This lecture will be held on the Davie campus of Florida Atlantic University in the Davie West (DW) building room 103 .
Salt marsh soils are the world’s most efficient carbon (C) sinks and have been so for millennia – but will they continue to be with warming climate and rapid rates of sea level rise? Over the last few thousand years the rate of sea level rise has enabled salt marsh vegetation to survive tidal flooding and accumulate C-rich soils, primarily through belowground production enhanced by contributions of mineral sediments deposited by tidal floodwaters. Globally, marsh soils store C, on average at a rate of 218 g m-2 yr-1, while emissions of the greenhouse gases methane and nitrous oxide are negligible. More importantly, marsh deposits hold at least 1,275 million metric tonnes of C globally. In recognition of their value as a C sink the carbon in salt marshes (along with that of mangroves and seagrasses) has been branded as “blue carbon” and is under consideration for the voluntary C market.
How will climate change affect the salt marsh blue C sink and its feedbacks to climate change? The impacts will be confounded. An increase in temperature will increase soil decomposition rates, but marsh production may also increase, particularly in high latitude marshes. At the same time, warmer temperatures should encourage poleward expansion of organisms including both native and invasive fiddler crabs which, as bioturbators may turn over this increased production, or enhance it further. Towards the equator mangroves are “invading” marshes. The vegetation shift may not decrease soil carbon stocks over the short term, but other ecosystem functions will change. The greatest threat is the increased rate of sea level rise. Its impact will be the most severe on those marshes where tidal amplitude is low and the coast is already subsiding, and increased hydroperiods will diminish plant production or the plants altogether. Urbanized lands present barriers to inland migration of marshes and the resulting coastal squeeze will decrease the area over which C can accumulate.
As much as possible, we should return what we have lost and not give up the existing marsh through compensatory mitigation. Inclusion of marsh C stocks and future storage potential may show that the mitigation formulas required make a project untenable. Degraded marsh not only has lower C sequestration potential, but is probably loosing soil C. It is imperative that we not only increase resilience of marshes but proceed quickly with restoration to renew the ability of all tidal wetlands to serve as C sinks and stem loss of ancient C.
Dr. Gail Chmura is an Associate Professor in the Geography Department at McGill University, past Director of Quebec’s Global Environment and Climate Change Centre and past president of the Atlantic Canada Coastal and Estuarine Science Society. She has conducted research on tidal wetlands along both the Atlantic and Pacific coasts; and over a wide range of latitudes, from Hudson Bay to the Gulf of Mexico. As a Fulbright Scholar she conducted research at the Netherlands Institute for Sea Research and as a US National Research Council Senior Fellow conducted research at the US Environmental Protection Agency’s Estuarine Ecology Lab. Recently, she was a lead author of the Coastal Wetlands chapter of the Intergovernmental Panel on Climate Change (IPCC) publication Guidelines on National Greenhouse Gas Inventories: Wetlands. Dr. Chmura has used techniques of paleoecology, modern ecology and geomorphology to study tidal marsh response to sea level change, impacts of climate change and human perturbations on coastal ecosystems, and ecosystem services of natural and recovering salt marshes. Presently, her lab’s research is largely focused on impacts of nutrient pollution on coastal ecosystems, assessment of soil carbon stocks and rates, and greenhouse gases fluxes in salt marshes.
Directions to the Davie Campus: Directions to the Davie Campus: From I‐95 North/South, take I‐595 west to Davie Road. At Davie Road make a left and go South to Nova Drive (2nd light). Turn right on Nova Drive and go West to College Avenue (1st light). At College Avenue make a left and the entrance to FAU will be your first left.
If you park across the street please use the cross walk in front of Davie West.