Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise
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MARSH RESILIENCE SUMMIT
Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise Molly Mitchell 1
&
Julie Herman 1 & Carl Hershner 1
Received: 22 October 2019 / Accepted: 7 October 2020 # Society of Wetland Scientists 2020
Abstract Tidal marshes are important ecological systems that are responding to sea level rise-driven changes in tidal regimes. Human development along the coastline creates barriers to marsh migration, moderating tidal marsh distributions. This study shows that in the Chesapeake Bay, USA an estuarine system with geographic and development variability, overall estuarine tidal marshes are projected to decline by approximately half over the next century. Tidal freshwater and oligohaline habitats, which are found in the upper reaches of the estuary and are typically backed by high elevation shorelines are particularly vulnerable. Due to their geological setting, losses of large extents of tidal freshwater habitat seem inevitable under sea level rise. However, in the meso/poly/euhaline zones that (in passive margin estuaries) are typically low relief areas, tidal marshes are capable of undergoing expansion. These areas should be prime management targets to maximize future tidal marsh extent. Redirecting new development to areas above 3 m in elevation and actively removing impervious surfaces as they become tidally inundated results in the maximum sustainability of natural coastal habitats. Under increasing sea levels and flooding, the future of tidal marshes will rely heavily on the policy decisions made, and the balance of human and natural landscapes in the consideration of future development. Keywords Tidal marsh . Sea level rise . Marsh migration . Ecological conflicts
Introduction Tidal marsh loss is a significant issue throughout the United States and there is growing concern about accelerating sea level rise and the impact it will have on marsh persistence. Significant marsh loss may dramatically change coastal and estuarine functions and potentially impact global nutrient/ biogeochemical cycles (Chmura 2013; Coverdale et al. 2014). Marsh loss associated with sea level rise, erosion and human activity has been documented throughout the United States (e.g. Nyman et al. 1994; Hartig et al. 2002; Bromberg and Bertness 2005; Mitchell et al. 2017). Tidal marsh extents are defined by the interaction of landscape elevations and tidal regime. As sea levels rise and the maximum extent of tidal inundation reaches higher elevations, tidal marshes are induced to migrate inland to maintain their * Molly Mitchell [email protected] 1
Virginia Institute of Marine Science, William & Mary, Gloucester Point, VA, USA
place in the tidal frame. In areas with low coastal elevations, tidal marshes can expand or maintain their size as they migrate across the landscape, resulting in a potential future gain of tidal marshes (e.g., Kirwan et al. 2016). However, in areas with higher elevations or where migration paths are blocked by shoreline structures or impervious surfaces, marsh loss has been docume
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