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For several years now researchers have come to find a perplexing missing amount of carbon dioxide in their data. Models have repeatedly missed the mark, and though researchers don't exactly know where all of the carbon emissions are coming from and where they are going, many assumed that the answer had to lie in the 'sink' of the world's oceans. But now researchers at the Imperial College London are finding that perhaps the rise in atmospheric carbon dioxide has something to do with forests-or rather, what humans leave behind.

Originally thought to have been net 'sinks' for carbon dioxide, known for large areas of forestry that absorbs the atmospheric chemical, the new study published this week in the journal Environmental Research Letters reveals that unaccounted land-use changes could in fact account for the excess carbon dioxide and why researchers were never able to find it from their models. In a new survey on partially-logged tropical rainforests researchers found that selective-logging could account for a more than three-fold increase in aboveground biomass of dead trees-totaling far more carbon dioxide production in its degradation than researchers ever thought was there.

"I was surprised by how much of the biomass dead wood accounted for in badly logged forests" lead author of the study, Dr. Marion Pfeifer says. "That such logged forests are not properly accounted for in carbon calculations is a significant factor. It means that a large proportion of forests worldwide are less of a sink and more of a source, especially immediately following logging, as carbon dioxide is released from the dead wood during decomposition."

As part of one of the largest ecological experiments on the Earth, the researchers survived within the Stability of Altered Forest Ecosystems (SAFE) sit in Malaysian Borneo to make their findings. And while the researchers saw first-hand how oil palm plantation behavior and logging had drastic effects on the carbon dioxide emissions of this forest in particular, they believe that their findings can also be found in other forests worldwide. Still, more research and replications will be necessary before the researchers are able to quantify these drastic changes in emissions, and then apply them to the projection models they use each and every year.

"This large and diverse landscape study provides a lot of field data backing up our research. We are confident in our conclusions" Dr. Pfeifer says. "However, more work needs to be done to apply the results to carbon emissions calculations, such as determining how fast the dead wood is decomposing."