SOURCE: Washington Post

DATE: December 20, 2019

SNIP: Deforestation and other fast-moving changes in the Amazon threaten to turn parts of the rainforest into savanna, devastate wildlife and release billions of tons carbon into the atmosphere, two renowned experts warned Friday.

“The precious Amazon is teetering on the edge of functional destruction and, with it, so are we,” Thomas Lovejoy of George Mason University and Carlos Nobre of the University of Sao Paulo in Brazil, both of whom have studied the world’s largest rainforest for decades, wrote in an editorial in the journal Science Advances. “Today, we stand exactly in a moment of destiny: The tipping point is here, it is now.”

Combined with recent news that the thawing Arctic permafrost may be beginning to fill the atmosphere with greenhouse gases, and that Greenland’s ice sheet is melting at an accelerating pace, it’s the latest hint that important parts of the climate system may be moving toward irreversible changes at a pace that defies earlier predictions.

In interviews, Lovejoy and Nobre said they decided to sound a dire alarm about the Amazon after witnessing the acceleration of troubling trends. The combination of rising temperatures, crippling wildfires and ongoing land clearing for cattle ranching and crops has extended dry seasons, killed off water-sensitive vegetation and created conditions for more fire.

The Amazon is 17 percent deforested, but for the large portion of it inside Brazil, the figure is closer to 20 percent. The fear is that soon there will be so little forest that the trees, which not only soak up enormous quantities of rainwater but also give off mist that aids agriculture and sustains innumerable species, won’t be able to recycle enough rainfall.

At that point, much of the rainforest could decline into a drier savanna ecosystem. Rainfall patterns would change across much of South America. Several hundred billion tons of carbon dioxide could wind up in the atmosphere, worsening climate change. And such a feedback loop would be tough to reverse.

That point of no return, commonly referred to by scientists as a tipping point, “is much closer than we anticipated,” Nobre said in an interview.

Higher temperatures and deforestation are drying out parts of the Amazon and posing a fundamental threat to the rainforest.

In the southern Amazon dry season in particular, temperatures are already 3 degrees Celsius higher than in the 1980s, and the dry season is getting longer, exceeding four months in some regions, Nobre said.

Particularly worrying, he said, is a recent study showing how trees are faring in more than 100 locations across the Amazon. Led by Adriane Esquivel Muelbert of the University of Leeds, researchers found forest transition has begun — trees accustomed to dry conditions are more likely to grow now while trees that require more moisture are disproportionately dying in places where climate changes are the greatest.

The impact of changes to the Amazon reach far beyond South America. The rainforest stores an immense amount of carbon in its enormous trees, and if they die, that carbon is released.