The state has more than 3,000 rivers and streams, lakes and ponds; 1,519 miles of coastline; and 27 watersheds.  It has 15,000 plant and animal species visible to the naked eye, and many more that cannot be seen, 175 species of vertebrate and invertebrate animals; and 250 species of native plants that are officially listed as endangered, threatened, or of special concern by the Massachusetts Division of Fisheries and Wildlife.  The loss of species often indicates the loss of their natural habitat or imbalances that upset the normal functioning of an ecosystem.  For instance, large amounts of pollutants and contaminants, out of proportion with the healing capacity of natural systems, can weaken the health of an ecosystem and have an adverse effect on the health of humans.  Conversely, the presence of a functioning habitat tells us that the ecosystem of which we are a part, is healthy.

Bostonis built on an estuary, and much of the city we see today is actually built on filled-in wetlands.  Wetlands, categorized either as “flats,” “pond-wetland,” “marsh-wetland” or “marsh-salt,” are found in 10 Boston neighborhoods — Allston/Brighton, Back Bay, East Boston, Fenway/Kenmore, Hyde Park, Mattapan, Roslindale, Roxbury, South Dorchester and West Roxbury.  According to the Boston Conservation Commission, there has been no significant filling of wetlands since the Wetlands Protection Act of 1972.  Wetlands act as natural water filters, guard against floods by absorbing and storing river overflow, and provide habitat for wildlife.  Wetlands and estuaries provide habitats for many species, and offer economic, educational, recreational and aesthetic value to humans.