Mongabay: Forest degradation releases 5 times more Amazon carbon than deforestation — Study

Tropical forests are subject to a range of disturbance types or degradation from small-scale mortality from natural processes affecting one or a few trees. This includes fire, flooding, landslides, selective logging or weather-related tree toppling. Image courtesy of K.C. Cushman.

This story came to me from tropical ecologist and Amazonian expert Miles Silman, my longtime friend and colleague at Wake Forest University, where we both teach. He made sure I got a copy of the study from which this story is based weeks before it was published.

In this pioneering research, made possible by intensive aerial lidar-driven data collection between 2016 and 2018, is a surprising finding: while deforestation gets all the attention from damaging the ecosystems services provided by the Amazon, forest degradation actually has a five-times greater impact on reducing the Amazon’s ability to store carbon and thus slow the rate of global warming.

“When countries report their forest and carbon changes, they mostly rely on deforestation because it’s much easier to see and quantify,” Ovidiu Csillik, lead author of the PNAS study who is formerly of the NASA Jet Propulsion Laboratory at the California Institute of Technology, told me in a phone interview. “But we’ve found that forest degradation is actually more important in terms of carbon loss.”

Imagine this: policymakers grab headlines and political capital by promising to curtail deforestation, as the new president of Brazil has done. That’s a good thing. But it turns out it’s more important to stave off or manage damage to tropical forests from flooding, landslides, wind disturbances, selective logging and road building. The reason: degraded land can often be rescued if action is taken soon enough; deforested land typically heralds an complete land-use change to ranching or farming.

While I had never met the lead author, Miles knows him because he joined the faculty at Wake Forest as a remote sensing expert in July 2024, a month before his study was published. I was clear with my editors at Mongabay about what could appear to be a conflict of interest; they agreed I should do the story and disclose the connection. That’s what we did. Also, this is my first story published on Mongabay’s newly updated and improved web site. All previous stories now show up in the new formatting.

Deforestation, or clearcut logging, is much easier to identify from most remote sensing but does not tell the whole story when it comes to a diminishing amount of carbon sequestration capacity in the Amazon, according to new PNAS research. Image by Marcos Longo.