Human action is accelerating the transition to a hypertropical climate, with heat and droughts that could lead to the mass death of trees in the Amazon.
The Amazon rainforest could be on the brink of drastic climate change, with temperatures rising and droughts intensifying. According to a new report published in the journal Nature, parts of the Amazon are beginning to experience what scientists describe as a “hypertropical” climatewith extreme heat and drought not seen on Earth for 10 million years.
Researchers warn that, although these conditions are currently rare, they are becoming more frequent and could dominate the Amazon climate by the end of the century, if greenhouse gas emissions continue unchecked, says the . Using 30 years of forest demographic data, the team found that the Tree mortality increases by 55% during these intense, hot droughts, highlighting the profound vulnerability of the ecosystem.
“When these hot droughts occur, this is the climate we associate with a hypertropical forest, because it is beyond the boundaries of what we consider tropical forest today,” said lead author Jeff Chambers. Hypertropical biomes last existed between 10 and 40 million years agowhen global temperatures were significantly higher than they are today.
The researchers highlight that This future is not inevitable. Chambers stressed that human decisions will determine whether the Amazon will fully transition to this extreme climate regime. “If we continue to emit greenhouse gases without any control, we will create this hypertropical climate sooner,” he said.
To understand why intense droughts are so lethal to trees, scientists examined forest responses during strong El Niño events in 2015 and 2023 at two study sites in the Amazon. They observed that when soil moisture fell below about a third of its capacity, trees drastically reduced transpiration by closing the pores in their leaves to conserve water. Although this response limits dehydration, it also blocks the absorption of carbon dioxidetriggering carbon deprivation.
As stress persisted, trees suffered hydraulic failures when air bubbles, known as embolisms, formed in the tissues responsible for water transport. “If there are enough embolisms, the tree just dies,” Chambers explained.
The implications go far beyond the Amazon. Tropical forests play a crucial role in absorbing carbon dioxide and regulating Earth’s climate. A large-scale loss of trees, combined with reduced carbon uptake by surviving vegetation, could weaken the Amazon’s ability to act as a a global carbon sinkpotentially accelerating climate change.
