Amazon at risk: deforestation, not just climate change, drives rainfall loss

The Amazon rainforest, often described as the "lungs of the Earth," is undergoing one of the most dramatic transformations in its history. A groundbreaking study published in Nature Communications reveals that deforestation — rather than global climate change — is the dominant driver of reduced rainfall in the region. This finding shifts the focus of conservation strategies: protecting forests is not just about biodiversity, but about safeguarding the hydrological cycle that sustains millions of lives.

The research question: local vs. global forces

For decades, scientists have debated whether declining rainfall in the Amazon is primarily due to global climate change or local deforestation. The study led by Marco A. Franco, Luciana V. Rizzo, Márcio J. Teixeira, and Paulo Artaxo set out to disentangle these effects by examining climate and land-use data between 1985 and 2020 across 29 subregions of the Brazilian Legal Amazon.

The results are striking. During the dry season, deforestation accounts for roughly 74% of rainfall reduction, while global climate change explains around 16% of the observed temperature increase. This means that the decline in rainfall is overwhelmingly linked to local forest loss rather than distant greenhouse gas emissions alone.

How the study was conducted

The researchers combined high-resolution land-use maps from the MapBiomas Project with official meteorological records. By applying parametric statistical models, they were able to separate the relative contributions of global and local drivers.

Although the authors acknowledge limitations — such as the complexity of coupled atmosphere–vegetation systems and the potential influence of land-use changes outside the study area — their analysis provides the first large-scale empirical quantification of these competing factors.

The key takeaway is clear: while climate change continues to drive long-term warming, halting deforestation would have immediate and measurable benefits for preserving regional rainfall.

Why deforestation dries the forest

Forests are not passive victims of climate; they actively generate it. Through evapotranspiration — the release of water vapor from trees — Amazonian vegetation recycles vast amounts of moisture back into the atmosphere. This process, sometimes referred to as the “biotic pump,” helps sustain rainfall even during the dry season.

When trees are cut down, this pump weakens. Less moisture enters the atmosphere, cloud formation declines, and dry-season rains diminish. In turn, higher temperatures and reduced soil moisture make the forest more vulnerable to wildfires, compounding the cycle of degradation.

What’s at stake: people, food, and energy

The consequences of this rainfall loss extend far beyond ecology. Reduced precipitation threatens:

• Water security: millions of people in Brazil and neighboring countries rely on rivers and aquifers replenished by Amazon rainfall.
• Agriculture: drier conditions reduce crop yields and stress livestock, threatening food security.
• Energy: hydroelectric plants, which supply much of Brazil’s electricity, depend on stable river flows.
• Communities: rural and Indigenous populations face growing risks from fire, drought, and disrupted livelihoods.

“Forest protection policies are a high-impact tool to maintain regional hydrology,” the authors conclude. Suggested measures include stricter satellite monitoring, improved land governance, and financial incentives like payments for ecosystem services.

Policy implications: a two-pronged strategy

The study calls for a dual approach:

1. Global action to reduce greenhouse gas emissions and limit long-term warming.
2. Regional action to halt deforestation and promote forest restoration, which can deliver rapid hydrological benefits.

Because the Amazon spans multiple countries, regional cooperation will be essential. Shared governance, stronger environmental enforcement, and cross-border agreements could play decisive roles in stabilizing the world’s largest rainforest.

Conclusion: a narrowing window for change

The Amazon’s fate is not sealed. The research shows that stopping deforestation could preserve rainfall and protect millions of lives, even as the world continues to grapple with global warming.

The science is unequivocal: protecting the forest is protecting the rain. And protecting the rain is protecting the future of the Amazon and all who depend on it.

Topics of interest

Climate