In the Brazilian Amazon, forests damaged by fires can remain, on average, about 2.6 degrees Celsius warmer for more than 30 years than areas untouched by flames.
The conclusion comes from a study published in the Environmental Research Letters. In the article, the scientists warn that the results suggest fire-induced changes to tropical forests slow their recovery and may weaken their capacity to cope with climate pressures and to store carbon.
The study’s lead author, Savannah S. Cooley, a researcher at Columbia University (United States of America) and the NASA Ames Research Center, explains that the work indicates that the flames have “significant ecological impacts on long time scales” and that the regeneration of burned forests is much slower or may not occur at all.
Scientists say that, unlike fire-adapted ecosystems, such as savannas and coniferous forests, the Amazonian tropical forests evolved in humid conditions where natural fires are rare. Therefore, many tree species that live there did not develop traits that would allow them to tolerate or recover from fire damage.
Moreover, burned tropical forests become more “thermally unstable,” the team says. Compared with intact areas or those affected by selective logging, they exhibit much larger temperature fluctuations throughout the day and have a much higher likelihood of crossing “tipping points,” thus preventing the trees from recovering.
Fires reduce canopy density, remove vegetation from the mid and lower layers, and decrease the area covered by leaves. All of this together reduces shade in tropical forests and evapotranspiration, which would help keep the forest relatively cool.
Based on the results obtained, especially thanks to satellite imagery, the study suggests that fires are the main cause of the prolonged thermal stress affecting degraded forests in the Amazon. Therefore, scientists argue that fire prevention and low-impact logging, keeping the forest canopy virtually intact, are “essential strategies to maintain the health of tropical forests.”
“Degraded tropical ecosystems, especially burned forests, are experiencing thermal stress,” reiterates Cooley. “But there is much we can do to minimize damage to biodiversity and to the species that are experiencing that stress,” she adds.
This can be achieved at the level of forest management, “helping to reduce fires in the Amazon,” as well as at the level of carbon mitigation, “continuing to aggressively and rapidly reduce emissions and transitioning to a sustainable, clean-energy-based economy,” says the researcher.
