Deep beneath the canopy of the largest rainforest in the world, there is a boiling river. The small tributary is found in eastern central Peru, and it eventually leads to the Amazon River. It is about four miles long and 16 feet deep in some places.
The water is heated by cracks in the Earth’s crust. At its warmest spots, the water can reach up to 200 degrees Fahrenheit, creating a harsh environment with air temperatures hotter than anywhere else in the Amazon. Locals know the river as “Shanay-Timpishka,” which translates to “boiled with the heat of the sun.”
The steamy river offers valuable insight into how plant and tree communities might respond to rising temperatures driven by climate change.
A team of biologists from the University of Miami visited the river in 2021 and recognized the boiling river as a sort of natural experiment.
“It really provides us a window into the future because the Amazon will get hotter whether we like it or not, so this allows us to understand what increases in temperature will do to the forest composition,” said Riley Fortier, the lead author of the study.
“It can tell us what species will be lost and what the makeup of the forest might be like in the future.”
In 2022, the team returned to Peru and mapped the trees and tropical plants in 70 different locations. They started upstream, where the temperatures were cooler, and worked their way down to the hottest part of the boiling river, where air temperatures often surpass 110 degrees Fahrenheit.
The team used onsite sensors to examine the forests and keep track of the temperatures. They saw that plant diversity declined in the hottest parts of the river.
Only plants adapted to extremely warm tropical climates were able to thrive next to the boiling river. The results of the study show how tropical rainforests in the Amazon could look as global warming continues.
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“Overall, the tree community is less diverse, so we see fewer species in hotter spots,” said Fortier. “And forest composition was also more homogenous in the warmest locations, whereas in cooler forest plots, there was more plant diversity.”
The researchers noticed that there was a drastic change in vegetation along the river. At the hottest part of the river, there was a greater range of species that grew in hotter areas of the Amazon, but this changed when moving just a short distance away from the hottest part of the river.
The hotter areas were drier and contained more vines and scrubby vegetation. The trees were also smaller and less diverse.
These kinds of changes are expected to be observed over the course of dozens of miles. However, the transition was seen in less than a mile.
The researchers will continue to analyze the boiling river. It is a unique system that can be useful for learning more about the natural world.
The study was published in Global Change Biology.
