Tropical climate

“ To a native, a tropical climate certainly offers fewer pleasures, pursuits, and occupations than a temperate one. The heat in the dry, and the moisture in the rainy season do not admit of the outdoor exercise and amusements, in which the inhabitants of a temperate zone can almost constantly indulge. ”

“ I say limited, because we cannot speculate on the entire transposition of a group of animals and plants from tropical to polar latitudes, or the reverse, as a probable or even possible event. We may believe the mean annual temperature of one zone to be transferable to another, but we know that the same climate cannot be so transferred. Whatever be the general temperature of the earth's surface, comparative equability of heat will characterize the tropical regions ”

“ These two directions are those of heat and cold. We cannot suppose that life would develop in any important degree in a region of perpetual frost, such as the polar regions of our globe. But we do not find any end to it as the climate becomes warmer. On the contrary, every one knows that the tropics are the most fertile regions of the globe in its production. The luxuriance of the vegetation and the number of the animals continually increase the more tropical the climate becomes. ”

“ Mountain Climate.—In the torrid zone altitude is chiefly important because of its effect in tempering the heat of the lowlands, especially at night. If tropical mountains are high enough, they carry snow all the year round, even on the equator, and the zones of vegetation may range from the densest tropical forest at their base to the snow on their summits. The highlands and mountains within the tropics are thus often sharply contrasted with the lowlands, and offer more agreeable and more healthy conditions for white settlement. ”

“ Temperate products from tropical highlands. Isothermal lines in anthropo-geography. Historical effect of compressed isotherms. Effect of slight climatic differences. Effect of climate upon distribution of immigration Climate and race temperament. Contrasted temperaments in the same nation. Complexity of the geographic problem. Monotonous climatic conditions. The effects of Arctic cold. Similarity of cultural development. Cold and health The small amount of tropical emigration Effects of tropical climate. Historical significance of deterioration The problem of acclimatization. ”

“ In India, the hill stations are crowded during the hot months by civilian and military officials. The climate of many tropical plateaus and mountains has the reputation of being a “perpetual spring.” Thus on the interior plateau of the tropical Cordilleras of South America, and on the plateaus of tropical Africa, the heat is tempered by the altitude, while the lowlands and coasts are very hot. The rainfall on tropical mountains and highlands often differs considerably in amount from that on the lowlands, and other features common to mountain climates the world over are also noted. ”

“ But evaporation is profoundly influenced by the velocity of the wind; and the wind, which in the Tropics represents the strength of the atmospheric circulation, depends on the thermal gradient between the equator and the poles; since there is no evidence of any appreciable change of temperature over the Tropics as a whole, while there was a very great fall in cold temperate and polar regions, the thermal gradient, and therefore, ultimately, the tropical and sub-tropical, rain and snowfall must have been very greatly increased. ”

“ It is probable that for many millions of years but one climate prevailed over the whole earth, which very closely resembled, or even surpassed, the hottest tropical climate of the present day. The highest north which man has yet reached was then covered with palms and other tropical plants, the fossil remains of which are still found there. The temperature of this climate at a later period gradually decreased; but still364 the poles remained so warm that the whole surface of the earth could be inhabited by organisms. ”

“ In that fortnight the plants on the mount had made great advances, showing the exuberance and growth of a tropical climate. It sometimes, nay, it often happens, that when the sun is the most genial for vegetation, moisture is wanting to aid its power, and, in some respects, to counteract its influence. ”

“ As no such tropical and equatorial animals or plants have been known to exist there, nor even herbage of any kind, on which such animals might subsist, since the memory of man, there was a time anciently when the climate suited their growth, and of course was very much warmer than it is known to be now, its temperature then corresponding to the temperature of the present equatorial regions, as it produced and subsisted anciently the animals and plants which the tropical regions produce and subsist at the present time, and which cannot subsist in any other climates. ”

“ The climate varies from the tropical warmth of the coast to cool on the plateaus and on the mountain sides. The trade winds do 170much to modify the heat and add to the agreeableness of the temperature. ”

“ THE subject of the influence of sunlight in the tropics has been the subject of extended discussion for many years, and the general opinion seems to be that the intensity of insolation is the most important factor influencing the physical welfare of the white inhabitants in those parts of the world lying within the regions which are generally considered as having a tropical climate. ”

“ Forest covering, whether temperate or tropical, depends for its occurrence all over the world upon an adequate rainfall. As we have seen in the tropics, this may be so great that coupled with the heat it produces a wealth of vegetation beyond the powers of description. Where it is less and the country cooler, the forests are of a different type, but even there the forest covering is, without interference, practically complete. Where, as in parts of Chile, southeastern Australia, and of Japan, there is a heavy rainfall but cool climate, there is a so-called temperate rain forest. ”

“ But the great fact to bear in mind is, that all tropical productions will have suffered to a certain extent. On the other hand, the temperate productions, after migrating nearer to the equator, though they will have been placed under somewhat new conditions, will have suffered less. And it is certain that many temperate plants, if protected from the inroads of competitors, can withstand a much warmer climate than their own. ”

“ The average temperature of these coast plains is sixty-eight degrees. The cool sea-winds equalize the climate so that the temperature changes little throughout the year and there is but slight variation between the north and the south. Under these favorable conditions the soil produces in rich abundance a great variety of tropical fruits. ”

“ Wholly overcast, dull days, such as are common in the winter of the temperate zone, occur frequently only on tropical coasts in the vicinity of cold ocean currents, as on the coast of Peru and on parts of the west coast of Africa. ”

“ As a general rule, we may say that in the temperate and frigid zones the seasons for plants and animals are ruled by heat and cold, but that in tropical and even in subtropical climates, rainfall and drought, themselves largely due to the same circumstances, are the ruling factors. ”

“ Figure 28 graphically presents the average monthly temperature and rainfall of typical places in North [208] America, and Figure 29 of places in the Old World. Here may be seen every phase of climate from tropical [209] to temperate and to cold, and from marine to continental. By studying the winds on Charts 15 and 16 and the ocean currents on Chart 13, the reader should be able to find an explanation for the different conditions shown. For example: Mazatlan and Vera Cruz are both on the coast of Mexico, the first on the west and the latter on the east. ”

“ It may be true that individual tropical shrubs and flowers do surpass everything in the rest of the world; but that is to be expected, because the tropical zone comprises a much greater land area than the two temperate zones, while, owing to its more favourable climate, it produces a still larger proportion of species of plants, and a greater number of peculiar natural orders. ”

“ Hardly less uncertain and irregular are the effects of climate. Hot countries usually differ widely from cold ones in all their organic forms; but the difference is by no means constant, nor does it bear any proportion to difference of temperature. Between frigid Canada and sub-tropical Florida there are less marked differences in the animal productions than between Florida and Cuba or Yucatan, so much more alike in climate and so much nearer together. ”

“ In other tropical regions, where a periodical climate is produced by differences in the moisture of the atmosphere, the long-lived plants prevail, and the ground is so occupied with them till the coming on of the dry season that the short-lived kinds can not find room upon it. ”

“ Different Degrees of Climatal Adaptation in Animals and Plants.—Plants differ greatly from animals in the closeness of their adaptation to meteorological conditions. Not only will most tropical plants refuse to live in a temperate climate, but many species are seriously injured by removal a few degrees of latitude beyond their natural limits. ”

“ Saussure has shown that an excess of watery saturation diminishes atmospheric pressure; and the effect of certain conditions of the atmosphere on the human economy in tropical climates cannot for a moment be denied: for example, when the weather is wet and cloudy, the sun obscured, and the air calm; all animal life languishes. ”

“ Except near the United States the coast lands are tropical or semi-tropical; and the products of the soil, which in many quarters is extraordinarily deep and rich, are those which naturally result from extreme humidity and heat. Next comes an intermediate zone varying in general height from about 2000 to about 4000 feet, where the rainfall, though less abundant than on the coast, is ample, and the climate far more salubrious than below. ”

“ The climate is now what we should call tropical and subtropical, but they have known glacial rigors like those in our world's past. There are only two great continental land masses, and many thousands of large islands. ”

“ Extending through 30 degrees of latitude, the climate naturally varies from the tropical one of Formosa, through all variations of the temperate, to the alpine one of the high mountains and the nearly arctic one of the Kurile islands. ”

“ On the enfeebling effect of moist tropical climates there is a general agreement, both as to the fact and the chief cause; but, as I have remarked in a preceding page, the circumstance that this is little or not at all experienced at sea is apparently anomalous. With regard to the direct effect of the sun’s rays on the surface of the body, and especially in the production of sun-stroke, the evidence of scientific travellers is conflicting, and the explanations offered are by no means satisfactory. ”

“ The only necessary condition seems to be a moderate amount of moisture; but even as to this there is wonderful contrast between the long rainless summer and slight winter rainfall of Valparaiso, and the tropical rains of Brazil on the one148 hand, and the continual moisture of Valdivia and Western Patagonia on the other. This is one of the examples which goes to show how much caution should be used in drawing inferences as to the climate of former epochs from deposits of fossil vegetable remains. ”

“ The result is that before it begins to ascend in the tropical updraught, being much moisture-laden, the atmosphere stores a good deal of heat. As it rises, rarefies, and cools, the moisture descends in the torrential rains which ordinarily fall when the sun is nearly vertical in the tropical belt. ”

“ The line beyond which grass will not grow is determined in part by temperature; it marks the limit beyond which grazing animals cannot thrive, and, with a few exceptions, cannot survive. Conditions of temperature, such as obtain in the temperate zones, stimulate both the bodily and the mental faculties of humanity. [6] Therefore they have resulted in a civilization fundamentally different from that of tropical regions. ”

“ The ocean is also the great source of moisture, and this, too, it distributes over the land through the agency of the wind. Where warm ocean currents, like the Gulf Stream and Kuro Siwa, penetrate into temperate or sub-polar latitudes, or where cool ones, like the Peruvian and Benguela Currents wash the coasts of tropical regions, they enhance the power of the ocean and wind to mitigate the extremes of temperature on land. ”

“ While the wide-reaching seasonal changes within the tropical province depend on the migrations of the planetary winds northward and southward with the sun, and are due primarily to astronomical conditions, there are equally well-marked variations in rainfall dependent on or regulated by geographical conditions. ”

“ The natural methods for conveying tropical heat into the higher latitudes, and also for excluding it therefrom, are so simple and efficient that on due consideration we are able to conceive how epochs possessing mild climates have been succeeded by periods of frigidity. ”

“ A further peculiarity in the climate, which tends to diminish370 below the normal amount the rate of decrease of temperature, is the comparative absence of strong winds, and the feebleness of the sea-breezes which are usually so conspicuous in the tropics. ”