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River strategies outline cleanup effort
Not all nutrients created equal from algal standpoint
New monitoring data find no nutrient trends in major rivers
With our often single-minded focus on meeting nutrient reduction goals here in the Chesapeake watershed, we lose sight of the fact that we are not alone in pursuit of this difficult task. Indeed, similar goals are being pursued in even larger and more politically complex watersheds covering most of the European continent.
I had a chance to compare notes while attending a workshop in Berlin this December. Leading scientific experts had prepared overviews of progress in addressing eutrophication in the Baltic Sea, North Sea coast and Black Sea. I thought Bay Journal readers might be interested in hearing about the struggles across the pond. European efforts, often more ambitious than those under way in the Bay, offer hope that our goals can be met, but raise questions about our ability to achieve large reductions from nonpoint sources of nutrients.
The Helsinki Commission (HELCOM) is the “Bay Program” for the Baltic. But it has to address a 1,700,000 km2 catchment area (about 10 times larger than that of the Chesapeake), including 14 nations and 85 million people.
In 1988, less than a year after the landmark Second Chesapeake Bay Agreement, HELCOM adopted a declaration for the protection of the Baltic marine environment in which the Baltic nations pledged themselves to reduce the discharges of nitrogen and phosphorus by 50 percent by 1995. According to Dr. Ragnar Elmgren of Stockholm University, this was later interpreted (as with the Chesapeake) to mean 50 percent of the anthropogenic discharges when it became clear that halving the total input including natural sources was practically infeasible.
Although some HELCOM countries (Denmark, Sweden, Germany and Finland) have been successful in greatly reducing anthropogenic phosphorus inputs by treating municipal and industrial wastes, none of the signatory countries has reached the 50 percent goal for nitrogen reduction.
Success in reducing agricultural and atmospheric sources of nitrogen has been particularly elusive. Curiously, only the Baltic States (Estonia, Latvia and Lithuania), Poland and Russia are considered to be close to the 50 percent nutrient reduction goal for the agricultural sector — and this is mainly the result of the economic recession and resulting decline in the use of fertilizers during the 1990s.
Nonetheless, Dr. Elmgren optimistically pointed out that in coastal regions where significant nutrient reductions have been achieved, such as the Himmerfjärden and Stockholm area in Sweden, dramatic improvements have been seen within one or two years. Recovery of the open Baltic Sea, however, will be a much longer-term proposition. The volume of the Baltic (21,000 km3) is more than 250 times that of the Chesapeake and there is a much longer turnover time for nitrogen (five to six years) and phosphorus (13 years). By comparison turnover times for nutrients in the water column of the Chesapeake are just three to four months.
Similar agreements for a 50 percent reduction of nitrogen and phosphorus discharges into the North Sea by 1995 were made under the auspices of the Oslo and Paris Commissions (OSPARCOM). In remarkably parallel evolution, this 50 percent goal was set in the declaration of the Second North Sea Conference in the same year (1987) that our 40 percent goal was included in the Second Bay Agreement.
In contrast to the Baltic, the North Sea has a much greater interchange with the ocean, significant tides and strong currents. Its susceptibility to eutrophication, then, is more restricted to estuaries and nearshore zones, particularly the German Bight off the Netherlands, Germany and Denmark. This region is influenced by discharges of major Western European rivers, the Scheldt, Meuse, Ems, Weser, Rhine and Elbe. The latter two are by far the largest of these.
The Wadden Sea, actually a series of broad lagoons characterized by expansive tidal flats, covers most of the coastal zone of this region. Wadden Sea environments have been enriched by nutrients brought in from the river-influenced North Sea more than by run-off from their small coastal watersheds. Dr. Karsten Reise of Germany’s Wegener Institute for Polar and Marine Research and Dr. Franciscus Colijn of the University of Kiel in Germany described the many resulting changes in the Wadden Sea, including the loss of eelgrass and an increase of green algal mats that smother the productive tidal flats.
German hydrologist Horst Behrendt has analyzed changes in the sources of nitrogen and phosphorus emitted from the Rhine (159,700 km2 catchment) and Elbe (134,900 km2) river basins during a period of active management between 1983–1987 and 1993– 1997 using monitoring data and GIS-based modeling. Nitrogen discharges into both rivers declined 29 percent during this period. This is based on total load; for comparison, the 40 percent of “controllable” load goal for the Chesapeake equates to about 21 percent of total load. Of course, the level of nitrogen enrichment of the Rhine was far greater than that for Chesapeake rivers in the first place. The main reason for the decrease in nitrogen inputs into these rivers was large reductions from municipal and industrial point sources (46 percent). The estimated decrease in diffuse inputs was only about 10 percent.
Total phosphorus emissions were reduced by an even greater amount, 60 percent and 52 percent for the Rhine and Elbe, respectively, mainly from the improved treatment of industrial and municipal waste water discharges. Dissolved phosphorus delivered to the river basin as a result of surface runoff from soils and from urban areas was essentially unchanged.
The Black Sea has a catchment of 1,875,000 km3 with a population of as many as 160 million people living in 17 countries, all of which — excepting Turkey, Austria and the former West Germany — were formerly in the Soviet Union or Warsaw Pact. The Black Sea, particularly its broad northwestern shelf region, has undergone profound changes since the early 1970s as result of eutrophication. These include the loss of 11,800 km2 of submerged algal beds (an area greater in extent than all of the tidal waters of the Chesapeake Bay), a “dead zone” of extreme hypoxia covering as much as 15,000 km2 (as big as or bigger than the dead zone off the Mississippi River; (See “Gulf of Mexico faces Baylike nutrient issues on a grand scale” December 1999 Bay Journal), and the dramatic collapse of many fisheries.
The real showstopper, though, was Dr. Laurence Mee’s (formerly coordinator of the United Nation’s Black Sea Environmental Programme) piecing together of the dramatic improvement in the conditions of the northwestern Black Sea resulting from the fall of communism. Over a two-year period (1989– 1991) the collapse of a centralized economy and subsidized agricultural production resulted in a decline in the application of phosphorus fertilizers in the Danube River basin of about 60 percent and of nitrogen fertilizers of about 50 percent. Similar reductions in fertilizer use occurred in other Black Sea river basins such as the Dnieper.
Within two years, substantial reductions in the discharge of nitrogen (by about 40 percent) and phosphorus (more than half) from rivers into the Black Sea were observed and reductions in nitrogen discharge continued to decline to the point where in 1997 they were less than 40 percent of 1987 or 1988 discharges, leading Dr. Mee to conclude that there is a lag time of about seven years for nitrogen and three years for phosphorus. To complete the story thus far, in 1996 the zone of severe hypoxia on the northwestern shelf of the Black Sea disappeared for the first time in 23 years. This “grand experiment” provides rather unambiguous evidence of the need to limit fertilizer application and nutrient losses in agriculturally intense watersheds that drain to coastal waters susceptible to eutrophication.
Mee also observed that crop production was proportionally much less affected by this economic disruption, suggesting that fertilizers had been applied in excess of requirements and with considerable wastage.
The turn of events also provided the Black Sea community with an empirical basis for identifying a loading cap below which hypoxia would be unlikely, without reliance on a model and all of its assumptions. The Istanbul Commission for the Protection of the Black Sea and the International Commission of the Protection of the Danube have therefore set as a goal of not exceeding the 1997 nutrient loading levels as the region economically recovers and develops. This is an unimaginably difficult task given the fact that in a number of countries environmental agencies have been reduced in size and demoted in status, as well as the elimination of funding for research institutions as new democracies struggle for their political and economic future.
Here are the lessons I took home, along with a few souvenirs from Berlin. (Unfortunately relics of the Wall proved far too expensive, not to mention too heavy.) First, we in the Chesapeake have a much easier challenge than our European counterparts. As big as it seems to us, the catchment area of the Chesapeake is only approximately the same size as that of the Rhine. Our scientific and management firepower per unit area is enormously greater (and, thank goodness, is regularly paid). We are just six states and a national capital in one relatively homogeneous, extraordinarily prosperous and largely monolingual nation. And, frankly, our goals are not as ambitious.
Second, as with the Chesapeake, the idealistic goals set for the North and Baltic seas in 1987-1988 have not yet been fully met. Much progress has been made, though, particularly with regard to phosphorous, and to some extent by treatment of point sources of nitrogen.
Third, successes in the reduction of nonpoint sources, particularly of nitrogen, have been more limited except where dramatically changed economic conditions in Eastern Europe resulted in a drastic reduction in fertilizer application and intense animal farming. In Western Europe, the implementation of agricultural management practices called for by the European Commission’s Nitrate Directive has not yet yielded the hoped-for reductions in loadings to rivers. While this may in part be due to the lag time associated with groundwater movement, the perestroika experiment in the Danube basin indicates that the response of water quality to reductions in nutrient losses from agriculture in large river basins can be surprisingly quick (a few years). This calls into question the effectiveness of various nitrogen management practices.
Finally, an analysis of results thus far in the Baltic Sea and North Sea rivers indicates that the ambitious nitrogen reduction goals are unlikely to be met by point and conventional nonpoint source controls. In both cases, it has been concluded that wetland and river basin restoration to reinstate nutrient traps and a more aggressive reduction of atmospheric sources of nitrogen are required.
Suggested Reading
- Jansson, B.-O. and K. Dahlberg. 1999. “The Environmental Status of the Baltic Sea in the 1940s, Today and in the Future.” Ambio 28: 312-319.
- Dittman, S. (ed.). 1999. “The Wadden Sea Ecosystem: Stability Properties and Mechanisms.” Springer Verlag, Berlin.
- Mee, L.D. and G. Topping (eds.). 1999. “Black Sea Pollution Assessment. Black Sea Environmental Series Vol. 10.” UN Publications, New York.
