WHAT DETERMINES USE OE EAND 1 29 



use because of their location and size, a condition which applies, 

 however, only to a very small per cent of our lands. 



I. Climate is invariably the principal factor. More than half 

 of N. America and Asia is too cold for agriculture; more than 35% 

 of North America, more than sixty per cent of Asia and Africa, 

 and more than eighty per cent of Australia are too dry for farming. 



About forty degrees Fahrenheit average yearly temperature 

 limits good farming; about 30°F. ends the useful forest, except pro- 

 tective woods. In the United States about twenty-five inches of 

 rainfall for the year limits the natural forest ; about fifteen inches 

 sets a limit to dry farming or farming without irrigation ; at ten 

 inches of rainfall the prairie changes to desert. 



In countries with an average j^early temperature less than fifty 

 degrees Fahrenheit and with dry summers and low relative humid- 

 ity all lean sandy lands have failed in maintaining satisfactory agri- 

 culture. 



Topography affects agriculture ; generally a five per cent slope 

 washes as soon as plowed ; a ten per cent slope gullies and is ruined. 

 Usually steep lands become stony and lean and millions of acres of 

 farm lands have been abandoned in Europe because of topography. 



Dense population commonly stimulates the use of land for 

 farming. In the United States millions of acres of good land are 

 not used or poorly used for lack of labor and demand. But while 

 it is generally true that dense population leads to the use of lands 

 for agriculture, this is no longer true to the same extent that it was 

 fifty or more years ago. Formerly the majority of the people lived 

 on the farm, today over sixty per cent' of the people of the United 

 States live in town. The people do not flock to the country, they 

 leave the country and move to town. It is the town which furnishes 

 employment and a safe and comfortable living. This is as true of 

 Europe as it is of the United States. The result is that millions of 

 acres of land even in the better populated parts of the United States 

 and the most densely populated states of Europe are not tilled, and 

 large areas have been abandoned to deteriorate into waste lands. 

 Dense population today, means cities, manufacture and commerce, 

 good wages and living in the city, higher wages and less farm labor 

 for the farm; and intensive use of good farm lands which justify 

 labor and machinery; and abandonment of poor farm lands. In 

 Europe this situation has shifted the use of lands from agriculture 

 to forestry for large areas ; it has led to regular appropriations by 

 the states and the development in this direction is more rapid today 



