Until about four decades ago, crop yields in agricultural systems depended mainly on internal resources, recycling of organic matter, built-in biological control mechanisms, and natural rainfall patterns. Agricultural yields were modest but stable. Production was safeguarded by growing more than one crop or variety in a field as insurance against pest outbreaks or severe weather. Inputs of nitrogen were gained by rotating major field crops with legumes. Growing many different types of crops over the years in the same field also suppressed insects, weeds, and diseases by effectively breaking the life cycles of these pests. A typical corn-belt farmer grew corn rotated with several crops including soybeans as well as the clovers, alfalfa, and small grains needed to maintain livestock. Most of the labor was done by the family with occasional hired help, and no specialized equipment or services were purchased from off-farm sources. In these types of farming systems the link between agriculture and ecology was quite strong and signs of environmental degradation were seldom evident.
The significance of biological diversity in maintaining such systems cannot be overemphasized. Diversity of crops above ground as well as diversity of soil life below ground provided protection against the vagaries of weather, market swings, as well as outbreaks of diseases or insect pests. But as agricultural modernization progressed, the ecology-farming linkage was often broken as ecological principles were ignored or overridden. Numerous agricultural scientists agree that modern agriculture confronts an environmental crisis. A growing number of people have become concerned about the long-term sustainability of existing food production systems. Evidence has accumulated showing that, while the present capital- and technology-intensive farming systems have been extremely productive and able to furnish low-cost food, they also bring a variety of economic, environmental, and social problems.
Evidence also shows that the very nature of the agricultural structure and prevailing policies in a capitalist setting have led to this environmental crisis by favoring large farm size, specialized production, crop monocultures, and mechanization. Today as more and more farmers are integrated into international economies, the biological imperative of diversity disappears due to the use of many kinds of pesticides and synthetic fertilizers, and specialized farms are rewarded by economies of scale. In turn, lack of good rotations and diversification take away key self-regulating mechanisms, turning monocultures into highly vulnerable agricultural ecosystems (agroecosystems) dependent on high chemical inputs.
The Expansion of Farm Specialization and Monocultures
Monocultures or near monocultures have increased dramatically worldwide, where the same crop (usually corn, wheat, or rice) are grown year after year in the same field, or very simple rotations are used (such as corn-soybeans-corn-soybeans). Also fields that in the past contained many different crops, or a single crop with a high degree of genetic variability, are now entirely devoted to a genetically uniform single crop. Available data indicate that the amount of crop diversity per unit of arable land has decreased and that croplands have also shown a tendency toward concentration in fewer hands. There are political and economic forces influencing the trend to devote large areas to monoculture, and in fact the economies of scale of such systems contribute significantly to the ability of national agricultures to serve international markets.
The technologies allowing the shift toward specialization and monoculture were mechanization, the improvement of crop varieties, and the development of agrichemicals to fertilize crops and control weeds, insects, and other crop pests as well as antibiotics and growth stimulants for agricultural animals. United States government …