The Western United States has lost up to 60% of its historic aspen (Populus tremuloides) stands over the last century, probably as a result of the successional tendency of aspen to be replaced by coniferous species in the absence of periodic fires. One of several major impacts of this change is the loss of understory forage as conifer canopy cover increases. We measured understory biomass in aspen stands ranging from 0% to 81% absolute conifer cover in the canopy and found that understory production declines exponentially as conifers replace aspen. We also did an economic analysis to determine the value of the forage that is not being produced by aspen sites due to the presence of coniferous species within the tree canopy. Study results indicate significant losses in forage, marketable through the sale of livestock, and losses in revenue generated through grazing fees for the USDA Forest Service.