CONCEPTS IN CONSERVATION—GABRIELSON 
by the incorporation, with the mineral 
particles, of the decaying remnants of 
many generations of plants and ani- 
mals. It is by this process that pro- 
ductive soils are built. 
When the white man arrived in 
North America, he found a continent 
in which these processes had been 
going on for geological ages. As a 
result highly productive soils, natu- 
rally some better than others, were 
found. This natural process permits 
the return of all materials to the soil 
and as long as it continues, soils build 
toward a more productive condition. 
When the soil-formation process is 
interrupted, as it is when man develops 
an agricultural program and begins to 
take away and market great quanti- 
ties of the products of the soil, it is 
inevitable that soil building ceases and 
soil exploitation is started. Man recog- 
nizes this fact every time he fertilizes 
a piece of land, plows under a green 
crop, or spreads animal and plant 
wastes upon the soil. 
Soils that are devoted to agricul- 
tural crops become more subjected to 
erosive agents and in the past the 
result has been that an accelerated 
erosion of the soils started immediately. 
Erosion has hastened the reduction of 
soil fertility far beyond any loss that 
came from the removal of the elements 
of fertility from the soil. Fluctuating 
streams, the choking of stream beds 
with silt at an extremely rapid rate, 
and other disastrous consequences 
follow destructive erosion processes. 
Soil destruction has been going on in 
America since the first settlers landed 
and is still affecting a major part of the 
land. Net results are easy to see. At 
the present time, something in excess 
of 100,000,000 acres of formerly good 
crop land is now completely unpro- 
ductive. Some of it will not return to 
productive capacity for many thou- 
sands of years and then only as a result 
of the slow natural soil-building 
process. Some of it can be brought 
back more rapidly by careful handling. 
Another 100,000,000 acres are seri- 
ously damaged and nearly all of the 
285 
present land used for agriculture has 
deteriorated appreciably because of 
our crude methods of exploitation. 
More than 100,000,000 acres of 
swamp, marsh, and lake lands have 
been drained by one device or another. 
In some cases drainage has produced 
good agricultural land and in others 
it has not. In either case, but little 
thought has been given to a compari- 
son of the value of land in its original 
condition and its value for agricul- 
ture, wildlife, and the preservation of 
natural resources after drainage. 
When the white man came to Amer- 
ica, he found a land that was ade- 
quately clothed in vegetation, nature’s 
major instrument for retarding erosion. 
Both the character and density of the 
vegetation varied with the fertility and 
character of the land, the amount of 
rainfall, and the climate. The eastern 
half of this country was largely an un- 
broken forested area. In midcontinent 
the grasslands and prairies were com- 
pletely clothed with a turf and in the 
more arid areas of the country desert- 
inhabiting plants with vast root sys- 
tems performed the function of soil 
protection. 
To a large extent this vegetative 
cover has been disrupted, some of it 
necessarily and some of it needlessly. 
Under conditions of natural growth 
the vegetative cover performed other 
functions in addition to that of inhibit- 
ing erosion. It forced water into the 
soil and held it there stored for the 
future use of the plants. It maintained 
ground-water tables and gradually fed 
the surplus water into the streams. 
The natural cover of vegetation held 
to a Minimum variation in stream flow, 
and the stored waters fed permanent 
streams and maintained ground-water 
levels with small variation even during 
long periods of drought. In other 
words, nature’s method for protecting 
the land, building its fertility and pro- 
ductiveness, and storing water is the 
natural mechanism by which the soils 
and vegetative resources can be main- 
tained to the greatest benefit to the 
human race. A wise national policy 
