THE ECONOMIC ASPECTS OF SOIL EROSION 
369 
turned fields. So Ion? as the earth is covered hy the normal 
forest growth the strong roots are likely to pass through the soil 
and fix themselves in the crevices of the underlying rocks and 
clamp, so to speak, the loose materials in their place. In this 
way it comes about that one of the effects of deforesting a coun- 
try, even where the lesser vegetation is allowed to develop, is to 
increase the rate at which the soil goes away to the streams. As 
yet this countiy has not been long enough exposed to the de- 
structive effects of tillage to afford striking instances of the effect 
of the reckless war which is waged upon the woods by the sav- 
ages who play that they are the agents of civilization. In Europe 
examples of the irreparable damage which may thus be wrought 
abound. Perhaps the most striking are to be found in the Aj)- 
enines, near Florence, where it is possible to walk for miles on 
mountain slopes without setting foot on anything but hare rock 
fields, which a century or so ago bore heavy forests nurtured 
in a fertile, if not deep, soil. The last of the IMedicis who held 
these woods as crown lands cut the timber without any provision 
for the replacement of the trees, with the result that the fine soil, 
before it had time to obtain protection from plants, was swept 
away. In this manner a great area has been doomed to age- 
long sterility and a region made desolate which might with 
proper management have continued to be helpful to man for an 
unlimited period. 
The mountainous countries of the Old World, with their vast 
reaches of bare rock slopes, which down to recent centuries were 
forest-clad, show the destructive effects of man’s heedless assault 
on the earth. In this countiy there has not been time for this 
l)rocess of destruction by the axman to manifest itself in a veiy 
serious way, yet in the Appalachians we can see the evil in rapid 
])rogress. South of Pennsylvania there is, according to my 
reckoning, based on observations in every state in that upland 
country, an aggregate area of not less than three thousand s(]uare 
miles where the soil has been destr()}’ed by the complete removal 
of the woods and the consequent ])assage of the earthy matter to 
tlie lowlands and to the sea. At the rate at which this process 
is now going on, the loss in arable or forestal)le land may safely 
he reckoned at not le.ss than one hundred s<puire Jiiiles ])cr 
annum ; in other words, we are each year losing to the uses of 
man, through unnecessary destruction, a productive capacity 
which may he estimated as sudicient to sustain a population of 
a thousand people. 
