Amazon’s diversity impoverished by forest fires
Researchers investigating the impacts of forest fires have found that species have been depleted and carbon stocks reduced in transitional areas of the Amazon and cerrado biomes. A study funded by the Serrapilheira Institute detected a shrinkage of up to 68 percent in the capacity to contain carbon dioxide in the biomass of forest vegetation repeatedly impacted by fire.
The scientists, led by Fernando Elias from the Federal Rural University of Amazonia, and Maurivan Barros Pereira, from the State University of Mato Grosso, looked at 14 forest areas, divided into three categories: those never impacted by fire, those burned once, and those having recorded multiple fires. They collected data such as the number of species and density of trunks, and calculated above-ground carbon stocks.
“The Amazon isn’t turning into one big savannah; it’s turning into a secondary forest—a poorer forest, with less carbon stock, a reduction of almost 70 percent,” Elias warned.
Risk of extinction
In order to understand how the floristic composition of forests is affected by fire, i.e. which species are most affected and what changes occur in diversity after a fire, the experts classified the species as cerrado, forest, and generalists species (seen in both).
The conclusion that there will not be a savannization of the Amazon, but rather an impoverishment of the forest, Fernando Elias said, was based on the observation that the number of savanna and generalist species remained the same after the disturbance caused by the fire, while the more sensitive forest species suffered a decline.
“The bark of some forest species is absent or very thin. So, in the face of a fire event, these species are vulnerable and suffer extreme mortality. Imagine a rare species occurring in a forest, and that forest catches fire. If it doesn’t have the ability to defend itself against this fire, it becomes locally extinct,” he stated.
Services
This impoverishment of the forest, in addition to representing the threat of extinction, is a threat to the planet and to humanity, the researcher added. “It leads to a poor forest, with species no longer able to generate or provide ecosystem services, such as rain regulation and carbon sequestration to mitigate climate change and pollination,” he noted.
Among the issues is the reduced ability to remove carbon dioxide from the atmosphere and retain it in the biomass. “In terms of carbon stock, we’ve observed that, with a single burn, reduction can reach nearly 50 percent in the stock values. And multiple burns caused losses of up to 68 percent,” he said.
In practice, this means that each burned area, apart from emitting greenhouse gases from the burning, also releases the carbon dioxide in the composition of each tree.
“The carbon stocks of the areas that have not been burned are 25.5 tons per hectare; and the areas that have burned once, 14.1. The areas that have been burned multiple times, eight. So you can imagine the difference between the area that has been burned multiple times and the area that has never been burned,” he went on to remark.
Vulnerability
The areas studied are located on the borders of the Brazilian states of Amazonas, Pará, and Mato Grosso, in a region that is part of the so-called Arc of Deforestation. According to the researchers, degradation also occurs because of farming activities near the forest and higher levels of drought than the deeper regions of the Amazon, which is why all the areas displayed greater vulnerability to the rapid advance of climate change. “These areas are often treated as cerrado, even though they have a high carbon stock and typically Amazonian species. And under in the Forest Code, in cerrado areas, you can deforest 80 percent,” Elias pointed out.
