Industrial waste from these past industries  have been deposited within the sandbanks of the estuary, consequently have being preserved by the natural blanket of the salt marsh.  Traces of mercury and other toxic substances have been found within the sediment of the marsh, under layers of compressed  soil and plant life. Preventing the fatal waste  interacting with the eco systems that are thriving above, suffocating the  impure, unnatural substances. 

Theorists believe that this contamination of industrial substances has resulted in rapid growth of the marshland, from none existent in 1940 to  80% of the estuary  in 2010. The industrial waste has acted as a form of catalyst, fertilising the sediment  of the sandbanks similar to that of the natural process of mitosis, the rapid regeneration of cells.