Why are wetlands at the mouth of the mississippi river disappearing?

The wetlands at the mouth of the Mississippi river is disappearing majorly because of the human activities that have greatly altered and destroyed the habitat. Human activities such as dredging the wetland for canal, draining and filling for agriculture, grazing and development purposes, etc are the major reasons why the wetlands are disappearing. 
The government is already pumping money into saving these wetlands.