SOIL EROSION HALL 305 



destroy every seedling tree as fast as it gets its head up ; they complete 

 and extend the destruction the woodcutters have begun. At the same 

 time, with their sharp hoofs they break the surface of the soil, in 

 other places they tread hard paths down which the rain begins to run 

 with gathering volume and velocity. In a very short time during the 

 rains gullies begin to form as the soil is washed downhill ; year by year 

 the gullies extend and bite deeper into the earth, until in no long time — 

 a generation or two — the hillsides that had been forest and upland 

 meadow get bared down to the hard infertile subsoil or to the rock 

 itself. Nor does the damage end there; the rainfall, running off the 

 bared hill country without a check, develops as a torrent lower down, 

 attacking the meadows bordering its course. The earth also that 

 has been washed off the hillsides is carried down to the plains where 

 the rivers lose their velocity; there it deposits and turns the river 

 into a chain of malarious swamps, it chokes it mouth, and destroys 

 any harbor that was there. Such has been the history of much of 

 the fairest land on the seaboard of the Levant; on the heights bare 

 rock where once forest and meadow flourished, rivers that are torrents 

 in winter and dry in summer, old seaports no longer accessible. The 

 destruction of the forest was thus a major factor in the decay of 

 Greece and Rome itself; it meant, in the first place, the loss of farming 

 land and of the agricultural population which formed the backbone 

 of the early armies of the republics. With the swamps came the 

 spread of malaria, which again has been invoked as one of the great 

 causes of the fall of ancient civilization. 



Cogent as have been these lessons, they were not always remem- 

 bered in the new countries opened up in the nineteenth century. 

 Forests were destroyed greedily and indiscriminately, but the more 

 evident consequences have been that the rivers became subject to 

 violent flooding due to the sudden run-off in the rains, and dams and 

 irrigation reservoirs began to silt up rapidly. The most spectacular 

 form of soil erosion is that exhibited by the vast dust storms which in 

 1934 and 1935 especially swept over the United States east of the 

 Mississippi. It was no new phenomenon, although before that time 

 it had not been considered politic to talk about such a blot on pioneer- 

 ing enterprise in the Middle West. Locally a vast area, which included 

 western Oklahoma, western Kansas, eastern Colorado, the Panhandle 

 of Texas, and parts of Wyoming, was known as the "dust bowl." 

 In 1934 it was estimated that on a single day 300 million tons of rich 

 topsoil was swept as far away as the Atlantic. There is a story that 

 in the diary of an old Nebraska doctor was found the entry: "June 

 14th. Hot as hell, wind 40 miles an hour, two Kansas farms go by 

 every minute." 



It is not the United States only that has been suffering thus from 

 wind erosion; across the northern border the conditions leading to 



