Teams of INSTAAR and USGS scientists have analyzed data from more than 4,000 rivers around the world that indicate humans are having profound and conflicting effects on the amount of sediment carried by rivers to coastal areas, with consequences for marine life and pollution control. The report found that humans are stirring up much more sediment than expected, about 2.3 billion metric tons annually, through regionally diverse patterns of agriculture and other soil erosion activities. However, manmade reservoirs are simultaneously reducing the flux of sediment reaching the world's coasts by about 1.4 billion metric tons per year. The net sediment transfer from an individual river to the ocean can greatly affect sensitive coastal zones, including nutrient balances, pollution levels, harbor dredging, coastal fish farms and coral reefs, coastal wetlands, and seagrass communities.
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