On February 14, a significant paper was released in Nature, stirring discussions within both the media and scientific circles. The study, titled “Critical transitions in the Amazon forest system,” examined the various elements leading to the Amazon Rainforest's decline—such as climate change, drought, diminishing rainfall, deforestation, wildfires, and “edge effects”—while creating models to forecast these developments. The researchers projected that by 2050, nearly 47 percent of the Amazon Rainforest could hit a “tipping point,” transforming it from a lush rainforest into extensive dry savannah and grassland.

This is not the first warning regarding the Amazon's precarious tipping point. Carlos Nobre, a renowned climate scientist and senior researcher at the Institute for Advanced Studies in São Paulo, Brazil, has devoted almost forty years to studying climate dynamics in the Amazon. After obtaining his Ph.D. in meteorology from the Massachusetts Institute of Technology (MIT) in 1983, Nobre worked as a visiting researcher at the University of Maryland, where he made groundbreaking contributions to understanding climate change and deforestation's impact on the Amazon. He is a distinguished member of the National Academy of Sciences, the International Science Council, and the Intergovernmental Panel on Climate Change (IPCC). He also co-authored the IPCC’s Fourth Assessment Report, for which he and his colleagues received the Nobel Peace Prize in 2007.

In this interview, Nobre reflects on his extensive research on climate change in the Amazon, insights from his latest research on the Amazon tipping point, and his aspirations and concerns for the rainforest's future.

An edited transcript of the interview follows.

Quentin: I heard that you and your colleague, Thomas Lovejoy, were the ones to introduce the term “the Amazon tipping point.” Is that accurate?

Nobre: Yes, while my colleague Thomas Lovejoy and I did use the term "tipping point" in our joint paper, we have been discussing this concept for many years. The phrase has been part of scientific discourse for about two decades, highlighting various critical points across the globe.

I was among the first to investigate the implications of deforestation and climate change on the Amazon. My initial paper on this topic was published in 1991, and although we didn't use the term tipping point then, we were essentially addressing the concept. I found that more than 50 percent of the Amazon could devolve into a degraded open-canopy ecosystem. Since then, climate scientists have pinpointed various tipping points, leading to a broader dialogue about phenomena such as permafrost melting and coral reef loss. Today, we recognize over 20 tipping points affecting our planet's climate.

Quentin: Can you elaborate on the recent Nature paper, “Critical transitions in the Amazon forest system”? What new findings did it present?

Nobre: This study reinforces that we are perilously close to the Amazon's tipping point. If deforestation, degradation, and global warming persist, we risk exceeding this critical threshold by 2050—much sooner than previously anticipated.

Quentin: How imminent is the Amazon tipping point?

Nobre: It varies. If we achieve zero deforestation and mitigate global warming, we might only lose 10 percent of the Amazon. However, if climate change and deforestation continue unchecked, we could witness the loss of up to half the Amazon by 2050.

I am particularly anxious about global warming. Predictions suggest that 2024 could be a record-breaking warm year. Although El Niño may fade by mid-year, the oceans remain excessively warm—this includes the Atlantic, parts of the Pacific, and the Indian Ocean—so even with La Niña, we may still set heat records. Our research indicates that to prevent surpassing the tipping point, we must limit global warming to 1.5 degrees Celsius. Unfortunately, we are on a trajectory to reach 2.5 degrees Celsius by 2050, which would likely trigger the Amazon's tipping point.

Quentin: What consequences could the tipping point have for the Amazon Rainforest's future?

Nobre: Shortly after the Nature paper was published, we released a separate study in Scientific Reports. While the Nature article assessed our proximity to the tipping point, the latter assumed we had already crossed it. It examined the implications for the Amazon's climate and its regional impact.

If the forest degrades, rainfall in the Amazon will diminish. This will subsequently reduce the “flying rivers,” which are vital for precipitation, and prolong the dry season across the region.

The degradation of the Amazon, even if it reaches a 50 percent reduction, would significantly lower water transport across South America—studies suggest a decrease of up to 30 percent. This would lead to less rainfall in areas south of the Amazon and exacerbate heat waves, resulting in higher temperatures. These changes would transform the forest into a degraded, open-canopy ecosystem with diminished water recycling capabilities. The reduction of flying rivers would lead to intensified heat waves and an extended dry season.

Quentin: What are these “flying rivers” in the Amazon?

Nobre: The flying rivers—or aerial rivers—are crucial for the region. The Amazon is densely populated with trees, averaging 600 to 700 per hectare. Most of its water is stored in the soil, where roots absorb moisture and transport it to the leaves, facilitating transpiration, a process essential for photosynthesis. The Amazon's efficiency lies in its dense root systems, which capture substantial soil moisture and recycle it into the atmosphere.

Research from the 1970s indicates that a single water vapor molecule from the Atlantic Ocean can be recycled five to eight times within the Amazon Basin before exiting. Near the Atlantic Coast, about 20 percent of rainfall is recycled by the Amazon's trees, whereas in the western Amazon, this figure rises to 50 percent. This recycled water flows southward, contributing to rainfall and snowfall in the Andes and is responsible for much of the precipitation across central South America. These "flying rivers" account for nearly 90 percent of the total discharge of the Amazon River.

Quentin: How far do these flying rivers reach?

Nobre: They extend throughout northern Argentina, Uruguay, Paraguay, and into central and eastern Argentina, as well as parts of Brazil—covering distances of three to four thousand kilometers.

Quentin: So, the effects of the Amazon tipping point will transcend the Amazon Basin, correct?

Nobre: Absolutely. South America has already felt the impacts of heat waves and drought. Our study indicates that losing the forest could have far-reaching global consequences, affecting areas as diverse as southwestern Asia, North America, and even Antarctica.

Quentin: Do you hold any hope for the Amazon Rainforest?

Nobre: Yes, I remain optimistic. Recently, we received encouraging news: a 50 percent reduction in deforestation throughout the Amazon. In early 2024, this trend continued. Brazil has initiated plans to restore 240,000 square kilometers of rainforest, while other Amazonian nations, including Colombia, are also considering restoration efforts.

However, even if all Amazonian countries successfully achieve zero deforestation and degradation, we still face the looming threat of global warming.

Another concern I want to address is the rising tide of populism worldwide. Many populist leaders reject climate science. For instance, take Argentina’s president, Javier Milei, or Brazil's former president, Jair Bolsonaro. If Trump were to regain the presidency, his recent statements suggest a focus on anti-immigration policies and subsidies for fossil fuels. During his previous term, U.S. emissions rose significantly. If he were to win again, other nations like China and India might follow suit, arguing that if the U.S. isn't concerned about greenhouse gas emissions, why should they be?

I am deeply troubled by this trend. Populism is surging in various countries, including Argentina, the Netherlands, Sweden, Turkey, Poland, and Hungary. Russia is also ramping up emissions amid the ongoing conflict in Ukraine. I share these concerns at numerous scientific conferences, and I've noticed that many of my peers express similar apprehensions.

Quentin: What actions are necessary to protect the Amazon Rainforest?

Nobre: We must prioritize large-scale restoration efforts, achieving zero deforestation and degradation. We currently have nearly two million square kilometers of degraded forest. If we halt deforestation and set a goal to restore one million square kilometers—50 percent of the degraded area—by 2050, we might avert the tipping point, provided global warming does not exceed 1.5 degrees. These are formidable challenges, but I remain hopeful that we, the Amazonian countries, can end the destruction of this critical ecosystem. My greater concern lies with global warming.

To cap global warming at 1.5 degrees, we would need to reduce global greenhouse gas emissions by 50 percent by 2030 and achieve net-zero emissions by 2050. Unfortunately, we are not moving in the right direction, which raises my alarm.