Flocks of shorebirds stilt through the shallows, lunging long bills at their abundant prey of fish, worms, crabs or clams. Within the sediments, whether mud, silt, sand, or rocks, live billions of microscopic bacteria, a lower level of the food web based largely on decaying plants. Estuaries are tidally-influenced ecological systems where rivers meet the sea and fresh water mixes with salt water. Tens of thousands of birds, mammals, fish, and other wildlife depend on estuaries. A healthy, untended estuary produces from four to ten times the weight of organic matter produced by a cultivated corn field of the same size.
Water draining off the uplands carries a load of sediments and nutrients.
As the water flows through salt marsh peat and the dense mesh of marsh grass blades, much of the sediment and nutrient load is filtered out. This filtration process creates cleaner and clearer water. Porous, resilient salt marsh soils and grasses absorb flood waters and dissipate storm surges. Salt marsh dominated estuaries provide natural buffers between the land and the ocean. They protect upland organisms as well as billions of dollars of human real estate.