What Forests Give

FORESTS AND EROSION

When we Americans look across the great country which is ours we see many streams that do not run clear, and rivers like the Missouri and the Tennessee which are always thick and brown because they are freighting away as much of our soil as they can carry.

If an army of men came marching to take the land from us, what would we do? We would send out an alarm like the one that Paul Revere carried during the Revolution, but it would go faster than any man on horseback could carry it. All up and down the valley the radios would say:

"The soldiers are coming to seize your land!"

Every telephone bell would ring furiously, and a voice would say:

"Hullo—hullo! An army is coming to take your land!"

Women would run out of their houses and call to their husbands at work:

"They are coming to take away our land!"

Airplanes would fly back and forth dropping leaflets saying: "Men are coming to steal away your land!"

The same words would be in large black type on the front pages of the newspapers and on placards at the courthouse in every county seat. Every preacher would announce it from the pulpit; every school teacher would tell the children.

Where the telephone lines did not reach, men would speed along the roads with the news in automobiles, and where the roads were too poor for cars, they would climb upon their farm horses and kick them into a trot and then into a heavy gallop till everyone knew that an army of men was coming to take their land.

We know what they would do. Each man would drop his work and take a gun if he had one, or the old sword that his grandfather had worn in the Civil War, or if he had nothing but an ax, he would catch that up and hurry to the nearest village where the men were gathering to fight the army coming to take away their land.

Our land is being taken away as no human enemy could steal it. It is being lifted up and carried off.

A, Shoestring Erosion. B, Gullying.

Ever since the world was, water and wind have been wearing the rocks into sand and rearranging the sand to suit themselves piling it up, smoothing it out, throwing it into the sea. Until the land had the help of plants, it had a hard time to keep its head above water.

The rain falling along the sides of a valley starts to run slowly downhill in a thin sheet. If there is nothing, to hold the soil in place, no armor to protect it, the film of water which flows down over bare ground, or ground planted to such crops as corn, cotton, and tobacco, which must have clear spaces between their rows, brings some of the topsoil with it. This is called "sheet erosion." If this is allowed to continue, the water digs narrow channels into the earth, gathers into tiny swift rivulets, picks up the soil, and arrives at the bottom of the hill thick with mud. The rivulets look like shoestrings, and this stage is called "shoestring erosion." And if this goes on, the rivulets join together, gouge out deep beds for themselves, and rush along with a heavy load of soil and sand to deposit in the nearest stream. This is called "gullying" and it is the last, most destructive form of erosion.

It is estimated that the Mississippi River alone carries 400 million tons of soil into the Gulf of Mexico every year; that 100 million acres that were once good farm land are gone, and we can never get them back again; that 125 million acres have been badly injured and another 100 million are seriously threatened. The erosion of the soil by water in the Mississippi Valley is an example of erosion elsewhere.

It is at this point that we ask the help of forests. As the treetops will hold back the wind, so the roots will hold back the soil. They will weave a net underground as the branches will weave one in the air.

A, Tree Roots Hold the Soil. B, Roots of the Elm.

If you examine the root systems of trees you will understand how they can anchor the soil. From the point where the tree seed sprouts, a tiny root starts down; but it has not grown more than an inch before it sends out along its sides little rootlets which work out into the soil. In their search for food and water, these rootlets go through the ground like threads drawn by a needle. They curve around the underground rocks, they search out the underground streams, they twist themselves into crevices between the rock strata, they weave themselves into a thick mesh underground, a heavy crumpled lace net from the surface of the soil down as deep as the water table if they can reach it, and in this net the soil is held. If you find a place where a bank of earth has been cut through, you will see everywhere near the surface the ends of the root threads holding the topsoil. If you look across an eroded field with a few trees still in it, you will see inside the circle held by their roots, the soil still in place, and probably grass still growing there. If you find some washed-out gully, you may see a part of its edge held firm by the interwoven roots of trees as a darn holds the heel of a sock. And perhaps you will find high above a washed-out ravine a great tree left holding the earth beneath it so firmly that neither wind nor water can steal it away. Trees everywhere, under every handicap, are trying to hold the land for us. There is nothing that will protect the land on steep slopes against erosion like a forest cover.