Population and Land Use in Developing Countries Report of a Workshop (1993) / Chapter Skim
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2 Population, Land Use, and Environment: A Long History
2 Population, Land Use, and Environment: A Long History
Pages 15-29
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From page 15... ...
Brief vignettes of the distribution of human activities at selected moments in history coupled with estimates of the kinds of impacts these activities apparently made on the environment provide a perspective on the modern scene. Despite large changes in land and environment in the past, the evidence suggests that the modern global combination of a very large population base, relatively rapid rates of population growth, and very rapid rates of technological change constitute a unique assemblage in human history, an assemblage posing new hurdles to adaptation and enhancing the rate of change.
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From page 16... ...
Understanding the vicissitudes of the natural system is particularly important in evaluating efforts at remediation of human impacts and in assessing the degree to which particular impacts are likely to be manageable if not reversible within varying periods of time. Temporal and spatial scales, however, are interrelated.
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From page 17... ...
Agriculture included upland farming, irrigation in the broad bottomlands of the major river valleys such as the Nile and the Indus and the practice of floodwater farming in small valleys on semiarid hillslopes. The impact of agriculture on the upland, including deforestation and grazing, particularly on limestone terrain, has long been recognized.
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From page 19... ...
Again, in the modern era in this region, huge irrigation developments in the nineteenth-century colonial period in India not only produced large increases in production but also, over time, were plagued with predicted problems of salinization and waterlogging. These huge irrigation systems were carefully designed and continue to operate today, although in a number of areas careful management is required to provide water while also improving drainage by lowering high water tables.
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From page 20... ...
The transformation of the European agricultural landscape has been accompanied by increases in agricultural productivity. Whereas productivity remained relatively constant for the prior several hundred years, crop yields began to increase in the seventeenth century and, in the nineteenth century, wheat yields in England, for example, increased by about 50 percent.
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From page 21... ...
In some tropical regions, recovery of the productivity of the land may be difficult if not impossible as a result of the loss of soil, reduction of filth, and removal of nutrients. It can be argued that the loss of productivity of the land resulting from reduction of fallow periods is directly attributable to increasing rates of population growth outstripping the land available for rotations of clearing.
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From page 22... ...
Unlike the potential impact of land erosion, the impact of storage of sediment in reservoirs is seen by roughly a onethird reduction in the amount of sediment transported in the lower Mississippi River (Williams and Wolman, 1984~. On the land itself, inorganic fertilizers have compensated for natural losses in natural organic material, increasing productivity and masking losses of the original material.
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From page 23... ...
Third, the period of European settlement from 1700 to 1980 is characterized by very high sedimentation rates, although similar sedimentation rates are also associated with earlier periods from 800 to 1300 AD, a warm period in the climatic record prior to western settlement. This warm period is also associated with a high rate of charcoal deposition.
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From page 24... ...
Most of the accelerated increase in agricultural productivity in the past half century is associated with the application of fertilizers and new plant varieties. Increase in the use of herbicides and insecticides made of new synthetic organic compounds unknown in nature poses potential environmental problems not significant in the earlier historical record.
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From page 25... ...
Earlier concepts of landscape equilibrium implied that vegetation, soil, and erosional processes achieved a relatively stable configuration under a particular prevailing climate. Additional work has demonstrated that such equilibria, if they exist, are exceedingly dynamic.
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From page 26... ...
Limited documentation of the relation between population change and land change lends caution to extrapolation into the future of observations of yield declines where sedentary agriculture replaces shifting cultivation, where salinization and waterlogging accompany modern irrigation systems, or where agriculture replaces forests as population grows. At the same time, the
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From page 27... ...
Measures of population must be correlative with the presumed scale of impacts. The tenor of the present debate over projections of land change, population, and environmental degradation appears more pessimistic today than were the global food production models projected a few years ago.
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From page 28... ...
1987 The industrial revolution and land transformation.
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From page 29... ...
U.S. Geological Survey Professional Paper 1286.
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