Nor must it be forgotten that, while our population is increasing, and our “wild lands” are being appropriated, the productive capacity of our soil is being steadily reduced, which, practically, amounts to the same thing as reducing its quantity. Speaking generally, the agriculture of the United States is an exhaustive agriculture. We do not return to the earth what we take from it; each crop that is harvested leaves the soil the poorer. We are cutting down forests which we do not replant; we are shipping abroad, in wheat and cotton and tobacco and meat, or flushing into the sea through the sewers of our great cities, the elements of fertility that have been embedded in the soil by the slow processes of nature, acting for long ages. [p. 27, 1]
George, Henry. (1934) 1981. Social Problems. New York: Robert Schalkenbach Foundation. ISBN: 0–911312–17-X.