Traditional, small-scale slash-and-burn cultivation—such as that practiced by the Guaraní people in South America – can be efficient and sustainable, with the natural environment eventually reclaiming and reintegrating old garden plots.
In such places, raising herbivores is often a more reliable lifestyle than farming, and the livestock convert wild vegetation that is indigestible to humans into meat and dairy products.
Agrarian societies are often larger and more complex than foraging, horticultural, or pastoral ones; the combination of high carrying capacity and stationary farmsteads enables dense populations and the development of cities peopled with nonproducing specialists.
Only a small fraction of people in industrial societies are farmers; the rest obtain money to buy their food by engaging in the complex business and service economy.
[6] The energy costs, pesticide use, and widespread erosion implicit in many forms of industrial food production have led to concerns about its long-term sustainability as a pattern of subsistence.