556 INTRODUCTION TO PLANT GEOGRAPHY [cHAP. 



use which man can make of the land. This involves, before all else 

 . . . Land-use classification [which] should relate to the physical 

 capacity of the land to produce given crops for an indefinite period 

 without exhaustion or waste of the land resource. It does not hold 

 that production of tilled crops is the highest use of the land, but rather 

 that this is true only for certain classes of land. Some land, for example 

 swampy areas, is poorly used if it is not devoted to muskrat or other 

 wildlife production, for efforts to produce more intensive crops only 

 result in a waste of time, labor, and materials.' 



In addition there are the areas — amounting for example in the 

 United States to about 2 per cent, of the total land — occupied by 

 roads, towns, and railways, all of which have to be chosen and 

 maintained with the greatest possible knowledge and care. Land 

 classification in the modern sense should therefore include also 

 inventory and over-all planning. 



A very general computation has given the following figures for 

 the occupation of the world's land surface before Man transformed 

 so much of it : 30 per cent, forest or arborescent scrub, 19 per cent, 

 grassland, 17 per cent, desert, and the remaining 34 per cent, poor 

 mountain or polar areas {cf. Fig. 65). Most of the disturbed tracts 

 are considered capable of reinstatement so far as vegetation-type is 

 concerned, and accordingly these figures may also be regarded as 

 at least potential ones for the future. Curiously enough, although 

 many forested areas of past or recent times are considered capable 

 of cultivation, the same proportion of about 30 per cent, of the total 

 land surface of the world is also believed to be cultivable, while 

 another 30 per cent., without being too cold or too dry to support 

 crops, is of poor grazing-land, marsh, waste, or otherwise unsuitable. 



Of the many ways of classifying land, perhaps the most practical 

 and valuable is according to use-capabilities. This is based, as it 

 should be for permanence, on natural characteristics such as soil 

 and other biological conditions — ignoring such immediate con- 

 siderations as financial aspects or the skill of the operating individual. 

 In this system the following eight classes are widely recognized with 

 reference to rural use, though of course urban, industrial, transporta- 

 tional, and recreational areas should also be established with due 

 reference to a scheme of land classification wherever possible. The 

 eight classes are placed in three major groups, namely. A, B, and C. 



A. Suitable for cultivation involving tillage 



I. Without special practices for the prevention of serious erosion 



