The World of the Coast
The World of the Coast
There is almost no limit of possibilitiesfor wildlife, scenery, and natural wonderswhere land meets sea.
Measured in geologic time, the windswept beaches, quiet bays, dramatic headlands, islands, and other coastal wonders we enjoy are brand new. Some 18,000 years ago the world's continental glaciers were at their peak; as they began to melt, sea levels rose steadily, claiming great swaths of land at the rate of nearly one kilometer each year, a phenomenon that continued until about 5,000 years ago.
What we know today as Chesapeake Bay was a network of broad, shallow river valleys before the seas spilled in to "drown" them, creating an estuary 200 miles long and from 3 to 25 miles wide. North Carolina's 320-mile-long chain of barrier islands was an uplifted area of dune fields on the mainland. And the Gulf of Mexico, which in previous eons had established a coastal plain as far north as present-day Kentucky and Missouri, was only slightly below its modern levels when the last glaciers departed; it rose, too, taking a sizeable bite of the Florida peninsula, and enlarging the Straits of Florida, isolating Cuba.
Throughout the world, these flooded coastal regions today display a striking uniformity of depththey're all beneath 100 to 200 meters of sea. Known as continental shelves, they may extend seaward for many miles, forming the transition between dry land and deep sea.
The reshaping of coastal areas today is largely the work of waves, ocean currents, wind, and rivers. Along much of the Atlantic and Gulf coasts, the continental shelf slips away gradually, allowing submerged offshore bars and barrier islands to form; these take the brunt of storms and moderate the destructive activities of waves, allowing lagoons, tidal marshes, sounds, and other productive wildlife habitats to form on the landward side. Along the coasts of California and Oregon, waves chisel away at steep shores, undercutting them from beneath. If the rocks are weak, the sculpted shoreline appears fairly uniform; if the rocks are more resistant, the result over time is spectacular architecturejagged cliffs, offshore islets, rock arches, submerged caverns, pinnacles, and other formationsbeautiful to see, and a vital component of the nesting, feeding, and brood-rearing needs of many wild species.
Coastal ecosystems encompass much more than surf and sand or boulders and tidepools. Fresh water, it turns out, is one of the key ingredients. Where rivers empty into bays and estuaries, salinity levels are reduced. These "brackish" waters are essential to the life cycles of everything from Gulf shrimp, oysters and abalone to herring, anchovy, and other small schooling fish. Without this immense food base, herons and egrets, dolphins, sea turtles, seals and sea lions couldn't survive.
Plant communities, too, are often remarkably diverse in coastal systems, progressing from beach grasses and low shrubs to adjacent forests of pine, oak, cypress, mangrove, and spruce-fir. The result is an incredible diversity of habitats in close proximity. Along the Pacific coasts of Oregon and Washington, Roosevelt elk spend their days in dense coniferous forests, and visit secluded inlets and beaches at night. In Florida, an American alligator may live just a mile or so away from a beach visited by Atlantic loggerhead sea turtles. In Virginia, bullfrogs, bobcats, and wild turkeys carry on their business in coastal woodlands and marshes, with shorebirds, fiddler crabs, and the occasional humpback whale as neighbors.
Details mentioned in this article were accurate at the time of publication