Thursday, 13 July 2006

Modeling of Sea-Level Rise and Deforestation in Submerging Coastal Ultisols.

Ahmed Hussein, Private Soil/Wetland Consultant, 24 Marshall Dr., 24 Marshall Dr., Egg Harbor Township, NJ 08234

Sea-level rise associated with global warming and adverse environmental implications in coastal areas have prompted interest in modeling the history of sea-level rise and its impact on deforestation during the pedogenic transformation of Ultisols (forest soils)to Histosols (coastal marshes). The modeling was based on data collected from sampling units along a marsh transect in Dorchester County, MD. In low-relief submerging environments, coastal marshes accrete vertically and migrate laterally over adjacent Ultisols to keep pace with sea-level rise. The marsh substrate is organic in nature overlying what once were upland forest soils. The history of sea-level rise was a two-step linear function, illustrating acceleration in the last two centuries. During the last 150 yr, the 210Pb-based rate of sea-level rise averaged 2.2 0.4 mm yr 1. Before the last few hundred years, the long-term 14C-based rate of sea-level rise was 1.12 0.2 mm yr 1. The rate of lateral migration of coastal marshes, which is also the rate of deforestation, showed similar acceleration following the history of sea-level rise. During the last 150 yr, the rate of deforestation averaged 3.29 2.1 m yr-1. Before the last 150 yr, the long-term rate of deforestation averaged 0.19 0.08 m yr-1. Modeled predictions of deforestation have shown that within a marsh ecosystem, where other controlling factors are at a steady state condition, slope of the adjacent upland controls the rate of deforestation. In the next century, the predicted rate of deforestation ranged from 2.5 to 10 m yr-1 averaging 6.3 3.8 m yr-1. Assuming that the present rate of sea-level rise remains constant, the time needed to complete the pedogenic transformation of Ultisols to Histosols is 180 35 yr. The most conservative future scenario of sea-level rise has reduced this time by 55%.

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