The storage of carbon in forested landscapes—in the form of plant and soil biomass—is a crucial component of forest ecosystem functioning, and a key tool for climate change mitigation. Net carbon storage has increased over recent decades in many eastern North American regions as forests have matured and increased in extent. However, the rate of this increase is declining as the dynamics of these processes change with changing land use patterns. LanDAT helps us understand the geography, timing, and causes of these changes.