The shape of trees: reimagining forest ecology in three dimensions with remote sensing

1. How ecologists think about aboveground forest structure and dynamics is fundamentally shaped by the data we can collect. This has historically been limited to what is possible with simple equipment such as a tape measure, which has often led to the three-dimensional complexity of the form of trees being reduced to the diameter of a trunk, and perhaps the height of the tree. While simple and pragmatic, this trunk-centric framework has some obvious limitations, as many of the major processes that influence how trees grow and interact with one another happen up in the canopy. For instance, the structural complexity of individual trees’ leaf and branch arrangements, and how trees fill canopy space, are direct drivers of individual tree and whole-forest productivity and dynamics, but remain poorly studied because they have traditionally been challenging to measure. 2. However, recent advances in remote sensing and data processing are revolutionising our ability to accurately measure tree and forest structure from leaves to landscapes. Not only do we have access to more accurate data on structure, but we also have data spanning a much broader range of spatial, temporal, and ecological scales, and new avenues of research that challenge how we understand forests are emerging. 3. Synthesis. Here, we review the new opportunities these technologies bring us to measure the physical structure of trees, and highlight the technological developments needed to maximise their value to the field of forest ecology. Today, perhaps for the first time, how ecologists choose to study aboveground forest structure and dynamics is limited more by creativity than by what we can measure