Looking back to understand how communities respond to sea level rise

Photo of coastal flooding on Camano Island by Joan Schrammeck

In the sea level rise planning world we do a good bit of fretting about what sort of responses we might expect from the human communities along the shoreline, experiencing impacts associated with sea level rise.  We often emphasize that there is no precedent for understanding how human communities will respond, given that the sea level change we are expecting is, itself, unprecedented.  But this, of course, is not true.  Sea level HAS risen during the Holocene:

Estimated sea level curves for the past 15,000 years for the Strait of Juan de Fuca and globally.  From here.

during time periods when the human population was also increasing, and even when humanity was beginning to settle into communities:

Estimated global population over the last 12,000 years.  From here.  

So it is perhaps not at all a stretch to imagine that there are some templates out there for understanding how people may have responded.  Indeed, its also not a stretch to imagine that the earliest occupants of the Olympic Peninsula observed and experienced sea level change, something i've mused on in the past, though the traces of those people on the landscape are few and far between.  A few more detailed examples are starting to emerge, though, that perhaps point to a variety of responses, including one just out of last week's 2021 AGU meeting.  In this case a fascinating bit of modeling examining how local sea level in Greenland probably responded to the advance of the Greenland ice sheet during the Little Ice Age suggests that sea level rose quite dramatically in places colonized by Icelanders, and may help to explain the sudden departure of those people back to Iceland.  So, perhaps, an example from the past of one of the three big strategies:  retreat.  

A photo, from Galili et al., showing the remnants of a submerged, 7000 year old sea wall off of the coast of present-day Israel.

In 2019 I was a bit obsessed with another widely-reported paper, published by a team from Israel, describing the remnants of a 7000 year old seawall that now sits under about 20 feet of water.  The authors presume that this is one of the earliest known examples of another of the big three strategies:  protect.  In this case, presumably, the approach was ultimately unsuccessful.