Sea level rise has been identified as a possible factor contributing to marsh loss in Jamaica Bay, New York. However, Jamaica Bay has also experienced increases in tidal ranges throughout as a consequence of natural and engineering modifications that occurred in the bay during the first half of the twentieth century. The increases in the elevations of high tides are of the same order as the increase in regional sea level that occurred since the early 1900s. Marsh inundation in the bay is thus greater than noted to date and greater than that in adjacent bays where tidal ranges have been more stable. Changes in tidal hydrodynamics may be one more factor to consider in the list of potential causes of marsh loss in Jamaica Bay.