Predicting where future salt marsh habitat will be, and how much we’ll have, can be tricky. Over the last year or so, Amy and I have been working with Steve Hartley and Dan Stone from U.S. Geological Survey on improved predictions of future salt marsh habitat for the South Atlantic.
At first, the idea was to combine existing NOAA models of future salt marsh with observed trends in salt marsh change from the Coastal Change Analysis Program (CCAP). That would be the best of both worlds – trends in observed salt marsh change with potential future change based on topography and future sea-level rise. As it turns out, that approach was really combining apples and oranges. One thing I didn’t realize is that most future salt marsh models are really predicting MAXIMUM future salt marsh. Whether or not marshes reach that maximum depends on many things. Based on what we’ve seen so far, South Atlantic salt marshes are not reaching that predicted maximum.
The big moment of realization came when we compared observed trends in salt marsh area to predicted future trends in subregions of the South Atlantic. The trends were in total conflict! Salt marsh area has been declining over time, then when the future marsh models took over, marsh area was immediately predicted to increase significantly. So, we switched to an approach that only uses the observed trends. We then use those trends to predicts probability of change to salt marsh or open water spatially across the South Atlantic.
We’re getting closer to having some results to share with you. For now, I just want to give you a heads up that this is coming – possibly this year. I’ll share some draft maps in future blogs.