February, 2013: Simulation model on long-term carbon dynamics in old-growth forest of the Amazon published in Proceedings of the National Academy of Science (PNAS)

The rate of tree mortality in the Amazon rainforest due to storm damage and drought is up to 15 percent higher than conventionally believed, reports a study published in the Proceedings of the National Academy of Sciences (PNAS). Comparing Landsat satellite images with on-the-ground observations and a computer simulation model developed by Noreca Consulting , a group of researchers found that roughly half a million dead trees across a 1000-square-mile plot of Brazilian rainforest went unaccounted for over a 20 year period.

The study suggests that carbon emissions from storm damage could be higher than previously estimated. "If these results hold for most tropical forests, then it would indicate that because we missed some of the mortality, then the contribution of these forests to the net sink might be less than previous studies have suggested," said lead author Jeffrey Chambers of the U.S. Department of Energy's Lawrence Berkeley National Laboratory, noting that a single storm in 2005 killed hundreds of millions of trees across the Amazon. "An old-growth forest has a mosaic of patches all doing different things. So if you want to understand the average behavior of that system you need to sample at a much larger spatial scale over larger time intervals than was previously appreciated. You don't see this mosaic if you walk through the forest or study only one patch. You really need to look at the forest at the landscape scale." "So, what's going to happen to old-growth tropical forests? On one hand they are being fertilized by some unknown extent by the rising CO2 concentration, and on the other hand a warming climate will likely accelerate tree mortality. So which of these processes will win out in the long-term: growth or death? Our study provides the tools to continue to make these critical observations and answer this question as climate change processes fully kick in over the coming years." Read more