Climate and Human History
OF late years a determined attempt has been made to rewrite history in economic terms. But this does not go deep enough. Man’s thought and social life are built on his economic life; but this, in its turn, rests on biological foundations. Climate and geology between them decide where the raw materials of human industry are to be found, where manufactures can be established; and climate decides where the main springs of human energy shall be released. Changes of climate cause migrations, and migrations bring about not only wars, but the fertilizing intermingling of ideas necessary for rapid advance in civilization.
Disease and hygiene play as important a part; half the population of the world is permanently below par on account of animal parasites such as the hookworm and the microscopic malaria germ; and disease may bring about the rise or fall of empires. Nor has selection ever ceased its rigorous activity. To pass from one mode of life to another is not a simple affair for a people; a settled agricultural life demands a very different temperament from hunting, and the hereditary makeup of the race must be altered if a people is to pass successfully from one to the other. Most migrations, too, are selective; to take but one example, the Puritans who first colonized Massachusetts did not bring with them a random sample of the genes responsible for the qualities of the English people. But selection is altered and reduced. The better care of the young and the elaboration of social life allow all sorts of variations, which otherwise would be snuffed out, to survive and often to play an important part in progress. Knowledge for knowledge’s sake is out of place in a primitive hunting tribe.
When the world’s climatic belts are sharply marked (as they are to-day, in contrast to epochs like the late Eocene, when climate was much more uniform), the temperate zones, flanked poleward by the subarctic and the arctic, are separated from the tropics by two dry belts, along which all the world’s great deserts are strung. The only zones where vegetation is abundant and man can easily flourish are the temperate and the tropical. But the temperate has another advantage. It contains the belt of cyclonic storms — in other words, of rapid and frequent changes of weather. And this type of climate, as Ellsworth Huntington has shown, is the one most stimulating to human energy and achievement.
We are still so ignorant of the earliest steps in the evolution of man from his simian ancestors that ideas as to the influence of climate on this phase of his history are highly speculative. It can scarcely be doubted, however, that the progressive desiccation of the world that took place in the late Tertiary Era helped to drive our ancestors down from the trees and out into the plains. We know that the Himalayas were elevated at this time; and it has been plausibly suggested that man originated to the north of them. For, as the land here grew drier, the forests shrank southward, where they were met by the impassable mountain barrier, and disappeared from Central Asia. Their anthropoid inhabitants were therefore forced either to disappear too or to become adapted to the new conditions, growing more terrestrial and more carnivorous. However this may be, men of a sort were undoubtedly in existence before the beginning of the Ice Age, half a million years ago. But until we shall have found new traces of Eolithic and Lower Paleolithic man in other parts of the world than Europe (which was doubtless a mere outlier of human development) we shall not be able to piece together the fascinating story of the influence of the different advances and retreats of the ice, or the slow progress of Old Stone Age man. We must content ourselves with the last chapter only.
When the ice of the Glacial Period was still in the early stages of its last retreat, the storm belt must have lain over North Africa, making what is now the Sahara green and fertile. It was through Africa and perhaps eventually from Southern Asia that Europe received its modern men, perhaps about 20,000 B.C. (Until about 4000 B.C. our dating must be regarded as provisional only; for the most part the chronology of Peake and Fleure, in their series, The Corridors of Time, is here followed.)
Gradually, as the ice withdrew northward, the belts of climate followed it up. The Sahara began to come within the limits of the dry belt. To-day, in certain parts of the Sahara, crocodiles and certain fresh-water fish exist in scattered oases. But these oases are isolated, without possible connections with other bodies of water. The water beasts that inhabit them are living in the sparse remnants of the well-watered, and indeed probably swampy, expanse of verdure that once spread over the Great Desert. This drying of the Sahara must have sent wave after wave of migrating men out of it, both northward and southward.
Meanwhile the zone of greatest fertility and greatest human vigor came all along the Mediterranean, through Mesopotamia and across to Turkestan. This again set great movements afoot. The Magdalenians, last of the Old Stone Age men, pushed northward with the forests in the wake of the retreating game of the treeless plains; till eventually, hemmed in between forest and sea, they were forced to lead a wretched existence as gatherers of shellfish and berries on the Baltic coast. The descendants of the other Stone Age peoples, who had remained behind in North Africa and Spain, evolved what is called the Caspian culture; later they too trekked northward and eventually fetched up in Western Asia.
As the open plains shrank before the advance of the forests, big game grew scarce, and men turned to other sources of food. They became food gatherers as well as hunters, eating nuts and berries and wild grain. This must have seemed a misfortune to those early hunters. But it was the spur to progress, for from food gathering to food growing, to real agriculture, was a natural step. It seems to have been somewhere before 5000 B.C., in the Near East, that the art of agriculture was discovered. Legend has it that Isis, the great goddess, found corn on Mount Hermon in Syria, and gave it to her sacred son. The legend may well contain two kernels of truth. It is probable that women rather than men first hit on the idea of planting grain, for the men’s work would still be afield, hunting; and it is probable that it was discovered somewhere in Syria or its near neighborhood. By 5000 B.C. grain growing had spread round from Palestine to Mesopotamia, and permanent settlements had come into being. The polish gained by stone implements used for hoeing probably gave men the idea of deliberately polishing their tools; if so, agriculture was the cause of the change to the Neolithic Culture. In any case, agriculture and polished neolithic stone implements appear at about the same time.
The arts of pottery and weaving were in all probability discovered about the same time as that of grain growing, and the first permanent houses were built. Domestic animals followed soon after; domestication seems first to have been learned by hunters, but the art spread rapidly and was extended and improved by the settled agriculturists. Metal working was not long behind, though for centuries only copper and gold were employed — copper for use and gold solely for ornament.
The Glacial Period did not die steadily away; it left the earth in a series of spasms or oscillations, a time of rapid retreat being followed by a standstill or even an advance of the ice, brought about, it would seem, by an elevation of the land. For a century or so about 4500 B.C., there was such an elevation. This seems to have had two interesting consequences. For one thing, the increased snowfall round the Mesopotamian basin gave rise to such violent spring floods, year after year, that some towns were abandoned, and the memory of the disastrous time has been preserved, it seems, in the story of Noah’s flood and the corresponding Mesopotamian legends. But more important was its effect on Egypt. In the centuries before this time, the Nile Valley seems to have been marshy and largely uninhabitable; the elevation must have drained it. And the long ribbon of marvelously fertile land thus provided for the use of man tempted in the agriculturists of neighboring countries. This, it appears, was the real beginning of the civilization of Egypt; but, once started on its career, its geographical position was such that it soon outstripped its rivals.
Thus, largely as a result of the pressure of changing climate on early man, hunting gave place to agriculture. Well before 4000 B.C. what we may call the Archaic Civilization, based on corn and a settled life, — with houses and pottery, woven fabrics and metal work, in addition, — was fully established, from Egypt round by Syria to the Tigris and Euphrates. This corner of the globe was predestined to be the cradle of the modern world — by its climate, by its great rivers, by the fact of its being the original home of wheat, by its being a natural meeting place for different streams of culture brought by different migrations of men, east and west as well as north and south.
Before 4000 B.C. there had been added to the achievements of settled man the art of writing, the framing of a calendar, irrigation, the wheel, and the making of fermented liquor. Through the whole of the next millennium this remarkable civilization was free to develop its own potentialities. It was a time of depression of land, a moist time over the steppes and the Arabian peninsula, and so a time when the nomad inhabitants of these regions could thrive and multiply in their own homes, not driven by drought to irrupt into the lands of their richer neighbors. To what height the Mesopotamian civilization reached is attested by the marvelous workmanship of the objects from Ur of the Chaldees, which date from about 3500 B.C. The organization of the State under a priest-king, even the welding of empires a million strong, stone architecture, the arch, written codes of law, seagoing ships — these were some of the achievements of this millennium.
But the available land in this corner of the world was being filled up by the natural increase of population; and this filling up coincided with a new elevation of the land and a new period of drought. Between them, the two caused such a movement in the world of man that the Archaic Culture, though made to totter in its original home, was forced to spread its influence far and wide over Europe, Africa, and Asia.
The new millennium dawned favorably enough. Egyptian civilization, borne along on its own momentum, reached new successes. Beautiful temples of stone, and the Pyramids, with their astounding exactitude and colossal size, date from its earliest centuries. Mathematics and astronomy take their rise; the State is run by a regular bureaucracy. A little later, in Mesopotamia, King Sargon comes on the scene, the first of the great conquerors to build an empire with armies.
For armies were another new invention. The primitive hunters had doubtless fought, but it had probably never been organized fighting; and the early food gatherers and cultivators seem to have been peaceable on the whole. There was assuredly never any Golden Age of Peace, as Perry and other enthusiasts imagine, but the early ages of human life were probably on the whole peaceful, because deliberate and organized warfare was not necessary and did not pay. War began as settled man quarreled over his property and his privileges. The idea of war soon spread to the less civilized peoples who fringed the settled lands; and it became possible for these peoples to practise war efficiently because they had passed from the state of hunters to that of nomads, disciplined herdsmen, and horsemen. The horse must have been domesticated on the steppes somewhere before 3000 B.C. A little later, drought began, and the nomads, lacking food at home, poured down on the settled lands with their horses. These were as terrible an innovation in warfare then as were the tanks in the wars of our own day some 4500 years later; and both Egypt and Mesopotamia were overrun and their civilization put in peril.
Meanwhile the pressure of population, of climatic changes, of invasions in the rear, forced the grain growers out in all directions. Not till about 3000 B.C. did any settle on the continent of Europe; but well before the close of the succeeding millennium they had spread over its greater part, to Thrace, to Germany, to Belgium, to France. And the push was felt by sea as well as by land. The whole Mediterranean became a great trade-lake, and the Ægean sailors had reached the Atlantic at latest by 2200 B.C. At the same time a great wave of migration spread eastward, and a new culture reached Northern India and right across to China, which thus seems to have received the first rude germs of her culture. It is possible that the American continent also received its first dose of civilization during this period, by a migration over the landbridge where now are the Behring Straits.
The maritime expansion continued into the next millennium, and so did the dry climate, which was especially marked in Northwestern Europe. Sea trade reached Ireland and Scandinavia. Ireland attained a very high level of culture, which was probably only made possible by this dry and bracing climate, before the excessive moisture of later centuries damped the energies of her inhabitants.
About 1800 B.C. there was again a change. The climate became gradually moister and cooler. From about 1200 B.C. to 200 A.D. there was a new cycle of wet and cold, reaching its maximum about 400 B.C. and then gradually falling off, to pass over to drought about 500 A.D. The belt of storm tracks again passed through the Mediterranean, giving opportunity for the rise of Babylonia and Assyria, Canaan and Phoenicia, of latter-day Crete and Egypt, of Mycemæ and Troy, Greece, Carthage, and Rome. North Africa was then the granary of the world. The Mediterranean was the focus of human energy, and, since the nomads could live comfortably on their steppes while the wet time continued, could pursue its destiny little troubled by barbarian invasions.
But the change of climate was disastrous to the northern lands. On them, cold and wet descended; the peat bogs spread; the forests died off as the swampy moors extended. There was a marked falling off of culture in Ireland and Scandinavia; and the worst cold spell, in the fifth and fourth centuries B.C., has apparently left its permanent trace in the northern legend of the Twilight of the Gods, which pictures a disastrous world bound in the grip of snow and ice.
After this, the classical Mediterranean civilization began to fail. Jones, some twenty-five years ago, suggested in a remarkable book that the downfall of Greece was due to malaria imported from Africa. Now that we know that a progressive desiccation was in progress at the time, the idea gains in probability. The rivers, drying up to a series of pools in summer, would afford countless new breeding places for the larvæ of the malaria-carrying mosquitoes. Malaria probably contributed to the downfall of Rome as well; but since Italy has more rainfall than Greece, the malaria-spreading change would have struck her later. But in addition the yield of agriculture in the Mediterranean began to grow less; and about the same time the first of a new series of barbarian invasions poured in.
For the period from 500 to 1000 A.D. was definitely a dry one. This it seems to have been which in the South drove the Huns and Goths to the limits of Europe, and stimulated the expansion of Islam from droughtstricken Arabia. But it brought new life to the swampy North. The culture of Ireland revived. In Scandinavia this was the great age of the Vikings, the Norsemen. As toward its close it grew Jess dry, the wet began to rob the Vikings of their livelihood and their lands as surely as the drought had robbed the steppe dwellers of theirs; and they poured forth in a burst of migration which took them across the Atlantic, and eventually, in the guise of Normans, as far as Sicily.
In the New World too the climatic changes were similar and had the same general effects, notably upon the story of the remarkable Maya civilization of Yucatan. The huge monuments of the Mayas are now buried in dense tropical jungle, which no primitive people could hope to keep at bay. After the first flourishing period of the Mayas, civilization retreated for centuries from Yucatan, but recolonized its northern part for a short time about 1000 A.D. The two flourishing periods of Maya history correspond with what we have called cold, wet periods. But these were wet only in regions at a certain distance from the poles. During these times, the storm tracks shifted farther toward the equator; and accordingly the dry belts between temperate and tropical were shifted equatorward too. To-day, Yucatan lies just south of where the northern dry zone passes over into the tropical. When the temperate rainy zone shifted south, the margin of the dry zone also was forced southward over Yucatan, the forest melted, and the Mayas could build an empire there.
In the temperate zones, after the short wet period of the eleventh century, there followed a series of minor and drier fluctuations. There was one cold spell in the thirteenth century. There was another in the first half of the seventeenth, in which the tradition of the ‘old-fashioned’ severe winter probably takes its origin (though doubtless perpetuated by the common failing of age to decry the present in favor of the past). Since then there has not been any great change. True, there have been shiftings of sea currents, such as that which brought the herrings to the Baltic, or that which sent the cod away from the coast of Brittany; but there have been no marked movements of the storm belt.
This long string of conclusions is drawn from the most diverse sources — from the deposits in northern peat bogs, from the old shore lines of the Caspian, from the salt lakes of Central Asia, from the now waterless cities, such as Palmyra, that once lay on great trade routes, from legend and historical record. But they find a wonderful corroboration within the trunks of the big trees of the western United States. Rain is the limiting factor of the tree’s summer growth, and so the size of the growth ring in its wood preserves for us the record of the season. By measuring the growth rings of over two thousand big trees, Douglass has given us a curve of climate which corresponds with remarkable accuracy with what we have deduced from other sources. Some of these trees date back four thousand years. In their trunks we can read of the dry periods which spread civilization over the world but spelled the ruin of the first Archaic Culture; of the ‘classical’ rainfall maximum, as Brooks calls it, which allownd Greece and Rome and Yucatan to achieve their destiny; of the new drought which brought the barbarians into the Holy City and raised the Norsemen to their first height of activity. And they record for us the final settling of the fertilizing, energy-giving belt of cyclonic weather in its present place, a thousand miles and more northward of its old position.
Thus climatic belts have not shifted seriously for almost a thousand years. What will happen to civilization when they move again we can hardly foresee; but we cannot suppose that shifting climate will respect our modern balance of power, any more than it spared the civilizations of Mesopotamia. Climate is inexorable.
The question of the effects of climate and other natural phenomena on human history is not all speculative. We can see some of its very practical ramifications in the problems of cattle, soil, and grasslands. Here the chemistry of soils enters in as well as climate, but the two are not without relation.
From time to time, in different parts of the world, cattle exhibit perverted appetites. They take to chewing bones, and will sometimes even devour the carcasses of other cattle that have died. These abnormal instincts are invariably the prelude to grave disorders. In typical cases the bones grow soft, the joints become swollen, the animals get thin and feeble and move stiffly and awkwardly; their hoofs grow abnormally long; sterility and abortion are common. Milch cows and young growing beasts are invariably the most seriously affected; and imported modern breeds suffer worse than the poorer native types. Sheep may be affected in the same sort of way; and horses too, though more rarely.
These outbreaks, which may inflict severe losses, may only recur every few years; or they may continue unabated for long periods. In every case they are confined to particular regions. In such a region, even in years when there is no actual disease, the animals are generally below par. Their fertility is very low; there is much infant mortality among the calves; growth is slow and stunted; milk yield is subnormal.
Much search has been made for the causes of this state of affairs. Bacteria have been blamed, and other parasites, and poisonous plants. But ail these were gradually eliminated. It became more and more evident that the cause was some deficiency in the beasts’ food; and since the food they eat draws all its supplies (save carbon and oxygen from the inexhaustible air) from the soil, the deficiency must ultimately lie in the soil.
Chemical analysis has confirmed this verdict. The cause of this poor performance and actual loss, specially grave in dry countries like Africa and Australia, is a deficiency of one or more of the elements supplied to plants from the mineral salts of the soil. The commonest deficiency is that of phosphorus or of calcium — or of both at once. Since both are necessary ingredients of bone, a shortage of either will prevent proper bone growth. Both are also necessary for the universal processes of metabolism in the body; and if the supply falls short of the vital minimum needed for tissue life, the tissues draw on the reserves held in the skeleton. The mineral framework of the bones is redissolved to be used up by the living cells, hungry for the missing elements, and the skeleton grows weak and soft. The milk too grows poor in calcium and phosphorus, the calf has to go short of them, and, as he is a rapidly growing organism, feels the lack even more acutely than his parents.
The depraved appetite for carcasses and bones is a last resort for getting back some of the missing elements into the system. It is, however, often disastrous, for many animals thus eat disease-producing bacteria in the decaying bones, and develop serious illness from this cause; and even if they avoid poisoning, the mineral shortage eventually becomes so acute that the animal sickens and dies. In other cases, mere stunting is the chief result. In the Falkland Islands, for example, whose pastures are very short of calcium, an ox will hardly reach five hundred pounds in weight, and the offspring of good breeds of horses grow up no bigger than ponies.
The symptoms vary a good deal from place to place, largely according as the defect is a defect mainly of phosphorus, — perhaps the commonest condition, — or of calcium, or of both. But they all agree in taking origin in a lack of necessary bone-building elements.
Here and there, though much more rarely, the cattle farmer attempts to ply his trade on areas where there is a shortage of other mineral constituents. When the missing element is iron, as in parts of Kenya and New Zealand, the animals suffer from a progressive aneemia; they grow thinner and thinner, and finally lose control of their limbs. In certain parts of the plain region of the United States and Canada, on the other hand, iodine is the defaulter, and farm animals (like the human population) suffer from the swelling of the thyroid known as goitre, with all the attendant symptoms of low chemical activity and stunted growth. In some areas, the lack of iodine is so pronounced that the young pigs lose all their hair and hardly any of them survive.
The shortages, as we have said, are primarily due to a deficiency native to the soil. It is surprising but true that there are great stretches of country which from the outset are unsuitable (without special treatment) for stock raising on any large scale, because the ground simply does not have enough of one or another chemical element. Countries composed of igneous rock often have a shortage of calcium. In much of the west of Scotland, where the soil is poor in calcium and phosphorus and the pastures have long been depleted by grazing without any return in the shape of artificial manure, the sheep are frequently afflicted with disease, there is a high rate of mortality among growing lambs, and the carrying capacity of the land is falling. Iodine is generally low in limestone districts, or where, as in parts of North America, the great meltings that followed the Ice Age have leached it out of the soil.
Phosphorus is the trickiest of all these elements. It is the one which usually is nearest to the border line, and there are very big tracts of phosphorus-poor soil. In addition, drought apparently makes it harder for plants to get phosphorus out of the ground, so that an arid climate will turn a soil that elsewhere would be adequate into a phosphorus-deficient one.
Why, then, are these regions of the earth’s surface not bare of wild animals? And how is it that man can generally thrive where his cattle sicken? The answer is that the demands are a matter of degree. No region is entirely without any of the essential elements. In nature, a balance is soon struck. The country supports what it can support. If animals fall sick, they are speedily eliminated; as soon as overmultiplication of any grazing animal brings down the supply of any element per individual to the danger point, migration relieves the pressure. Man, on the other hand, attempts more intensive operations. He wants the land to carry the maximum amount of stock, and to carry it all the time. Furthermore, different animals make very different demands on the mineral resources of the soil. It is the quickgrowing beast which suffers, because it has to lay by a large quantity of calcium and phosphorus in its skeleton, of iron in its blood, of iodine in its thyroid, all in a short time; while the slower-growing kinds escape — just as in man a degree of shortage of vitamins which is almost without effect on grown men and women may produce serious rickets in growing children.
Now cattle are in any case quickgrowing animals. A human infant takes six months to double his weight after birth; a calf, in spite of his much greater size, takes only about a month and a half. And in domestic breeds of cattle man has intensified this quick growth, since his prime aim is the biggest possible return of meat in the shortest possible time. Besides, he breeds for milk-yielding capacities so enlarged as to be almost unnatural. Whereas, for instance, in the natural state cows at one lactation produce two or three hundred gallons of milk, we ask the best modern breeds to give us up to a thousand gallons. The native cattle of Nigeria have their first calf at about six years; a well-fed cow of a modern breed has hers at three. In beef breeds, the rate of putting on flesh has been doubled. In all these ways, domesticated cattle have been deliberately bred to make more demands upon the soil than other beasts, and the better they are as cattle, the more demands they must make. Accordingly, when good European bulls have been used to grade up native cattle in India or Africa, the result has frequently been merely that the sickness and mortality due to mineral deficiencies have leaped up.
Man the stock breeder has thus been putting new and unprecedented demands upon the mineral resources of the world’s soil. But that is not all. He has also been depicting those resources without making any return. As Dr. Orr says in his recent book, Minerals in Pastures: ‘Accompanying the visible movement of milk and beef, there is a slow invisible flow of fertility. Every cargo of beef or milk products, every ship ton of bones, leaves the exporting country so much the poorer.’ For, in nature, animals die where they live, and the constituents of their bodies are returned to their native soil. But man changes all that. He ships off the bodies of his animals or the products of those bodies to distant countries, and in every exported pound of meat or cheese or bone meal so much phosphorus and so much calcium and iron and magnesium have been extracted from the soil and removed from the country’s shores. Richardson calculates that since 1870 the export of animals from Victoria alone has taken out of its soil the equivalent of two million tons of superphosphates.
As we are now beginning to see, man’s difficulties about grassland and the products of grassland are not merely due to local and natural deficiencies. They are due too to deficiencies of his own making, and these artificial deficiencies are cumulative and world-wide. In old days, the cattle of mineral-deficient areas would make periodic journeys to salt licks, where the instinctive cravings for the elements they lacked would save them from disease and death. It is interesting to find the same instinctive cravings in man. In some parts of Africa, where mineral deficiency is serious, the black children spend their pennies, not on sweets, but on lumps of unpurified salt, imported from distant salt pans and full of all the elements for which their systems are crying out. To-day, fencing has often made the cattle’s annual ‘cure’ impossible. In one part of Kenya, for instance, the settling of the country happened to put an important salt lick on to land allocated to whites, to the great detriment of the native cattle, which either could not get at their necessary supply of minerals, or strayed and trespassed in search of it, and were lost to their owners. Economic restrictions may have the same effect. In the old days of the heavy French tax on salt, you could tell without a map when you crossed the boundary in the Jura from France to Switzerland by looking at the cattle. The French cows looked poorly, the Swiss beasts fine and healthy.
The next step was the discovery that the amount of mineral which would prevent disease in a pasture was not enough to give the best results. By adding more, up to a definitely ascertainable point, sheep and cattle could be made to grow faster, to yield more milk, and especially to be more fertile.
Thus what began as a study of local cattle diseases has turned into a problem of the soil chemistry of grasslands. The problem is one of first-rate importance. Cereals may be the staff of life; but the products of grass are more varied. Grass gives us not only meat, but also wool, leather, milk, butter, cheese, and various valuable by-products from bones and hides and horns. The value of the products of grass consumed annually in Britain alone is over £400,000,000, and the quantity of this which is imported makes nearly a quarter of the country’s total imports. And some countries, like New Zealand, live almost wholly by grass.
The question at issue becomes the question of the future of the world’s grass. We have spent an enormous amount of energy on improving wheat and maize, and have hardly given a thought to grass; but there is little doubt that by proper attention to the ecology and genetics of grasses we could double the output of the world’s pastures.
For one thing, proper dosing with mineral salts helps the growth of plants which make greater demands on the soil, and so takes the ecological succession a stage further to a richer herbage. In dry areas it often helps also by conserving more moisture in the soil. Then there arc strange and subtle interrelations between grass and the beasts that eat it. Their trampling and their browsing alter conditions for the herbage. Too little grazing may allow scrub or moor to invade the pasture; too much may impoverish the sward. Such problems are especially prominent in new countries — in New Zealand, for instance, there seem to have been no indigenous grazing creatures, save possibly the giant flightless bird, the moa; yet to-day 94 per cent of the country’s exports are the products of grass-eating animals. Here, to clear scrubland for sheep, not only must the scrub be cut and rooted up and burned, but cattle must be introduced to keep the bracken and brush from winning back the land they have lost. As Dr. Stapledon says, ‘Cattle, no matter how prices rule, are essential to the reclamation and maintenance of scrublands. They are implements as necessary to the wool grower on hilly, scrubby country as the plough to the producer of wheat on the plains.’ Trampling, too, prevents the grass from getting coarse and rough. The amount of grazing a pasture will stand depends a good deal on climate. If grassland (as in so much of Europe and New Zealand) is not the natural climax of plant life, but is only a ‘sub-climax,’ which would go on to a richer type of vegetation, such as forest, if left to itself, then it will stand very heavy grazing. If, however, the climate is so dry that grass of sorts is the natural climax, it has fewer reserves, so to speak, and heavy grazing may seriously damage it.
But the amount of grazing will also depend on the kinds of grasses there are to be grazed. In New Zealand the native vegetation, unused to being nibbled down to the ground, succumbs to this new treatment. A judicious mixture of the right grasses and clovers from all over the world (only we must remember that what is right for one place may be very wrong for another!) is rapidly raising the productive power of grass. This will soon get to a limit; but then the geneticist can step in and continue the process by deliberately breeding richer and more resistant pasture plants. A beginning has been made with this at places like the Grass Research Station at Aberystwyth, and the results already obtained, together with the comfortable knowledge of what has been actually achieved with wheat, warrant great hopes for the future.
We could easily double the productive power of the world’s grasslands by deliberately working for types of beast that make greater demands on the grass, and types of grass that make greater demands on the soil. We have only got to make sure that we can continue to provide the soil with the necessary chemical ingredients. But to achieve this result we need the services, not only of the farmer and the scientific agriculturist, but of the plant and animal geneticist, the soil chemist, the systematic botanist, and the ecologist; nature cannot be improved upon without the amassing of a deal of knowledge and the expenditure of a deal of pains.