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Wildfires drive savanna expansion in the heart of the Amazon

Publicado em 04 maio 2021

White sand savanna is expanding in the heart of the Amazon as a result of repeated wildfires, according to a study published in the journal. Ecosystem..

The study was supported by FAPESP and was conducted by Bernardo Monteiro Flores, a postdoctoral fellow in ecology at the Federal University of Santa Catarina (UFSC) in Brazil, and Milena Holmgren, a professor of environmental science at Wageningen University. Netherlands.

“The Amazon rainforest edge has long been regarded as the most vulnerable part due to the expansion of the agricultural frontier. This deterioration of the forest along the so-called” deforestation arc “. [a curve that hugs the southeastern edge of the forest] It keeps happening and is very annoying. However, our study has detected the emergence of savanna in the heart of the Amazon, far from the agricultural frontier, “Flores told Agência FAPESP.

The authors investigated a floodplain area in the middle of the Negro River near Barcelos, about 400 km upstream of Manaus, the capital of the State of Amazonas. The town has an expanding area of ??white sand savanna, but the forest ecosystem remains predominant. They blame the increasing frequency and severity of wildfires in the broader context of global climate change.

“We used satellite imagery to map 40 years of wildfires and gathered detailed information on-site to see if the burnt forest areas were changing,” Flores said. “Analysis of the abundance and soil characteristics of tree species at different times in the past shows that wildfires can kill virtually all trees and the clay topsoil can be eroded by annual floods and become increasingly sandy. I found that there is. “

It was also found that as the burnt forests of the floodplain recover naturally, there are major changes in vegetation species, native herbs expand, forest tree species disappear, and white sand savanna tree species predominate. It was.

Low elasticity

Where did the savanna tree seeds come from? According to Flores, the white sand savanna is part of the Amazon’s ecosystem, covering about 11% of the biome. They are ancient savanna, very different from the Cerrado with its outstanding biodiversity, but still inhabited by many endemic plant species. They are called Campinas by the locals. Seen from above, the Amazon is a forest sea surrounded by the small islands of the savanna. The seeds of savanna plants are distributed by water, fish and birds, and when they reach a burnt area with degraded soil, they germinate more easily than forest species and re-inhabit the area.

“Our research shows that the Amazon’s native savanna coverage is expanding and may continue to expand. White sand, not along the’deforestation arc’where exotic grass is spreading. The savanna is located in remote areas throughout the basin where it already exists, “says Flores.

It is important to emphasize that Amazon floodplain forests are much less elastic than highland terrafarm forests. It burns more easily, after which its topsoil is washed away and deteriorates much more rapidly. “The floodplain forest is the Amazon’s” Achilles heel. ” There is on-site evidence that floodplain forests will collapse first as the Amazon climate dries and wildfires become more severe and frequent. “

These two factors, the drier climate and the more serious and frequent fires, are already involved as part of the ongoing climate change crisis. According to the study, wildfires in central Negro during the severe Ernino period of 2015-16 burned down seven times the total area destroyed by fires in the last 40 years.

“Further loss of floodplain forests could not only emit large amounts of carbon accumulated in trees, soil and flark, but also reduce the supply of resources used by locals, such as fish and forest products. New discoveries increase the urgency of protecting remote areas. Forest areas. For example, fire management programs need to be implemented to reduce the spread of wildfire in the dry season. ”

For more information:
Bernardo M. Flores et al, White-Sand Savannas Expand at the Core of the Amazon After Forest Wildfires, Ecosystem (2021). DOI: 10.1007 / s10021-021-00607-x

Quote: Wildfire Promotes Savannah Expansion in Central Amazon (May 4, 2021) May 4, 2021 Obtained from amazon.html

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Wildfires drive savanna expansion in the heart of the Amazon

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