractives, fishing and transportation.
- The Madeira is particularly vulnerable to hydrological extremes and reached its lowest level ever recorded in September 2024.
- The Amazon has been warming since the 1980s, suffering 15 extreme droughts so far.
MADEIRA RIVER, Brazil — While the Amazon Rainforest’s historical drought was peaking in September 2024, the Paraizinho community, in the southern Amazon, went through its most calamitous times.
There, 33 families rely on the Madeira River, whose waters rinse the traditional floodplain agriculture, to flow production to governmental programs that distribute food to local schools about 10 kilometers (6.2 miles) downstream. However, in 2024, there was no nutrient-rich freshwater to irrigate their small-scale crops of bananas, watermelons, pumpkins and other crops.
This scenario is becoming more frequent in the Amazon, and it worries traditional communities and Indigenous populations who rely on the Madeira as the 2025 dry season approaches and the Amazon — and the planet — gets warmer.
“There was a shortage of everything we cultivate here in the community, and the well we used for water supply dried up,” João Mendonça, a local health agent and the president of the Association of Paraizinho’s Farmers, told Mongabay.
Historically, rainfall in the Amazon drops from June to November (also known as the Amazon’s summer, even though it occurs in Brazil’s winter and spring).
“We had to get drinking water in the city. We also practice artisanal fishing but weren’t able to catch almost any fish – even for our own consumption it was difficult,” Mendonça said.
The Madeira River, the largest tributary of the Amazon River, is particularly vulnerable to hydrological extremes. Its levels are highly influenced by the North Tropical Atlantic, which has mainly been responsible for the most extreme weather events in this basin since 1994, environmental engineer Nicole Laureanti, a researcher at INPE, Brazil’s space agency, told Mongabay.
“When the Atlantic warms, there’s a shift in the trade winds that bring moisture from the ocean to the Amazon,” Laureanti said. “The Madeira is the southernmost subbasin, thus this influence is more intense. The extremes are more impactful in the region because shorter rainy periods bring severe consequences to the dry season.”
Since 1994, the Madeira Basin has faced three years of severe floods and four extreme droughts. During the latest, the river reached its lowest level ever recorded in September 2024. Much of its flow, an annual average of 4,565 cubic meters (161,000 cubic feet) each second, relies on rain from October to March. In a recent study led by Laureanti, researchers identified that the Brazilian portion of the Madeira River lost almost 10% of its flow (400 m3/s or 14,125 ft3/s) in discharge per decade over the last 20 years. In Bolivia and Peru, the reduction was much lower (100 m3/s or 3,530 m3/s).
“If this trend continues, regardless of what the atmosphere and the Pacific and Atlantic oceans are manifesting, in 10 years it may have this reduction of 400 m3 again,” Laureanti said.
At the Madeira River Sustainable Development Reserve, the 2024 drought came as a harsh glimpse of the future. Banana, watermelon, pumpkin and pepper crops were lost and the few items harvested couldn’t be moved as riverbeds went dry.
“Climate change worries us a lot, because it affects our income,” Silvana Cabral, president of the Santa Maria do Uruá community association, told Mongabay. “The lakes from which we took our everyday food were very dry, as we had never seen before. There was almost nothing in the shops. I experienced hunger up close.”
In the Diahui Indigenous Territory, wells were almost empty due to the low levels of Maici, Amazônia and Taiuí rivers.
“The water becomes polluted, and sometimes it dries completely,” Nilcélio Jiaui, general coordinator of the Organization of the Upper Madeira’s Indigenous Peoples, told Mongabay. “We have to dig wells near the headwaters, but the water is not totally clean, and it usually gives us skin or worm diseases.”
An even more extreme Amazon
The Madeira starts at the foot of the Bolivian Andes Mountains and runs 3,315 km (2,060 mi) until it reaches the Amazon River, in Amazonas state, impacting a region that spans almost a quarter of the Amazon Basin, through Bolivia, Brazil and Peru.
In 2024, the Amazon drought was a consequence of the warming of the Equatorial Pacific (a phenomenon known as El Niño) and the North Tropical Atlantic, which reduced the moisture flow entering the rainforest. As a result, the Amazon saw its rainfall reduced by up to 70% of the expected for 2024, according to the Geological Survey of Brazil.
“The Madeira is a little further below the equatorial region. It is also influenced by El Niño, but more directly by the trade winds of the Tropical Atlantic region,” Laureanti said.
The Amazon has been warming since the 1980s, according to a recent article. Since 1906, there have been seasonal extremes in the Amazon in 27 years: 15 with extreme droughts, 11 with severe floods and one year with both.
In the 21st century alone, four extreme droughts and four severe floods have already ravaged the Amazon. “It means that our climate is getting more irregular. The extremes are becoming more extreme for both sides, and the impacts are becoming greater,” said meteorologist José Marengo, from Brazil’s natural disaster monitoring center, CEMADEN, one of the study’s lead authors. “This did not happen in the 1960s and 1970s, when the planet was relatively colder.”
Brazil’s Civil Defense recorded almost 5,700 occurrences of natural disasters in Amazonian states from 1995 to 2024, among which 64% were hydrological events, like floods, and 20% were climatological episodes, such as droughts, according to a survey made by news outlet InfoAmazonia.
In the last four years, a sequence of two severe floods (2021, the largest ever recorded, and 2022, the fourth-worst) and two unprecedented droughts (2023 and 2024) reached the rainforest. These were the worst events observed in the Amazon Basin in more than 120 years of data, also affected by the melting of the Andes glaciers.
“These extremes can be an indicator that climate change is already affecting the region,” Arthur Matos, coordinator of the hydrological alert systems of the Geological Survey of Brazil, told Mongabay.
Since the late 1970s, the dry season in the southern Amazon has become longer, resulting in the delay of the rainy season by almost a month, and precipitation decreased by 17% in the August-October period, according to Marengo’s article. This combination contributes to more forest loss and makes the vegetation more vulnerable to fires. The study highlights negative trends in discharge rates of the Ucayali, Solimões, Madeira and Amazon basins.
On the other hand, the main tributaries of the Amazon Basin’s northwest, such as Marañón and Caquetá-Japurá rivers, have recorded an increase in discharge during the rainy season since the 1990s, reflecting higher precipitation in the Amazon lowlands in Colombia, Ecuador and northern Peru.
Fewer fish in the river
Fishing activities have been affected hard by the changes in Madeira in recent years. Dams from hydropower plants have caused irregular river flow, impacting migratory patterns and breeding (piracema) in fish. This has resulted in a reduction in fish stocks and a 39% decline in annual catches in the municipality of Humaitá. Consequently, fishing has become more costly and demanding, forcing fishers to travel farther to maintain productivity, and some have resorted to illegal activities. The unpredictable river levels and abrupt changes further disorient fish. Ultimately, these issues have led to a decline in fish landings, negatively impacting the local economy and serving as the primary protein source for riverine communities.
The Madeira also faces significant mercury contamination, primarily stemming from illegal gold mining activities. Miners use mercury to extract gold from riverbed sediments, often discarding it directly into the river. While initial data indicate that total mercury levels in the river water are currently below Brazil’s recommended limit, they are considered elevated relative to other rivers. Predatory fish species in the Madeira have been found to have mercury levels exceeding the safe limit for human consumption, raising concerns about potential health impacts on local communities that rely on fish as a primary food source. Researchers from Harvard and Amazonas State University are actively monitoring mercury levels in the water, sediments and fish to better understand the extent of the contamination and its potential consequences.
Extreme dry years exacerbate these problems in the Madeira Basin, the most diverse in the Amazon. During the wet season, the Madeira fills and creates flooded forests called igapó.
“The fish enters that forest area and eats the ripe fruits that fall into the water,” Samuel de Moraes, president of Humaitá’s Fishers Association, told Mongabay. “This doesn’t happen in the extreme drought because the fruit trees are not in the igapós anymore. So the fish can’t feed and become too weak to reproduce.”
According to Moraes, fish production in Humaitá dropped from 800 tons in the early 2010s to 100 tons per year. “The fisherman’s life became tough here,” he said.
Fishing of most commercial species is forbidden in the Brazilian Amazon during their reproductive period, from Nov. 15 to March 15. To compensate for this, the Brazilian government pays artisanal fishers a minimum wage for each month of restriction. In 2025, they received an additional payment as emergency aid to help offset their losses from the recent extreme drought.
A bleak future
In 2024, most of the rivers of the Amazon Basin dried up in the first year that the planet exceeded 1.5ºC (2.7°F) of warming compared with preindustrial levels — the Paris Agreement’s main target.
“This is the critical threshold that we should avoid so that the extremes are not so extreme, and so that adaptation is possible,” Marengo said.
According to the United Nations Environment Programme (UNEP), it’s still possible to put the world on track to meet the target. However, the current nationally determined goals would lead the planet to an increase ranging from 2.6-3.1ºC (4.7-5.6°F) over this century.
In his study, Marengo and colleagues evaluated the future climate of the Amazon, under two scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC).
If temperatures increase between 2ºC and 3ºC (3.6°F and 5.4°F) by 2100, the Amazon would be on average 2ºC warmer, with small changes in rain patterns.
If it goes up to 3.2ºC (5.8°F) to 5.4ºC (9.7°F), the average temperature in the Amazon could rise by more than 6ºC (10.8°F) by the end of the 21st century. The central and eastern Amazon could experience a rain deficit of up to 40%.
The differences in the scenarios are on the order of 10% in the eastern and southern Amazon, where the Madeira is situated, changing the likelihood of events such as wildfires, droughts and floods. There are also projections of a substantial increase in consecutive dry days and days of intense precipitation. Under a warming over 4ºC (7.2°F), the Madeira, Tapajós and Xingu rivers’ discharge rates would become more sensitive to precipitation changes.
In both scenarios, drier conditions are also expected to the south of the Andean Amazon region, which comprises the Madeira’s headwaters in Bolivia and Peru.
If the Amazon reaches its tipping point due to the climate crisis and land use changes, the rainforest could collapse and it would cease to be a sink and become a source of carbon, according to multiple studies.
Amid this bleak future, Marengo considers it necessary to expand the number of weather stations and integrate the hydrological and meteorological systems between Amazonian countries, in order to minimize socioeconomic and environmental losses. As a mitigation strategy, he said he believes curbing deforestation and investing in forest restoration are priorities.
The Geological Survey of Brazil has worked on flood alerts since 1989 and has recently expanded its scope for drought forecasts. “With this prior knowledge, it is necessary that municipalities and states have adequate public policies for better adaptation and coexistence with critical events,” Matos said.
Laureanti highlights the Drought and Flood Forecast System for the Madeira River Sustainable Development Reserve, developed and implemented by Amazonas State University in partnership with INPE. Researchers from the Earth Climate System Modeling Laboratory known as Labclim produce diagnostics and prognostics three months earlier on variables such as precipitation, air temperature, river level and discharge rate and flooded areas in the Madeira Basin. This tool is currently being expanded for all of Amazonas state and allows navigation planning months in advance.
“The solution has to be governmental. Some regions do not have the resources to guarantee the maintenance of their livelihoods during the dry season, so it is necessary to have alternatives for local populations that will spend four or five months a year without having their income resources,” Laureanti said.
Banner image: A young river dweller docks on the bank of the Madeira River in the late afternoon, near the town of Borba, Amazonas. Image by Bruno Kelly.
Hydropower plants disrupt fishers’ lives in Amazon’s most biodiverse river basin
Citations:
Laureanti, N. C., Tavares, P. D., Tavares, M., Rodrigues, D. C., Gomes, J. L., Chou, S. C., & Correia, F. W. (2024). Extreme seasonal droughts and floods in the Madeira river basin, Brazil: Diagnosis, causes, and trends. Climate, 12(8), 111. doi:10.3390/cli12080111
Marengo, J. A., Espinoza, J., Fu, R., Jimenez Muñoz, J. C., Alves, L. M., da Rocha, H. R., & Schöngart, J. (2024). Long-term variability, extremes and changes in temperature and hydrometeorology in the Amazon region: A review. Acta Amazonica, 54, e54es22098. doi:10.1590/1809-4392202200980
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