Matters of Scale - Arteriosclerosis of the Earth

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Number of large dams (at least 15 meters high) that were blocking the world's rivers as of 1950
5270
Number that had been built by 1985
36562
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Number of large dams in China as of 1950
2
Number that had been built by 1985
18820
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Average frequency of major floods of the Rhine River in Karlsruhe, Germany (7.6 meters or more above the flood level) between 1900 and 1977
once every 19 years
Average frequency during the last 19 years, after extensive river engineering which eliminated natural flood controls
once every 2 years
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Number of salmon caught in the Rhine River (Germany and Holland) annually, 100 years ago
150000
Number caught annually by the end of the 1950s
0
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Millions of pounds of salmon and steelhead caught in the Columbia River by commercial fishermen in 1884
42.2
Millions of pounds caught in 1994
1.2
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Sources: Janet N. Abramovitz, Worldwatch Paper 128, Imperiled Waters, Impoverished Future: The Decline of Freshwater Ecosystems (Washington, D.C.: Worldwatch Institute, 1996).