The reason is the lingering effect of the recent El Nino event. Forecasts from NASA and the University of California-Irvine, and from the International Research Institute for Climate and Society suggest that because of how El Nino reduced precipitation in the region earlier this year, the Amazon is far drier than usual, and primed to burn once the dry season reaches its height this summer (the fire season runs from June through November with a September peak).
According to the NASA/U.C. Irvine forecast, the Amazon is currently “far drier than 2005 and 2010 — the last years when the region experienced drought.” The years 2005 and 2010 also saw major blazes in the Amazon.
Indeed, the NASA/U.C. Irvine researchers shared data suggesting that the storage of water in the Amazon in March of 2016, as measured by NASA’s twin GRACE satellites (which detect gravitational anomalies at the Earth’s surface), is far lower now than it was in March during these prior years.
“We have the possibility of killing hundreds of thousands of trees in the Amazon in 2016, if you let these fires start,” says Paulo Brando, an Amazon fire expert at the Woods Hole Research Center and Ipam (the Amazon Environmental Research Institute).
If these forecasts are verified, there will be a great deal at stake. It isn’t just that huge, dangerous clouds of smoke could reach major urban areas ranging from Manaus to Rio. It’s that the fires risk helping to tip the Amazon into a new state that scientists fear — one in which it will be drier, store less carbon, cycle less water and generate less rainfall.
That would be disastrous for the Earth’s climate overall. The Amazon alone stores an enormous amount of carbon, 120 billion tons worth. Put that stuff in the atmosphere and the result would be justly termed catastrophic.
“At risk is maintenance of the hydrological cycle and the Amazon as a system,” says Thomas Lovejoy, an ecologist and Amazon expert at George Mason University, by email. “When the drought is combined with more people using fire AND more people who are inexperienced using fire, the opportunity for things to get out of control gets considerably larger.”
Amazon fire seasons don’t just happen — the rain forest doesn’t just burn in a massive way on its own. But logging, slash-and-burn agriculture and other human-induced changes have altered the landscape. Thinning out the forest also dries it out — the forest canopy then cannot block sunlight, and the understory and ground leaf layer become hotter and drier. Then, the trees are more flammable and fires can also spread more easily.
But it’s really the consequences of those fires in drought years that have scientists worried.
First, a bad drought and fire year could deliver a great deal of carbon to the atmosphere, worsening global warming. The 2005 drought, a later study found, contributed between 1.2 and 1.6 gigatons (or billion tons) of carbon to the atmosphere. That corresponds to between 4.4 and 5.87 billion tons of carbon dioxide, with the upper end about on par with what the entire United States emits in a year. “Amazon forests … appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change,” the study concluded.
Last year, when El Nino induced droughts led to huge tropical blazes in Indonesia, the result was about 1.75 billion tons of carbon dioxide equivalent emissions, according to the Global Fire Emissions Database. Thus, Amazon fires can be even worse than that. (They’re also very different, in that the Indonesian fires were burning into deep underground peat stocks, whereas in the Amazon, the vegetation being burned is above ground.)
But an even deeper fear is that extreme fires could transform the Amazon itself, and that carbon loss is just one indicator of that. The idea of Amazon “dieback” — that the forest could dry out, store less carbon, and produce less rainfall as the climate warms in a devastating feedback cycle — has long circulated in scientific circles. And while it is far from clear how soon it could occur, it definitely continues to worry researchers studying the system.
As Lovejoy put it to me in a prior story about the Amazon: “The obvious thing is, you don’t want to find out where the tipping point is by tipping it.”
There is published research suggesting the southern Amazon dry season is already getting longer in a warming world. There’s also research suggesting that fires during drought years, in interaction with the way that humans have already changed the landscape, could play a key role in transforming the Amazon into a less dense forest and more fire-prone state.
The Woods Hole Research Center’s Brando, and his colleague Marcia Macedo, were part of a team of scientists who produced a 2014 study reporting on how drought conditions in 2007 affected southeastern Amazon fires and, subsequently, the regrowth of the forest. They found truly dramatic effects on dried-out trees, noting not only that the trees burned and died at far higher rates in hot and dry conditions, but also that the landscape changed afterward to support less dense forests but also more flammable grasses.
Perhaps worst of all was how the drought interacted with the ways humans had already changed the forest, by chopping down trees and thus creating a more fragmented forest landscape with more “edges” that are exposed to sunlight from all directions, and so hotter and more dried out. The study found some of the worst fires in fragmented areas — showing that in effect, humans have weakened the system by chopping down trees, and then droughts and fires come along and make it all worse in a kind of one-two punch.
The study concluded that “feedbacks between fires and extreme climatic conditions could increase the likelihood of an Amazon forest ‘dieback’ in the near-term.”
“This will be the fourth big drought in the last 20 years and these extreme climate events will only become more frequent/severe (with climate change),” said Macedo by email. “That means Amazon forests will have less time to recover and become less resilient over time — and healthy forests are critical for carbon storage and the hydrological cycle.”
It is important to note that so far, what we are looking at are bad fire forecasts for this summer in the Amazon — but not a catastrophe at this point. The forecasts may not be realized. (That happens!) And the forecasts could also drive at least some action in Brazil and other Amazon countries to take steps to prevent people from starting fires, blunting the potential consequences of drought.
That’s the good news. The bad news is that scientists continue to talk about the Amazon in the same way they talk about, say, West Antarctica or the overturning circulation of the Atlantic Ocean — as a delicate system that we could tip, with enormous consequences.