Amazon rainforest approaches tipping point where it may turn into savanna
Large swaths of the lush Amazon rainforest may eventually turn into a grassy savanna as a result of logging and burning, according to a team of researchers who have discovered that it has lost resilience over the last two decades.
The rainforest is rapidly approaching a tipping point where trees may perish in droves, as the study, published in Nature Climate Change, has found that the Amazon’s resilience (its ability to rebound from disasters such as droughts or fires) has been steadily declining throughout more than three-quarters of the rainforest since the early 2000s.
This reduced resilience could result in a widespread tree and shrub death, with serious consequences for biodiversity, global carbon storage, and climate change.
Why is the Amazon rainforest so important?
The Amazon rainforest is the world's largest rainforest, extending more than 2 million square miles in northern South America, primarily in Brazil but also in Peru, Colombia, and six other countries. It's a largely untamed jungle that is Earth’s most biodiverse region. It's brimming with plants and trees and animals of all types and sizes, many of which are still unknown to science.
It has long been assumed to operate as a carbon sink, meaning it rapidly absorbs significant amounts of carbon dioxide from the atmosphere, and it plays an important role in regulating the world's oxygen and carbon cycles.
The Amazon has existed for more than 50 million years; however, it's presently under threat from human activities such as destructive fires set to clear areas for ranching and agriculture, as well as mine for oil and gas, copper, iron, and gold.
'Profound' implications for the global climate and biodiversity
A team of researchers from the University of Exeter, the Potsdam Institute for Climate Impact Research, and Technical University of Munich, who are jointly investigating climate change tipping points, examined the Amazon rainforest to determine the extent of the destruction.
Based on three decades of satellite data, their findings reveal concerning trends in the "health" of the Amazon rainforest. According to the researchers, around one-fifth of the rainforest has already been lost, compared to pre-industrial levels.
More than 75 percent of the forest shows signs of resilience loss, with trees taking longer to recover from the consequences of droughts since the early 2000s. These droughts are mostly caused by climate change as well as human influences like deforestation and fires.
The researchers examined vegetation cover using two satellite data sets: one that measured optical depth of vegetation using microwaves and another that utilized infrared instead.
According to the researchers, the loss of resilience was faster in areas of the rainforest that had less rainfall and were closer to the most visible indicators of human activity like large farms and major roadways, and this cycle of damage could trigger "dieback".
A critical threshold of rainforest dieback
It's unclear when that tipping point would be reached; however, one thing is certain: the consequences for climate change, biodiversity, and the local community would be "devastating".
Once this devastating process begins, the researchers predict it would take only decades before a "significant chunk" of the Amazon is turned into savanna, which is a much different ecosystem composed of a mixture of grassland and trees.
"Many researchers have theorized that a tipping point could be reached, but our study provides vital empirical evidence that we are approaching that threshold," co-author Niklas Boers, of the Potsdam Institute for Climate Impact Research and the Technical University of Munich, said in a press release.
With fires, drought, and land clearing, the rainforest has already changed tremendously, releasing more heat-trapping gases than it stores in plants and soil. A first-of-its-kind study previously found that the Amazon is most likely a new contributor to the warming of the Earth, suggesting the rainforest is warming Earth's atmosphere rather than cooling it as it used to do.