Thursday, December 20, 2018

Sea Level Rise - more than an abstraction

I know that, even as I write this, coastal Washington is getting hammered by some severe storms and coastal flooding.  It sort of feels like I should be focusing on that at the moment.  But the fact of the matter is, I'm on the east coast visiting my parents in Gloucester County, Virginia...and I've got other things on my mind.  I had the chance to meet up with Matt Kirwan, faculty at the Virginia Institute of Marine Science who has largely focused his research on the response of salt marshes to sea level rise. Matt took me down to Guineau, a low marshy peninsula between the York River, Mobjack Bay and Chesapeake Bay proper.  In general this part of the east coast is one of our national hot spots for sea level rise, with historical trends at the nearby Gloucester Point tide gauge approaching 4 mm/yr.

Matt uses historic map's like this 1905 Coast and Geodetic Survey map to find formerly agricultural and forested lands that have been converted to salt marsh
One thrust of Matt's research focuses on measuring the transition of uplands into salt marshes, using both sedimentological approaches (i.e. coring salt marshes) and mapping.  We didn't have a chance to core, but Matt readily pointed out areas of salt marsh that used to be forest land or agricultural lands.  It was also easy to see places where the transition to salt marsh was actively occurring.  In the photo at the top of this post, for example, tree trunks and dead pine trees are readily observable at the interface of this marsh and forest.  As sea level rises, the marsh is moving inland.  Interestingly Matt's work has also suggested in some cases that the leading edge of the marsh may be less response to sea level rise than the landward edge.  In other words the marsh may be much more resilient to sea level rise than previously thought, at least in cases where the marsh is unconstrained by armoring, diking or topography.  

Another view of tree stumps sticking through the marsh surface...evidence of recent habitat transitions.
The signs of sea level change were also evident in the agricultural land we drove past.  Large patches of bare earth in the fields are evidence of high salinity pore water, rendering sections of field unharvestable year after year.  I was astonished to learn that the farmers continue to plant these sections year after year.  The very definition of hope.

Bare spot in a soybean field...too saline for any ag crops to grow.
Finally, I couldn't help but post this photos.  This area was also hit hard in 2003 by Hurricane Isabel and there has been some adaptation as a result of that event:

A trailer raised precariously high on stilts...anything to avoid flood insurance!

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