A changing climate poses unprecedented potential for coastal wetland loss, exacerbating anthropogenic impacts and reducing the resilience of these ecosystems. The central Texas coast presents an ideal location to study a subtropical wetland transition zone. The Mission-Aransas National Estuarine Research Reserve (MANERR), located in Port Aransas, Texas, is characterized by warm annual temperatures, variable rainfall patterns, and high evaporation rates. The climate and low-lying shoreline elevation of the shallow bay systems in the MANERR make the emergent vegetation especially susceptible to changes in climate. Coastal foundation ecosystems, like salt marshes, are at risk of displacement due to tropicalization, drought conditions, sea level rise, and extreme high tide events. To investigate the spatiotemporal change in emergent vegetation, we ask (1) how wetland plant communities vary over time and across sites in the MANERR and (2) whether the dominant species have changed over time across sites. Salt marsh and mangrove vegetation surveys began in 2011 as part of the established NERRS biomonitoring program and have grown to encompass a total of four locations. At each site location, we annually record percent cover, stem density, trunk diameter, and maximum canopy height along five 20-meter transects.
Results/Conclusions
Within the MANERR, black mangroves (Avicennia germinans) have a historical presence but are observed to be growing denser and expanding. Preliminary results indicate that decreases in salt marsh cover are due to unvegetated (bare ground and water) and wrack covers becoming increasingly dominant while A. germinans is slowly but consistently increasing in abundance. Throughout the monitoring period, A. germinans’ mean canopy height remained below 1 meter. The cooler winter temperatures of the subtropical environment appear to keep A. germinans from having a dominant presence at the expense of salt marsh vegetation species. Post-Hurricane Harvey is an opportunity for transformation, and decision-makers are focused on coastwide resiliency. Monitoring the salt marsh-mangrove ecotone for change has a significant applied importance to management decision-making. Detecting change at the local level will provide key information to quantify the implications to critical ecosystem services and provide a baseline as upcoming industrial development projects may impact the estuarine wetlands.