Coastal wetland plant zonation is driven by species-specific tolerances of several environmental parameters such as inundation, sulfide concentration, and salinity, as well as inter-specific competition. Rising sea levels and reduced frequency of cold events are driving mangrove expansion landward and northward in Florida, resulting in a substantial conversion of salt marsh habitat. The Critical Coastal Habitat Assessment is a long-term monitoring study that identified changes in elevation, plant species, soil composition, and water quality across nine permanent transects in Tampa Bay, Florida from 2014–2016 to 2023. During this period, mangroves expanded extensively into salt marsh and salt barren habitats, with the average individual mangrove zone length increasing significantly from 25.7 ± 18.9 m to 40.9 ± 28.2 m (paired t-test, t = -2.40, df = 12, p = 0.034), displacing previously dominant marsh species such as Juncus romerianus and Spartina patens. The width of salt barrens and salt marshes decreased as mangroves expanded inland and the landward migration of salt marshes was limited by the relatively steep slope to coastal upland habitat. Local sediment accretion rates (2.0 – 4.2 mm/yr) suggest a limited ability for Gulf Coast salt marsh habitats to keep pace with sea-level rise, and highlight the need for maintaining undeveloped, natural buffer zones at appropriate elevations upslope of coastal wetland habitats to allow for landward migration. Information gained from this study will inform appropriate and effective management responses to the accelerating loss of salt marsh habitat.