What Forests Give

WIND AND FORESTS

How about that other thief that is stealing our land the wind? For longer than man has been on earth the wind has been busy picking up the soil in one place and laying it down in another. There are parts of eastern China where the wind has laid down 60 feet of soil which it probably brought from the dry lands far to the west and the bare mountainsides to the south. Great deposits of wind-blown earth are also found in Washington and Idaho. Until plants—grasses and trees—began slowly to creep over the land and to hold it in place with their roots, there was nothing to prevent the wind from carrying the sand wherever it chose.

But we no longer think that what has never been done never can be done. We know that a slow wind carries no dust. Why not slow up the wind?

Wind is such a simple thing! Air traveling from one place to another! Usually from a place where it is heavy and thick because it is cool, to a place where it is light and thin because it is warm. Air acts exactly like the people of a crowded country who emigrate to a new land where there is more room. Our immigration laws slow up the rush of people just as a bank of trees will slow up the rush of wind.

Everyone who has taken refuge from a blow on the lee side of a grove, knows that trees keep off the wind. We know too that a wall of trees will protect tender grain from the wind over a strip 20 times as wide as the highest of the trees. For only wind blowing along the surface of the earth steals the soil or damages the crops. If we can raise it above the surface—build walls of trees to change its currents we can save the fields. There are in the Dakotas, eastern Montana, and Wyoming more than 2,700 successful shelterbelts. There are successful shelterbelts in Kansas, Nebraska, Iowa, Missouri, and other States small ones that protect a little land, save the soil in some farmer's cornfield from the thieving winds. In Germany much of the soil is protected by banks of trees called "wind mantles."

A, Dust Storm in Texas. B, Dust in South Dakota.

We can no more afford to have our land blown away than to have it washed away. Because of what the wind brings and what it takes away, the people who live in parts of the prairies and the plains are becoming less comfortable and less prosperous year by year. Whether trees can be planted so as to protect this land from the wind depends on how much moisture those winds bring with them. And what the wind brings depends on where it comes from. If it has blown over a warm ocean it has sucked up water like a sponge if it has blown over a desert it comes heavy with sand and dust.

The winds that blow over the United States can take on a load of moisture from any of three great reservoirs; the Atlantic Ocean, the Pacific Ocean, or the Gulfs of Mexico and California. They can sometimes collect a cloud or two from the Great Lakes and even from the Arctic Ocean, but these are what might be called l. c. l. freight—less than carload lots.

Those that blow in from the Atlantic between the last of April and the first of September, which is the growing time of trees, drop their first rain upon the market gardens of the southern tidewater and the coastal plains of New England. They make the next delivery of rain upon the forests of the Appalachian ranges and carry some over to the eastern edge of the prairies. But on those rare occasions when a wind from the Atlantic carries clear across the Mississippi Valley, it reaches the High Plains and the Southwest, where the soil is blowing away, without a cloud on board.

When the west winds start to blow in from the Pacific before the beginning of the spring, the high, icy peaks of the Rockies reach up to them almost at the coast, chilling the air so that it cannot carry much moisture and must drop it as snow and rain upon their high ranges and into the narrow valleys between. These winds swing over the mountains, down through the "Inland Empire", and by the time that they reach the High Plains and the Southwest, they too bring nothing that will grow trees.

But after the last snow has been laid on those jagged outcrops of the Rockies that extend into the Southwest, the north winds check themselves—the air hesitates, stands still, and then allows itself to be pushed back by the wet winds that surge up from the two great gulfs at the south. No high mountains rob these winds of their precious freight—they come north through a series of parallel valleys that might have been made by giant fingers dragging up from the south through the earth's surface while it was still soft. Up these valleys the spring winds flow in great rivers of air, carrying heavy freight of clouds, and along the mountain sides, which are their banks, they deliver part of it in rain.

From the upper rim of a canyon it is sometimes possible to see this freight unloaded. As the night comes on the wind rests itself, and the vapor it carries begins to condense. Little clouds form and gather together into a thick mist that fills the valley from rim to rim; the mist seethes quietly against the walls, rises to flow a little over the land, then sinks almost to the river below. All night it swells and falls in soft waves that drench the valley, but when the morning sun whips it, the mist flings itself up over the edge and follows away with the wind.

So long as these winds of spring follow the direct path from either of the two gulfs, they bring water. But let them shift so that they pass first over the great desert plateau of Mexico, and they sweep up the parallel valleys taking up moisture rather than depositing it. They lift up little clouds of dust from the bare watercourses and add to it the sweepings of the desert floor and the dry, powdery soil which the incautious plowman has left exposed. Instead of clouds of rain, these winds load themselves with clouds of dust.

As they stream up over the high plains and on across the tilled fields that were once the prairies, they become veritable Angels of Death. That comfort and prosperity which we have been so many decades trying to establish, they destroy as they go. In 1934 great stretches of dry, powdered earth rose up on the spring winds and traveled as far east as the Atlantic, sifting down on the fields between. In 1936 the winds came again on the heels of a great drought and carried away another heavy load of soil from the high plains and with it buried homesteads further on, to the roof. In 1937 the dust storms came again. What this meant for both those whose soil was blown away and those on whose land it was dropped, was poverty.

Many things must be done to save the people of that part of the country we call the "dust bowl." The Plains must be covered again with grass so that the soil cannot blow. When the infrequent rain does come it must be stored in ponds and reservoirs. But most important of all, trees must be planted in the path of the wind. For trees, if anything, can slow it up, and a slow wind carries no dust.

The answer of the Forest Service to the cry for help that has come from the Great Valley is the shelterbelt! This is the plan.

To grow on a strip of land 100 miles wide and 1,250 miles long, stretching from the Canadian border down into Texas, a wall of trees. This strip is not to be a straight band. It swings in a broadly curving line between the ninety-ninth and one hundredth meridian along the rim of the long-grass prairies. It follows the eastern edge of the high plains, where there is just enough rain to grow trees that do not require much moisture.

This shelterbelt is no solid uniform band of trees spread across the country like a streak of green paint. Trees will be planted around fields, farms, and school houses; they will be planted in solid blocks along ravines or on sandy soils where their roots can reach underground water; but over most of the 1,250 miles they will be planted in strips that will look from the air like thousands of short lines drawn on the map at right angles to the direction from which those dust storms come. Each line will be made up of 20 rows of trees planted from 4 to 6 feet apart with 6 to 8 feet between the rows.

The kinds of trees have been selected with reference to the soil, the temperature, and, most of all, the rainfall. Wherever in the North there is 16 inches of rain a year and in the South 22 inches, trees will grow. They will be taller in North Dakota with its 16 inches than in Texas with 22, because in a warm climate water evaporates more rapidly.

Southwest forests.

Consider what will happen in the center of Nebraska, for instance, when the shelterbelt has grown.

North of the Platte and south of the Niobrara River, the hot air is growing so thin and light that it rises, and other air starts from the dry Mexican plateau to take its place. It begins to pick up sand north of the Rio Grande and from the dry stream beds where the early spring floods have run down to the Pecos. It sings through the spines of the giant Sahuaro cactus and whips the long spiny grey stalks of the Ocotilla against the ground and catches up wisps of dust from the tops of the New Mexico mesas. It tears up through the Texas Panhandle and gathers up the bare plowed earth from the high land in western Kansas faster and faster till in the middle of Nebraska it strikes a low bank of quiet air. The wind must change its direction to get past it and there is no place to go but up. It drops some of its load of dust and rises, but in rising, it loses speed. That low bank of quiet air is packed close against a row of short leafy shrubs— caragana, chokecherry, buckthorn, buffaloberry, sumac, willow, and lilac.

The wind lifts above this thick hedge only to be met with a higher barrier—Russian-olive, plum, willow, and Russian mulberry. No possibility of rushing through that! It lifts again and collides with more willows and with red cedar and Austrian pine. Higher still it finds green ash, American elm, Chinese elm, bur oak, and hackberry; and at the very top, tall cottonwoods and more willows. Down from the top on the other side, the trees are planted to make a more acute angle, for the wind sweeping up from the highest trees does not get down to the ground again till it has gone horizontally nearly 20 times the height of the trees. If the tallest row of trees in the shelterbelt is a hundred feet high—and that is no great height for a really ambitious tree—then the wind will not get down to the ground again for 2,000 feet, and within a mile it will come upon another tree wall like the one it has just hurdled, set straight across its path. Nothing to do but rise over that in the same way—a little more slowly because it had not had space enough to get back its old speed and then another obstructing green wall and another and another to hinder it and slow it down. And when it has hurdled over a hundred of them in quick succession and been a little slowed up at each one, why perhaps it is not such a violent, swashbuckling wind as it started out to be, but a gentle domestic zephyr going too slowly to carry a load of dust and ready to turn a windwill or rock a cradle in the treetop instead.

A, Effect of Shelterbelt on Wind Velocity. B, Shelterbelt—Nebraska

The shelterbelt trees are chosen because they can form a thick mesh from close to the ground to their highest branches—a net to catch the wind, a wall to stop it, a revetment to toss it high above the earth, a dam for the swift rivers of air. They must be full-leafed, bushy, branching things set close together. At the bottom such a mat of underbrush as the woodsman despises because it catches at his clothes, tears his hands, and beats him back when he tries to pass through; above that a tight-meshed fabric knit by the forest, and at the top, like the ridge pole of a house, the tossing, billowing crowns of trees which are naturally tall growing and which, by being crowded together, have had to reach far up to get light to live by.

The perpetual harvest provided for by the shelterbelt will consist not of wood but of the crops which the farmers grow on the land from which it keeps the wind and dust.

Neither are these shelterbelts intended for woodland pastures. A cow is as fond of a young and tender tree as we are of new asparagus. Shall we plant green ash seedlings for cattle feed? All the shelterbelts are to be protected by fences, and it is estimated that this part of the work will require 210,000 miles of fence for which will be needed 65,000,000 posts, 3,400,000 spools of barbed wire, 32,000 kegs of staples to fasten the two together. When these incredible lengths of fence are in place, a cow can do no more than look and long.

If it will be 40 years before enough seedlings can be grown to plant all the shelterbelt; it will be much longer before it is full-grown; but its effect will begin in 5 years. It does not matter that trees have not grown upon these high plains since the Rocky Mountains rose up between them and the Pacific. The fact that 2,000,000 acres have been planted there in the last 60 years shows that they will do it. We can as well change the character of that region by planting trees as we did by planting corn.

Material crops are not all that this great planting of trees will give. There is the rest and relief that come from shade; there is the security that comes with a respite from the conflict against perpetual wind; there is that intangible thing the beauty that trees about the homestead give and the pride and contentment that come from the possession of something lovely. For though there is one beauty of the plains and another of the woods, there is a greater beauty of the two together.