What common thread ties together such seemingly diverse coastal problems as red tides, fish kills, some marine mammal deaths, outbreaks of shellfish poisonings, loss of seagrass habitats, coral reef destruction, and the Gulf of Mexico’s “dead zone”? Over the past 20 years, scientists, coastal managers, and public decisionmakers have come to recognize that coastal ecosystems suffer a number of environmental problems that can, at times, be attributed to the introduction of excess nutrients from upstream watersheds. The problems are caused by a complex chain of events and vary from site to site, but the fundamental driving force is the accumulation of nitrogen and phosphorus in fresh water on its way to the sea. For instance, runoff from agricultural land, animal feeding operations, and urban areas plus discharge from wastewater treatment plants and atmospheric deposition of compounds released during fossil-fuel combustion all add nutrients to fresh water before it reaches the sea.
The introduction of excess nutrients into coastal systems, or nutrient enrichment, has a number of impacts. One of the most common effects is acceleration of a natural process known as eutrophication—that is, the increasing organic enrichment of an ecosystem.1 Large inputs of nutri-
ents (nutrient over-enrichment) can lead to excessive, and sometimes toxic, production of algal biomass (including harmful red and brown tides), loss of important habitat such as seagrass beds and corals, changes in marine biodiversity and distribution of species (with impacts on commercial fisheries), and depletion of dissolved oxygen (hypoxia and anoxia) and associated die-offs of marine life. Each of these impacts carries associated costs. A single harmful algal bloom, taking place in a sensitive area during the right season, might cost the region millions of dollars in lost tourism or lost seafood revenues.
Nutrient over-enrichment is a significant problem for the coastal regions of the United States. Because rivers transport the vast majority of nutrients reaching coastal waters, the concentration of land-borne nutrients tends to be high near the mouths of rivers. These areas of mixed fresh and marine water, referred to as estuaries, tend to be relatively slow moving and biologically rich water bodies that are particularly susceptible to the effects of nutrient over-enrichment. Of 139 coastal sites (138 estuaries plus a portion of the Gulf of Mexico) examined in the only comprehensive examination of the extent of eutrophic coastal conditions conducted to date (Bricker et al. 1999), 44 were identified as experiencing conditions symptomatic of high overall levels of nutrient over-enrichment (e.g., showing symptoms such as low dissolved oxygen, nuisance and toxic algal blooms, loss of submerged aquatic vegetation). Problem areas occur on all coasts, including those of California, Florida, Louisiana, Maryland, Massachusetts, New York, North Carolina, Texas, and Washington, but problems are particularly severe along the mid-Atlantic coast and the Gulf of Mexico. Unless actions are taken to reduce inputs, conditions are predicted to worsen over the next 20 years at many of these sites.
Estuaries and coastal zones are among the most productive ecosystems on earth. There is strong concern that the natural resources they represent are in danger from eutrophication and other problems caused by excess input of nutrients. The major nutrients that cause eutrophication and other adverse impacts are nitrogen and phosphorus. In coastal
nutrient over-enrichment) such as nitrogen and phosphorus. The term eutrophication is sometimes loosely used to describe any result attributable to anthropogenic nutrient loading to a system, but eutrophication per se is not necessarily caused by human action. It is, however, one of the processes that can be triggered by nutrient over-enrichment. The distinction in this report between nutrient over-enrichment and eutrophication is an important one, since nutrient over-enrichment can lead to a number of problems other than just eutrophication of coastal waters (such as coral reef decline), and the excessive primary production associated with eutrophication often leads to a secondary set of problems (such as hypoxia). Confusing cause and effect can impede mitigation, as remediation efforts may not bring about desired effects if those efforts are improperly targeted.
marine ecosystems, nitrogen is of paramount importance in both causing and controlling eutrophication. This is in contrast to lakes and other freshwater systems, where eutrophication is largely due to excess inputs of phosphorus.
The effect of human activity on the global cycling of nitrogen is immense, and the rate of change in the pattern of use is extremely rapid. The single largest change in the nitrogen cycle comes from increased reliance on synthetic inorganic fertilizer, which was invented during World War I and came into widespread use in the late 1950s. Inorganic fertilizers account for more than half of the human alteration of the nitrogen cycle, and approximately half of the inorganic nitrogen fertilizer ever used on the planet has been used in the last 15 years. Although production of fertilizer is the most significant way human activity mobilizes nitrogen globally, other human-controlled processes contribute to the problem by converting atmospheric nitrogen into biologically available forms of nitrogen, such as combustion of fossil fuels and production of nitrogen-fixing crops (crops such as soybeans and other legumes that can make use of nitrogen taken directly from the atmosphere) in agriculture. Overall, human fixation of nitrogen (including production of fertilizer, combustion of fossil fuel, and production of nitrogen-fixing agricultural crops) increased globally some 2- to 3-fold from 1960 to 1990, and continues to grow.
The problems caused by nutrient over-enrichment are significant and likely to increase as human use of inorganic fertilizers and fossil fuels (the two dominant sources of nutrients) continues to intensify. Much remains to be learned about the geographic extent and changing severity of impacts caused by nutrient over-enrichment, the relative susceptibility of different coastal ecosystems (both large and small), and the most effective nutrient control strategies. There is also a great need to better translate existing knowledge into effective policy and management strategies. This requires an understanding of complex oceanic, estuarine, and watershed processes. With this better understanding, more effective techniques may be developed for reducing and preventing nutrient pollution, eutrophication, and associated impacts.
Nutrient over-enrichment and its adverse impacts can cause extremely complex and variable problems. Often, impacts are caused by the accumulation of nutrients contributed by multiple local sources, and thus solutions will, by necessity, need to involve grassroots participation. The complexity of sources, fates, and effects of nutrients, coupled with the complex socioeconomic and political issues associated with the problem, will require coordinated local, state, regional and federal efforts involving an extremely varied group of stakeholders. Developing an effective strategy for reducing the impacts of nutrient over-enrichment requires an
understanding of which nutrients are important, the sources and transport mechanisms for those nutrients, how human activities have altered their abundance, and effective mechanisms to reduce their inputs.
A NATIONWIDE STRATEGY TO ADDRESS NUTRIENT OVER-ENRICHMENT
A number of state, regional, and federal programs are in place that strive to protect and restore coastal waters and habitat in various ways. However, there is no comprehensive national strategy to address excess nutrient inputs to coastal waters. There are no easily implemented and reliable methods or sources of data for citizens, elected officials, and agency staff who live in or are responsible for managing a coastal area (or a watershed that may drain into it) to determine sources of nutrients and potential impacts to coastal waters. In addition, although many federal agencies are making significant efforts to deal with different aspects of nutrient over-enrichment in coastal settings, coordination among these agencies remains inadequate.
Because of the severity of nutrient-related problems and the importance of the coastal areas at risk, the nation needs to develop and implement a national strategy to combat nutrient over-enrichment in coastal areas, with the goal of seeing significant and measurable improvement over the next 20 years. Because both the causes and effects of nutrient over-enrichment are site-specific, development of this National Coastal Nutrient Management Strategy does not mean the national implementation of either uniform source-reduction goals or uniform management or policy approaches. Rather, it means the development of a national, coordinated effort to provide local decision-makers and those responsible for implementing management activities with the information they will need to determine appropriate source reduction goals and methods at the local level. Providing local decision-makers and managers with this information base will allow site-specific and, where necessary, regional or even federal implementation of policies designed to yield significant and measurable improvement in the environmental quality of impaired coastal systems.
Specifically, the committee believes that implementation of the recommendations contained in this report will provide local decision-makers and managers with an information base that could be used to determine what can and should be done to halt the degradation of many of the coastal waters identified in the National Oceanic and Atmospheric Administration (NOAA) National Estuarine Eutrophication Assessment as demonstrating symptoms of severe or worsening eutrophication. The committee believes implementation of the recommendations will dramati-
cally enhance efforts of coastal and watershed managers and other individuals or groups attempting to mitigate the effects of nutrient over-enrichment in these and other estuaries. Improvements in all impaired coastal bodies could be achieved over the next 20 years, while preserving the environmental quality of now-healthy areas.
What are reasonable goals for improvement? In the committee’s opinion, at a minimum, federal, state, and local authorities should work with academia and industry to2:
reduce the number of coastal water bodies demonstrating severe impacts of nutrient over-enrichment by at least 10 percent by 2010;
further reduce the number of coastal water bodies demonstrating severe impacts of nutrient over-enrichment by at least 25 percent by 2020; and
ensure that no coastal areas now ranked as “healthy” (showing no or low/infrequent nutrient-related symptoms) develop symptoms related to nutrient over-enrichment over the next 20 years.
It was beyond the charge and resources of the committee to identify specific coastal areas for priority attention. All 44 of the areas identified by NOAA’s National Estuarine Eutrophication Assessment as exhibiting severe symptoms certainly should be considered as areas where greater effort is needed. Additional study could help further target priorities, especially if it included careful consideration of economic issues and opportunities for stakeholder input. Such work could take significant time and effort, and decision-makers should not be tempted to defer action while waiting for “perfect” knowledge. The committee believes that nationwide implementation of the recommendations in this report, across the full range of systems from small to large and problems from the simple to the complex, will start the nation on a course to achieve the goals stated above. Additional focus on areas subsequently identified for priority attention will then add to cumulative improvement. Thus, the goals listed above are intended to reflect nationwide achievement. Targeting some subset of the impaired coastal areas (for instance, focusing on impaired water bodies associated with small watersheds or simpler ecosystems) in an effort to simply meet these numeric goals would be contrary to the national interest and the spirit of this report.
Working to reduce the effects of nutrient over-enrichment nationwide over the next two decades will be a challenge, but the committee
believes that these general goals are realistic. The setting of such numeric goals is somewhat subjective, but the committee believes that such targets are important to encourage action. The goals were set after thorough discussion and are, in the committee’s view, both achievable given current methods and challenging enough to facilitate real progress. Many of the principles espoused in this report have already been implemented on a smaller scale in Europe (e.g., Rhine and Elbe watersheds) and the United States (e.g., Tampa Bay and Chesapeake Bay) and have resulted in significant reduction in nutrient loads received from nonpoint sources (Behrendt et al. 1999, Belval and Sprague 1999, Johansson and Greening 2000). Achievement of these goals should not be seen as an end in itself. Rather, they are a first step toward reversing the effects of nutrient over-enrichment in the nation’s coastal waters and preventing impairment of “healthy” coastal areas.
How would these goals be accomplished? The key to addressing coastal nutrient problems is understanding that nutrient inputs to coastal waters are affected directly and significantly by activities in the watersheds and airsheds that feed coastal streams and rivers, and building this recognition into planning as well as implementation of management solutions. Thus, people involved as scientists, technicians, and managers for local watershed and coastal programs will play a fundamental role in an effective national strategy to address the problems associated with nutrient over-enrichment. These individuals will be the front line of both policy-making and project implementation. Chapter 2 presents the major findings and recommendations of this report and emphasizes the important role local decision-makers and program managers will play in this national effort. The recommendations suggest ways to develop and implement an effective nutrient management strategy at the local and state level, and the important role federal agencies must play now and in the future.
By focusing on source reduction, actions can be targeted to most effectively reduce and reverse the problems caused by nutrient over-enrichment in coastal areas. Watershed-specific sources like urban stormwater runoff and inappropriate nutrient management at the farm level often can be addressed most effectively by local activities under local leadership, with activities typically quite site-specific. Chapter 2 provides a detailed decisionmaking framework to assist local officials and program managers, including discussions of useful information sources and research needs. However, while significant improvements can be achieved through local action, these managers alone cannot be expected to bring adequate resources and knowledge to bear on such a complex problem, nor are they always able to work at the scale of larger watersheds. Sometimes, broader participation is necessary to have significant impact.
Thus, a truly national strategy must challenge local, state, and federal agencies to work together, and to create partnerships with academia and the private sector. Federal leadership is essential to support and coordinate the research and development needed to provide new approaches and technologies that can be used by local and state agencies charged with reducing and reversing the impacts of nutrient over-enrichment. Perhaps even more importantly, federal leadership is critical for dealing with nutrient sources in large watersheds that span multiple states or jurisdictions or sources distant from the coast. In particular, federal leadership is needed to ensure adequate management of atmospheric forms of nitrogen.
The key federal agencies involved in increasing understanding of nutrient issues, providing technical assistance to state and local managers, and developing new ways to address these problems are the Environmental Protection Agency (EPA), NOAA, U.S. Geological Survey (USGS), U.S. Department of Agriculture (USDA), and National Science Foundation (NSF). NOAA and EPA are primarily responsible for research, policymaking, and management related to eutrophication, in part through the tools provided by the Clean Air, Clean Water, and Coastal Zone Management Acts. USGS has important scientific and data-collection responsibilities, and USDA has a long history of addressing pollution from agriculture. NSF funds research into ecological and biological processes that may be affected by nutrient over-enrichment. Together, these federal agencies have the potential to offer significant resources to help local, state, and regional decision-makers address nutrient pollution problems.
RECOMMENDED FEDERAL ACTIONS
Implementation of an effective National Coastal Nutrient Management Strategy will require coordinated effort, and federal agencies will play an important role. Specifically, the committee recommends that the appropriate federal agencies take the following actions:
Expand monitoring programs so efforts to reduce the impacts of nutrient over-enrichment in coastal settings are supported by coherent, consistent information. The United States lacks a coherent, consistent strategy to monitor the effects of nutrient over-enrichment in coastal settings. One consequence is that the economic and ecological impacts are difficult to estimate with any accuracy. A national monitoring program would involve a partnership of local, state, and federal agencies, as well as academic and research institutions. Participants would agree to use consistent measures of biological, physical, and chemical properties, as
well as consistent procedures, quality control, and data management techniques. In addition, representative coastal systems (i.e., index sites) should be selected as sites for long-term, intensive monitoring and study to better understand the causes and impacts of nutrient enrichment on the structure and function of coastal systems and possible mitigation strategies. Accurate estimates of nutrient inputs to estuaries are essential for management, and data on long-term trends are invaluable for determining how changing land use practices or other human activities can change the nutrient load to an adjacent waterbody. Thus inland monitoring, such as is now done by the USGS, should be adapted to include the specific objective of assessing nutrient inputs to coastal areas, especially estuaries, and monitoring how these change over time. USDA should develop monitoring programs to track the long-term effectiveness of various management approaches, especially for recommended Best Management Practices to achieve reduction of nitrogen and phosphorus from nonpoint sources.
Develop more effective ways to provide consistent and competent data, information, and technical assistance to coastal decision-makers and managers. This might include a federally-managed national clearinghouse that links federal, state, and local programs and access to on-request assistance. A web-based descriptive database would be extremely valuable, especially if it includes direct links to the information and data described.
Exert federal leadership on issues that span multiple jurisdictions, involve several sectors of the economy, threaten federally managed resources, or require broad expertise or long-term effort beyond the resources of local and state agencies. There are many important roles for federal leadership in addressing nutrient problems. For instance, the federal government should continue to move toward setting clear guidelines for nutrient loads, which are essential to successful nutrient management strategies. EPA efforts to develop nutrient criteria and standards on a regional and watershed basis should continue, and should incorporate complexities such as the interaction among physical, chemical, and biological factors; seasonality and timing of inputs; and the random nature of hydrologic forcing functions. These efforts should, however, focus on identifying sources and setting maximum loads, rather than on limiting the ambient concentration of a given nutrient in a receiving waterbody. The federal government also can design incentives to encourage innovative source reduction and control, especially related to reducing the impacts of agricultural practices. Federal leadership will play a key role in successfully dealing with
atmospheric deposition of nitrogen, since this issue clearly involves multiple jurisdictions.
Develop and implement a process to identify and correct overlaps and gaps in existing and proposed federal programs that deal with nutrient over-enrichment. This effort should give particular attention to ensuring that programs meet the needs of local managers and improving coordination among the many agencies and organizations with relevant programs. It should plan how gaps will be addressed; for instance, it should identify ways to improve understanding of sources, fate, transport, and impacts of atmospheric deposition of nutrients. Implementation of the Clean Water Action Plan would go a long way toward improving the federal effort. Given the widespread impacts of nutrient over-enrichment, nutrient management should be an important consideration during reauthorization of the Clean Water Act, Clean Air Act, and Coastal Zone Management Act.
Develop a susceptibility classification scheme that allows managers to understand the susceptibility of a given estuary to nutrient over-enrichment. Coastal waters vary considerably in their susceptibility to nutrient over-enrichment based on many factors such as depth, water residence time, flushing, dilution, stratification, and biology. Management could be more effective, and costs could be reduced, if a mechanism for determining susceptibility were available. Because of the tremendous variability in how different coastal water bodies may respond to a given nutrient load, systematic use of such a classification scheme is a prerequisite for taking lessons from one site to another (and to avoid repeating mistakes). Much work remains to be done in this area, and many classification schemes and susceptibility indicators are under development. However, those that emphasize the role that circulation, stratification, mixing, dilution, and turbidity play in predicting how a given waterbody will respond to a specific nutrient load hold the greatest promise. When index sites are selected, they should reflect the variability that coastal waterbodies exhibit in terms of susceptibility.
Improve models so they are more useful to coastal managers. Monitoring is expensive, so managers increasingly rely on models for understanding nutrient effects and forecasting trends. However, because coastal waterbodies vary greatly in their response to a given nutrient load, models must be verifiable and realistically reflect the complex set of processes at work. Creating a single model, or small group of models, that successfully addresses all the variability among waterbodies is probably unreasonable.
However, assembling a suite of models, each tailored to deal with a different class of waterbody, may offer greater promise and provide coastal managers with more options. In many cases, what is needed is a better or more accurate understanding of how a small number of parameters affect the response of an estuary, rather than a more complex or robust model.
Conduct periodic, comprehensive assessments of coastal environmental quality. Lack of detailed study of the scope and impacts of nutrient over-enrichment limits our capability to understand impacts, predict trends, or determine if management actions are having the intended results. The nation needs to conduct a periodic (i.e., every 10 years), comprehensive reassessment of the status of nutrient problems in coastal waters, similar in scope to the NOAA National Estuarine Eutrophication Assessment (Bricker et al. 1999).
Expand and target research to improve understanding of the causes and impacts of nutrient over-enrichment. In particular, work is needed to study atmospheric deposition of nutrients, including sources, fate, transport, and impacts. Research is also needed to understand the relative roles of nitrogen and phosphorus in different freshwater and marine systems, and how these may change seasonally. Better understanding is needed of the role of specific nutrients and conditions in causing harmful algal blooms and the implications for all levels of the food web, from fish to humans. Finally, research is needed that increases our understanding of the effects of nutrient inputs on economically valuable resources (e.g., oysters, fish stocks, etc.) so that we are better prepared to do the analyses necessary to compare costs and benefits and set acceptable restoration goals.
In general, the committee believes the most appropriate approaches for combating nutrient over-enrichment and its impacts will involve a combination of voluntary and regulatory mechanisms. Flexibility is key, especially for local problems, if programs are to achieve goals at minimal cost. It will be important to use an adaptive management approach, so that lessons are learned as techniques are tried and adjustments are made in response to improved information. Other regions or localities can learn from success and failure in particular situations. Because nutrient over-enrichment is caused by “upstream” activities, it may prove necessary to form commissions or other multi-jurisdictional groups to involve diverse groups of stakeholders.