Mersea Harbour is under threat from the erosion by storm wave action of Cobmarsh, Packing Marsh and Old Hall. If these natural saltmarsh wavebreaks disappear, the harbour will be exposed and eventually become unviable for moorings, oyster layings and many commercial and leisure marine activities.

There will be severe loss of habitat for vulnerable birds including the rare Little Tern as well as many animal and plant species. The harbour could disappear within the next 20-30 years. The jetty itself could be lost within 10 years!