GC53A-1190
Linking Historic Wetland Soil Accretion and Sea-Level Rise Data with Landcover Change in the US

Friday, 18 December 2015
Poster Hall (Moscone South)
James Robert Holmquist, University of California Los Angeles, Los Angeles, CA, United States
Abstract:
Coastal marsh loss in the US due to sea-level rise and other anthropogenic factors has important ramifications for carbon sequestration, endangered species habitat, water quality, and myriad other ecosystem services. We compiled 486 reports of 137Cs dated cores from coastal marshes in North America and compared vertical accretion rates to relative sea-level rise (RSLR) from the nearest NOAA tide gauge between 1963 and the core collection year. There was a positive linear correlation between RSLR and vertical accretion. When RSLR was greater than 5 mm/yr RSLR outpaced accretion on average indicating a possible limitation to positive feedback within the system. We also calculated net-accretion (vertical accretion - RSLR) and summarized regional variation according to both coastal zone and watershed boundaries. From 1963 to present the West Coast has been the most historically resilient to RSLR, the Gulf Coast has been the most vulnerable, and the East Coast has been intermediate and variable. We compared regional trends in net-accretion to land cover change using 1996-2010 Coastal Change Analysis Program maps with freshwater wetland area constrained by tidal categories from the National Wetlands Inventory. Watersheds with historic net-accretion falling below -3.9 mm/yr in the Gulf Coast were much more likely to have massive losses of coastal wetland area from 1996-2010, up to 10% of 1996 wetland area in some cases. Areas with higher net-accretion did not show change, except for some gains in the San Francisco Bay. The Mississippi Delta mouth is a notable data anomaly with positive historical net-accretion as well as a net-loss of wetland surface to open water which may identify an important limitation of soil coring techniques in areas with dynamic sediment deposition.