Influences of Geographic Environment / On the Basis of Ratzel's System of Anthropo-Geography

by Ellen Churchill Semple

Climate in the interplay of geographic factors.

The foregoing chapters have therefore been indirectly concerned with climate to no small degree, but they have endeavored to treat the subject analytically, showing climate as working with or against or in some combination with other geographic factors. This course was necessary, because climatic influences are so conspicuous and so important that by the older geographers like Montesquieu[1410] and others, they have been erected into a blanket theory, and made to explain a wide range of social and historical phenomena which were properly the effect of other geographic factors.

Direct and indirect effects of climate.

For a clear understanding of climatic influences, it is necessary to adhere to the chief characteristics of the atmosphere, such as heat and cold, moisture and aridity, and to consider the effect of zonal location, winds and relief in the production and distribution of these; also to distinguish between direct and indirect results of climate, temporary and permanent, physiological and psychological ones, because the confusion of these various effects breeds far-fetched conclusions. The direct modification of man by climate is partly an a priori assumption, because the incontestable evidences of such modification are not very numerous, however strong the probability may be. The effect of climate upon plant and animal life is obvious, and immediately raises the assumption that man has been similarly influenced. But there is this difference: in contrast to the helpless dependence upon environment of stationary plants and animals, whose range of movement is strictly determined by conditions of food and temperature, the great mobility of man, combined with his inventiveness, enables him to flee or seek almost any climatic condition, and to emancipate himself from the full tyranny of climatic control by substituting an indirect economic effect for a direct physical effect.

The direct results of climate are various, though some are open to the charge of imperfect proof. Even the relation of nigrescence to tropical heat, which seems to be established by the geographical distribution of negroid races in the Old World, fails to find support from the facts of pigmentation among the American Indians from Alaska to Tierra del Fuego. Nevertheless climate undoubtedly modifies many physiological processes in individuals and peoples,[1411] affects their immunity from certain classes of diseases and their susceptibility to others, influences their temperament, their energy, their capacity for sustained or for merely intermittent effort, and therefore helps determine their efficiency as economic and political agents.

While producing these direct effects, climate also influences man indirectly by controlling the wide range of his life conditions dependent upon the plant and animal life about him. It dictates what crops he may raise, and has it in its power to affect radically the size of his harvest. It decides which flocks and herds are best suited to his environment, and therefore directs his pastoral activities, whether he keeps reindeer, camels, llamas, horses or horned cattle. By interdicting both agriculture and stock-raising, as in Greenland whose ice cap leaves little surface free even for reindeer moss, it condemns the inhabitants forever to the uncertain subsistence of the hunter. Where it encourages the growth of large forests which harbor abundant game and yield abundant fruits, as in the hot, moist equatorial belt and on rainy mountain slopes, it prolongs the hunter stage of development, retards the advance to agriculture. Climate thus helps to influence the rate and the limit of cultural development. It determines in part the local supply of raw material with which man has to work, and hence the majority of his secondary activities, except where these are expended on mineral resources. It decides the character of his food, clothing, and dwelling, and ultimately of his civilization.

Effect of climate upon relief.

The very ground under man's feet, moreover, feels the molding hand of climate. In one region a former age of excessive cold has glaciated the surface and scoured off the fertile loam down to the underlying rock, or left the land coated with barren glacial drift or more productive clays. In another, the cold still persists and caps the land with ice and snow, or, as in the tundra, underlays it with a stratum of frozen earth, which keeps the surface wet and chilled even in the height of summer. In yet other regions, abundant moisture combined with heat covers the ground with a pad of fertile humus, while some hundred miles away drying trade winds parch and crack the steppe vegetation, convert most of its organic substance into gases, and leave only a small residue to enrich the soil. Rain itself modifies the relief of the land, and therefore often decides in a slow, cosmic way what shall be the ultimate destination of its precious store of water. A heavy precipitation on the windward side of a mountain range, by increasing the mechanical force of its drainage streams, makes them bite their way back into the heart of the system and decapitate the rivers on the leeward side, thus diminishing the volume of water left to irrigate the rainless slope. Thus the hydra-headed Amazon has been spreading and multiplying its sources among the Andean valleys, to the detriment of agriculture on the dry Pacific slope; thus the torrents of the Western Ghats, gorged by the monsoon rains from the Indian Ocean, are slowly nipping off the streams of the ill-watered Deccan, [See map page 484.] All these direct and indirect effects of climate may combine to produce ultimate politico-geographical results which manifest themselves in the expansion, power and permanence of states.