The following explains a little more about the project:

Parker River NWR, in partnership with the Mass Audubon and other local conservation organizations, has been actively mapping and controlling perennial pepperweed in Essex County since 2006. Perennial pepperweed is a non-native, invasive plant that has been invading salt marshes and roadsides throughout New England. If left unchecked, this plant will form a monoculture, excluding all other native vegetation. This, in turn, would eliminate habitat for the native animals that inhabit the marsh. The goal of the Perennial Pepperweed Program is to control the spread and eventually eradicate pepperweed in Essex County, Massachusetts. 

To successfully accomplish our goal of eradication, we must eliminate every plant. A single plant can produce several hundred seeds per year, which can easily be spread by floating along the water. Acting now will help protect clear land, and reduce the impact in areas already infested by it.