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Abstract

The current distribution of coastal wetlands is the product of 4,000 years of near static sea level. The rise in sea level that we see today began several centuries ago. Evidence will be presented that coastal wetlands are not in equilibrium with sea level, and that the rate of sea-level rise (SLR) is approaching a tipping point. Salt marsh plant biomass and sediment accretion rates are functions of the relative elevation of the marsh surface. There is an optimum elevation for plant productivity, and there are upper and lower limits of relative elevation determined by hypoxia at one extreme and osmotic stress at the other. Provided that marsh elevation is super-optimal for plant growth, a rise in relative sea level will stimulate primary production and sedimentation, thereby raising the surface elevation. Relative marsh surface elevation declines as the rate of SLR increases. When relative elevation falls to a level that is suboptimal for the vegetation, a further increase in relative sea level depresses primary production and sedimentation, leading to the conversion of vegetated marsh to open water. This transition is a tipping point and is influenced by the variability in rate of SLR. The model demonstrates that a marsh can be dynamically stable and will tolerate a greater maximum rate of SLR, provided that the rate is variable and declines periodically to a level that allows the marsh to recover.


Speaker Bio

Dr. James Morris is the Director of the Belle Baruch Institute for Marine and Coastal Sciences, Professor of Biological Sciences and Distinguished Professor of Marine Studies at the University of South Carolina. He served as a Program Officer at the National Science Foundation from 2003-2005 and was a visiting professor at Aarhus University, Denmark in 1990. His academic background includes degrees in environmental sciences, (BA, Univ. Virginia), biology (MA, Yale) and forestry and environmental studies (PhD, Yale). He held a postdoctoral fellowship at the Marine Biological Laboratory, Woods Hole before moving to South Carolina. Morris has authored about 80 peer-reviewed publications and has served on numerous committees and panels for various agencies, including the US National Science Foundation, the Irish National science foundation, the National Research Council, and the IndoFlux committee of India. Dr. Morris has long-term funding from NSF for research at North Inlet, SC on effects of sea level change on coastal wetlands, and he is principal investigator of a NOAA project focused on the effects of sea-level rise in Pamlico Sound, NC and is a co-principal investigator of the NSF, Plum Island Long Term Ecological Research site in Massachusetts.

Funding provided by the Climate Program Office, National Oceanic & Atmospheric Administration to the University of Wisconsin Sea Grant Institute.
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