We will evaluate the consequences of human-driven species extinctions for multiple ecosystem functions in New England salt marshes. This study will 1) characterize the food web network structure of New England salt marshes in general, 2) survey multiple marshes and characterize their food web structure and ability to perform multiple functions, and 3) perform an experiment to verify the causal links between food web structure and ecosystem function in salt marshes. In addition to a literature review and an observational study of food webs, we will perform a caging experiment using a novel manipulation of the food web structure based on techniques from the Biodiversity Ecosystem Function literature. This experiment will be a first of its kind, designed to explicitly link food web structure to shifts in ecosystem function, rather than targeting the impact of any single species. The experiment also allows evaluation of single speciesí impacts, and compares the relative importance of marine vs. terrestrial components of the salt marsh food webs to ecosystem functions.