The largest uncertainty in humans’ contribution to climate change from land use is the fate of carbon that was belowground in pre-modified forests. In a recent study published in AoB PLANTS, Dean et al. produced high-resolution 3D-models of the rarely measured zone near the base of large, mature trees by using photogrammetry. The models led to equations linking the easy-to-measure trunk diameter and ground slope to attributes such as tree buttress shape, humus mound, wood and hollow area, and root volume. The equations can be used for carbon accounting. The 3D-models are irreplaceable, being for increasingly rare, large trees, and may be useful to other scientific endeavours.