Deforestation in the Amazon is associated with declining rainfall in the Iguaçu River basin, in the southern Brazilian state of Paraná, according to a study by the Federal University of Paraná (UFPR) published in July in the peer-reviewed journal Brazilian Journal of Biology. The researchers compared forest-loss data from Brazil's space research institute INPE and the NGO Imazon with records from 64 rain gauge stations between January 2011 and December 2023, and found a correlation: periods of heavier Amazon deforestation lined up with lower rainfall in the Paraná basin.
The basin is central to the state's economy. It covers the eastern, southern, southwestern and western regions of Paraná, spans 35 municipalities and holds about 60% of the state's grain production and 23% of its livestock farming, the research found. It also contains five large reservoirs that account for roughly 41% of Paraná's hydroelectric generation, based on data from the state power company Copel and the national water agency ANA cited in the study.
How the forest feeds southern rains
The link runs through atmospheric moisture transport, a phenomenon known in Brazil as flying rivers: the forest releases water vapor that flows in corridors toward distant regions. About 40% of the rain that reaches Paraná is connected to moisture originating in the Amazon, said Ana Carolina da Silva, one of the study's authors.
"The Amazon is not an isolated system in the country's North; it affects all of South America, including Paraná. The greater the deforestation observed in the Amazon, the lower the rainfall volumes recorded in the state tend to be."
The Portal Amazônia news site, reporting on the study with material from the science agency Agência Bori, said forest loss jumped from 2020 onward and reached 2,095 sq km in a single month, in July 2021. In the author's assessment, human pressure outweighed the climate: weakened environmental enforcement mattered more to the rise in deforestation than the weather conditions of the period, which was partly marked by La Niña. In 2020 the Amazon recorded more than 222,000 fire hotspots, up 120% from the average of previous years.
The warning for crops and power plants
When rains fail, losses show up quickly in the basin's fields. Soybeans, corn, wheat and barley are the most exposed crops, and drought at critical stages of the growing cycle cuts both the volume and the quality of the harvest, said Ana Paula Kowalski, head of the technical and economic department of Faep, Paraná's farmers federation. In extreme events, farmers log drops of 10% to 20% in productivity, and a prolonged drought can leave soybean yields 15% to 25% below a target of 3,500 to 4,000 kg per hectare. In the 2021/2022 season, a dry spell between December and January cut the state's soybean output by about 50%.
The study does not attribute every drought in Paraná to Amazon deforestation. The state has a varied climate and is frequently hit by shifting air masses, as Kowalski noted, and the research shows a correlation between the two phenomena. The path proposed by the researchers is direct: stop the clearing in the North and tie agricultural and energy planning to forest conservation, treating the Amazon's tree cover as part of southern Brazil's water security. "The data suggest that this region of Paraná will face strong impacts on power generation and water supply if this keeps happening," Ana Carolina said.