The Amazon Is Morphing Into a ‘Hypertropical’ Climate—and It’s as Apocalyptic as It Sounds

When it comes to regulating Earth’s climate, few ecosystems play a more important role than the Amazon rainforest. But what happens when global warming dramatically alters the Amazon’s climate?

A study published Wednesday in Nature suggests a major shift is already underway. The findings show that the Amazon is transitioning to a new “hypertropical” climate with unprecedented hot drought conditions (severe dry spells amplified by extreme heat) that haven’t been seen on Earth for tens of millions of years. This shift is a direct result of rising global temperatures, the researchers concluded.

By 2100, the rainforest could experience up to 150 days of hot drought conditions each year, potentially leading to mass tree die-offs, according to the study. This exposes a dangerous feedback loop: As human-driven climate change stresses the Amazon, the rainforest’s capacity to mitigate climate change is shrinking.

“It all depends on what we do,” lead author Jeff Chambers, a professor of geography at UC Berkeley, said in a statement. “It’s up to us to what extent we’re actually going to create this hypertropical climate. If we’re just going to emit greenhouse gasses as much as we want, without any control, then we’re going to create this hypertropical climate sooner.”

The Amazon’s rapid breakdown

The Amazon is one of the world’s largest carbon sinks. Its hundreds of billions of tropical trees remove massive amounts of carbon dioxide from the atmosphere, storing it in their biomass and the soil. Still, humans are emitting greenhouse gases far faster than the Amazon and other natural carbon sinks can absorb them, causing the global temperature to rise.

As climate change intensifies extreme weather events such as hot droughts, more trees are succumbing to stress. At the same time, rampant deforestation is clearing large swaths of the Amazon. This not only decreases the rainforest’s capacity to absorb carbon but also emits large amounts of carbon as dead trees decompose. It’s a double whammy.

A 2021 study found that the southeastern portion of the Amazon is already emitting more carbon than it absorbs, and scientists worry that the whole rainforest could soon follow suit. This new study underscores such concerns, showing that the Amazon’s climate is transitioning to a state most trees won’t be able to survive.

How hot droughts kill tropical forests

Chambers and his colleagues synthesized multiple datasets to investigate how hot droughts affect the Amazon. First, using more than 30 years of demographic data gathered from two study sites north of Manaus, Brazil, the team found that tree die-offs increase significantly in the year after intense droughts.

They then analyzed data gathered from the two sites during droughts caused by El Niño in 2015 and 2023. When soil moisture content dropped below 32%, trees at both sites experienced rapid declines in their transpiration rates, increasing hydraulic stress.

This can cause air bubbles to form in the tree’s xylem—the vascular tissue that transports water from roots to leaves. Similar to the way embolisms block blood flow to the brain and cause strokes, these air bubbles can lead to lethal hydraulic failure and carbon starvation.

“Normally, plants are pretty good at trying to compartmentalize and just say, OK, I’m willing to sacrifice that branch to keep this core piece alive,” Chambers explained. “But if there are enough embolisms, the tree just dies.”

His team also analyzed data from five different Earth system models, finding that the Amazon is shifting to a hypertropical state that has no analog today but was present in the tropics between 10 and 40 million years ago. This type of climate is warmer than the 99th percentile of historical tropical climates, with more frequent and intense droughts. These conditions increase tree mortality rate by 55%, according to the study.

In just 75 years, this could be the Amazon’s new normal. The only way to slow this transition is to reduce greenhouse gas emissions and slow global warming. The question now is whether the global community will act or allow the Amazon to morph into an ecosystem that cannot survive.