Through her numerous books, Rachel Carson alerted the public to the link between human actions and their environmental effect. Critical edge is that portion of upland that runs along the border of the marsh. This buffer zone is part of the salt marsh system in that it sends fresh water into the marsh, provides food, cover, breeding habitat and travel corridors for wildlife that live in the coastal zone, and protects the marsh from adverse impacts of human activities. The intermittent stream is one of the obvious links between the forested upland and the salt marsh. Clean water from the upland seeps into the ground and then emerges in the stream.
Fresh water flows into the marsh, mixes nutrients with seawater and helps keep the marsh productive.
Here you see all the parts of this coastal Maine salt marsh. From critical edge through creeks, salt pannes, marsh grass, beach and ocean, it is a network of soils, water, plants and wildlife that functions as a whole, forming a unique and fragile community.