Sea level rise submergence simulations suggest substantial deterioration of Indian River Lagoon ecosystem services by 2050, Florida, U.S.A.

Randall W. Parkinson, Levente Juhász , Shimon Wdowinski, Valerie Seidel, Zhaohui Jennifer Fu

The Indian River Lagoon is a 250-km-long Estuary of National Significance located along the east-central Florida coast of the USA. NOAA tidal data generated at a station located in the central reaches of the estuary indicate sea level rise has accelerated over the duration of record to an average of 9.6 ± 1.6 mm year−1 (2003–2022). It is expected to continue accelerating over the duration of this century. This investigation simulated submergence of the estuary using the on-line geospatial tool Future Shorelines to evaluate the effects of sea level rise on a suite of natural and built attributes that either contribute to (i.e., boat ramps, spoil islands, seagrass) or degrade (septic and wastewater treatment systems) ecosystem services. The simulations are based upon the median NOAA high sea level rise trajectory in target years 2050, 2070, and 2100. By 2050, 23% of the public motorized boat ramps and 87% of the spoil islands that provide recreation and conservation services will be largely to completely inundated. Seven percent of the known or likely septic systems in the watershed will be submerged by 2050. Sea level rise does not compromise any of the eleven wastewater treatment plants considered in this study over the next 25 years. Seagrass distribution is expected to decline 34% by 2050 due to a reduction in substate area above the light-dependent median depth limit. By 2100, all ramps, spoil islands, over 27,000 (22%) septic systems, and six wastewater treatment plants will be inundated. By then, the average water depth will exceed the median depth limit for seagrass throughout most of the estuary. Ecosystem service mitigation strategies are presented for the attributes considered. The development of the submergence simulation tool and discussion of mitigation options benefited by collaboration with project partners responsible for resource management in the study domain. This coproduction ensured the simulation outputs and mitigation options were realistic and actionable. The risks to estuarine ecosystem services induced by urbanization and sea level rise are reported worldwide and the methodological approach of this study offers a novel means of developing or enhancing mitigation strategies.