ABSTRACT
In North America, the beginning of the twentieth century saw an agriculture based on animal traction, animal manure, and mechanical weed control, with relatively low productivity. In the twenty-first century, tractors have replaced horses and bullocks; chemical fertilizers have replaced animal manure; and herbicides have largely replaced cultivation as the primary means of weed control. Coupled with advances in plant breeding, these changes have dramatically increased productivity per unit of land and per unit of labor. This increased productivity has had tremendous benefits both for farmers and for society as a whole but has also resulted in unintended effects on the environment and on rural communities. This is not surprising to those familiar with what Merton (1976) refers to as the law of unintended consequences.
