Climate-driven range expansions of individual species are well-documented; however, corresponding community shifts are not. This lack of widespread community change may indicate communities can resist wholesale change with the arrival of new species. In the northern Gulf of Mexico, climate change is driving the expansion of black mangroves (Avicennia germinans) into areas traditionally dominated by smooth cordgrass (Spartina alterniflora). This study investigates the effects of these changes on the species composition of animals and habitat structure in Louisiana, U.S. with implications for how species expand their range under shifting climactic regimes. Using quantitative nekton sampling and satellite imagery analysis over two decades, we observed a substantial increase in winter temperatures of 3.5°C and a significant regime shift from marsh to mangrove habitats. Despite these remarkable physical and habitat changes, the species composition remained stable, suggesting that local species interactions may mitigate the effects of climate-driven range expansions. Our findings highlight the resilience of estuarine communities to rapid environmental changes and emphasize the need for further research on the indirect effects of habitat shifts on food web dynamics.

Ecogeomorphic theory predicts that plant-sediment feedbacks regulate carbon storage in coastal vegetated ecosystems. Yet, grazers, which remove plant biomass and alter sediment properties, remain an understudied driver of carbon cycling. We used field-derived and remote sensing data to examine how consumer fronts of the keystone grazer, Sesarma reticulatum, mediate carbon storage, flux, and recovery in salt marshes. We observed accelerating rates of Sesarma front migration that led to a decrease in carbon stocks by 40-70%. Despite latitudinal differences, front migration rate had no effect on carbon stocks, flux, or replacement time. Lastly, when we included Sesarma disturbance in carbon flux calculations, we found that it may take 5-100 years for marshes to replace lost carbon, if at all. Combined, we show that small grazers cause a net loss in carbon stocks as they move through the landscape, and irrespective of migration rate, these grazer-driven impacts persist for decades.