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Nothing, however, is to be compared with the multiplying environmental impacts of human activities since 1950, a period dubbed by historians as “The Great Acceleration.” In the words of the United Nations Millennium Ecosystem Assessment, “over the past 50 years, humans have changed ecosystems more rapidly and extensively than in any comparable period of time in human history, largely to meet rapidly growing demands for food, fresh water, timber, fiber, and fuel. This has resulted in a substantial and largely irreversible loss in the diversity of life on Earth.” The post-WWII global economic order promoted liberal and accelerated trade, capital investment, and technological innovation tethered to consumer markets, mostly free of environmental impact considerations. The resultant economic growth, and the corresponding drawdown of natural resources, are nonlinear    in character, which is, exhibiting an unpredictable and exponential rate of increase.

All systems, human and natural, are characterized by nonlinear change. We are habituated to viewing our history as a legible story of “progress,” governed by simple cause-and-effect and enacted by moral agents, with the natural world as a backdrop to scenes of human triumph and tragedy. But history, from a sustainability viewpoint, is ecological rather than dramatic or moral; that is, human events exhibit the same patterns of systems connectivity, complexity, and non-linear transformation that we observe in the organic world, from the genetic makeup of viruses to continental weather systems. The history of the world since 1950 is one such example, when certain pre-existing conditions—petroleum-based energy systems, technological infrastructure, advanced knowledge-based institutions and practices, and population increase—synergized to create a period of incredible global growth and transformation that could not have been predicted at the outset based upon those conditions alone. This unforeseen Great Acceleration has brought billions of human beings into the world, and created wealth and prosperity for many. But nonlinear changes are for the bad as well as the good, and the negative impacts of the human “triumph” of postwar growth have been felt across the biosphere. I will briefly detail the human causes of the following, itself only a selective list: soil degradation, deforestation, wetlands drainage and damming, air pollution and climate change.

Soil degradation

Since the transition to agriculture 10,000 years ago, human communities have struggled against the reality that soil suffers nutrient depletion through constant plowing and harvesting (mostly nitrogen loss). The specter of a significant die-off in human population owing to stagnant crop yields was averted in the 1970s by the so-called “Green Revolution,” which, through the engineering of new crop varieties, large-scale irrigation projects, and the massive application of petroleum-based fertilizers to supplement nitrogen, increased staple crop production with such success that the numbers suffering malnutrition actually declined worldwide in the last two decades of the 20 th century, from 1.9 to 1.4 billion, even as the world’s population increased at 100 times background rates, to 6 billion. The prospects for expanding those gains in the new century are nevertheless threatened by the success of industrial agriculture itself. Soil depletion, declining water resources, and the diminishing returns of fertilizer technology—all the products of a half-century of industrial agriculture—have seen increases in crop yields level off. At the same time, growing populations in developing countries have seen increasing clearance of fragile and marginal agricultural lands to house the rural poor.

Practice Key Terms 4

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Source:  OpenStax, Sustainability: a comprehensive foundation. OpenStax CNX. Nov 11, 2013 Download for free at http://legacy.cnx.org/content/col11325/1.43
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