Washington (AFP)

The thousands of fires in the Amazon today do not look like the big forest fires in Europe or North America: they are mostly wildfires and branches in cleared areas, say experts.

Their dramatic multiplication thus illustrates above all the acceleration of deforestation, for the traffic of wood, to create agricultural lands or for other human activities.

"In the tropics, not just in the Amazon, fire is used extensively for land management," says Jeffrey Chambers of Lawrence Berkeley, a US national laboratory, a specialist in tropical forests. "That's how people get rid of agricultural waste, and in general fires do not enter the forests."

"A rainforest is not usually flammable" because it is wet, says Jeffrey Chambers at AFP.

In California, conversely, forbidden to burn any waste, because very dry forests can ignite with a spark.

In the Amazon, when a forest is cleared, the trunks are washed away but the rest of the vegetation is burnt on site during the dry season, which lasts from July to November. For farmland, or grasslands, vegetation and weeds are also piled up, waiting for the dry season. That's what's burning right now.

The authorities noticed this by crossing the location of the fires with the map of deforestation, followed closely by satellites. "And here is, there is a very strong correlation between deforestation and heat points this year," said AFP Ane Alencar, scientific director of the Institute for Environmental Research on the Amazon (IPAM).

Even when the fire manages to penetrate the dense forest, called "primary" when it is intact, it often remains contained in the vegetation on the ground and does not generally reach the top of the trees, 30 meters higher. The effect is just as devastating, but it is delayed, because the tree trunk wounds will take time to destroy ... The image will differ from the gigantic furnaces that Europeans or Americans are used to seeing at home.

The human use of fire to manage land explains the astronomical number of fires recorded by the Brazilian authorities since January: more than 75,000.

- A carbon tank escapes -

The fires make deforestation "visible", insists Paulo Brando, from the University of California at Irvine and the Woods Hole Research Center, and right now in Sao Paulo.

"Fires are the final phase of deforestation," he told AFP.

The deforestation of the Amazon rainforest really began in the 1970s, reaching its annual maximum in the late 1990s and early 2000s. In 2004, about 28,000 square kilometers of forest were cleared in Brazil alone. Amazon covers nine countries but Brazil contains 60%).

Then deforestation slowed down considerably. Before resuming in 2014, but without ever reaching the peaks of the previous decade. Last year, about 7,500 km² disappeared, according to the Brazilian National Institute of Space Research (INPE).

But the trend reversal is worrying. In July alone, more than 2,000 km² disappeared.

In addition, the dry season is not over. Will fires largely bite on intact forests?

"At this stage, we see above all an increase in fires related to deforestation, which we do not know if they will escape to primary forests.All depend on the relative drought of the coming months," says Paulo Brando.

What will be the impact on climate change?

Forests contain carbon stored in trees and vegetation: about 459 tonnes per hectare in the Amazon, says Diego Navarrete, of the NGO The Nature Conservancy.

When a tree is cut, the carbon eventually returns to the atmosphere at the end of the cycle of use of that wood, when it decomposes. When vegetation is burned immediately, as it is now, this carbon immediately returns to the atmosphere. In both cases, the carbon will be released.

Just make the multiplication to realize that the bill of the last months already reaches hundreds of millions of tons of carbon.

© 2019 AFP