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Science 15 April 2005:
Vol. 308. no. 5720, p. 321
DOI: 10.1126/science.308.5720.321b
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Many large river systems that support a wide variety of ecosystems have been impacted by human needs. Nilsson et al. (p. 405) present a global overview of how dams have fragmented the world's largest river systems. Nearly half of the world's large river systems have major dams or diversions that either fragment ecosystems or reduce or regulate flow. Syvitski et al. (p. 376) describe a method for quantifying the impacts of anthropogenic activity, such as building dams, on the delivery of sediments to the coasts. They present an analysis of how sediment fluxes have changed between the past, when human influence was negligible, and the present. Their quantitative, global, river-by-river survey of the majority of the world's rivers reveals that human activities, like irrigation or agriculture, have increased fluvial sediment erosion, but that the rate of sediment delivery to the coasts has decreased because of trapping in artificial reservoirs.




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