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GCE III - Key Finding in 2013

    Tidal fresh forests are not keeping up with sea level rise

    As sea level rises, tidal freshwater forests and their delivery of ecosystem services face a tenuous future as they will be subject to increasing inundation from salt water. In a paper in Global Change Biology, Craft (2012) evaluated soil accretion in tidal forests in coastal Georgia using 137Cs and 210Pb. Soil accretion rates averaged 1.3 and 2.2 mm yr-1, respectively, and was substantially lower than the recent rate of SLR along the Georgia coast (3.0 mm yr-1) (Fig. 1). They conclude that accelerated SLR is likely to lead to decline of tidal forests and expansion of oligohaline and brackish marshes. In a related study, Jun et al. (2013) evaluated how increased inundation by either fresh or salt water would affect N and P storage in tidal forest soils. The results indicate that soils from areas that are not currently experiencing saltwater intrusion removed significant amounts of inorganic N from the water column when inundated with freshwater, but released it when inundated with salt water. This suggests that tidal forest soils, which normally sorb nutrients, could release it as a consequence of saltwater intrusion, potentially contributing to estuarine eutrophication downstream.


    Fig. 1 Mean 137Cs and 210Pb soil accretion of tidal forest and marshes along the Ogeechee, Altamaha and Satilla rivers, Georgia, USA. The 137Cs marsh data are from Loomis and Craft (2010). The 210Pb marsh data are from C.B. Craft (unpublished). Means separated by the same letter are not significantly different (p<0.005) according to the Rayn-Einot-Gabriel-Welsch multiple range test. From Craft (2012).


This material is based upon work supported by the National Science Foundation under grants OCE-9982133, OCE-0620959, OCE-1237140 and OCE-1832178. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.