Acclimatization

ACCLIMATIZATION, the process of adaptation of plants, animals, and humans to life in geographical regions remote from their original homeland and differing from it in climatic and other living conditions. Each species of plants and animals has a more or less definite area of distribution over the earth's surface, and each zoogeographical region is characterized by its own climatic and other conditions of existence. Often, with the participation of man, animals, marine and river currents, wind, or other factors, an animal or plant can be introduced into a geographical region foreign to it. If in the new region the organism has managed to change its organization and way of life so that it proves capable of surviving in the new conditions, and if in the new region it continues to produce offspring capable of further reproduction, then in such a case it is possible to speak of the acclimatization of the given species. However, the concept of acclimatization suffers from a certain uncertainty due to the complexity of the concept of climate itself, which encompasses the entire totality of atmospheric (temperature, humidity, air currents), hydrological, and geographical-geological conditions of a given area. Therefore, clarifying the elementary biological mechanism of acclimatization is often an almost insoluble task. Ultimately, the acclimatization of living beings relies on their ability to adapt (see), which in many cases can be reduced to the action of elementary physical-chemical factors of the environment. Identifying these two concepts would, however, be incorrect, although in the literature, for example, the survival of freshwater organisms in salt waters and vice versa is often designated precisely as acclimatization. In other cases, the mechanism of acclimatization represents such a complex interweaving of climatic-geographical factors that clarifying the role of each of them individually may prove completely impossible. The process of acclimatization is accelerated even more in cases where, to the action of the climatic factor itself, there are added biological relationships between various living beings inhabiting a given geographical area and forming part of its biocenosis (see). Hence it is understandable why in some cases the acclimatization of one species or another persistently fails, despite the fact that there appear to be no obstacles of a climatic nature to this. For example, for a long time the acclimatization of vanilla on the island of Java did not succeed, despite favorable climatic conditions. The actual obstacle to acclimatization turned out to be that in Java there were none of those insects which, in the homeland of vanilla, in South America, contribute to its pollination. Finally, there are also such cases where acclimatization is unfeasible not due to climatic obstacles, but because in the new place the given organism does not have the opportunity to freely follow its natural instincts. For example, the acclimatization of bison in Europe proved impossible because they did not encounter here the conditions for those long migrations (nomadism) which are characteristic of them in their natural environment. This same reason (along with senseless extermination) led to the extinction of bison in their homeland, in America, in connection with the construction of a railroad across the continent, which blocked the path of their habitual migrations. Regarding the term 'survival' of an organism in new climatic or, in general, new conditions, it must first be said that survival (adaptation) can possess varying degrees and character. An organism may, for example, live in new conditions but not reproduce: in the Askania-Nova zoo (see) more than a dozen years lived large parties of flamingos and red-breasted geese, but neither the one nor the other proceeded to nesting and egg-laying. An organism may retain the instinct of reproduction in new conditions and, however, not produce viable offspring: in the same Askania-Nova, African ostriches lay fertilized eggs but do not incubate them to the end. An organism may, finally, both live and reproduce, and produce viable and fertile offspring; examples of this are various antelopes, llamas, yaks, American ostriches, and other animals in Askania-Nova. Such are the various degrees of adaptation. Along with this, the character of adaptation can also be different: an organism is capable of living and reproducing in new conditions, sometimes preserving the old forms of its life, sometimes acquiring, in relation to the new conditions, new forms of vital manifestations. In other cases, a significant change in periodic processes is observed, which is most clearly revealed during migration from the southern hemisphere to the northern or vice versa. Thus, the Australian black swan, the rhea ostrich, and the South American black-necked swan, upon acclimatization in the south of Ukraine, begin to nest and hatch chicks in the month of March—April (i.e., our spring), while in their old homeland they nest in November—December (the spring of the southern hemisphere). In some cases, changes in organization are also observed: the gnu antelope (Connochaetes gnu), upon arriving from its old homeland (Central Africa) to Askania-Nova, acquires a warm woolly coat by winter, which it does not have in its old homeland. However, not all animals are equally pliable: the Australian Cape Barren goose and the emu on the northern coast of the Black Sea still preserve the period of their homeland and attempt to nest in the cold of our Ukrainian winter (in November—December, corresponding to the summer of the southern hemisphere). It is interesting that in the Moscow Zoo the emu nests no longer in December, but in February—which stands in obvious connection with the greater sharpness in the change of climate from Australia to Moscow than from Australia to Askania. In phenomena of acclimatization, the composition of plant and animal communities (biocenosis), in which the acclimatized organism has to live, also plays a large role. A new form entering the biocenosis of a given place most often perishes or spreads only very weakly; in the case of successful acclimatization, it leads to a change in the biocenosis itself. Thus, the sparrow, which acclimatized on the Sandwich Islands, displaced almost all native birds; conversely, the Chinese pink, which is found here only in old parks and immediately perishes when it goes out into the open field, where it is displaced by wild-growing grasses, serves as an example of the limitation of life by the biocenosis. The conditions created by the biocenosis are the main reason that the majority of acclimatized animals and plants can exist only in an environment of domestication. The difference between acclimatization and domestication boils down, mainly, to the fact that the latter presupposes the patronage of the acclimatized species by man, while the former consists in adaptation to natural conditions new to the organism by way, mainly, of an independent and free struggle for existence. It is extremely difficult to draw a distinction between genuine acclimatization and domestication for each individual species. However, some examples are very striking. Thus, A. Agassiz already pointed out that all 130 species of weeds of the northwestern states of North America are of European origin, and that the local grasses have retreated to the west; in New Zealand there exist no fewer than 250 species of acclimatized plants, of which one hundred species have spread far throughout the country, displacing the local flora; cases of the displacement of representatives of the local fauna by alien animals are no less well-known. A large number of our tree species, which are considered at the present time to be ordinary trees of the European part of the USSR, acclimatized here, starting from the XVI—XVII centuries, at first under the direct patronage of man, and then in the literal meaning of the word acclimatization. Siberian cedar, larch, fir, yellow acacia, Salix acutifolia (a species of willow that has received particularly wide distribution and significance in the strengthening of sands and in basketry), laurel-leaved and fragrant poplar, Caucasian cherry, and a number of others, the majority of which have major significance in the forestry and woodworking industry—all these tree species have fully acclimatized among us and grow freely alongside native species. The number of useful plants requiring special care, but feeling excellent in the environment of climatic conditions new to them, is extremely large. Thus, a telling example of a high capacity for acclimatization is the potato, which was brought from its homeland—America—to Europe, in the XVIII century received wide distribution in France, from the beginning of the XIX century began to be introduced in Russia, and is now widely distributed throughout the globe, growing under the most unfavorable conditions of soil and climate; corn, which has spread from America throughout the globe (up to 52° N. lat.); further, hemp, the homeland of which, as is believed, is the coast of the Black Sea, is now distributed not only throughout Europe, but grows well in Asia, Africa, and North America; rice from Asia has spread to all continents of the globe; wheat, rye, and barley, apparently, were already in prehistoric times distributed from northern Persia and the Caucasus throughout the world.

Some plants of industrial importance have been acclimatized in the USSR quite recently: in the 1860s, ramie, or China grass, began to be grown in the Caucasus; in the 1870s, bamboo; in the 1880s, oranges, lemons, tea, and Japanese persimmon; American cotton, which is of such exceptional importance in industry, began to be cultivated in Turkestan only from the 1870s. Excellent examples of successful acclimatization are the ornamental plants of the southern coast of the Crimea—laurel, cypresses, magnolia, and others. Classic examples of genuine animal acclimatization are the complete feralization and exceptional spread of horses and cattle in the South American pampas, noted by Darwin and Wallace, where they were brought by the Spaniards after the discovery of America; the same applies to donkeys in Quito (Central America), pigs in America, and rabbits in Australia. The most striking examples of the acclimatization of animals that have economic significance and therefore spread, mainly through the mediation and under the protection of man, are: the widespread acclimatization of the chicken, domesticated within India in the 12th century B.C., which reached Europe, apparently, in the era of the Roman Empire, and was brought to America by Columbus; the turkey was brought to Europe from America in 1530. In the middle of the 19th century, the first scientific society for the study of the ability of animals and plants to acclimatize (Société d'acclimatation) was organized in Paris; similar societies were subsequently organized in other countries. In 1857, the "Russian Society for the Acclimatization of Animals and Plants" was formed in Moscow, which continues to function to this day. Within the USSR, systematic acclimatization experiments are being conducted at the Nikitsky Garden on the southern coast of the Crimea, in the Sukhumi Botanical Garden, in the Ukrainian zoo "Askania-Nova," and in the Moscow Zoo; at present, a Department of Naturalization of Tree Species is being organized at the Institute of Applied Botany of the Lenin Academy of Agricultural Sciences.

The acclimatization of man is, strictly speaking, the adaptation of man to a new climate. But if in relation to other living beings the concept of "acclimatization" can be limited to the action of a single climatic-geographical factor, then in application to man it inevitably also includes socio-economic and socio-hygienic elements. Thus, when studying human acclimatization, in many cases it is almost impossible to isolate the effect of the climatic factor, and therefore the very application of the term "acclimatization" to man in its narrow sense is often not entirely accurate. Furthermore, to study the genetic side of man, it is necessary to observe several generations. Therefore, despite all its theoretical and practical importance, the question of human acclimatization has not been sufficiently studied. The study of the influence of climate on human races is very important for the history of culture, since climate and race in their interrelations have been the greatest factors of civilization. The main center for the study of the acclimatization of human races is currently America (Boas, Hrdlicka, Pearl). The difficulty of such a study of acclimatization is compounded by the fact that in our time, when, under the conditions of the colossal influence of socio-economic and socio-hygienic factors on man, all European races have mixed, such concepts as "white race," "European," "Frenchman," "German," etc., do not represent anything genetically homogeneous, but are extremely mixed, heterozygous: under the name, for example, "Frenchman," there are essentially hidden representatives of different races—Bretons, Provençals, Basques, etc., who, moreover, live under different economic conditions. Undoubtedly, the ability of a human to acclimatize in Algeria or Tunisia will be completely different for a Breton Frenchman than for a Provençal or a Basque. In the question of human acclimatization, it is necessary to distinguish between individual acclimatization, i.e., the ability of individual members of a given race to survive in one climate or another, and absolute acclimatization, in which not only individual specimens survive, but also their offspring. Individual acclimatization occurs more often and, provided that hygienic conditions are observed, is achieved more easily than absolute acclimatization. In the case of absolute acclimatization of mixed races (at present they are almost all such), it is not the entire race as a whole that acclimatizes, but only its individual components. Regarding the question of the acclimatization of European races in the tropics, Ruge came to the conclusion that "the climate of the tropics is harmful to Europeans. The latter were able to fully acclimatize only in Queensland (Australia); in all other places of the hot belt that were considered suitable for Europeans, the European colony is always maintained by a constant influx of fresh blood from the metropolis; in the absence of this influx, it degenerates. The study of the influence of the tropical climate on Europeans has shown that their body temperature rises by several tenths of a degree, and their respiration and pulse quicken; in a humid climate, evaporation through the lungs and skin decreases, as a result of which restless sleep, severe nervousness, weakening of the will, mental instability, and a decrease in work capacity appear." As a consequence of this, Europeans must spend several months a year either in the mountains or leave for Europe, and they must necessarily raise their children in Europe. The tropical climate acts on representatives of different races differently; for example, the Portuguese acclimatized in India almost completely, the Italians acclimatized better than the English, etc. Besides purely climatic reasons, the acclimatization of Europeans in the tropics also depends on their higher susceptibility to tropical diseases (malaria, yellow fever) than that of the natives, who acquire a certain degree of immunity to these diseases from childhood. When inhabitants of the tropics move to the temperate zone, the influence of the temperate climate affects them less disastrously, and they can survive in a cold climate. But due to cold humidity, these migrants suffer more often from diseases of the respiratory organs and tuberculosis. Of course, socio-hygienic factors are also significant here. How great the morbidity is, is shown by the statistics of England, where among those suffering from tuberculosis there are many more brunettes than blondes; this can be explained by the circumstance that, although the dark-haired race immigrated to England from the south and in very distant times, it has still not fully adapted to the northern climate. On the other hand, the morbidity of Negroes in America from influenza is less than that of whites. Boas and Pearl studied the effect of acclimatization in the broad sense of this word on European immigrants in America. In their opinion, America represents a melting pot for immigrants, in which all nationalities—English, Slavs, Jews, Italians, etc.—turn into Americans. Boas's data on the acclimatization of European immigrants in America show that their very first offspring born in America exhibit certain changes, and the speed with which these changes develop also depends on the number of years spent in America by the mother before the birth of the children studied. These changes are different for different races. But in general, together with socio-economic factors, they lead to the development of an average American type; thus, the cephalic index of Jews born in Europe is 83.0, and in America—81.4; of Sicilians born in Europe—77.7, and in America—81.5, i.e., in one race it increases, and in the other it decreases, approaching in both the average value—81. At the same time, Pearl's studies showed that the first generations of immigrants have a much higher vital index (the ratio of the number of births to the number of deaths) than their offspring. Extremely interesting is the acclimatization of the Jewish race, which settled during the so-called diaspora throughout Europe and Asia. By the time of the dispersion, it was a very mixed conglomerate of various elements that had entered into it: Armenoids, Aryans, Philistines, Amorites, Hittites, and other peoples of Western Asia. Having settled in different countries of Europe, they mixed relatively little with the local races; therefore, the following distribution of them by cephalic index represents rather the result of the acclimatization of Jews in the broad sense than their mixing with other races. Cephalic indices: Hyper-dolichocephals (76), Dolichocephals (76–77), Sub-dolichocephals (78–79), Mesocephals (80–81), Sub-brachycephals (82–83), Brachycephals (84–85), Hyper-brachycephals (86). This table demonstrates the difference in the cephalic indices of Jews, which also depends on the fact that during their acclimatization in different countries, only those of their representatives survived who were closest to the native population in their anthropological characteristics, which is evident from the following table: Countries: Average cephalic index of Jews: 81.05, 81.82, 82.45, 81.91, 82.45; of non-Jews: 81.88, 82.91, 81.40, 82.13, 82.31, 83.33, 84.40. Similar observations exist in relation to height, color of eyes, hair, and others.