Amazon Rainfall Declines with Deforestation

Draft script:

Conservation International is a non-profit organization committed to protection. It is well-known, as indicated by actor Harrison Ford serving as Vice Chairman of the Conservation International Board. He is prominently featured on the Conservation International website, where this quote is attributed to him: “There is no more room for distractions, and no time for delay. There is no one else coming to save us. This is it. We are it. Let’s get to work.”

I appreciate Ford’s words, as well as his willingness to serve on the board of this organization. I agree that “[t]here is no more room for distractions, and no time for delay. There is no one else coming to save us.”

I also agree that “[t]his is it. We are it.” Collectively, our species is responsible for the worst Mass Extinction Event in planetary history. The only part with which I disagree with Ford is the idea that we’re not working hard enough to save the living planet. “Let’s get to work” can mean different things to different people. For example, I suspect most billionaires will assume that getting to work translates to making more money for themselves. If there’s serious work to be done, the masses will be called on to make sacrifices and fix whatever ails the living planet. Unfortunately, this predicament is beyond repair.

After all, it’s a little late to fix the predicament in which we are collectively embedded. The signature line I’ve quoted before in this space comes from the 2007 film, No Country for Old Men. It’s expressed by actor Barry Corbin, playing uncle Ellis: “You can’t stop what’s coming. It ain’t all waiting on you. That’s vanity.”

After all, even the designed-to-fail Intergovernmental Panel on Climate Change has reported that Earth is amid the most abrupt change in planetary history, a change that is irreversible. The IPCC reached this conclusion with two reports published less than a year apart. In Global Warming of 1.5°C, published on 8 October 2018, the signature line relies on two peer-reviewed papers: “These global-level rates of human-driven change far exceed the rates of change that have altered the Earth System trajectory in the past …; even abrupt geophysical events do not approach current rates of human-driven change.”

The IPCC addresses the matter of irreversibility with five peer-reviewed papers in the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Irreversible climate change is attributed to an overheated ocean: “Ocean acidification and deoxygenation, ice sheet and glacier mass loss, and permafrost degradation are expected to be irreversible on time scales relevant to human societies and ecosystems.”

Conservation International posted an article on its website on 15 September 2025. The article is titled News spotlight: Deforestation linked to dramatic decline in Amazon rainfall. Here’s the lede: “The Amazon rainforest, known for lush green canopies and an abundance of freshwater, is drying out.”

The following one-sentence paragraph introduces a peer-reviewed paper: “Deforestation is largely to blame, according to a new study.” The research was published in the renowned Nature series of peer-reviewed papers.

The following paragraph provides a short summary of the peer-reviewed paper: “The study, published in Nature Communications, found that roughly 75 percent of the drop in rainfall can be directly linked to deforestation, Sachi Kitajima Mulkey reported for The New York Times.”

The New York Times quotes the Assistant Professor at the University of São Paulo who led the study: “We were expecting to see deforestation as a driver, but not this much. It tells us a lot about what’s going on in the biome.”

The article at Conservation International includes an excellent overview of the research and its conclusions in five short paragraphs: “In the Amazon, more than 40 percent of the region’s rainfall comes from trees, which release water vapor into the air through a process known as evapotranspiration.

It’s simple math: fewer trees means less moisture in the air.

Scientists have long known about the connection between deforestation and declining precipitation, but it’s a difficult effect to study and quantify as weather changes can appear far from areas where the deforestation actually occurred.

Indeed, the study also connects deforestation to higher temperatures in the Amazon, generally, finding that the hottest days increased by roughly 2 degrees Celsius, in part due to deforestation.

To understand the impact, the researchers pored over 35 years of annual data from key sections of the Brazilian Amazon, using satellite data and advanced analytical methods to measure changing climate and weather patterns, while sifting out other influences like evolving landscapes.”

I can assure you that “sifting out other influences” is no easy task. Scientists constantly struggle to correctly attribute causation. Considering the myriad factors that influence every aspect of our daily lives, you can imagine the difficulty attributing outcome to input. Life is complicated. The Amazon region is replete with life, thereby making its study particularly challenging.

A Professor of climate and meteorology at the University of São Paulo, a co-author of the peer-reviewed paper, told The New York Times that climate change and deforestation have altered the Amazon, as is common knowledge. Until this study, he said, “nobody knew exactly what each of these things contributed.”

The following four paragraphs in the article at Conservation International indicate how bad the outcome could be: “The authors also note that a 75 percent drop in precipitation is an average across the Amazon Basin — areas with higher levels of deforestation experienced even greater rainfall declines.

This is because years of deforestation have pushed the rainforest into a vicious cycle: As large areas are cleared of trees, the forest loses its ability to retain moisture and recycle that water back into the atmosphere. This contributes to longer periods of drought, which in turn spur intense fire seasons that destroy even more trees.

If this cycle of destruction continues, the rainforest could be pushed to an ecological tipping point, transforming permanently into a dry savanna.

The continued deforestation of the Amazon would be disastrous for the Earth’s climate. Conservation International studies have shown that the Amazon rainforest stores more irrecoverable carbon — carbon that, if emitted into the atmosphere, could not be restored in time to prevent the worst impacts of climate change — than any other region on Earth.”

Never mind that the rainforest has already been “pushed to an ecological tipping point,” as reported in the peer-reviewed literature at least 15 years ago. I reported this unfavorable outcome in my Climate Change Summary as the twenty-second self-reinforcing feedback loop.

I now turn briefly to the peer-reviewed, open-access paper in Nature Communications. Published on 2 September 2025, it is titled How climate change and deforestation interact in the transformation of the Amazon rainforest. It was created by 12 scholars. The Abstract tells the tale: “The Amazon rainforest is one of Earth’s most diverse ecosystems, playing a key role in maintaining regional and global climate stability. However, recent changes in land use, vegetation, and the climate have disrupted biosphere-atmosphere interactions, leading to significant alterations in the water, energy, and carbon cycles. These disturbances have far-reaching consequences for the entire Earth system. Here, we quantify the relative contributions of deforestation and global climate change to observed shifts in key Amazonian climate parameters. We analyzed long-term atmospheric and land cover change data across 29 areas in the Brazilian Legal Amazon from 1985 to 2020, using parametric statistical models to disentangle the effects of forest loss and alterations of temperature, precipitation, and greenhouse gas mixing ratios. While the rise in atmospheric methane … and carbon dioxide … mixing ratios is primarily driven by global emissions (>99%), deforestation has significantly increased surface air temperatures and reduced precipitation during the Amazonian dry season. Over the past 35 years, deforestation has accounted for approximately 74% of the ~21 mm dry season decline and 16.5% of the 2°C rise in maximum surface air temperature. Understanding the interplay between global climate change and deforestation is essential for developing effective mitigation and adaptation strategies to preserve this vital ecosystem.”

There is no doubt the Amazon Basin is a vital ecosystem. If we are to survive much longer, preserving the Amazon Basin is critical. However, I suspect we are already well into the domain of too little, too late.