Anna Júlia Lopes*
Deforestation is the main factor responsible for the reduction in rainfall in the Legal Amazon over recent decades. A study published in the journal Nature Communications shows that forest clearing accounts for 74% of the drop in precipitation during the dry season recorded over the past 35 years, and contributes to 16.5% of the increase in maximum air temperature in the region. The article was led by USP (University of São Paulo) and included participation from IPAM (Amazon Environmental Research Institute).
Researchers analyzed data collected between 1985 and 2020 and found that the combination of deforestation and global climate change is transforming the forest.
Julia Shimbo, a researcher at IPAM and scientific coordinator of the MapBiomas network, was one of the authors of the publication. She explains that the study aimed, for the first time, to clarify what is happening to the Amazon’s climate.
According to Shimbo, to achieve the results presented in the article, historical data on land use change and deforestation were cross-referenced with climate data (temperature and rainfall levels). As shown in MapBiomas Collection 10, released on September 15, the Amazon lost nearly 50 million hectares over the past 40 years (the same period used in the article), which represents a loss of about 13% of the forest’s native vegetation.
Given the success of the publication, the authors decided to launch a free module on the MapBiomas network, of which IPAM is a part, that allows users to visualize the data cross-referencing (land use vs. climate data). The new module is expected to be released later this year.
The article shows that the most preserved areas remain relatively stable, but the so-called “deforestation arc” is already experiencing increased droughts, more intense heat, and a risk of changes to the climate regime.
This warning comes at a critical moment. In 2024, Brazil recorded the most severe drought in its history, with serious impacts on agriculture, energy generation, and water supply in various regions. At the time, the Amazon faced one of the most severe droughts ever recorded, exacerbating an environmental crisis in the region, with a combination of low rainfall, high temperatures, and uncontrolled use of fire.
“With a scenario of more deforestation, rising temperatures, and less rain, we not only lose vegetation but also have a forest more susceptible to fire and degradation. The forest loses its climate resilience to prepare for global climate changes,” says Shimbo, who refers to the so-called “hammer effect,” a concept mentioned in a previous IPAM article that describes high pressure on ecosystems, resulting in the loss of much of the forest’s biodiversity and services.
According to the study’s authors, the loss of forest cover directly affects the water cycle, reducing the humidity that sustains rainfall within the biome and in other parts of the continent. This process increases the Amazon’s vulnerability to forest fires, harms agriculture, and threatens global food security.
As IPAM has highlighted on several occasions, the forest is responsible for irrigating Brazilian agriculture through its rainfall regime, since more than 90% of agribusiness in the country lacks its own irrigation systems. With Amazon deforestation, reduced rainfall compromises crops in Brazil and across the continent, affecting agricultural production and putting global food supply at risk.
According to the researcher, beyond affecting Brazilian agriculture, a hotter and drier Amazon creates a “cascade effect,” also impacting traditional peoples and communities who depend on forest services.
In Shimbo’s view, the main goal right now is to eliminate deforestation in the region. After that, she says, priorities should include ensuring that conservation units and Indigenous territories are properly protected, and encouraging the private sector to seek strategies for more sustainable forest management, considering that most deforested areas are on private rural properties.
Another point raised by the ecologist is the issue of Undesignated Public Forests (FPNDs). As IPAM studies have already shown, the growing illegal occupation of these areas is currently one of the main drivers of deforestation in the Amazon. Shimbo advocates for an urgent designation of these forests, which are considered more vulnerable precisely because they do not yet have a legally defined purpose.
*Journalist at IPAM