For the first time, scientists at the University of São Paulo have quantitatively distinguished the individual impacts of deforestation and global climate change on the Amazon rainforest, revealing stark insights into the biome’s evolving climate dynamics. This pioneering research, newly published in Nature Communications, supplies critical data that could shape future mitigation and adaptation efforts, particularly as the world prepares for the forthcoming United Nations Climate Conference (COP30) in Belém, Brazil. By employing advanced parametric statistical models, the researchers have for the first time isolated the extent to which indigenous land-use changes and broader planetary warming contribute to shifts in rainfall and temperature patterns during the Amazon’s critical dry season.
Deforestation within the Brazilian Amazon accounts for an estimated 74.5% of the documented rainfall reduction during the dry season, subtracting roughly 15.8 millimeters of annual precipitation, while global climate change underpins the remaining decrease. The forest loss also explains approximately 16.5% of the observed 2.0 °C temperature increase over the same period, with the greater share attributed to global warming originating largely from industrial activity in Northern Hemisphere nations. These findings represent a crucial “attribution partition,” quantifying the relative influence of local anthropogenic land modifications and worldwide greenhouse gas emissions on Amazonian climate fluctuations.
Professor Luiz Augusto Toledo Machado, who helmed the study from USP’s Physics Institute, emphasizes this work’s significance in disentangling the previously conflated drivers of the Amazon’s changing climate. “While many studies have documented escalating temperatures and diminishing rainfall, this is the first clear breakdown of how much is due to deforestation tied to Brazil itself, versus external global emissions,” he explains. By constructing parametric surface equations that integrate annual variability and deforestation data, the team was able to decompose the cumulative climatic shifts into their component sources, setting a new standard for ecosystem-specific climate attribution.
The researchers underline that the largest climatic disruptions occur early in the deforestation trajectory. Pronounced variations in temperature and precipitation emerge sharply once forest cover is reduced by as little as 10% to 40%. According to co-author Professor Marco Aurélio Franco, “The initial stages of deforestation impose disproportionate impacts, so preserving the standing forest is paramount. Transitioning these lands to pasture or other uses risks triggering amplified local warming and severe rainfall declines.” Their statistical analysis pinpoints this initial deforestation threshold as a climatic tipping point, beyond which recovery of ecosystem equilibrium becomes drastically more difficult.
Remote sensing datasets, including the extensive land-use classifications by the MapBiomas collaborative network, afforded the study a robust spatial and temporal scope over 35 years. These data, combined with long-term reanalyses of atmospheric greenhouse gas concentrations, revealed that atmospheric CO₂ and methane increases in the Amazon are overwhelmingly driven (>99%) by global emissions rather than local deforestation. Though deforestation reduces the forest’s capacity to sink carbon locally, this does not translate into a significant localized elevation of atmospheric CO₂ concentration, given the global scale of greenhouse gas accumulation.
The Amazon’s role in regional and global hydrological cycles is profound, often described through the concept of “flying rivers”—large atmospheric flows of moisture sustained by the forest’s transpiration processes. Trees extract groundwater and release it as vapor, driving cloud formation and precipitation not only locally but throughout South America, including the Cerrado biome. The study confirms that deforestation disrupts this vapor recycling mechanism, intensifying the dry season and exacerbating forest fire frequency, which in turn further degrade the forest’s vegetation and resilience.
Recent international research, including prior work by USP experts, has elucidated how aerosol nanoparticles generated within the Amazon’s atmosphere interplay with electrical discharges and daytime-nighttime chemical reactions to form rain-inducing clouds. This complex “aerosol machine” is tightly linked to forest health. As deforestation escalates, these processes weaken, diminishing cloud formation potential and leading to cascading rainfall deficits. Such physical-chemical insights underscore how land-cover changes ripple through atmospheric chemistry, altering weather and climate patterns in ways that threaten the rainforest’s survival.
The cumulative land degradation between 1985 and 2023 has already resulted in the loss of 14% of the Amazon’s original vegetation, an area roughly equivalent to France. While recent deforestation rates have declined slightly to 4,495 km² annually, the persistence of forest degradation—particularly from recurrent fires—continues to challenge conservationists. The dry season, stretching from June to November, remains the focal window when these impacts are most visible, as precipitation reductions and temperature rises converge to heighten vulnerability.
Looking forward, the researchers warn that the continuation of deforestation at current or higher rates threatens to push the Amazon past critical climate thresholds. Their models project accelerating precipitation declines and temperature increases during dry seasons, intensifying seasonal extremes and undermining the biome’s ecological resilience. These hydrometeorological shifts are already affecting the South American monsoon, leading to drier conditions that imperil the rainforest’s long-term stability and its essential climate regulation functions.
The implications extend beyond local ecosystems. Alterations in the Amazon reverberate across continental weather systems, influencing agriculture, water security, and biodiversity throughout Brazil and neighboring countries. Extreme drought events in 2023 and 2024 serve as ominous indicators of a rapidly shifting baseline, highlighting the urgent need for integrated strategies that address both land-use practices and global greenhouse gas emissions. This new research provides policymakers and environmental stakeholders with a precise “climate ledger” that clarifies responsibilities and informs sustainable development pathways.
This study, supported by the São Paulo Research Foundation (FAPESP) and conducted in collaboration with the Chinese Academy of Sciences, marks a breakthrough in our understanding of the Amazon’s vulnerability amid converging environmental crises. The scientific community now possesses clearer evidence tying local deforestation directly to tangible climatic consequences, alongside the overarching global warming trend. Ultimately, the findings reinforce the critical imperative to protect and sustainably manage the Amazon rainforest to secure its indispensable climate services for Brazil and the world.
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Subject of Research: The interactive effects of deforestation and global climate change on the Amazon rainforest’s climate, with emphasis on rainfall and temperature changes during the dry season.
Article Title: How climate change and deforestation interact in the transformation of the Amazon rainforest
News Publication Date: 2-Sep-2025
Web References: https://agencia.fapesp.br/54089; https://www.fapesp.br/en
References: DOI 10.1038/s41467-025-63156-0 (Nature Communications)
Image Credits: Luiz Augusto Toledo Machado (IF-USP)
