Bogotá, Colombia – the droughts have withered the crops in Peru, the fires have burned the Amazon and the hydroelectric dams in Ecuador have had difficulty maintaining the lights on as the rivers dry. Scientists say that the cause can be at the top of the tropical jungle, where the invisible “flying rivers” transport the rain from the Atlantic Ocean through South America.
A new analysis warns that the relentless deforestation is interrupting that flow of water and suggests that the continuous loss of trees will worsen droughts in the southwest of the Amazon and, eventually, it could cause those regions to pass from the tropical jungle to a dry savanna: grasslands with much less trees.
“These are the forces that really create and support the Amazon jungle,” said Matt Finer, principal researcher of the Amazon Conservation Andean Amazon Monitoring project, which tracks deforestation and climatic threats throughout the basin and carried out the analysis. “If you break that pump by carving too many forests, the rains stop reaching where they have to go.”
What are flying rivers and how do they work?
Most of the Amazon rains begin on the Atlantic Ocean. Wet air is pushed into the interior by constant winds that blow west throughout Ecuador, known as the Alisios winds. Then, the forest acts as a pump, effectively transmitting water to thousands of kilometers west as the trees absorb water and then release it again in the air.
The Brazilian climatologist Carlos Nobre was one of the first researchers who calculated how much of the Atlantic water vapor would move through the Amazon basin and eventually leave it. He and his colleagues coined the term “flying rivers” at a scientific meeting in 2006, and interest grew as scientists warned that the weakening of the rivers could lead the Amazon to a turning point in which the tropical jungle would become a savanna.
That is important because the Amazon jungle is a vast warehouse of carbon dioxide that greatly drives the heating of the world. Such change would devastate wildlife and indigenous communities and threaten agriculture, water supply and climatic stability far beyond the region.
Warning signals in Peru and Bolivia
The Finer group analysis found that southern Peru and Northern Bolivia are especially vulnerable. During the dry season, the flying rivers sweep the southern Brazil before reaching the Andes, precisely where deforestation is more intense. Tree loss means that less water vapor is transported west, which increases the risk of drought in emblematic protected areas such as the Manu National Park of Peru.
“Peru can do everything right to protect a place like Manu,” said Finer. “But if the deforestation continues to affect the bomb in Brazil, it is possible that the rains that support it never arrive.”
Nobre said that up to 50% of the rains in the west of the Amazon, near the Andes, depend on the flying rivers.
Corine Vriesendorp, director of Amazonica Conservation Science, based in Cusco, Peru, said the changes are already visible.
“The last two years have brought the driest conditions that the Amazon has ever seen,” said Vriesendorp. “The ecological calendars used by indigenous communities (when to plant, when to fish, when animals are reproduced) are increasingly discouraged. Having less rain and more unpredictable will have an even greater impact on their lives than what climate change is already having.”
Farmers face failed crops, indigenous families fight against the interruption of fishing and hunting seasons, and cities that depend on hydroelectric energy see power cuts as rivers that provide energy dry.
The forest forms a fragile pump
Maap researchers found rain patterns depending on when and where flying rivers cross the basin. In the wet station, its northern route flows mainly on intact forests in Guyana, Surinam and northern Brazil, maintaining the strong system.
But at the dry season, when forests are already stressed by heat, aerial rivers cross the southern Brazil, where deforestation fronts extend along the roads and farms, and there are simply less trees to help transport moisture.
“It is during the dry months, when the forest needs water, when the flying rivers are more interrupted,” Finer said.
Finer pointed out the roads that can accelerate deforestation, and pointed out that the controversial BR-319 road in Brazil, a project to pave a road through one of the last intact parts of the south of the Amazon, could create a completely new deforestation front.
The debate on the turning point
For years, scientists have warned about the inclination of the Amazon towards the savannah. Finer said the new study complicates that panorama.
“It is not a unique and sudden collapse,” he said. “Certain areas, such as the southwest of the Amazon, are more vulnerable and will feel the impacts first. And we are already seeing the first signs of rainfall in favor of the wind of the deforesting areas.”
Nobre said the risks are evident. Amazon forests have already lost about 17% of their coverage, mainly due to livestock and soybeans. Those ecosystems recycle much less water.
“The dry station is now five weeks longer than it was 45 years ago, with 20 to 30% less rain,” he said. “If deforestation exceeds 20 to 25% and heating reaches 2 degrees Celsius (35.6 degrees Fahrenheit), there is no way to prevent the Amazon from reaching the turning point.”
What can be done?
Protecting intact forests, supporting indigenous territorial rights and restoring deforested areas are the clearest paths to follow, the researchers say.
“To avoid collapse, we need zero deforestation, degradation and fires, immediately,” said Nobre. “And we must start large -scale forest restoration, no less than half a million square kilometers. If we do that and maintain global warming below 2 degrees, we can still save the Amazon.”
Finer said that governments should consider new conservation categories specifically designed to protect flying rivers, safeguarding not only the earth but also atmospheric flows that make tropical jungle possible.
For Vriesendorp, that means regional cooperation. He praised Peru for creating vast parks and indigenous reserves in the southeast, including Manu National Park. But, he said, “this cannot be resolved by a single country. Peru depends on Brazil and Brazil depends on its neighbors. We need solutions for the entire basin.”
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