Popular Science Monthly/Volume 19/June 1881/The Value of our Forests
|THE VALUE OF OUR FORESTS.|
IT may be considered as now established, by the most careful and intelligent investigation of the subject, that the highest welfare of almost any country demands that from one fifth to one fourth of its surface shall be covered with trees, and that these shall be, to a good degree, in masses. England will at once be adduced, perhaps, as a country not well wooded, and yet one which compares favorably with others in regard to the conditions of living and her competency to secure the welfare of all classes of her people. But England is specially favored in other respects. She has a moist and equable climate secured to her by her surrounding seas and high latitude, while the general shape of her surface and her geological constitution exempt her from the alternations of flood and drought which in so many other countries result from the absence of forests.
Whether the forests insure a greater rainfall in their vicinity than is received upon an equal area of open land has been disputed among scientific men, though the preponderance of opinion now seems to favor the conclusion that the rainfall is most abundant in wooded regions. This corresponds also with the prevalent belief of the common people, the unscientific but practical observers.
A special committee of the Royal Academy of Vienna, reporting in 1874 upon a "Memoir of Mr. Hofrath Wex upon the Diminution of the Water of Rivers and Streams," used the following language upon this particular point: "The question of the influence of forests upon the amount of precipitation has for some time engaged the attention of naturalists. Such an influence has been asserted, partly from theoretic considerations and partly on account of the entire change presented by the climatic relations of the countries in which the forests have disappeared.... It is probable that such influence exists; but while on the one hand its consequences may be over-estimated, on the other hand there is want of direct proof, inasmuch as the rain measurements have been continued for too short a time, both at stations situated within the woods and outside of them in the open fields....
"The commission consequently concluded that an influence of the woods upon the amount of rain deposited, and especially upon the yearly contribution, is probable, although direct observation does not give sufficient evidence to determine its extent, or positively its existence."
Dr. Rogers, of Mauritius, gives this testimony: "So late as 1864 the island was resorted to by invalids from India, as the 'pearl' of the Indian Ocean—it being then one mass of verdure. But, when the forests were cleared to gain space for sugar-cultivation, the rainfall diminished, the rivers dwindled down to muddy streams, the water became stagnant in cracks, crevices, and natural hollows, while the equable temperature of the island entirely changed, drought was experienced in the midst of the ocean, and thunder-showers were rarely any longer witnessed.... The hills were subsequently planted with trees, and the rivers and streams resumed their former dimensions."
The Island of Ascension was formerly almost a barren rock. The supply of water was very scanty, derived solely from a few springs, and water was often brought from the Cape of Good Hope, and even from England, for the needs of the garrison. About twenty-five years ago the planting of trees and shrubs and the cultivation of the soil were undertaken vigorously. The water-supply has increased with the progress of this work, until now it is excellent, and the garrison and ships visiting the island are supplied with abundance of water and vegetables of various kinds.
Observations in France by M. Fautrat, reported to the Academy of Sciences, showed that, in a dense wood of five hundred hectares, a rain-gauge fixed on a tall poplar received much more water than one of similar height three hundred metres beyond the borders of the woods. Experiments continued during two years confirmed the first results, and an instrument placed over a forest of Pinus sylvestris, at twelve metres' elevation, received ten per cent. more water than one at the same height in the open fields.
But, however the case may be as to the effect of forests upon the amount of rainfall, there can be no doubt that they secure a more equable distribution of the rains than is usual in the open country. They are also great storehouses of moisture. By their myriad leaves they intercept the moisture of the passing clouds or the damp winds, and convey it to the ground, or hold it within their embrace ready to be given out again to a drier atmosphere and to surrounding objects. It is well known, also, that the leaves of the trees, as they fall from year to year and decay, form a spongy soil, which absorbs the rains that fall upon it, and retains them, when otherwise, where there is any declivity, the water would run off almost immediately. The roots of the trees, likewise, penetrating deeply into the ground, conduct a considerable portion of the moisture falling from the clouds far below the spongy surface-soil. Shaded by the leaves and branches of the trees, the moisture thus stored up is not soon evaporated, as it would be from the open ground, but passes off slowly into the surrounding air, and imparts its benefits in the largest measure to the adjacent lands.
While thus sending out their moisture upon the cultivated fields around them, and thereby favoring the growing crops, the forests aid the work of husbandry in another way. By their very mass they serve as a mechanical barrier against the winds, which are often so injurious to crops. Every one who has visited the forest with any frequency knows that he is obliged to go but a short distance within its borders to escape the influence of even a violent wind. So it is also well known that the woodmen engaged in felling trees in the forest, which they usually do in the winter, find no inconvenience from cold winds, as these penetrate the wood but a short distance, even when the trees are stripped of their leaves. And as the woods shelter those within them from the winds, so do they protect the adjacent fields from the blasts which would otherwise sweep over them, and, by their cold, their mechanical force, and their desiccating influence, prove very injurious to crops. The presence of a forest is often, on this account, in its effect upon adjacent lands, equivalent to a change of latitude of several degrees. This is sufficient to make the cultivation of certain crops successful which otherwise could not be undertaken. There are districts of France and Italy where the olive and the orange once flourished, but where now, on account of the change of climate resulting from the extensive removal of the forests which formerly abounded, they can no longer be grown with success. It is not going too far to say that, if one fourth of the land now under cultivation were converted into forests and groves so disposed as to form barriers against the coldest and strongest or most prevalent winds, the remaining three fourths would have more value for agricultural purposes than the whole has at present. This would result from the greater variety of crops which could be raised, their earlier maturity, the greater certainty of growth, and the larger aggregate yield, while there would be, in addition, the large product of the forest itself, to be used, as occasion might demand, for fuel and lumber.
The effect of trees in preventing or diminishing the evaporation from the ground caused by the passage of drying winds is far from being properly appreciated. We often speak of the effect of wind in drying muddy roads as being greater than that of sunshine, while we fail to recognize the fact that the desiccating effect is the same upon the fields as upon the roads.
Forests have a very obvious influence also in preventing the occurrence of floods and droughts. When the rains fall upon the open, unwooded country, unless it is of a quite level character, they flow off at once into the beds of the neighboring streams, and pour their united flood into the larger rivers, swelling their volume rapidly to such an extent that their waters can not be confined within their banks, but break out and overspread the adjacent lands, carrying destruction oftentimes to the growing crops, covering fertile fields with masses of gravel and rubbish of various sorts, interfering with manufacturing interests, and often destroying life itself. These floods are succeeded by periods of drought. The flow of water in the streams shrinks away, often leaving their beds almost dry. As a consequence, crops and herds suffer, the mill-wheels are stopped or turn but slowly and feebly, the transportation of merchandise is impeded, and the various industries of life suffer. The forests prevent such a deplorable condition of things. The spongy soil formed by their fallen leaves, accumulated for years, retains the rain which falls upon it as in a great reservoir, and obliges it to flow off gradually instead of with a sudden flood. The difference in the operation in the two cases may be likened to that between the flow of the rain from a smoothly shingled house-roof and from one covered with thatch. In the one case the water runs at once to the ground without any impediment. In the other it sinks into the straw to a considerable depth and trickles thence for days perhaps after the rain has ceased to fall. So, our hillsides and mountain-slopes, where the forests are most usually found, are the world's great roofs or water-sheds, from which, if they are thatched with trees, the water flows off slowly and in the most desirable manner into the streams and upon the lands of the regions below, but, if stripped of this protecting covering, then with sudden and disastrous flood which no art of man can withstand.
This is well illustrated by the report of the effect of a storm in two neighboring ravines in the valley of the Durance in southeastern France, the Ravine de St. Phalez and the Ravine de la Combe d'Yeuse. St. Phalez runs north and south, has a basin of reception fifty hectares (one hundred and twenty-five acres) in extent, is well cultivated and has an argillaceous soil. Combe d'Yeuse is much more steep, has a basin of reception of two hundred and fifty hectares (seven hundred and twenty-five acres), and is covered with pines and oaks. In other respects the two ravines are alike.
In September, 1864, an abundant rainfall took place. On the morning after the rain the ravine of St. Phalez was flowing with a small stream. The Combe d'Yeuse was dry. During the day a waterspout struck the mountain and prevailed for not more than forty minutes; hardly bad it begun when the torrent of St. Phalez became awful; it filled the ravine from bank to bank, seizing and carrying off rocks which had been used to form a road, which was considered safe against all contingencies. At the same time, that of Combe d'Yeuse and all those traversing wooded lands remained dry or carried a comparatively insignificant quantity of water.
The forest conservator describes a second scene on the same spot in the following October. In a few minutes after the rain began, the torrent of St. Phalez gushed forth with the same destructive effect as before. But after an entire day of rain a small stream appeared coming down the Ravine d'Yeuse, which increased for three days and then for two declined. The only damage done was to a little footpath. "Thus we have," says the reporter, "two torrents very near to each other, and exposed to the same conditions, except that the basin drained by the one comprises fifty hectares of cultivated lands, that of the other two hundred and fifty hectares of woodlands. The first receives and allows to flow away the waters of the greater part of a storm in a few hours at most, causing thereby considerable damage; the second, which has received a greater quantity of rain, stores it—keeps it for two days—evidently retaining a portion of it, and takes three or four days to yield up the surplus, which it does in the form of a limpid and inoffensive stream."
So also in the colder latitudes, where during the wintry months the moisture of the atmosphere is precipitated in the form of snow and accumulates often to a great depth, the conservative influence of the forest is very obvious. The temperature of the woods is warmer in winter, as it is cooler in summer, than that of the open ground. Sheltered from the winds and, to a considerable degree, from the cold, the snows themselves forming a protecting covering, the earth seldom freezes in the forest, and the warmth from the ground below gradually melts the snow and so feeds the springs and streams as to maintain in them an equable flow. As the warmer sun and wind of advancing spring-time begin to heat the surface of the ground, the screen of the trees prevents their influence from being so sensibly felt in the woods as in the open fields. The result is, that the snows dissolve gradually, and the resultant water, sinking in the first place and for the most part into the spongy, leafy soil, flows away gently, as do the rains of summer-time, into the valleys and fields below. But, when the forests have been removed, the case is very different. The snows, no longer screened from the sun's rays and the warm winds by the interposed foliage or even the naked trunks of the trees, are rapidly dissolved, often before the earth beneath or the ground over which the waters must flow has been unlocked from the wintry frosts. As a necessary result, thousands of rivulets are formed almost at once, which are precipitated into the adjacent streams, whose rapidly increased volumes are hurried to the larger streams below, and thus we have our spring floods, often so destructive to property as well as life.
There is another aspect in which the forests are to be regarded, but in which we have hardly begun to consider them properly, and that is the economical one, as the continuous producers of fuel, and of lumber for use in the mechanic arts. With our boundless area of cheap lands, covered originally with forests to such an extent that the trees have been regarded as an obstruction to agriculture, and so to be swept away often by fire rather than to await the slower process of the axe, we have thought little of the forest as anything of permanent value. Added to this the practically unlimited area of our coal-fields has served to prevent any apprehension of loss from the destruction of the forests. That there is ever to come a time when we may suffer from a scarcity of wood for fuel or for the arts, hardly seems to have entered many minds.
Very different is the settled feeling in other countries in respect to the value of the forests. When in some portions of Europe the peasant has to travel miles on foot to bring home, as the result of a whole day's labor, an armful of wood to burn, and can afford to bake bread but once in six months because fuel is so scarce and dear; and when England, with only four or five per cent. of woodland, is gravely and anxiously figuring out the time when her coal-fields will be exhausted, and her vast manufacturing interest will be at the expense of purchasing its fuel from other countries or suffer inevitable decline or extinction—the importance of the forest, in an economical as well as in a political point of view, becomes at once apparent. The coal-fields are not growing, and never can be made to grow again. They were deposited ages since, once for all, and, so far as we can see, are to have no successors or substitutes but the living trees, following each other from generation to generation.
It is not to be wondered at, therefore, that the European nations, having learned its value by its loss in greater or less measure, see the forest to be an important factor in all that constitutes national life and comfort, and have given it a place in their thoughts and in their practical arrangements which we have not in ours. It is not surprising that they should establish schools for the special purpose of teaching all that relates to the growth and preservation of the forest, that they should make it a matter of national and political concern, and that the literature of the subject should be so extensive that it is estimated that from the German press alone as many as a hundred volumes and pamphlets on forestry, in some of its aspects, are issued annually.
Germany has given much attention to her forests ever since the days of Charlemagne, who is said to have afforested the Ardennes and established the forest of Osnabrück. The sovereigns of Germany have treated the woodlands not merely as preserves for game and places for royal enjoyment in its pursuit, but have encouraged their cultivation for the production of fuel and timber, as well as for their value in other respects. It will indicate the careful attention given to the forests in Germany, when we find it officially reported that the net returns of the forests are from two to twelve thalers per hectare (two and a half acres), and the value of the land together with its crop is estimated at fifty-two and a half thalers per hectare.
England, now having a smaller percentage of forest than any country of Europe, with the exception of Spain and Portugal, was well wooded at the remotest historical period; but as early as the thirteenth century, in the time of Henry III, she found it necessary to import pine lumber, and apprehension began to be felt of the failure of the forests.
Hardly anything has been done in England compared with what has been done in Germany, France, and other Continental countries, to establish and protect the forests. Individuals have done something, as for instance the Duke of Athol, who, in the early part of the present century, planted several thousand acres of the barren hillsides of Scotland with the larch. His successors in the dukedom have followed his worthy example and extended the woodland area, and demonstrated that the work of forestry, rightly prosecuted, is pecuniarily profitable as well as desirable in other respects. It is only within the last few years that the English Government has shown any considerable interest in this subject. Some action has been taken for the purpose of protecting the forests in her colonies from destruction, and quite recently a few thousand acres in England itself have been planted with oaks for the purpose of meeting the future demands of the navy.
The subject of the preservation of the woods is one of the highest practical importance. Man has often acted very unwisely in the exercise of his lordship of the forest, and has suffered greatly, and continues to suffer, in consequence. Great districts once populous, and powerful as populous, have been almost converted into deserts, some of them quite into deserts, and their people diminished in numbers and in power, as the result of a wanton destruction of their forests. France and other European countries have been swept by disastrous floods, or rent by torrents rushing down their mountain-slopes, and carrying masses of rock and gravel into the valleys and plains below, because the forests which would have held the floods in check have been recklessly consumed; and now forest schools are established, and all the power and wealth of governments are put forth for the purpose of staying these evil effects, if possible, by replanting the mountain-sides with trees, and thus restoring the protection which Nature had originally provided. Climates have been changed for the worse, the agricultural productiveness of countries has been lessened, provinces have been depopulated, the health and happiness of nations have been diminished, by the destruction of the forests; and now science and art and governmental authority are invoked to unite their powers for the purpose of remedying the evil results.
We are treading the same course that other nations have trod. Says Humboldt, "Men, in all climates, seem to bring upon future generations two calamities at once—a want of fuel and a scarcity of water." With our comparatively sparse population and our continental stretch of forest, it has hardly entered our minds that we could be improvident in the use of our woodlands. It has seemed to us that we had enough, and that for ever; and so we have consumed the forests with a recklessness which has perhaps never been surpassed. We have even sacrificed them by carelessness, or in the wantonness of a temporary greed, utterly regardless of the future. Forests which have been the growth of centuries have been swept off in a day. The lumberman cuts the few noblest trees, or takes only the choicest portions of them for the purposes of the arts, and burns the rest to ashes, thereby precluding another growth upon the spot. The miner does the same, cutting off the already sparse forests, and taking no pains to replace them. And so it is happening that our forest area, particularly in the more recently settled portions of the country, is rapidly diminishing. The opening of the great agricultural regions of the Ohio and the Mississippi Valleys, with their superior attractiveness, has lessened the value of much of the Eastern lands for the purpose of tillage, and, in some portions of New England particularly, what were once corn-fields and pastures, have been abandoned by the cultivator and a growth of trees has come in. But as a whole our forest area has been diminishing for a long time, and never more rapidly than within the last decade. Serious evils have already come from this wasting of the woods, but they have been spread over so wide a stretch of territory that attention has not been called to them in a way to arouse general attention or lead to their remedy. Our streams have a diminished flow of water, while they are marked by alternations of floods and droughts, much greater than formerly prevailed. They are not navigable for so long distances, nor for so large a class of boats, as they once were, nor do they furnish so large or so uniform a supply for the mill-wheels as they did in earlier times. Changes of climate have also resulted, affecting the health of the people and the productiveness of the fields. These effects have been noticed in a multitude of cases. But, in most instances, they have been regarded as isolated and local occurrences, and have not been attributed to their true cause.
In some of our Western States which are almost treeless, the beneficial influence of forests has been forced upon the attention of the people. It has been found that life may not be worth living, though on the richest soil, if that be all. A writer of acknowledged authority, in a lecture before the Illinois Industrial University, speaking of the importance of trees as a shelter of crops from injurious winds, says, "I think it may be safely estimated that an average of one twelfth part of all our crops of grain and large fruits is destroyed by violent winds, which such a system of protection, or its equivalent in groves, would so far check as to prevent the destruction." Another, whose words are quoted in the "Iowa Horticultural Report" for 1875, speaking of the wintry storms of the Northwest, sometimes known as "blizzards," says, "More people have been frozen within the last year in northwest Iowa and west Minnesota than were ever murdered by the Indians in those counties since their settlement." And he says, in regard to a remedy: "I see none that would do but timber-planting. It alone would stop these terrible winds, modify the climate, and furnish landmarks for the traveler." So Professor Lacy, of the State University, in an address to the Minnesota State Forestry Association, says: "The Minnesota State Forestry Association was organized to meet and deal with the stern realities of facts. It was organized to meet the fact that over more than one third of the great State of Minnesota the winds rush with a howling fury and with a bitter cold that neither beast nor fruit-tree can resist or withstand, and for miles not a single forest-tree rears its head in protest. It was organized to meet the fact that, in a climate which affords six months of winter, much of it fearfully severe, there are thousands of farms on which there does not grow one particle of fuel, and on which it can not be obtained without the expenditure of both money and labor by a people often destitute of means. It was organized to meet the fact that for miles and miles there is not a single landmark to guide the benumbed and benighted traveler. It was organized to meet the fact that to induce human beings to make their houses on such farms is downright inhumanity.... The force of the winds on our Western prairies can not be conceived of by you who have always lived within the area of forests. They are simply terrible to endure and appalling to contemplate. They carry death alike to the unprotected beast and the more tender forms of arboreal life."
It is not surprising that people living amid such exposures of life and property, and seeing so manifestly as they do that these are attributable to the absence of trees, should bestir themselves in seeking the appropriate remedy, that they should organize, as they have done, forestry associations, appoint arbor-days, and engage the aid of the State itself in offering bounties for tree-planting, and in exempting forest plantations for a time from taxation. The latter has been done in several of the Western States, and already the work of tree planting has wrought a perceptible change on many a farm, as to appearance, comfort of living, and productiveness. But the work that is needed is a great one, a work not to be accomplished by planting in a few States or portions of States lines of quick-growing, soft-wooded trees, which may make tolerable wind-breaks in five or six years. This is hardly more than a makeshift at the best. The work is broader and more comprehensive than that, and one which for its due accomplishment needs an intelligent comprehension of the facts involved in the case, and their far-reaching relations. It is a matter not of present or local exigency merely, but of general and abiding importance. The future of the whole country is involved in it.
Champollion is reported as saying in reference to the great desert of Northern Africa: "And so the astonishing truth dawns upon us that this desert may once have been a region of groves and fountains, and the abode of happy millions. Is there any crime against Nature which draws down a more terrible curse than that of stripping Mother Earth of her sylvan covering? The hand of man has produced this desert, and, I verily believe, every other desert upon the surface of this earth. Earth was Eden once, and our misery is the punishment of our sins against the world of plants. The burning sun of the desert is the angel with the flaming sword who stands between us and paradise."
An awakening of general interest on this subject is needed. To this end the most important step is to get before the people as widely as possible the facts showing the importance of the forests in their relations to climate, to water-supply, to floods and droughts, to commerce and manufactures, to agriculture and to health; the rapidity with which we are destroying our forests and bringing upon ourselves the natural and inevitable results of that course. The history of other nations, as related to their treatment of the forests, should be made widely known, and the danger that this land, or portions of it, by the reckless destruction of its forests, may be converted into a desert, as other lands have been. Thus may we hope to arouse a general interest in the trees, and a disposition to cherish them as our best friends. Meanwhile, let tree-planting be encouraged. Let it be shown, as it has been again and again, that much of our poor and what is commonly regarded as waste land can be made to yield a handsome profit by being devoted to the growth of trees; and that our rough hills and mountain-sides can thus be made of direct pecuniary value, while at the same time they are rendered objects of beauty and the means of protecting our springs, maintaining the flow of our streams, and promoting health and prosperity. With this awakened interest in the forests, sylviculture will come to be one of our arts. We want an intelligent and scientific observation of the facts in regard to trees as related to our various soils and situations. The adaptation of trees to one climate or another, their comparative value for one purpose or another, the obstacles to successful planting—these, and many other things, need to be known as they are not yet known. Some things we can learn from the experiments which have been made and the knowledge which has been gained in Europe. But so different are the trees there and here, and so different the conditions of soil and climate, that the problem set before us is virtually a new one, which must be worked out carefully and patiently on our own ground. The most important advance in this direction yet made here, so far as we know, has been by the Bussey Institute, in connection with the Arnold Arboretum, at Brookline, Massachusetts. Under the able and judicious management of Professor Sargent, it has already fine plantations of forest-trees, has diffused much valuable information in regard to the growth and importance of trees, and has secured the planting of a large number in various parts of the country. On the foundation of such institutions will naturally be built up in due time schools of instruction in forestry like those of Europe, which will have a recognized and permanent place among us. The European schools of forestry will form the subject of another article.