Surface fires in Amazonian forests could contribute as much as 5% of annual carbon emissions from all anthropogenic sources during severe El Niño years. However, these estimates are based on short-term figures of post-burn tree mortality, when large thicker barked trees (representing a disproportionate amount of the forest biomass) appear to resist the fires. On the basis of a longer term study, we report that the mortality of large trees increased markedly between 1 and 3 years, more than doubling current estimates of biomass loss and committed carbon emissions from low-intensity fires in tropical forests.