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DOI: 10.1126/science.1109454 , 376 (2005); 308Science et al.James P. M. Syvitski,Sediment to the Global Coastal OceanImpact of Humans on the Flux of Terrestrial www.sciencemag.org (this information is current as of October 17, 2007 ):The following resources related to this article are available online at http://www.sciencemag.org/cgi/content/full/308/5720/376version of this article at: including high-resolution figures, can be found in the onlineUpdated information and services, http://www.sciencemag.org/cgi/content/full/308/5720/376/DC1 can be found at: Supporting Online Material http://www.sciencemag.org/cgi/content/full/308/5720/376#otherarticles, 1 of which can be accessed for free: cites 8 articlesThis article 49 article(s) on the ISI Web of Science. cited byThis article has been http://www.sciencemag.org/cgi/content/full/308/5720/376#otherarticles 8 articles hosted by HighWire Press; see: cited byThis article has been http://www.sciencemag.org/cgi/collection/oceansOceanography : subject collectionsThis article appears in the following http://www.sciencemag.org/about/permissions.dtl in whole or in part can be found at: this articlepermission to reproduce of this article or about obtaining reprintsInformation about obtaining registered trademark of AAAS. is aScience2005 by the American Association for the Advancement of Science; all rights reserved. The title CopyrightAmerican Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by theScience on October 17, 2007 www.sciencemag.orgDownloaded fromImpact of Humans on the Flux ofTerrestrial Sediment to theGlobal Coastal OceanJames P. M. Syvitski,1*Charles J. Vo¨ro¨smarty,2Albert J. Kettner,1,3Pamela Green2Here we provide global estimates of the seasonal flux of sediment, on a river-by-river basis, under modern and prehuman conditions. Humans have simul-taneously increased the sediment transport by global rivers through soilerosion (by 2.3 T 0.6 billion metric tons per year), yet reduced the flux ofsediment reaching the world’s coasts (by 1.4 T 0.3 billion metric tons peryear) because of retention within reservoirs. Over 100 billion metric tons ofsediment and 1 to 3 billion metric tons of carbon are now sequestered inreservoirs constructed largely within the past 50 years. African and Asianrivers carry a greatly reduced sediment load; Indonesian rivers deliver muchmore sediment to coastal areas.Coastal retreat has major implications for hu-man habitat, because 937% (2.1 billion peoplein 1994) of the world_s population live within100 km of a coastline, and approximately 44%live within 150 km of a coastline (1). Coastalretreat is directly influenced by the reduction ofriver-supplied sediment (2). Thus, a goal of theInternational Geosphere Biosphere Programme(IGBP) and its core project, Land Ocean In-teraction in the Coastal Zone (LOICZ), hasbeen to survey the terrestrial sediment supplyto the coast and to analyze human perturbationof this flux (3). Changes in sediment supplycan greatly influence the benthic environ-ment of coastal estuaries (4), coral reefs (5),and seagrass communities (6). In addition, nu-trient fluxes, particularly carbon, are intimatelytied to the flux of sediment (7), which hasimplications for coastal fisheries (8). Sedimentdelivery will also affect harbor maintenanceand the potential for burial of pollutants (9).Yet even with such environmental impor-tance, G10% of the world_s rivers have beenmonitored for their sediment delivery to thecoastal zone or have observational data onthem available to researchers (3). Of the riversthat have been monitored, most have had theirsediment-gauging activities terminated (3). Toaddress this paucity of data, we describe aglobally consistent method for the estimationof the sediment flux near river mouths. Wecombine databases and models to determinethe prehuman and modern delivery rate ofsediment to the coast, including seasonal at-tributes, on a river-by-river global basis.Global river discharge. A recent updateto the Simulated Topological Network 30minute (latitude  longitude) (STN-30p) forpotential river flow paths (10) provides thespatial framework for organizing environmentaldata into distinct river basins. STN-30p is madeup of È60,000 grid cells at 30¶ spatial resolutionfor the continental land mass. These cells define6292 river basins with drainage areas 9100km2. 4464 of these (i.e., those basins that arenot covered by the ice sheets of Antarctica,Greenland, and portions of the CanadianArchipelago) have a positive discharge to theocean or sea and are analyzed in this work.STN-30p catchment areas have a 7.5% absoluteerror, with a 2% positive bias (11).The University of New Hampshire waterbalance and transport model (WBM/WTM),based on the STN-30p network, provides afundamental structure for analyzing sedimentflux distribution by river basin, continent,climatic zone, and receiving ocean or sea(12). WBM/WTM estimates of discharge areconstrained by observed hydrographic data(11, 13). Selected (663) gauging stations fromthe Global Runoff Data Centre (GRDC) ar-chive were coregistered to the STN-30p net-work, and these represent 76 Mkm2(72%) ofthe world’s actively discharging landmass. Theaccuracy of GRDC discharge measurements isÈ10 to 20%, which is much higher than whatRESEARCH ARTICLES1Environmental Computation and Imaging Facility,Institute of Arctic and Alpine Research (INSTAAR), Uni-versity of Colorado, Boulder, CO 80309–0450, USA.2Water Systems Analysis Group, Institute for theStudy of Earth, Oceans, and Space, University ofNew Hampshire, Durham, NH 03824, USA.3AppliedEarth Sciences, Delft University of Technology, Delft,Netherlands.*To whom correspondence should be addressed.E-mail: james.syvitski@colorado.edu105104103102100100101102103104105Observed Suspended Load (kg/s)101ART Model Predictions of Suspended Load (kg/s)Ganges 25Mekong 22Orinoco 10Orange 14Pearl 21Niger 13Tana 15Fraser 5Brazos 9Mae Klong 24Indigirka 19Chao Phryra 23Kuskowim 2Ebro 12Colville 1Pyasina 18Squamish 4South 7Lockhart 26Nottaway 8Ta z 1 7Normanby 27Rakaia 29Homathko 3Flinders 28Negro 11Amur 20Mackenzie 6Nile 16tropical >25°Cwarm temperate 10-25°Ccold temperate 0-10°Cpolar <0°C1234569871015111213141617181920212223242526282729Orange (post dam)Ebro (post dam)Nile (post dam)Fig. 1. Comparing observations of sediment loads with ART model


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