On the family farms of yesteryear, farmers relied on natural processes to fertilize and protect their farms. In the mid-20th century, the Green Revolution brought new technology to farming that allowed farmers to produce more food on less land, relying on chemicals to protect crops and livestock from diseases and pests and causing farms to burgeon from family businesses to industrial operations. Although farms now produce large amounts of food for little money, these new methods have not been without repercussions.
Traditionally, farms have functioned as a closed system. Farmers grew crops, which fed the animals, and the animals produced manure that nourished the next generation of crops. As David A. Fahrenthold explains in the Washington Post, changes in U.S. agriculture have shifted the role of manure from fertilizer to toxic waste as small farms give way to large operations with thousands of animals producing more manure than can possibly be used. According to Fahrenthold, manure runoff is one of the leading causes of aquatic dead zones. The U.S. Department of Agriculture adds that manure runoff also contributes to outbreaks of food-borne illness when animal wastes pollute fields used to grow crops.
Just like manure, in appropriate quantities, fertilizer promotes healthy plant growth. However, overuse and misuse of fertilizers high in nitrogen and phosphorus also have devastating consequences for the environment and human health. According to the North Carolina State University, fertilizer pollution contributes to aquatic dead zones, areas in bodies of water where living organisms cannot survive. Even in water, fertilizers have their intended effect: They increase plant growth. The increased growth of algae, though, uses up oxygen needed by other organisms. Additionally, when fertilizers leach into groundwater, blue-baby syndrome, a fatal condition in young children, can result.
As animal farming operations increase in size, the amount of dust they produce reaches potentially hazardous levels. Both soil and manure, when dried, can become airborne as dust, carrying pathogens to neighboring properties. Risk from dust is especially high for farmers and workers. According to the Penn State Cooperative Extension, a condition called "farmer's lung," caused by inhaling harmful particles, may cause permanent lung damage and even death.
By their very nature, pesticides are poisons, meant to kill nuisance insects and animals that destroy crops. When pesticides contaminate water, they can cause harmful effects on people and animals as well. According to the Iowa State University Extension Service, pesticides can reach water in several ways. Pesticides sprayed onto crops can drift into ponds and streams. Runoff also occurs, with pesticides being washed into surface waters, carried away through soil erosion or leaching into groundwater supplies.