Tipping points

Marshes sit on a knife-edge. It only takes a small change in wave exposure, current velocity, or tidal inundation to cause the marsh edge to expand or erode. This project is searching for the point at which hydrological forcing tips the marsh edge from an expanding to an eroding state.

When you think about it, the transformation is incredible. With only a small change in hydrological condition, the tidal landscape totally changes, becoming either a saltmarsh or a mudflat. In ecology, this is known as a regime shift. The point at which an ecosystem shifts is known as a tipping point.

I’m using Mini Buoys to detect the exact point at which waves, currents, and inundation duration causes a saltmarsh to tip into an eroding or expanding state. 20 Mini Buoys are now gathering data along a 10 km stretch of the Caerlaverock saltmarsh in the north-west Solway Firth, Scotland.

The Mini Buoys will be out for a year. Early results show a clear shift from erosion to expansion as inundation duration drops below 140 minutes per day.  I’ll be defining that exact threshold soon, so watch this space!

This work is supported by the UKRI GCRF Living Deltas Research Hub and the University of Glasgow.