New study: Fire and fragmentation leave Amazon forest vulnerable to windstorms

A new study shows fire-damaged trees are especially vulnerable to windstorms for several years or even decades — especially the largest, and most carbon-rich trees.

Woodwell Climate Research Center (formerly Woods Hole Research Center) Assistant Scientist Paulo Brando is part of a team releasing the new research in the Journal of Ecology. The discovery was made in the same study area at the heart of a 2014 landmark paper. That previous study compared the fire resilience of three connected plots in the Amazon forest — one burned annually, one burned every three years, and a never-burned control plot. A fortuitously-timed windstorm allowed the team to take their study one step further: How does fire affect tropical forest’s durability in windstorms, and what can that tell us about their survival in a climate-changed future?

The Amazon has already lost 800,000 square kilometers of forest, an area equivalent to 1/10th of the lower 48 United States, much of it to intentional burning to clear land for agriculture.

The original study established that fires leave surviving trees more vulnerable to other stressors like drought for decades to come. When a short, high-intensity windstorm swept through the study area, Dr. Brando and the team realized they had a chance to examine a new variable.

“Suddenly this storm sweeps through and there are chairs flying around our camp,” Brando said. “But as we were cleaning up, we had a moment of realization that we’d just sampled the tree plots the week before with a three-dimensional laser scanning system called LiDAR. We had a unique opportunity to study, with high certainty and in great detail, how each of the three plots survived the storm.”

Their study showed that not only were trees in the burned plots more likely to be uprooted or snapped (often at the height of fire scars), but that damage was much more likely to prove fatal over the following years. The damage was greatest around the edges of the plots, showing the compounding dangers of forest fragmentation.

“The lesson is that even areas that look like they’ve survived initial burning will continue degrading in ways that are unpredictable, non-linear, and worsened by global warming. We can’t separate out the effects of burns, drought, and global warming – they can interact in unpredictable ways,” Brando said. “It’s critically important that we learn all we can about how to protect its remaining canopy, especially for the oldest and largest trees that provide the most wildlife habitat, cycle the most moisture through the ecosystem, and store huge amounts of carbon.”