Brazil's Rainforests Releasing More Carbon Than Previously Estimated

As deforestation continues in tropical rainforests, more and more carbon is being released. Now, scientists have found that far more common has been lost than previously thought, which could affect models that predict carbon emissions.

In this case, the effect of degradation has been underestimated in fragmented forest areas, which are becoming far more common. This was due to the fact that before now, it was impossible to calculate the loss of the biomass at forest edges, and the higher emission of carbon dioxide. Now, though, researchers have closed this particular gap in knowledge.

In order to estimate the addition carbon emissions, the researchers integrated results from remote sensing, ecology and forest modeling. Initially, they modeled the percentage loss of carbon in forest border after deforestation of the surrounding area. These losses of the differently fragmented and differently sized forests were determined in comparison to large, unchanged forests in the Amazon and in the Brazilian coastal tropical forests. In all, the researchers defined a strip of 100 meters that runs from the edge of the forest into the inner forest as the peripheral area.

It's these peripheral areas that are causes for concern. Temperatures rise since the sun's rays are stronger, and there's also more wind. This means that stress increases for trees in peripheral areas.

"Tree mortality increases, so that they can't store as much carbon as healthy trees in the center of the forest, the core area," said Sandro Putz, the lead author of the new study, in a news release.

After collecting data, the scientists used a forest simulation model. In the end, they found that the percentage loss of stored biomass rises in inverse proportion to the size of the remaining rest of the forest.

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

The findings reveal the importance of keeping forest segments intact for carbon storage. By fragmenting these forests, more carbon is being released into the atmosphere, which can contribute to warming temperatures.

The findings are published in the journal Nature Communications.