In the physical economics of converting raw material into the finished product of building, we will ultimately account for what Lionel Robbins described as "a relationship between ends and scarce means." In seeking his potential "alternative uses" in an exchange already taking place at a global scale, it would be grandiose to suggest that the sole solution to pending planetary crisis is the adoption of mass timber in the construction of new, densely built environments. But as the window for climate action narrows and shifting urban demographics create new demands for physical resources, it seems obvious that the carbon held both in forests and, potentially, in an array of urban buildings is an asset we should develop and manage.