History: Small to Large
Agricultural practices have changed dramatically in the last fifty years as global population has grown. Over the next fifty years, global demand for food is expected to double (Tilman 2002). Traditions of subsistence farming and organic methods have been increasingly replaced with large scale methods that have coincided with an increased use of nitrogen and phosphorus and pesticides. While new practices have allowed for a dramatic increase in food production, they have also reduced the ability of ecosystems to provide vital services. The average land use of a single farm has more than doubled over the last century (Arth et. al 2007). Due to increased efficiency in the agricultural industry, the number of farmers in the United States has significantly decreased, now accounting for less than two percent of the country’s labor (Arth et. al 2007).
With the rise of intensive agriculture, most farmers today utilize mono-crop systems, the planting of a genetically singular crop. Mono-crop systems have become more economically rewarding, partly because government agricultural subsidies tend to favor mono-cropping (Lean, 6; 2006). Cultivating only a single species, however, can stress the fertile topsoil and reduce genetic diversity. Mono-crop systems are often accompanied by an increase in both farm size and dependency on technology. Such large, intensive farming systems lend themselves to greater waste production and greenhouse gas emissions. Additionally, mono-cropping increases the susceptibility of plants to disease as a single pathogen has the potential to destroy an entire crop. Rice farms in China have successfully combated diseases that coincide with mono-cropping by planting genetically dissimilar strains of rice in a field (Tilman 2002).
Agriculture and Water
Agriculture is also highly dependent on water availability. Over 70 percent of the global freshwater supply is used for agricultural purposes (Lean, 24; 2006). Compared to the 10 percent used for domestic purposes, agriculture is the overwhelming contributor to water-stressed regions. Water must be used more efficiently if the needs of the global population are to be met. However, irrigation proves vital in supplying global food needs. Although only 16 percent of agricultural land is irrigated, this area accounts for 40 percent of global food supply. The implementation of new technology such as drip irrigation (where water is carried through tubes directly to the crop) has the potential to greatly increase water-use efficiency (Tilman 2002). Agricultural runoff due to the synthetic fertilization of farmland and new farming practices also contributes to water contamination through the addition of chemicals and soil into the water system. This runoff is rich in nitrates and phosphorus, both of which pollute drinking water and cause eutrophication (the destruction of aquatic life due to an overabundance of algae) (Filson 24). Intensive land use heightens soil erosion, increasing the amount of runoff to surrounding water bodies, and inefficient land use degrades once fertile land, forcing expansion into more fragile areas. These are directly linked to both deforestation and desertification.
Pesticides are chemicals that are used in the agriculture industry to repel and/or kill pests which threaten crop yield (EPA 2007). This category includes substances such as insecticides and herbicides (EPA 2007). These chemicals contaminate water sources as they seep into groundwater and as they are carried into streams and lakes by runoff water (Carpenter et. al 1998). Pests often evolve to develop resistance to these chemicals, creating a need for stronger, more harmful substances which increase environmental degradation and risk to human health (Insecticide Resistance Action Committee 2007).
Fertilizers are nutrient additions to the soil, either organic or synthetic, that most commonly include phosphorus, nitrogen and/or potassium (EPA 2007). The application of nitrogen and phosphorous into the soil can greatly increase crop yields. Between 1960 and 1995, global fertilizer use for nitrogen increased by seven times its previous amount. However, only 30-50% of this amount is actually taken up by plants allowing much of it to be washed away from fields into the surrounding ecosystem. As previously explained, this can lead to over-enrichment of the surrounding ecosystem and eutrophication. Using organic fertilizers tends to reduce the risk of runoff by slowly releasing nutrients into the surrounding crops (Tilman 2007).
Assessing the Problem
Changing priorities are putting stress on the worldâ€™s agricultural systems. Enough food is produced globally to adequately feed eight to ten billion people, yet many still suffer in hunger (Tilman 2007). The problem lies with distribution; not only are agricultural products not reaching starving populations, but they are simultaneously being pulled in other directions. An increasing demand for meat and animal products, particularly among affluent societies, requires more agricultural output for that purpose (Clay 14). Biotechnology and the search for alternative fuel sources such as ethanol will also put stress on agricultural production, drawing important resources from food production. Currently, over 20% of the corn crop in the United States goes to ethanol production; and this number is projected to increase as the government continues its support for ethanol production (Krauss 2007).
Agriculture is closely linked with other environmental challenges, especially the chemical industry, climate change, water quality and deforestation. Worldwide, a growing human population increasingly relies on unsustainable agricultural practices. As world population approaches nine billion, global food demand is expected to at least double in the next fifty years (Lean, 10; 2007). In attempting to meet increased food demands, societies worldwise run the risk of depleting their natural resources and degrading the environment. Improvement in agricultural practices requires a global system of research and technology dissemination. Agriculture cannot be sufficiently addressed without attention to other environmental issues.
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