Chapter 2: Agroecology and Agroecosystems [Ch. 2 in Agroecosystems Analysis, American Society of Agronomy, Madison, WI. 2004. pp. 19-30] Stephen R. Gliessman Program In Community and Agroecology Department of Environmental Studies University of California, Santa Cruz,CA Introduction Agriculture is more than an economic activity designed to produce a crop or to make as large a profit as possible on the farm. A farmer can no longer only pay attention to the objectives and goals for his or her farm and expect to adequately deal with the concerns of long-term sustainability. Discussions about sustainable agriculture must go far beyond what happens within the fencesof any individual farm. Farming is now viewed as a much larger system with many interacting parts, including environmental, economic, and social components (Gliessman, 2001; Flora, 2001). It is the complex interactions and balance among all of these parts that have brought us together to discuss sustainability, determine how we move towards this broader goal, and how an agroecological perspectivefocused on sustainable agroecosystems is a way to achieve such long term objectives. Much of modern agriculture has lost the balance needed for long-term sustainability (Kimbrell, 2002). With their excessive dependence on fossil fuels and external inputs, most industrialized agroecosystems are overusing and degrading the soil, water, genetic, and cultural resources upon which agriculture hasalways relied. Problems in sustaining agriculture’s natural resource foundation can only be masked for so long by modern practices and high input technologies. In a sense, as we borrow ever-increasing amounts of water and fossil fuel resources from future generations, the negative impacts on farms and farming communities will continue to become more evident. The conversion to sustainableagroecosystems must become our goal (Gliessman, 2001). In an attempt to clarify my own thinking about agroecosystems, I often think of agriculture as a stream, and farms are different points along that stream. When we think of an individual farm as a "pool" in a calm eddy at some bend in the stream's flow, we can imagine how many things "flow" into a farm, and we also expect that many things "flow" out of itas well. As a farmer, I work hard to keep my pool in the stream (my farm) clean and productive. I try to be as careful as possible how I care for the soil, which crops I plant, how I control pests and diseases, and how I market my harvest. Back in the days when there weren't as many farms, fewer people to feed, and smaller demands on farmers and farmland, I could keep my farm in pretty good shape.I could keep my “pool” in the stream pretty clean, and did not have to worry very much about what was going on "downstream" from my farm. But such a strategy has become much more difficult today. I find that I have less and less control over what comes into my "pool." I face a variety of "upstream impacts" that in combination can threaten the sustainability of my farm. This includes the inputsinto my farm that either I purchase or which arrive from the surrounding area. They include labor availability and cost, market access for what I produce, legislated policies that determine how much water I use, pesticides I apply, or how I care for my animals, not to mention the vagaries of the weather! My pool can become quickly muddied.
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I must also increasingly consider that the way I take care of my “pool” can have "downstream effects" in the stream below. Soil erosion and groundwater depletion can negatively affect other farms than my own. Inappropriate or inefficient use of pesticides and fertilizers can contaminate the water and air, as well as...