Marshs and wetlands are not only a great source of wildlife and are critical to the marine environment, but they also provide a filtering mechanism for soil and other run-off to keep our estuaries and rivers clean. Unfortunately, until recently, marshes and wetlands were allowed to be filled in and used as land for development. This, in turn, has led to increased pollution of our estuaries and rivers -- and the ocean marine environment. An example of where human activity to fill in marshes and wetlands has adversely affected the environment is the case of the Chesapeake Bay. In this example, the expansion of urban sprawl and the filling in of marshes and wetlands has led to the significant degradation of the Chesapeake Bay, the largest estuary in North America and once a source of what seemed unlimited wildlife and fish. This is no longer the case as state and federal officials fight to save the bay.