The Hairston, Smith, and Slobodkin (1960) paper stimulated 40 years of interest on how communities are organized. Their “green world” perspective, in which terrestrial vegetation was considered to be resource rather than consumer limited, failed to acknowledge a significant role for mammals, especially ungulates. As such, its conclusions differed from comparable overviews developed for aquatic ecosystems in which the character of the producer level is determined by consumers, especially on marine intertidal shores. I argue here that omission of mammals as influential grazers distorted their perspective. Experimental studies published since 1960 identify mammals as strong interactors, that their grazing can dominate the rate of primary production, alter floristic composition, and change successional trajectories. When strong interactions have been documented in other ecosystems, they are often associated with a significant increase in indirect effects, alternative assemblage states, and even trophic cascades. Although these features will be more difficult to identify in terrestrial communities because of slow rates of assemblage response and experimental intractability of the interactors, they should be sought.