The Earth as Modified by Human Action.

by George P. Marsh.

PREFACE TO THE FIRST EDITION.

The object of the present volume is: to indicate the character and, approximately, the extent of the changes produced by human action in the physical conditions of the globe we inhabit; to point out the dangers of imprudence and the necessity of caution in all operations which, on a large scale, interfere with the spontaneous arrangements of the organic or the inorganic world; to suggest the possibility and the importance of the restoration of disturbed harmonies and the material improvement of waste and exhausted regions; and, incidentally, to ill.u.s.trate the doctrine that man is, in both kind and degree, a power of a higher order than any of the other forms of animated life, which, like him, are nourished at the table of bounteous nature.

In the rudest stages of life, man depends upon spontaneous animal and vegetable growth for food and clothing, and his consumption of such products consequently diminishes the numerical abundance of the species which serve his uses. At more advanced periods, he protects and propagates certain esculent vegetables and certain fowls and quadrupeds, and, at the same time, wars upon rival organisms which prey upon these objects of his care or obstruct the increase of their numbers. Hence the action of man upon the organic world tends to derange its original balances, and while it reduces the numbers of some species, or even extirpates them altogether, it multiplies other forms of animal and vegetable life.

The extension of agricultural and pastoral industry involves an enlargement of the sphere of man's domain, by encroachment upon the forests which once covered the greater part of the earth's surface otherwise adapted to his occupation. The felling of the woods has been attended with momentous consequences to the drainage of the soil, to the external configuration of its surface, and probably, also, to local climate; and the importance of human life as a transforming power is, perhaps, more clearly demonstrable in the influence man has thus exerted upon superficial geography than in any other result of his material effort.

Lands won from the woods must be both drained and irrigated; river-banks and maritime coasts must be secured by means of artificial bulwarks against inundation by inland and by ocean floods; and the needs of commerce require the improvement of natural and the construction of artificial channels of navigation. Thus man is compelled to extend over the unstable waters the empire he had already founded upon the solid land.

The upheaval of the bed of seas and the movements of water and of wind expose vast deposits of sand, which occupy s.p.a.ce required for the convenience of man, and often, by the drifting of their particles, overwhelm the fields of human industry with invasions as disastrous as the incursions of the ocean. On the other hand, on many coasts, sand-hills both protect the sh.o.r.es from erosion by the waves and currents, and shelter valuable grounds from blasting sea-winds. Man, therefore, must sometimes resist, sometimes promote, the formation and growth of dunes, and subject the barren and flying sands to the same obedience to his will to which he has reduced other forms of terrestrial surface.

Besides these old and comparatively familiar methods of material improvement, modern ambition aspires to yet grander achievements in the conquest of physical nature, and projects are meditated which quite eclipse the boldest enterprises. .h.i.therto undertaken for the modification of geographical surface.

The natural character of the various fields where human industry has effected revolutions so important, and where the multiplying population and the impoverished resources of the globe demand new triumphs of mind over matter, suggests a corresponding division of the general subject, and I have conformed the distribution of the several topics to the chronological succession in which man must be supposed to have extended his sway over the different provinces of his material kingdom. I have, then, in the introductory chapter, stated, in a comprehensive way, the general effects and the prospective consequences of human action upon the earth's surface and the life which peoples it. This chapter is followed by four others in which I have traced the history of man's industry as exerted upon Animal and Vegetable Life, upon the Woods, upon the Waters, and upon the Sands; and to these I have added a concluding chapter upon Man.

It is perhaps superfluous to add, what indeed sufficiently appears upon every page of the volume, that I address myself not to professed physicists, but to the general intelligence of observing and thinking men; and that my purpose is rather to make practical suggestions than to indulge in theoretical speculations more properly suited to a different cla.s.s from that for which I write.

GEORGE P. MARSH.

December 1, 1868.

PREFACE TO THE PRESENT EDITION.

In preparing for the press an Italian translation of this work, published at Florence in 1870, I made numerous corrections in the statement of both facts and opinions; I incorporated into the text and introduced in notes a large amount of new data and other ill.u.s.trative matter; I attempted to improve the method by differently arranging many of the minor subdivisions of the chapters; and I suppressed a few pa.s.sages which teemed to me superfluous. In the present edition, which is based on the Italian translation, I have made many further corrections and changes of arrangement of the original matter; I have rewritten a considerable portion of the work, and have made, in the text and in notes, numerous and important additions, founded partly on observations of my own, partly on those of other students of Physical Geography, and though my general conclusions remain substantially the same as those I first announced, yet I think I may claim to have given greater completeness and a more consequent and logical form to the whole argument

Since the publication of the original edition, Mr. Elisee Reclus, in the second volume of his admirable work, La Terre (Paris, 1868), lately made accessible to English-reading students, has treated, in a general way, the subject I have undertaken to discuss. He has, however, occupied himself with the conservative and restorative, rather than with the destructive, effects of human industry, and he has drawn an attractive and encouraging picture of the ameliorating influences of the action of man, and of the compensations by which he, consciously or unconsciously, makes amends for the deterioration which he has produced in the medium he inhabits. The labors of Mr. Reclus, therefore, though aiming at a much higher and wider scope than I have had in view, are, in this particular point, a complement to my own. I earnestly recommend the work of this able writer to the attention of my readers.

George P. Marsh

Rome, May 1, 1878.

THE EARTH AS MODIFIED BY HUMAN ACTION.

CHAPTER 1.

INTRODUCTORY.

Natural Advantages of the Territory of the Roman Empire.--Physical Decay of that Territory.--Causes of the Decay.--Reaction of Man on Nature.-- Observation of Nature.--Uncertainty of Our Historical Knowledge of Ancient Climates.--Uncertainty of Modern Meteorology.--Stability of Nature.--Formation of Bogs--Natural Conditions Favorable to Geographical Change.--Destructiveness of Man--Human and Brute Action Compared.--Limits of Human Power.--Importance of Physical Conservation and Restoration--Uncertainty as to Effects of Human Action.

Natural Advantages of the Territory of the Roman Empire.

The Roman Empire, at the period of its greatest expansion, comprised the regions of the earth most distinguished by a happy combination of physical conditions. The provinces bordering on the princ.i.p.al and the secondary basins of the Mediterranean enjoyed in healthfulness and equability of climate, in fertility of soil, in variety of vegetable and mineral products, and in natural facilities for the transportation and distribution of exchangeable commodities, advantages which have not been possessed in any equal degree by any territory of like extent in the Old World or the New. The abundance of the land and of the waters adequately supplied every material want, ministered liberally to every sensuous enjoyment. Gold and silver, indeed, were not found in the profusion which has proved so baneful to the industry of lands richer in veins of the precious metals; but mines and river beds yielded them in the spare measure most favorable to stability of value in the medium of exchange, and, consequently, to the regularity of commercial transactions. The ornaments of the barbaric pride of the East, the pearl, the ruby, the sapphire, and the diamond--though not unknown to the luxury of a people whose conquests and whose wealth commanded whatever the habitable world could contribute to augment the material splendor of their social life--were scarcely native to the territory of the empire; but the comparative rarity of these gems in Europe, at somewhat earlier periods, was, perhaps, the very circ.u.mstance that led the cunning artists of cla.s.sic antiquity to enrich softer stones with engravings, which invest the common onyx and cornelian with a worth surpa.s.sing, in cultivated eyes, the l.u.s.tre of the most brilliant oriental jewels.

Of these manifold blessings the temperature of the air, the distribution of the rains, the relative disposition of land and water, the plenty of the sea, the composition of the soil, and the raw material of the primitive arts, were wholly gratuitous gifts. Yet the spontaneous nature of Europe, of Western Asia, of Libya, neither fed nor clothed the civilized inhabitants of those provinces. The luxuriant harvests of cereals that waved on every field from the sh.o.r.es of the Rhine to the banks of the Nile, the vines that festooned the hillsides of Syria, of Italy and of Greece, the olives of Spain, the fruits of the gardens of the Hesperides, the domestic quadrupeds and fowls known in ancient rural husbandry--all these were original products of foreign climes, naturalized in new homes, and gradually enn.o.bled by the art of man, while centuries of persevering labor were expelling the wild vegetation, and fitting the earth for the production of more generous growths. Every loaf was eaten in the sweat of the brow. All must be earned by toil. But toil was nowhere else rewarded by so generous wages; for nowhere would a given amount of intelligent labor produce so abundant, and, at the same time, so varied returns of the good things of material existence.

Physical Decay of the Territory of the Roman Empire.

If we compare the present physical condition of the countries of which I am speaking, with the descriptions that ancient historians and geographers have given of their fertility and general capability of ministering to human uses, we shall find that more than one-half their whole extent--not excluding the provinces most celebrated for the profusion and variety of their spontaneous and their cultivated products, and for the wealth and social advancement of their inhabitants--is either deserted by civilized man and surrendored to hopeless desolation, or at least greatly reduced in both productiveness and population. Vast forests have disappeared from mountain spurs and ridges; the vegetable earth acc.u.mulated beneath the trees by the decay of leaves and fallen trunks, the soil of the alpine pastures which skirted and indented the woods, and the mould of the upland fields, are washed away; meadows, once fertilized by irrigation, are waste and unproductive because the cisterns and reservoirs that supplied the ancient ca.n.a.ls are broken, or the springs that fed them dried up; rivers famous in history and song have shrunk to humble brooklets; the willows that ornamented and protected the banks of the lesser watercourses are gone, and the rivulets have ceased to exist as perennial currents, because the little water that finds its way into their old channels is evaporated by the droughts of summer, or absorbed by the parched earth before it reaches the lowlands; the beds of the brooks have widened into broad expanses of pebbles and gravel, over which, though in the hot season pa.s.sed dryshod, in winter sealike torrents thunder; the entrances of navigable streams are obstructed by sandbars; and harbors, once marts of an extensive commerce, are shoaled by the deposits of the rivers at whose mouths they lie; the elevation of the beds of estuaries, and the consequently diminished velocity and increased lateral spread of the streams which flow into them, have converted thousands of leagues of shallow sea and fertile lowland into unproductive and miasmatic mora.s.ses.

Besides the direct testimony of history to the ancient fertility of the now exhausted regions to which I refer--Northern Africa, the greater Arabian peninsula, Syria, Mesopotamia, Armenia and many other provinces of Asia Minor, Greece, Sicily, and parts of even Italy and Spain--the mult.i.tude and extent of yet remaining architectural ruins, and of decayed works of internal improvement, show that at former epochs a dense population inhabited those now lonely districts. Such a population could have been sustained only by a productiveness of soil of which we at present discover but slender traces; and the abundance derived from that fertility serves to explain how large armies, like those of the ancient Persians, and of the Crusaders and the Tartars in later ages, could, without an organized commissariat, secure adequate supplies in long marches through territories which, in our times, would scarcely afford forage for a single regiment.

It appears then, that the fairest and fruitfulest provinces of the Roman Empire, precisely that portion of terrestrial surface, in short, which, about the commencement of the Christian era, was endowed with the greatest superiority of soil, climate, and position, which had been carried to the highest pitch of physical improvement, and which thus combined the natural and artificial conditions best fitting it for the habitation and enjoyment of a dense and highly refined and cultivated population, are now completely exhausted of their fertility, or so diminished in productiveness, as, with the exception of a few favored oases that have escaped the general ruin, to be no longer capable of affording sustenance to civilized man. If to this realm of desolation we add the now wasted and solitary soils of Persia and the remoter East that once fed their millions with milk and honey, we shall see that a territory larger than all Europe, the abundance of which sustained in bygone centuries a population scarcely inferior to that of the whole Christian world at the present day, has been entirely withdrawn from human use, or, at best, is thinly inhabited by tribes too few in numbers, too poor in superfluous products, and too little advanced in culture and the social arts, to contribute anything to the general moral or material interests of the great commonwealth of man.

Causes of this Decay.

The decay of these once flourishing countries is partly due, no doubt, to that cla.s.s of geological causes whose action we can neither resist nor guide, and partly also to the direct violence of hostile human force; but it is, in a far greater proportion, either the result of man's ignorant disregard of the laws of nature, or an incidental consequence of war and of civil and ecclesiastical tyranny and misrule.

Next to ignorance of these laws, the primitive source, the causa causarum, of the acts and neglects which have blasted with sterility and physical decrepitude the n.o.blest half of the empire of the Caesars, is, first, the brutal and exhausting despotism which Rome herself exercised over her conquered kingdoms, and even over her Italian territory; then, the host of temporal and spiritual tyrannies which she left as her dying curse to all her wide dominion, and which, in some form of violence or of fraud, still brood over almost every soil subdued by the Roman legions. [Footnote: In the Middle Ages, feudalism, and a nominal Christianity, whose corruptions had converted the most beneficent of religions into the most baneful of superst.i.tions, perpetuated every abuse of Roman tyranny, and added new oppressions and new methods of extortion to those invented by older despotisms. The burdens in question fell most heavily on the provinces that had been longest colonized by the Latin race, and those are the portions of Europe which have suffered the greatest physical degradation. "Feudalism," says Blanqui, "was a concentration of scourges. The peasant, stripped of the inheritance of his fathers, became the property of inflexible, ignorant, indolent masters; he was obliged to travel fifty leagues with their carts whenever they required it; he labored for them three days in the week, and surrendered to them half the product of his earnings during the other three; without their consent he could not change his residence, or marry. And why, indeed, should he wish to marry, when he could scarcely save enough to maintain himself The Abbot Alcuin had twenty thousand slaves, called SERFS, who were forever attached to the soil. This is the great cauue of the rapid depopulation observed in the Middle Ages, and of the prodigious mult.i.tude of monasteries which sprang up on every side. It was doubtless a relief to such miserable men to find in the cloisters a retreat from oppression; but the human race never suffered a more cruel outrage, industry never received a wound better calculated to plunge the world again into the darkness of the rudest antiquity. It suffices to say that the prediction of the approaching end of the world, industriously spread by the rapacious monks at this time, was received without terror."--Resume de l'Histoire du Commerce, p. 156.] Man cannot struggle at once against human oppression and the destructive forces of inorganic nature. "When both are combined against him, he succ.u.mbs after a shorter or longer struggle, and the fields he has won from the primeval wood relapse into their original state of wild and luxuriant, but unprofitable forest growth, or fall into that of a dry and barren wilderness. The abbey of Saint-Germain-des-Pres, which, in the time of Charlemagne, had possessed a million of acres, was, down to the Revolution, still so wealthy, that the personal income of the abbot was 300,000 livres. Theabbey of Saint-Denis was nearly as rich as that of Saint-Germain-des-Pres.--Lavergne, Economie Rurale de la France, p. 104.

Paul Louis Courier quotes from La Bruyere the following striking picture of the condition of the French peasantry in his time: "One sees certain dark, livid, naked, sunburnt, wild animals, male and female, scattered over the country and attached to the soil, which they root and turn over with indomitable perseverance. They have, as it were, an articulate voice, and when they rise to their feet, they show a human face. They are, in fact, men; they creep at night into dens, where they live on black bread, water, and roots. They spare other men the labor of ploughing, Bowing, and harvesting, and therefore deserve some small share of the bread they have grown." "These are his own words," adds Courier, "and he is speaking of the fortunate peasants, of those who had work and bread, and they were then the few."--Pet.i.tion a la Chambre des Deputes pour les Villageois l'en empeche ce danser.

Arthur Young, who travelled in France from 1787 to 1789, gives, in the twenty-first chapter of his Travels, a frightful account of the burdens of the rural population even at that late period. Besides the regular governmental taxes, and a mult.i.tude of heavy fines imposed for trifling offense, he enumerates about thirty seignorial rights, the very origin and nature of some of which are now unknown, while those of some others are as repulsive to humanity and morality, as the worst abuses ever practised by heathen despotism. But Young underrates the number of these oppressive impositions. Moreau de Jonnes, a higher authority, a.s.serts that in a brief examination he had discovered upwards of three hundred distinct lights of the feudatory over the person or the property of his va.s.sal. See Etat Economique et Social de la France, Paris, 1890, p.

389. Most of these, indeed, had been commuted for money payments, and were levied on the peasantry as pecuniary imposts for the benefit of prelates and lay lords, who, by virtue of their n.o.bility, were exempt from taxation. The collection of the taxes was enforced with unrelenting severity. On one occasion, in the reign of Louis XIV., the troops sent out against the recreant peasants made more than 3,000 prisoners, of whom 400 were condemned to the galleys for life, and a number so large that the government did not dare to disclose it, were hung on trees or broken on the wheel.--Moreau de Jonnes, Etat Economique et Social de la France, p. 420. Who can wonder at the hostility of the French plebeian cla.s.ses towards the aristocracy in the days of the Revolution?

Rome imposed on the products of agricultural labor in the rural districts taxes which the sale of the entire harvest would scarcely discharge; she drained them of their population by military conscription; she impoverished the peasantry by forced and unpaid labor on public works; she hampered industry and both foreign and internal commerce by absurd restrictions and unwise regulations. [Footnote: Commerce, in common with all gainful occupations except agriculture, was despised by the Romans, and the exercise of it was forbidden to the higher ranks. Cicero, however, admits that though retail trade, which could only prosper by lying and knavery, was contemptible, yet wholesale commerce was not altogether to be condemned, and might even be laudable, provided the merchant retired early from trade and invested his gaits in farm lands.--De Officiis, lib. i.,42.] Hence, large tracts of land were left uncultivated, or altogether deserted, and exposed to all the destructive forces which act with such energy on the surface of the earth when it is deprived of those protections by which nature originally guarded it, and for which, in well-ordered husbandry, human ingenuity has contrived more or less efficient subst.i.tutes. [Footnote: The temporary depopulation of an exhausted soil may be, in some cases, a physical, though, like fallows in agriculture, a dear-bought advantage.

Under favorable circ.u.mstances, the withdrawal of man and his flocks allows the earth to clothe itself again with forests, and in a few generations to recover its ancient productiveness. In the Middle Ages, worn-out fields were depopulated, in many parts of the Continent, by civil and ecclesiastical tyrannies, which insisted on the surrender of the half of a loaf already too small to sustain its producer. Thus abandoned, these lands often relapsed into the forest state, and, some centuries later, were again brought under cultivation with renovated fertility.] Similar abuses have tended to perpetuate and extend these evils in later ages, and it is but recently that, even in the most populous parts of Europe, public attention has been half awakened to the necessity of restoring the disturbed harmonies of nature, whose well-balanced influences are so propitious to all her organic offspring, and of repaying to our great mother the debt which the prodigality and the thriftlessness of former generations have imposed upon their successors--thus fulfilling the command of religion and of practical wisdom, to use this world as not abusing it.

Reaction of Man on Nature.

The revolutions of the seasons, with their alternations of temperature and of length of day and night, the climates of different zones, and the general conditions and movements of the atmosphere and the seas, depend upon causes for the most part cosmical, and, of course, wholly beyond our control. The elevation, configuration, and composition of the great ma.s.ses of terrestrial surface, and the relative extent and distribution of land and water, are determined by geological influences equally remote from our jurisdiction. It would hence seem that the physical adaptation of different portions of the earth to the use and enjoyment of man is a matter so strictly belonging to mightier than human powers, that we can only accept geographical nature as we find her, and be content with such soils and such skies as she spontaneously offers.

But it is certain that man has reacted upon organized and inorganic nature, and thereby modified, if not determined, the material structure of his earthly home. The measure of that reaction manifestly const.i.tutes a very important element in the appreciation of the relations between mind and matter, as well as in the discussion of many purely physical problems. But though the subject has been incidentally touched upon by many geographers, and treated with much fulness of detail in regard to certain limited fields of human effort and to certain specific effects of human action, it has not, as a whole, so tar as I know, been made matter of special observation, or of historical research, by any scientific inquirer. Indeed, until the influence of geographical conditions upon human life was recognized as a distinct branch of philosophical investigation, there was no motive for the pursuit of such speculations; and it was desirable to inquire how far we have, or can, become the architects of our own abiding place, only when it was known how the mode of our physical, moral, and intellectual being is affected by the character of the home which Providence has appointed, and we have fashioned, for our material habitation. [Footnote:G.o.ds Almagt wenkte van den troon, En schiep elk volk een land ter woon: Hier vestte Zij een grondgebied, Dat Zij ona zelven scheppon llet.] It is still too early to attempt scientific method in discussing this problem, nor is our present store of the necessary facts by any means complete enough to warrant me in promising any approach to fulness of statement respecting them.

Systematic observation in relation to this subject has hardly yet begun, and the scattered data which have chanced to be recorded have never been collected. It has now no place in the general scheme of physical science, and is matter of suggestion and speculation only, not of established and positive conclusion. At present, then, all that I can hope is to excite an interest in a topic of much economical importance, by pointing out the directions and ill.u.s.trating the modes in which human action has been, or may be, most injurious or most beneficial in its influence upon the physical conditions of the earth we inhabit We cannot always distinguish between the results of man's action and the effects of purely geological or cosmical causes. The destruction of the forests, the drainage of lakes and marshes, and the operations of rural husbandry and industrial art have unquestionably tended to produce great changes in the hygrometric, thermometric, electric, and chemical condition of the atmosphere, though we are not yet able to measure the force of the different elements of disturbance, or to say how far they have been neutralised by each other, or by still obscurer influences; and it is equally certain that the myriad forms of animal and vegetable life, which covered the earth when man first entered upon the theatre of a nature whose harmonies he was destined to derange, have been, through his interference, greatly changed in numerical proportion, sometimes much modified in form and product, and sometimes entirely extirpated. [Footnote: Man has not only subverted the natural numerical relations of wild as well as domestic quadrupeds, fish, birds, reptile, insect, and common plants, and even of still humbler tribes of animal and vegetable life, but he has effected in the forms, habits, nutriment and products of the organisms which minister to his wants and his pleasures, changes which, more than any other manifestaion of human energy, resemble the exercise of a creative power. Even wild animals have been compelled by him, through the destruction of plants and insects which furnished their proper aliment, to resort to food belonging to a different kingdom of nature. Thus a New Zealand bird, originally granivorous and insectivorous, has become carnivorous, from the want of its natural supplies, and now tears the fleeces from the backs of the sheep, in order to feed on their living flesh. All these changes have exercised more or less direct or indirect action on the inorganic surface of the globe; and the history of the geographical revolutions thus produced would furnish ample material for a volume.

The modification of organic species by domestication is a branch of philosophic inquiry which we may almost say has been created by Darwin; but the geographical results of these modifications do not appear to have yet been made a subject of scientific investigation.

I do not know that the following pa.s.sage from Pliny has ever been cited in connection with the Darwinian theories but it is worth a reference:

"But behold a very strange and new fashion of them [cuc.u.mbers] in Campane, for there you shall have abundance of them come up in forme of a Quince. And as I heare say, one of the channced so to grow first at a very venture; but afterwards from the seed of it came a whole race and progenie of the like, which therefore they call Melonopopones, as a man would say, the Quince-pompions or cuc.u.mbers"--Pliny, Nat. Hist., Holland's translation, book xix, c.5

The word cuc.u.mis used in the original of this pa.s.sage embraces many of the cucurbitaceae, but the context shows that here means the cuc.u.mber.

The physical revolutions thus wrought by man have not indeed all been destructive to human interests, and the heaviest blows he has inflicted upon nature have not been wholly without their compensations. Soils to which no nutritious vegetable was indigenous, countries which once brought forth but the fewest products suited for the sustenance and comfort of man--while the severity of their climates created and stimulated the greatest number and the most imperious urgency of physical wants--surfaces the most rugged and intractable, and least blessed with natural facilities of communication, have been brought in modern times to yield and distribute all that supplies the material necessities, all that contributes to the sensuous enjoyments and conveniences of civilized life. The Scythia, the Thule, the Britain, the Germany, and the Gaul which the Roman writers describe in such forbidding terms, have been brought almost to rival the native luxuriance and easily won plenty of Southern Italy; and, while the fountains of oil and wine that refreshed old Greece and Syria and Northern Africa have almost ceased to flow, and the soils of those fair lands are turned to thirsty and inhospitable deserts, the hyperborean regions of Europe have learnod to conquer, or rather compensate, the rigors of climate, and have attained to a material wealth and variety of product that, with all their natural advantages, the granaries of the ancient world can hardly be said to have enjoyed.