Black Carbon from Slash and Burn Practices Still a Problem in Brazil
Although nearly 40 years have passed since Brazil banned slash-and-burn practices in its Atlantic Forest, the destruction lingers. New research reveals that charred plant material is leaching out of the soil and into rivers, eventually making its way to the ocean. So much of this "black carbon" is entering the marine ecosystem that it could be hurting ocean life, although further tests will be needed to confirm this possibility.
People have used fire to shape Earth's vegetation for millennia. In Brazil's Atlantic Forest, Europeans began burning trees to make way for settlements and agriculture in the 16th century. What once blanketed 1.3 million square kilometers and ranked as one of the world’s largest tropical forests had shrunk to 8% of its former size by 1973, when protective laws were put in place.
But that's not the end of the story, according to researchers led by Carlos Eduardo de Rezende, an aquatic biogeochemist at the State University of Norte Fluminense in Rio de Janeiro, and Thorsten Dittmar, a marine geochemist at the Max-Planck Institute for Marine Microbiology in Bremen, Germany. The team discovered high levels of black carbon in the region's soil and in the Paraiba do Sul River, the largest river that exclusively drains the area once occupied by the Atlantic Forest. Locals still burn sugarcane each year as a preharvest way of prepping the soil, but the researchers found that this could not account for the amount of black carbon they were seeing.
To figure out how much black carbon the burned forest originally released, Rezende and colleagues looked to the neighboring Amazon forest for clues. Other studies reported black carbon rates for burning tracts of virgin Amazon rainforest, so they extrapolated those figures to match the historical range of the slashed-and-burned Atlantic Forest, which once had similar woody tree species to the Amazon. They calculated that torching the Atlantic Forest released about 200 to 500 million tonnes of black carbon. Given the material’s half-life, they estimate that it will take between 630 and 2200 years for just half of the black carbon to leach out of the region's soils.
Burning snag via Shutterstock.
Read more at Science.