Migrating Upward and Landward Through Space and Time. Migrating upward and landward through space and time. This is a famous phrase among coastal scientists. It describes the behavior of a beach, or other coastal environments such as a tidal wetland, a reef, or an estuary, when the sea level is rising. It means that a coastal environment needs unrestricted access to the adjacent land or it will drown under the rising water. Rising sea level forces coastal environments to migrate up onto the land, replacing formerly terrestrial environments with tidal environments. Dunes become beaches, streams become estuaries, and fields (and neighborhoods) become wetlands. If this route of migration is blocked, the coastal environment will disappear.
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