AGRICULTURE IS PRIMARY SOURCE OF NUTRIENT POLLUTION IN U. S central and western Europe Figure 2: Nitrogen and Phosphorous Discharges to U.S. Surface Waters from show the highest levels(Eea Point and Nonpoint Sources(in thousands of metric tons per year) 1999: 174). In general, phosphorous concentrations SOURCE NITROGEN PHOSPHOROUS have decreased significantly onpoint sources since 1985, mostly due to Croplands 3,20 615 use Pastures 292 95 treatment and the reduced of phosphorous in detergents Rangelands 242 However, phosphorus levels Forests 1,035 remain a problem in most er rur 659 regions of Europe (EEa 1999: 174). Despite some Total nonpoint discharges 6,663 1,658 positive trends, the overal Total point sources 1,495 30 state of many European rivers Total discharge(point nonpoint) 8 2,015 with respect to nutrient Nonpoint as a percentage of total concentrations remains poor Source: Carpenter et aL. 1998. CEEA1998:194-196 Figure 3 shows water watersheds that have been lower fertilizer application quality data for the United intensively used and modified rates, compared to Europe. States for the 1980s. For the by human activity, such as the More detailed and recent 1980-89 period, nitrate Weser, Seine, Rhine, Elbe, and data available in Europe show concentrations remained egal. High levels are also distinct regional trends in the latively stable, with most found in such watersheds in concentrations of nitrates and monitoring stations showing China, South Africa, and the ph phosphorous in rivers. Nitrate no discernable trend. This Nile and Mississippi basins loadings are highest in areas probably reflects the fact that (UNEP/GEMS 1995: 33-35). with intensive livestock and nitrogen fertilizer use in the In South America, nitrate crop production, especially in concentrations in the the northern parts of western Steady increases in the 1970s monitored watersheds are Europe. Nitrate concentrations Fertilizer application rates elatively low and follow increased for the period 1974- are lowest in Finland, Norway, 1981 and nitrate human land use. The highest and Sweden. Overall nitrate nitrate concentrations are concentrations in monitored concentrations increased as found in the Uruguay European rivers have not well during that period watershed, where some of the changed significantly since Average nitrate concentration most intensive agriculture on 1980, despite lower nitrogen were greater in agricultural and the continent is found. Nitrate fertilizer application rates since urban areas than in forested also greater the 1990s(EEA 1998: 194-197: areas( Smith et al 1994: 122) in the Magdalena watershed of EEA 1999: 176-177) Trends in phosphorou Colombia than in the less Similar regional patterns are concentrations in the United densely populated watersheds also evident in phosphorous greater of the amazon basin trends. Rivers in Finland improvement, with five times (UNEP/GEMS 1995: 33-35) Norway, and Sweden have the more states showing The nitrate concentrations in lowest phosphorous downward trends than upward South America correspond to concentrations, whereas areas trends. Decreases were more from southern england likely to be found in the East Midwest, and the great Lakes OEarthTrends 2001 World Resources Institute. All rights reserved. Fair ed on a limited scale and for educational©EarthTrends 2001 World Resources Institute. All rights reserved. Fair use is permitted on a limited scale and for educational purposes. 3 watersheds that have been intensively used and modified by human activity, such as the Weser, Seine, Rhine, Elbe, and Senegal. High levels are also found in such watersheds in China, South Africa, and the Nile and Mississippi basins (UNEP/GEMS 1995:33-35). In South America, nitrate concentrations in the monitored watersheds are relatively low and follow human land use. The highest nitrate concentrations are found in the Uruguay watershed, where some of the most intensive agriculture on the continent is found. Nitrate concentrations are also greater in the Magdalena watershed of Colombia than in the less densely populated watersheds of the Amazon basin (UNEP/GEMS 1995:33–35). The nitrate concentrations in South America correspond to lower fertilizer application rates, compared to Europe. More detailed and recent data available in Europe show distinct regional trends in the concentrations of nitrates and phosphorous in rivers. Nitrate loadings are highest in areas with intensive livestock and crop production, especially in the northern parts of western Europe. Nitrate concentrations are lowest in Finland, Norway, and Sweden. Overall nitrate concentrations in monitored European rivers have not changed significantly since 1980, despite lower nitrogen fertilizer application rates since the 1990s (EEA 1998:194–197; EEA 1999:176–177). Similar regional patterns are also evident in phosphorous trends. Rivers in Finland, Norway, and Sweden have the lowest phosphorous concentrations, whereas areas from southern England across central and western Europe show the highest levels (EEA 1999:174). In general, phosphorous concentrations have decreased significantly since 1985, mostly due to improvements in wastewater treatment and the reduced use of phosphorous in detergents. However, phosphorus levels remain a problem in most regions of Europe (EEA 1999:174). Despite some positive trends, the overall state of many European rivers with respect to nutrient concentrations remains poor (EEA 1998:194-196). Figure 3 shows water quality data for the United States for the 1980s. For the 1980–89 period, nitrate concentrations remained relatively stable, with most monitoring stations showing no discernable trend. This probably reflects the fact that nitrogen fertilizer use in the United States leveled off after steady increases in the 1970s. Fertilizer application rates increased for the period 1974– 1981, and nitrate concentrations increased as well during that period. Average nitrate concentrations were greater in agricultural and urban areas than in forested areas (Smith et al. 1994:122). Trends in phosphorous concentrations in the United States showed greater improvement, with five times more states showing downward trends than upward trends. Decreases were more likely to be found in the East, Midwest, and the Great Lakes SOURCE NITROGEN PHOSPHOROUS Nonpoint sources Croplands 3,204 615 Pastures 292 95 Rangelands 778 242 Forests 1,035 495 Other rural lands 659 170 Other nonpoint sources 695 68 Total nonpoint discharges 6,663 1,658 Total point sources 1,495 330 Total discharge (point + nonpoint) 8,158 2,015 Nonpoint as a percentage of total 82% 84% Source: Carpenter et al. 1998. AGRICULTURE IS PRIMARY SOURCE OF NUTRIENT POLLUTION IN U.S. WATERS Figure 2: Nitrogen and Phosphorous Discharges to U.S. Surface Waters from Point and Nonpoint Sources (in thousands of metric tons per year)