The independent effects of bottom-up and top-down forces are well-understood in a wide variety of aquatic and terrestrial ecosystems. It is now necessary to examine how these often conflicting selection pressures interact, both in the laboratory and the field. The goal of this session is to bring together scientists studying the interaction of bottom-up and top-down forces in both aquatic and terrestrial ecosystems. In addition to examining the relative strength of these factors in aquatic and terrestrial communities, we aim to consider how (1) environmental gradients and (2) diversity at both the species and genotypic levels potentially impact the interaction of bottom-up and top-down forces. Our definitions of “bottom-up” and “top-down” are purposely broad to include a diverse group of studies and perspectives: bottom-up forces include nutrient and resource availability, and top-down forces include parasites, herbivores, and predators. In order to facilitate communication across these diverse fields, speakers in the session study a broad range of ecosystems, including salt marshes, rivers, lakes, grasslands, and arctic tundra, and employ a variety of observational, experimental, and theoretical approaches. The session is structured such that aquatic and terrestrial studies alternate to highlight similarities and differences between systems. The session will conclude with a unique talk considering the impacts of both aquatic and terrestrial top-down forces on a single plant as a suggestion for future research directions to consider the relative importance of bottom-up and top-down effects at the interface of aquatic and terrestrial ecosystems.