THE GRASS PROBLEM.
The heart of North America is a Grassland. This region is being given a new significance by reason of the Air Age and its reorientation of the world outlook in terms of circumpolar land-masses, - just a century after the Anglo-American forest man met for the first time the problems of living in a grassland. The eastern extremity of the grass country is a triangular prairie peninsula between the Great Lakes and the Ohio river, the point extending east as far as Indiana, with detached outlying openings farther east in Ohio and Pennsylvania, south in Kentucky and Tennessee, and north in Michigan. From this eastern forest boundary, the grassland extends westward through passes in the Rocky Mountains across the continental divide to the southwestern deserts, and farther north, to the famous prairie of the inland empire of the Pacific northwest. To the northward, the grassland extends through the prairie provinces of Canada to the northern forest boundary line, and to the southward into the Mexican desert plains.
The region is occupied by a wide variety of grasses with their associated plants, and of animals; forms of life mostly characteristic of, and peculiar to, the environment. There is present also, a minority representation of forms of life typical of other regions, especially along the boundary transitions. The grassland is complete in itself, a relatively stabilized product of nature, the outgrowth of climate, soil, vegetation, animals, and microorganisms, all interacting together. This general kind of region is not unique to North America but is a characteristic formation, of greater or lesser extent, occupying parts of all continents, unique only in respect to the particular species of biological forms that enter into the combinations.
Why are the prairies and plains a grassland? As early as 1870, Charles A. White, of the Iowa Geological Survey, commented that "the question of the origin of the prairies has become more hackneyed perhaps, than any other of the speculative questions which North American geology affords," and in addition he challenged the assumption of the forest men: "There seems to be no good reason why we should regard the forest as any more a natural or normal condition of the surface than the prairies are" (White Report 1:132, 133). "There is comparative uniformity on the nature of [the]... floral covering [of the prairies]", observed Shimek (1911), "they are marked ... definitely by the presence of a flora which is wholly distinct from the smaller (chiefly herbaceous) flora of the forest." The essence of these arguments is that the uniformity of vegetation is a positive characteristic, an evidence of completeness in nature, and not a sign of something deficient.
The use of the term prairie is not uniform, but there is good precedent for distinguishing between prairie and plains, the word prairie being limited to that portion of the grassland with forest along the streams lying east of an irregular north-south line falling mostly between the 96 and the 98 meridians, the tall-grass or true prairie. In their westward movement across the continent, the Anglo-Americans met the prairie first in the small occasional openings in the forest, as in Ohio and Kentucky-"oak openings" and "barrens"-, "but it was not until the white man crossed the Wabash river ... that he beheld the prairies in all their splendor, and all their monotonous magnitude" (Shimek, 1911)
There were fairly heavy forests along the streams and in some areas some distance back from the steams. The uplands, varying in topography, were covered with tall grasses, the most conspicuous being the bluestems. The Big Bluestem occupied the lower prairie and the Little Bluestem occupied the high prairie. Indian grass was present and in some habitats locally dominant. Gradually to the westward the proportion of forest to grassland diminished, until forests in any proper sense of the word gave way to the almost uninterrupted grass covering. West of the prairie boundary, not far from the 98 meridian, is a mixed grass low plains, tall and short grasses.
Among the latter through the central region the most important are the grama and the buffalo grasses. Farther west, roughly, west of the 100 meridian is the short grass country in which the grama and the buffalo grasses were dominant. Still farther to the west and southwest the grasses gave way to the typical desert forms of life.
Why are the prairies and plains a grassland? As yet there is no fully satisfactory explanation. A quantity of literature on the question accumulated during the nineteenth century, before scientific skills were applied to the search for a more comprehensive answer. This was reviewed carefully in 1911 by Shimek, both chronologically and in terms of the alleged factors responsible for the "treelessless of the prairies." The word "treelessless" was characteristic of the literature in question, which, with few exceptions, assumed as axiomatic that the presence of forests was natural and the absence of them was an unmistakable sign of deficiency, an abnormality of nature. In popular and scientific opinion, prairie fires had been held responsible for "the treelessness of the prairies." Shimek rejected the prairie fire argument: "Prairie fires were an effect rather than a cause, and where acting as a cause were local." The accidents of seed distribution, the grazing and trampling of the bison, and other alleged causes were declared "of remote interest and not to be taken into account on any attempt at the explanation of the prairie as a whole." He pointed out that the Iowa prairie afforded a conspicuous example of grass growing on diverse geological formations, and on different soils, using the term soil in the sense then current. Furthermore, the total annual rainfall was not in itself the determinant, because Iowa prairie and forest were found on opposite sides of the same ridge, and oak openings have existed farther east in the heart of the forest.
The growth of forests or the growth of grass, in Shimek's opinion, was the result of a combination of climatic factors. The artificial growth of trees could not change climate, and furthermore, the artificial growth of trees was possible only where the relative balance of factors adverse to trees was slight and man's efforts might be sufficient locally to redress such unfavorable influences. By the same token, when such human influences were withdrawn, in due course, nature would eliminate the trees and restore the grass (1913).
Shimek's was the most comprehensive historical review of the available literature to that date, and in its negative conclusions eliminated from the discussion most of the irrelevant factors alleged as causes, or at least challenged them explicitly. On the positive side, his conclusions were less satisfactory. The relatively new science of ecology was devising new methods of attack, and was developing an essentially new outlook on vegetation and animal life in relation to environment. As Americans had met the problem of the prairie early in the nineteenth century, they had harmonized their folkways to the realities of the changing situation through their own native resourcefulness, and prior to the time when science had much to offer. In the twentieth century, science was approaching the same issues, devising more exact techniques of analysis, going over much the same ground, and arriving at conclusions which enlarged the sum total of understanding of the grassland.
Part one of this book is devoted to a survey of the sciences that seem to have a bearing on the relations of man with his geographical setting--considering them in both time and space. The development of each of the sciences is approached historically. To the historian, this seems the best means of establishing perspective, both on the science itself and on the interrelations of the sciences with the main course of social change. The reader is informed by this procedure on what scientific knowledge was available for social utilization at any time.
These chapters are probably not what scientist in each of the respective fields would write, and what the scientists would write might not be of the most direct value to the historian. In any case, the important fact is that the historians and the geographers should possess a working knowledge of science if there is to be any understanding of cultural adaptation to the grassland. These chapters may serve also as a guide to further reading of the scientific literature, and if the summaries or interpretations are inaccurate in fact or emphasis, the underlying studies may be examined for verification and correction.