How can the Amazon rainforest, one of the wettest places in the world, be the scene of thousands of fires every year?

Only in Brazil, which houses 60% of the so-called “lung of the planet”, the number of forest fires grew by 84% in just one year to reach 74,155 between January and August 2019. And of these, more than half They occurred in the Amazon.

In the world’s largest rainforest, the humidity is so high that, in certain areas, its forests are capable of creating their own rainy season with the water vapor that transpires their leaves.

Why then there are several outbreaks of fire burning uncontrollably for more than two weeks?

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Unlike the wildfires that are unleashed every summer in Europe, those of the Amazonian territory have been little studied.

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Even so, the few investigations that have been done on this subject point to the fact that this jungle, which is distributed in nine South American countries, has become more flammable in recent decades.

Image copyright REUTERS Image caption The flames in the jungle are not very high, so you have to fight them from the ground.

Unlike European forests, the Amazon enjoys a natural barrier against fire.

First, because the canopy formed by the treetops allows moisture to be trapped at the bottom, known as undergrowth. This high level of humidity makes it difficult for the flames to ignite or spread.

And, second, because the chances of natural fires in this region are very slim, as Jos Barlow, a professor of Conservation Sciences at Lancaster University, told Brazil from BBC World.

“There is little evidence of natural forest fires in the Amazon because that would require that there be dry rays, that is, without rain.”

“This is common in some parts of the world, but not in the Amazon.”

Therefore, the vast majority of fires that occur in this sparsely populated region are initiated by humans, as noted by experts who began to register the first foci in the 80s. “They highlighted the links with livestock and livestock. logging, because livestock involves burning trees and logging makes the forest more flammable, “said Barlow.

“But, in recent years, there are a number of more complicated cases that are making fires so prevalent today,” he added.

One of them is that, once a forest has been a victim of llamas, it tends to be more susceptible to this being repeated.

“Where a forest burns and the mortality of the trees is high, let’s say that 40% or 50% of the trees die, they fall and leave the roof more clear. This makes the undergrowth drier and also adds fuel in the shape of leaves and branches, making it more likely to burn again. “

And every time there are more fires.

Smoke days

The increase in fires in the Amazon basin is not new, although its intensity is.

Already in 2009, Ilan Koren, an atmospheric researcher at the Weizmann Institute of Science, in Israel, warned on the EarthSky portal: “If you look at satellite images of the Amazon, most of South America, during the dry season, you will see that many days do not you can see the surface due to the presence of smoke . “

A few years earlier, Koren had participated in a study that showed that the number of forest fires in the Amazon rainforest had doubled between 1998 and 2005.

His research also claimed that the smoke prevented clouds from reflecting the sun’s rays normally, causing the Earth’s climate to receive more solar energy than normal.

The effect of climate change

Another element that has made the jungle more vulnerable to flames is climate change, as Barlow explained: “Only temperature rises, which are already occurring in the Amazon, make the jungle more flammable.”

The Amazon rainforest is so large that rainy seasons vary from one area to another, as the professor explained.

In the south, the area affected by the current fires, today is a dry season. And, although as NASA said on its website, ” it is not unusual to see fires in Brazil at this time of year due to high temperatures and low humidity,” current fires worry experts like Barlow.

“What is disturbing now about these fires is that they are happening in the southern part of the Amazon rainforest, where it is dry season. We do not know how bad they will be when the dry season reaches the central part, which will happen in October or November.”

A warmer climate makes the forest drier, but also generates anomalies such as the intensification of the frequency of the El Niño phenomenon.

“And the central and eastern areas of the Amazon tend to be the most affected when El Niño arrives strongly. Therefore, the concern is now in Brazil.”

Another consequence of so many variations and climatic anomalies is that now the dry season, the one with the highest fire risk, lasts longer with each passing decade.

Hopes for this to be reversed are few: according to the Intergovernmental Panel on Climate Change (IPCC), in 2100, dry seasons in the Amazon will last between three and 10 days.

Logging and deforestation

Logging and deforestation, authorized or not, have also contributed to making the forest more flammable.

” Deforestation is known to reduce rainfall locally, so it makes the forest drier. It also increases the edges of the forest and it is known that these are drier and therefore more flammable areas,” Barlow explained. .

What do we lose if we lose the Amazon?

“In addition, much of the jungle is being cut down, leaving holes in the canopy that form the treetops. This causes the undergrowth to become drier and more likely to burn and also adds a lot of fuel to the atmosphere because it leaves you branches and leaves of the same feeling, which in case of ignition produce more heat “.

When the jungle burns for the first time, the flames are very small, as the expert explained: “They are barely 30 centimeters high and burn very slowly, so they only advance between 100 and 200 meters a day.”

As the canopy does not reveal what is happening in the undergrowth, fires in the Amazon can only be fought from the ground and often go unnoticed.

“It is a disaster that moves slowly and only reaches the press after having been burning for days.”