Areas devoid of vegetation are called eat outs and the swim canals are called runs . Nutria are a primary force in accelerating marsh loss in the Blackwater basin by attacking the very structure that holds the marsh together, the vegetative root mat. The root mat is especially critical because much of the marsh in the Blackwater basin is a type of floating marsh above a layer of fluid mud. Once the nutria chew through the mat and expose the mud, tidal currents and wave action lead to erosion. Plants that are stressed from too much water from flooding are unable to recover from damage by nutria.
Areas destroyed by nutria become permanent, open water ponds.
The objective of the study is to demonstrate whether exclusion of nutria from quarter-acre fenced plots, located randomly in the marsh, can stabilize or restore marsh vegetation. Comparative measures are being made in unfenced control plots. After two growing seasons the vegetation within exclosures has made some slow recovery, but vegetation in unfenced control plots continues to decline. This finding provides scientific evidence that nutria are directly instrumental in marsh loss along the Blackwater River, and it establishes that the marsh has some limited, capability to recover in the absence of nutria. The preliminary conclusion is that areas heavily damaged by nutria are also highly vulnerable to tidal erosion which lowers the denuded marsh surface and limits recolonization by vegetation.