Based on lessons from Lazarsfeld’s studies in 1940 and 1944, this chapter defines communication effects as all audience responses resulting from exposure to the communication ecosystem, namely, the entire information environment. A five-level model of media effects is adopted, based on research on the hierarchy of audience responses and mass media effects, from which nine propositions are derived and tested with the National College Student Science Literacy Survey (NCSSLS) data. The hierarchical associations among the audience’s water-energy-food (WEF) nexus agenda, objective knowledge, attitudes, and behavioral intentions are confirmed, although the positions of the audience’s WEF-nexus agenda and frame in the hierarchy need further clarification. The tests also confirm the immediate message effects at the level of objective knowledge and long-term message effects at all levels as a result of keeping up with science news. Further explication of concepts and testing with new data are needed to improve the model, which advises strategic environmental communicators to provide a plethora of cognitive information about the WEF nexus to the public before adding attitudinal and call-for-action components to their promotional messages.