The Amazon rain forest is facing dangers from climate change and droughts, which are leading to frequent wildfires in the ecosystem.
Fires are normally rare in the rain forest, due to thick tree cover that keeps the ground cool and wet.
Deforestation and climate change are combining to create "tinderbox" conditions in many areas of the Amazon, according to researchers from Penn State University. The ecosystem may reach a "tipping point" where fires create enough damage to make recovery difficult, new research reveals.
"We documented one of the highest tree mortality rates witnessed in Amazon forests. Over the course of our experiment, 60 percent of the trees died with combined drought and repeated fire. Our results suggest that a perfect firestorm, caused by drought conditions and previous fire disturbance, crossed a threshold in forest resistance," Jennifer Balch, an assistant geography professor at Penn State who led the study, said.
Over eight years, researchers set fire to plots of the Amazon rain forest, each of which was nearly 125 acres in size. By studying deaths of the trees, investigators were able to study how drought affects both the intensity of fire and tree mortality. The southeast area of the Amazon, where the experiment was performed, is especially vulnerable to climate change, according to the study.
The period of time during which the research was conducted included 2007, during which there was a severe drought in southeastern regions of the Amazonian rain forest. That year, fires destroyed 10 times more forest than in an average year, according to Douglas Morton at NASA. That amounts to an area the size of a million soccer fields.
"Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change," Balch and her team wrote in the article announcing the results of the study.
A thinning of tree cover not only makes the ground drier, but can encourage the growth of highly-flammable grasses in areas between forest and grassland called edge space.
"Efforts to end deforestation in the Amazon must be accompanied by programs and policies that reduce the accidental spread of land management fires into neighboring forests and effectively control forest fires when started," researchers wrote in the article announcing their findings.
The Penn State researchers believe their findings may help climatologists refine their models of climate change, which do not usually account for an increase in the number of fires in rain forests.
Study of the effects of drought and deforestation on wildfires in the Amazon was published in the Proceedings of the National Academy of Sciences of the United States of America.
