What distinguishes a barrier beach from other beaches? Simply this: narrow and
long, and rising only slightly above the high-water mark, barrier beaches are
hiding something. Behind each barrier beach is a sheltered body of water, a
shallow, landlocked lagoon. Barrier islands are long and narrow, too. But
they are islands, separated from the mainland. The lagoons that shelter behind
them communicate directly with the open sea. Barrier islands are also wider than
barrier beaches, and they're usually higher as well. Many boast dunes and
vegetated slopes, and some conceal protected saltwater marshes in their lee.
I'm oversimplifying, of course. The origins of barriers are much debated in the
literature. But whatever their genesis, they're easy enough to spot. Take a look
at the map of North America in any good world atlas.
You'll see a bulwark of barriers extending from Long Island all the way down the
Atlantic coast to Florida, and continuing westward along the Gulf of Mexico. The
Outer Banks of North Carolina are barriers. And Cape Canaveral, the spaceport on
Florida's east coast, perches on one. Don't think that barriers are exclusively
American, though. More than ten percent of the world's coastlines are guarded by
barrier islands, and many large freshwater lakes have barriers of their own.
No matter what their nationality, barriers and lagoons are inseparable
companions, and because the barrier shelters its partner from all but the worst of
the sea's assaults, lagoons play host to a startling variety of extraordinarily
diverse ecosystems. Some lagoons those protected by barrier beaches
are landlocked, but many are extensions of the sea and subject to the rhythm of
the tides. Water pours in and out through tidal inlets, nourishing salt
marshes and tidal flats.
Not all lagoons support salt marshes, of course. They require gently shelving
shores, conditions that are common enough along the Atlantic and Gulf coasts of
North America, but rare in the active tectonic landscape of the Pacific, where no
more than one-fifth of the shoreline is suitable. Even on the Pacific coast,
however, salt marshes can be seen in protected bays and sheltered coves, on
Alaska's arctic slope, and along the Baja peninsula. And wherever natural lagoons
and salt marshes are found, you can bet wildlife will be found there, too. Salt
marsh grasses anchor the sediments from which they spring. When the grasses die
and wither, their remains accumulate as a fertile organic mulch. Over time, this
mulch becomes peat, sustaining a living community of incredible richness in the
process. Tidal flats attract an army of crawling and burrowing invertebrates.
These, in turn, attract larger predators. Shore birds and land animals scavenge
along the flats when the tide goes out. Fish swim in the tidal waters and graze
among the roots of the grasses in the salt marsh. It's a marine Garden of Eden.
Unfortunately, Eden is under siege. People flock to America's beaches in order
to escape the coastal cities' stifling summer heat, and more and more of them are
deciding they don't want to leave when the sun goes down. Oceanfront property is
the hottest seller in an already superheated real estate market, and a small
swathe of North America's dwindling stock of salt marsh is lost to development
every day. It's death by a thousand cuts agonizing, slow, and sure.
And people aren't the only threat. The hungry sea still waits just outside the
barrier, eager to stake its own claim to a piece of Paradise. No barrier island
can withstand the full force of an ocean storm without sacrificing something of
itself. When the sea attacks the shore, the land has no choice but a fighting
retreat. Hurricane-force winds and plunging surf tear away at the fabric of the
barrier. Storm surges dredge inlets where none existed before, making barrier
beaches into islands, and opening landlocked lagoons to the action of the tides.
But even in the fiercest hurricanes, the sea gives as well as takes. Storm
waves wash over the crests of barriers, quarrying sand and gravel from the beaches
on the seaward side and dropping it to leeward. These "overwash sediments"
actually increase the height of the barriers and prolong their life. Without
overwash, the barriers would eventually sink below the rising sea. Global
warming's not to blame for this, by the way at least it's not the only
culprit. The sea has been rising since the last continental ice sheets started to
melt. We're just hurrying things along. That's enough, though. A lot of oceanfront
property is going to get wet feet in the coming decades.
Lagoons are shaped by the sea's tough love, too. Each storm increases the
burden of silt and sand borne by local streams and rivers. Much of that runoff
ends up in lagoons, where it's trapped in the salt marsh grasses. As storm follows
storm, the shoreline builds outward, encroaching on the shallow waters. In time,
the whole lagoon may be transformed into a salt marsh. Eventually, that too will
The sea giveth, and the sea taketh away. Nothing lasts forever, and the
continents' seaward defenses are no exception. When extraordinary storm swells
breach or overwhelm barrier islands, the coast stands naked, exposed to the full
power of the ocean. Catastrophe then becomes commonplace. We humans find this hard
to accept. We fall in love with barrier islands and beaches. We build homes on
them, savoring the sweeping views and salt air, and we tell ourselves that these
will always be ours to enjoy. But we're doomed to disappointment. Once a barrier
is surveyed, platted, paved, and built, it loses its ability to retreat. It can no
longer roll with nature's punches. It can only stand and take each blow on the
chin. The result is certain. Only the length of the match is in doubt. The sea
wins every bout on its card.
As a child playing in the sand, I got my first inkling of the power of the sea.
Later, as a geologist, I learned to question the seeming certainty of solid land
and embrace the constancy of change. Later still, now a paddler making her
first tentative forays along the coast, I caught glimpses of the richness and
majesty of the living ocean. And I saw how much had already been lost.
Nothing lasts forever. I know this. So do you. But barrier islands and beaches,
along with their lagoons and inlets and salt marshes, are essential parts of the
coastline's intricate, elastic armor. They absorb the force of the waves' knockout
blows, and tame the wildness of the raging seas. They offer shelter to all manner
of creatures, and safeguard the ocean's legacy of life. They also bring pleasure
to millions of people who are content to visit and then leave: beachcombers,
birdwatchers, sun-worshippers, surfers, and kayakers alike. That's no small thing,
even if the dollar value of "quality of life" continues to elude the economists.
Yes, change is inevitable, but change that comes too quickly can overwhelm. We
live for the moment, and our moment is brief. The sea's time is not our time. It
has infinite patience. It tests the coast's armor every day, and every day it
finds the armor weaker. One day it will strike, giving no quarter and granting no
parole. No coast is safe, no bulwark perfectly secure. This much, at least, is
obvious, even to little engineers: If you don't want to see your work swallowed up
by the hungry sea, be sure you build all your sandcastles well away from the
farthest reach of the waves.
Copyright © 2004 by Verloren Hoop Productions. All rights