Salt Marshes Under Siege

摘要

An attentive observer sees the richness of life during a single walk along a salt marsh. Gulls circle in the air, and mute swans swoop in to land along the marsh's edge. Dense stands of grasses and other plants―waving gently in the ocean breeze―cover seemingly every spot of ground, from the shore's edge to the tree line. When the tide flows out, crabs scurry back and forth along the muddy edge. In spite of this rich diversity and lush plant life, danger lies ahead for all salt marshes, especially those along the eastern coast of North America. A salt marsh develops when salt-tolerant plants colonize shoreline sediments on wave-protected shores. The plants bind the sediments, and the vegetation retards water movement and promotes further sedimentation. In New England, a salt marsh creates a series of four strips of habitat. Along the shore, which floods twice most days, cordgrass (Spartina alterniflora) dominates plant life. As ground level rises, marsh hay (Spartina patens) takes over in the so-called seaward edge of the high marsh. At the terrestrial edge of the high marsh, black rush (Juncus gerardi) dominates the landscape. Finally, a band of shrubs marks the inland-most stripe of salt marsh, usually against a line of trees.