THE SAND DROWNS THE SEA, THE SEA TAKES THE SAND

THE WEALTH OF AMERICA IS BASED on the black soils of its prairies, whose broad flat expanses are often compared to a sea. When I was in Chase County, Kansas, I perceived directly that this was no empty metaphor.

I’d gone to pee against a fencerow by the highway, making use of my mammalian ability to jettison concentrated, excess salts. As I stood looking into the prairie, I noticed in a nearby gully that there was a thick white layer beneath about a foot and a half of black loam.

Ducking under the barbed wire, I walked along the gully, until I began to hear a crunching beneath my feet. Littering the ground were whitened hunks of coral, the shells of a kind of horned clam, and button-sized wheels of calcium, the remains of sea creatures that had died on this spot more than 250 million years ago. Quite literally, this soil—now half a continent away from the roiling surf of either the Atlantic or Pacific oceans—was once a seabed.

The sea can be a source of both fertility and sterility. A man in Malta once thought he would create a saltworks by digging shallow basins atop a headland fifty feet high and supplying them by drawing up water through a hole he drilled down to the level of the sea caves. The water in these pools simply drained away through the pores in the rock, so he never got his salt. Worse, when the driven waves pressed into the sea caves beneath, they caused a jet of water to shoot out of the hole sixty feet into the air, spraying crops of the whole neighborhood and damaging or destroying them. They tried to stop up the hole with stones, but every year, the winter surf blew the rocks out again.

Sodium salt is one of the worst poisons that can affect a soil, yet the best agricultural soils in the world exist at the boundary between the sea and the land. The Dutch polders, having been formed by rivers delivering their alluvial sediment to the sea, are matchlessly fertile, once they have been leached of this sodium. Thirteen of the sixteen elements that plants need to have are derived from the minerals in soil, particularly from rich alluvium. In Lincolnshire, British farmers fertilized their fields by “warping,” that is, by allowing the seawater to cover them at high tide, giving them a coat of rich slime derived from the sediments of river deltas.

So valuable are the soils deposited at the seaside that governments have elaborated incredible hypotheses for staking a claim to them. Napoleon, for example, reasoned that since the entire Netherlands were really a deposit of the Rhine River, therefore, they belonged to whoever owned the sources of the Rhine. In other words, they belonged to Napoleon.

The shoreline, this place of pummeling, where even the air may be poison to a crop plant, is the probable first home of all living things. In the beaches and estuaries, the tidal flats and saltmarshes, the submarine canyons that mark former river bottoms, the mangrove swamps and the flocculated benthic soils that form where the deltas drop their load, is the most diverse habitat on Earth.

It is as though the Earth had tried to produce as much variety as possible in the hope that some of it would make the transition from water to air. A single tidepool on the Pacific coast may contain several thousand different species of invertebrate organisms alone, from the sand-colored brittle star beneath a rock, to the bubble-gum-pink nudi-branch called Hopkin’s Rose, clinging to a frond of kelp.

In the littoral zone the Earth performed its great experiments with maintaining salts in the body. Here were the first creatures that did not need to be surrounded by seawater. Essentially, because the tide rose and fell, they had to be prepared for both wet and dry. Crabs and other crustaceans, especially the isopods, were the early possessors of a tough cuticle that allowed them to store water in the dry periods, and so to store up the salts that they would need for their metabolism.

The shore is a laboratory of salts. The kelps of the littoral zone have been known to be good fertilizer since the fourth century at least. In Elizabethan times, they were called “the poor man’s manure.”

But kelp is not the only creature that takes up the salts brought to the sea. The sodium, the calcium, the magnesium, the potassium, and the bicarbonates combine chemically into either limestone or dolomite, forming seabottom layers that someday, like the sea-formed limestones of the Midwestern soils, will make fertile soils.