SPATIOTEMPORAL ANALYSIS OF CHANGES IN A SOUTHERN NEW JERSEY SALT MARSH ECOSYSTEM

Salt marsh ecosystems are critical due to their fertile habitat, ability to store and sequester carbon, and valuable services, such as coastal protection, recreation, food production, and heavy metal remediation. Salt marshes are rapidly disappearing because of sea-level rise and the presence of human infrastructure, which impedes landward migration. The Seven Mile Innovation Lab (SMIIL) is comprised of about 62 km² of tidal marsh ecosystem in southern New Jersey. To gain a better understanding of the salt marsh, its natural processes, and the consequences of direct human impact, we conduct a spatiotemporal analysis of Ring Island in SMIIL over the past century through the use of Geographic Information System (GIS) mapping of historical orthophotographs. We use the methods of Schepers et al. (2017), which studied the spatiotemporal development of conversion of vegetated areas to open-water pools in a Chesapeake Bay salt marsh. We map features on Ring Island using coverages from 1930, ~1950, 1970, 2002, 2015, and 2020 available from the New Jersey Geographic Information Network. We will also orthorectify aerial photographs from the 1950s. The vegetation will be mapped for each year and separate layers will be made to calculate the proportion of tidal pools and tidal channels, and the area of human-driven sediment placement in relation to the total area of Ring Island. Manual digitization will be done using a conservative interpretation at a scale of 1:2,500, and only areas larger than 50 m² will be characterized as water. Individual areas smaller than 50 m² will be removed and replaced by its surrounding class. Schepers et al. (2017) found a general increase of conversion to open water over 29 years and suggested pooling development beginning far from channels and gradually expanding. Our analysis seeks to provide an understanding of Ring Island’s projected future responses to sea-level rise and human manipulation.