The Amazon rainforest is changing rapidly. New research indicates it may soon enter a “hypertropical” climate, a state that hasn’t existed in the last 10 million years. This shift could lead to severe droughts, threatening the trees that make up this vital ecosystem.
Scientists predict that by 2100, extreme droughts could sear the Amazon for up to 150 days a year, even during the normally wet season. Jeff Chambers, a geography professor at the University of California, Berkeley, explains that these hot droughts signify a climate beyond our current understanding of tropical forests. This information comes from a study in the journal Nature.
Historically, these hypertropical conditions prevailed between 40 and 10 million years ago, during periods known as the Eocene and Miocene. During the mid-Eocene, global temperatures averaged about 82°F (28°C)—a staggering 25°F warmer than today. Research suggests forests then had fewer mangroves and evergreen trees compared to now.
Currently, the Amazon experiences only a few dry weeks each year, but climate change is extending this season. Hotter-than-normal days are becoming more frequent. Chambers and his team analyzed 30 years of temperature, humidity, and moisture data from northern Manaus, Brazil. They found during droughts, trees struggle for water and can’t absorb carbon dioxide (CO2), crucial for their growth.
As trees close their leaf pores to conserve water, they also block CO2 absorption. Some trees die from a lack of this essential gas. A drop in soil moisture below 33% can create bubbles in the tree’s sap, akin to blood clots, halting normal fluid circulation. Chambers points out that a critical threshold for tree collapse was consistently observed during different El Niño years, highlighting this as a significant finding.
Currently, about 1% of trees in the Amazon die each year, but this could rise to 1.55% by 2100. While this might seem small, it will greatly impact the ecosystem. Fast-growing trees like the yellow ipê and Shihuahuaco are particularly vulnerable to these conditions, suggesting that slower-growing species may eventually prevail as temperatures continue to rise.
This transformation may not be limited to the Amazon. Rainforests in western Africa and Southeast Asia could also be heading for a hypertropical phase. These shifts have serious implications for carbon levels in our atmosphere, as rainforests play a crucial role in absorbing CO2.
Looking ahead, the future of the Amazon depends significantly on global efforts to reduce CO2 emissions. “It’s really up to us,” Chambers warns. “If greenhouse gas emissions continue unchecked, we’ll experience these abrupt climate changes sooner rather than later.”
For more on the implications of climate change on forests, consider checking out resources from the Nature journal or the latest assessments from the IPCC.
