Lonely Tree Problem Spikes Brazil's Carbon Emissions

Brazil is a major contributor to greenhouse gas emissions, but not with cars and power plants. Experts have long suspected that when the natural carbon sink that is Brazil's vast rainforests is diminished, great waves of captured carbon is released back into the atmosphere. Now, new research is suggesting that it's even worse than we thought, with forest fragmentation exacerbating this problem.

A study recent published in the journal Nature Communications details how the effect of rainforest degradation has been underestimated in fragmented forest regions, with lonely trees not doing their expected share of carbon cleanup.

According to the authors of the study, who hail from the Hemholtz Centre for Environmental Research (UFZ), assessments of rainforest loss has focused primarily on deforestation itself, estimating how much carbon is dumped back into the atmosphere by measuring how much forest was cleared away. But what about the forest that remains?

Like a boom-town can decline as more and more people move away, the remaining trees in Brazil tend to be less healthy in the wake of their neighbor's disappearance. Destruction of local systems along a fragmented forest's edge contributes to an unmeasured carbon dump.

"Tree mortality increases, so that they can't store as much carbon as healthy trees in the center of the forest, the core area" Sandro Pütz, the main author of the study, explained in a recent release.  (Scroll to read on...)

In order to calculate these degradation effects, the UFZ scientists used the forest simulation model FORMIND to determine the percentage loss of carbon of forest fragments of different sizes. They found that the percentage loss of stored biomass rises in inverse proportion to the size of the remaining rest of the forest.

They then applied these findings to satellite images of Brazil's Amazon and costal rainforest fragmentation. It turns out the coastal tropical forest is in the worst shape, taking up only 11 percent of its original surface and having split into 245,173 fragments.

Pütz and his colleagues found that declining microclimate at these forest edges is leading to more than 68 million metric tons of carbon emissions in 10 years.

"This is an enormous loss in relation to the small total area of the Brazilian Atlantic Forest," the researcher said.

The Brazilian Amazon is 20 times larger than the coastal forests, but is doing no better, consisting of over 300,000 forest fragments and contributing to a net dump of 600 million metric tons of carbon.

Andreas Huth, who contributed to the work, adds that this information "is a forgotten process in the global carbon circulation. However, this effect should urgently be taken into account."