Appreciating transitions in space, time

ON THE BAY

Edges: The Chesapeake exemplifies the rich, fertile environment produced at points of natural intersection.

July 09, 2004|By Tom Horton | Tom Horton,SUN STAFF

BREAKING NEWS that didn't make the front page:

In the warm, wet sand of late spring, on a tidal Southern Maryland river, delicate little four-clawed prints emerge from the water. Several yards farther is an identical track heading back.

Find where they converge in a thicket of beach grass. The smooth sand in the apex of tracks offers no clue that anything ever happened there, but gentle probing reveals a freshly laid nest of leathery, cream-colored terrapin eggs.

Most will produce males because the beach faces north and east, and its incubating sands remain relatively cool. A nearby south-facing strand, hotter, will hatch out mostly females.

Downriver, a homeowner worried by minor erosion has riprapped his shoreline with stone -- obstacle enough to ensure a terrapin will never again crawl out to nest.

In June, a full moon bathes the fringes of an Eastern Shore marsh. As the tide nears its zenith, dark, cantaloupe-sized forms glide laterally back and forth along the sandy shallows, just a few feet offshore.

Periodically, one intercepts a larger version of itself heading purposefully onshore from the depths. The smaller, male horseshoe crabs clasp the rear of the big females, who haul them ashore to spawn.

They've done this each year since a hundred million years before the dinosaurs appeared. "Cruisin' for chicks," a biologist once described the males' moonlight patrols. Some things have been popular forever.

July 4, kayaking the western side of Smith Island, I'm surrounded by choppy, muddy water -- except for a couple of acres where the water remains wonderfully clear, calm, its surface glistening green, flecked with gold in the morning sun.

It's a bed of widgeongrass, one of the bay's dozen or so types of submerged aquatic vegetation (SAV), bursting with seed that resembles tiny kernels of ripe corn.

Gaze down into a magical world as the wind scoots you across this shallow, submerged meadow. Blue crabs lie mating. A flounder startles from the bottom. A shower of silver minnows fling skyward, followed by the great, swift hump of some predator just under the grass mat.

What a different world was this bay before pollution killed off tens and perhaps hundreds of thousands of acres of these aquatics. What an inadequate term SAV is to describe them.

A theme connects the above threads through much of what is fine and essential about the estuary, and is perhaps fundamental to all of nature.

It has to do with edges. Life loves those joints, intersections, overlaps and seams where land joins water, forest borders field, shallows fall off to channels, fresh water cedes to salt.

On larger scales, edges of transition such as weather and the seasons stir animals to move great distances, motivated by a restlessness most humans feel as well.

When ecologists recently attempted to calculate the value of earth's natural resources, the astounding thing was not that it was in the tens of trillions of dollars, rather that nearly half came from 10 percent of the planet -- the edges -- wetlands, SAV, coral reefs, the rich fishing grounds of the continental shelves.

The fecund junctures of land and water the Chesapeake has in hyperabundance -- a tidal shoreline that, if all its nooks and crannies were unkinked, would stretch thousands of miles.

The bay's natural edges range from sand dune and cliff to salt marsh and wild rice; from submerged grass beds and oyster bars to forested banks and blooming hibiscus.

Little blue crabs use the shallow edges for safety from big fish. Ospreys and eagles dine sumptuously there, as do soft-crab-stalking herons, egrets and ibis. The edge is home to otter, beaver, muskrat and mink; also the young of shad and herring.

Then there is the historical edge. Last week I picked up bottles washing from a marsh that took me back to my youth (nickel Cokes and milk delivered to the door), and to the War of 1812 (medicine bottles discarded from British warships).

Recent finds of native tools on a Chesapeake cove, matching tools used in Europe some 13,000 years ago, make some scientists think an edge was crucial to settling North America.

How could primitive people sustain themselves on such a voyage? At the time, ice probably clogged the Atlantic to a latitude about that of present-day Maryland.

But edges of ice and open water are among the richest environments on earth. Minerals from melting glacial ice support a fantastic abundance of mammals, fish and birds that might have been hunted along the way.

One more species, of course, loves the edge. The bulk of the world's people live near rivers, oceans and lakes. In few places is waterfront in more demand than on the Chesapeake.

This recalls a quote from Bengt-Owe Jansson, a Swedish ecologist visiting here:

We feel the greatest personal freedom is to be able to walk all the way down the waterline. Freedom for you is buying land all the way down the waterline.

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