Salt marshes are considered some of the most biologically diverse and ecologically important regions on Earth, containing thousands of species of robust salt-tolerant plants, crabs, fish, mollusks, zooplankton, algae, and bacteria. Isolated between topographic headlands, laterally continuous behind protective barriers, or associated with extensive delta landscapes, salt marshes are regulated by a variety of physical forces such as waves, tides, rivers, and storm surges, but they are also impacted by climatic variations in temperature and precipitation, riverine flooding, local tectonics, and subsidence (i.e., a deltaic process that describes the lowering of the land surface). Biological forces also play important roles in controlling salt marsh landscapes as many species shape geomorphic development. As these landscapes form and evolve, there exist significant interactions between biology, hydrology, and geology; thus it is impossible to consider salt marsh geomorphology – i.e., how the landscape changes over time – without taking into account these principal interactions.