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Fire and drought may push Amazonian forests beyond tipping point

Date:
April 14, 2014
Source:
Woods Hole Research Center
Summary:
Future simulations of climate in the Amazon suggest a longer dry season leading to more drought and fires. Scientists have published a new study on the impacts of fire and drought on Amazon tree mortality. Their article found that prolonged droughts caused more intense and widespread wildfires, which consumed more forests in Amazonia than previously understood.

Future simulations of climate in the Amazon suggest a longer dry season leading to more drought and fires.
Credit: Doug Morton, NASA, Goddard Space Flight Center

Future simulations of climate in the Amazon suggest a longer dry season leading to more drought and fires. Woods Hole Research Center scientists Michael Coe, Paulo Brando, Marcia Macedo and colleagues have published a new study on the impacts of fire and drought on Amazon tree mortality.

Their paper, published in PNAS, found that prolonged droughts caused more intense and widespread wildfires, which consumed more forests in Amazonia than previously understood.

Over an eight-year period, the team repeatedly burned 50-hectare forest plots in southeast Amazonia to learn how fire frequency and weather conditions affected tree deaths. The surprise, according to Dr. Coe, was "the importance of drought. The forest didn't burn much in average years, but burned extensively in drought years." Climate change is expected to cause shorter more intense rainy seasons and longer dry seasons, with more frequent droughts like those observed in this study. According to Dr. Coe, "We tend to think only about average conditions but it is the non-average conditions we have to worry about."

NASA satellite data provide a regional context for results from the experimental burns. In 2007, fires in southeast Amazonia burned 10 times more forest than in an average climate year, "an area equivalent to a million soccer fields" according to co-author Douglas Morton of NASA.

Large portions of Amazonian forests are already experiencing droughts and are increasingly susceptible to fire. "Agricultural development has created smaller forest fragments, which exposes forest edges to the hotter dryer conditions in the surrounding landscape and makes them vulnerable to escaped fires," said Dr. Macedo. "These fragmented forests are more likely to be invaded by flammable grasses, which further increase the likelihood and intensity of future fires."

According to lead-author Dr. Paulo Brando, "This study shows that fires are already degrading large areas of forests in Southern Amazonia and highlights the need to include interactions between extreme weather events and fire when attempting to predict the future of Amazonian forests under a changing climate."

"None of the models used to evaluate future Amazon forest health include fire, so most predictions grossly underestimate the amount of tree death and overestimate overall forest health," said Dr. Coe. The results of this project show that extreme droughts may interact with fires to push Amazonian forests beyond a tipping point that may abruptly increase tree mortality and change vegetation over large areas.


Story Source:

The above story is based on materials provided by Woods Hole Research Center. Note: Materials may be edited for content and length.


Journal Reference:

  1. Paulo Monteiro Brando, Jennifer K. Balch, Daniel C. Nepstad, Douglas C. Morton, Francis E. Putz, Michael T. Coe, Divino Silvιrio, Marcia N. Macedo, Eric A. Davidson, Caroline C. Nσbrega, Ane Alencar, and Britaldo S. Soares-Filho. Abrupt increases in Amazonian tree mortality due to drought–fire interactions. PNAS, April 14, 2014 DOI: 10.1073/pnas.1305499111

Cite This Page:

Woods Hole Research Center. "Fire and drought may push Amazonian forests beyond tipping point." ScienceDaily. ScienceDaily, 14 April 2014. <www.sciencedaily.com/releases/2014/04/140414154448.htm>.
Woods Hole Research Center. (2014, April 14). Fire and drought may push Amazonian forests beyond tipping point. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2014/04/140414154448.htm
Woods Hole Research Center. "Fire and drought may push Amazonian forests beyond tipping point." ScienceDaily. www.sciencedaily.com/releases/2014/04/140414154448.htm (accessed September 22, 2014).

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