Biologists have become increasingly interested in understanding the links between population processes and ecosystem processes. Ecological interactions, and the evolutionary changes that they mediate, have important effects on the transfer of energy and the cycling of matter at ecosystem scales. Simultaneously, ecosystem processes provide the energy and materials by which ecological and evolutionary change takes place. Elucidating the mechanisms by which population and ecosystem processes are linked is fundamental to our ability to understand and manage judiciously Earth’s ecosystems. In this talk, I introduce the concept of the “phytochemical landscape,” and suggest that it provides the nexus through which population process and ecosystem processes are linked. The phytochemical landscape is based on the dazzling array of primary and secondary metabolites synthesized by the primary producers (e.g. land plants, algae, bacteria) of our aquatic and terrestrial ecosystems. Because the phytochemical landscape is both a cause and a consequence of variation in trophic interactions and nutrient dynamics, it serves as the nexus through which powerful feedback loops link population and ecosystem processes.