Making ecosystem reality checks the status quo

Making Ecosystem Reality Checks the Status Quo

G. Allen Burton,* Dick De Zwart, Jerry Diamond, Scott Dyer, Katherine E. Kapo, Matthias Liess,and Leo Posthuma

Holistic approaches to assessing stressors and managingaquatic ecosystems should be the rule; instead, they are theexception. Disjointed, overlapping, and competing environ-mental regulatory actions—all with the noble mission ofprotecting and restoring the environment—can no longerbe justified.

For at least 60 years, environmental regulatory programs in theUnited States, Europe, and other developed countries haverelied heavily on various forms of assessing chemical risk tomanage and protect ecosystems. Water quality, primarilyfocused on chemical regulation, emerged from the need tocontrol water pollution problems caused by poor or nonexis-tent wastewater treatment. The result has been largely a single-chemical approach to environmental management and regu-latory programs. To protect aquatic life uses for example,many countries developed water quality criteria for selectedpriority compounds. Legally enforcing these criteria (such asthe Clean Water Act in the U.S.) has undoubtedly reducedchemical pollution, and many aquatic systems have benefited.Abundant information demonstrates, however, that single-chemical standards are just one approach to assess, manage,and regulate aquatic systems. For example, toxicity testing(e.g., the U.S. Environmental Protection Agency’s [U.S. EPA]whole effluent toxicity program [WET]) has been used suc-cessfully to help assess effects of chemical interactions and theeffects of unknown chemicals that may be present. Suchtesting, however, addresses only direct toxicity effects. Manyaquatic systems are impaired by non-chemical stressors,including invasive species, habitat degradation from agricul-ture and urbanization, and flowmodifications or are influencedby complex interactions among chemicals and other stressors(e.g., nutrients) that are not addressed using either a single-chemical approach or mixture toxicity testing.

The Current ConundrumUsing a suite of indicators that address many types ofstressors or sources of ecological impairment is critical forimproving environmental management. Approaches that inte-grate information obtained from different indicators that leadto a sensible and efficient plan resulting in improved environ-mental conditions are needed. Numerous weight-of-evidence(WoE) approaches have been suggested but rarely are theseused consistently in regulatory programs. For example,

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ET&C FOCUSFocus articles are part of a regular series intended to sharpen understanding of current andemerging topics of interest to the scientific community.

All Supplemental Data may be found in the online version of thisarticle.

* To whom correspondence may be addressed:([email protected]).

Published online in Wiley Online Library(wileyonlinelibrary.com). DOI: 10.1002/etc.1747

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Environmental Toxicology and Chemistry, Vol. 31, No. 3, March 2012 459

the U.S. EPA’s Causal Analysis/Diagnosis Decision Informa-tion System (CADDIS) approach provides a framework forlinking stressors with observed biological impairment (www.epa.gov/caddis). Environment Canada’s EnvironmentalEffects Monitoring Program also considers multiple stressorsusing several types of endpoints. The European Union’s WaterFramework Directive (WFD) describes an integrativeapproach that considers other stressors and legislation,yet new directives and regulatory enforcements still focuson a single-chemical approach. Recently, the U.S. EPAreleased a draft document—‘‘Identifying and ProtectingHealthy Watersheds: Concepts, Assessments, and Manage-ment Approaches’’ (www.epa.gov/healthywatersheds)—toaddress the need for integrative efforts. This is a step forward,but reinforces that wide-ranging approaches to holistic man-agement have not significantly impacted the regulatory proc-ess—at least to date. The norm across North America andEurope remains a single-chemical approach to regulate aquaticecosystems. Indeed, the National Association of Clean WaterAgencies (NACWA) noted that a ‘‘meaningful, functionalwatershed approach remains elusive’’ and identified severalobstacles to implementing such an approach, includingaddressing agricultural nonpoint sources, adaptive manage-ment based on science, and breaking down programmaticregulatory and enforcement silos [1]. In general, the U.S.EPA and individual states have implemented IndependentApplication, which requires that each of the three measuresof integrity—chemical criteria, WET, and biocriteria—beevaluated separately. Each of these measures alone, however,fails to answer questions about biological health effectively.

By combining physical habitat, chemical conditions, WET,and biological assessment data, a more realistic assessment ofbiological community health and impacts will result. Thisintegrated, multiple-stressor approach could help ensure thatresources are directed toward mitigating the most limitingstressors, whether they are physical or chemical, to improvebiological communities.

Several environmental lawyers were surveyed in preparingthis article. All agreed that water quality regulatory programsare driven by broad-based comparisons of chemical concen-trations with established water quality standards. Further,regulations tend to emphasize assessing and controllingpoint source discharges and disregard other stressors inbodies of water being examined (G.A. Burton, Universityof Michigan, unpublished data). Such a policy approachraises a crucial question: Are our regulations effective atmanaging ecosystems exposed to mixtures of chemicals,let alone a wide range of chemical, physical, and biologicalstressors? In our view, focusing on chemical water quality,based on complying with single-chemical standards, resultsin oversimplifying complex factors that cause undesirableecological conditions. What results is a distorted view of theimportance of point sources and chemical factors.

Examples abound in which regulatory management actionshave been driven based solely on numeric chemical thresh-olds being exceeded. These actions result in questionable

environmental protection or limited restoration success. Cer-tain risk-driven criteria based on single-species tests, forexample, may be much lower than natural background con-centrations, such as for naturally enriched constituents suchas aluminum, copper, and other metals. According to risk-based criteria principles, this could lead to policies designedto reduce national emissions, and, indeed, this has been thecase. An alternative would be to elevate the standards so theydo not fall below background concentrations and not use risk-based criteria for the aforementioned constituents. For exam-ple, the Alaska Department of Environmental Conservationhas developed an approach to address certain naturally ele-vated metals. The Louisiana Department of EnvironmentalQuality has developed a similar approach to address naturallydepressed dissolved oxygen regimes in habitats such asbayous. From a broader perspective, using additional regionalecological information regarding the origins of certain com-pounds (an approach used to develop nutrient criteria orthresholds in some U.S. ecoregions, for example) would bea more realistic risk management approach that considerslocal natural background concentrations. Solely using a risk-based method, applied nationwide, would not help reachenvironmental goals in these cases.

Another example is the U.S. water quality assessments such asthe National Water Quality Inventory Report to Congress,which characterizes information as reported by each state,routinely includes more stream miles impaired by sedimenta-tion and other habitat-related stressors than any other cause,including chemicals. The causes of increased sedimentationinclude changes in hydrology, increased impervious surfaces,improper storm water management, and farming practices thatpromote excessive erosion. A single-stressor focus to regulat-ing aquatic ecosystems (i.e., a chemical standards focus)undermines introducing approaches that would prioritize stres-sors or considering cause-effect relationships. As a result, thebureaucratic process—such as measuring which chemicalstandards are exceeded—drives aquatic ecosystem manage-ment and restoration rather than ecological and toxicologicalprinciples. Yet doesn’t it make sense to consider an integratedpolicy cycle for water management that takes into accountdiverse factors that affect ecosystem quality? Might this bemore effective than continuing to regulate and manage eco-systems via separate programs? If so, what would be needed?

Our Solution: Ecosystem RealityChecksEcosystem Reality Checks (ERC) should be a required stepbetween assessing risk (the science) and management actions(society). They should be holistic, as promoted in CADDISand other eco-epidemiological approaches that rely on WoE.This means they should address ecological status (endpoints)relevant to the sources of stress and incorporate outcomes thatpropose alternative, iterative management options.

A generalized framework for an ERC process is shown inFigure 1. From the center to the end, the color ramp represents

460 Environmental Toxicology and Chemistry, Vol. 31, No. 3, March 2012

an increase in scientific inquiry, regulations, and intra- andinteragency involvement to confirm ecosystem diagnostics,that is, the ERC. The beginning, at the center of the cycle, is asingle regulatory program with the goal of reducing risks to asingle chemical. To begin the process, fate and toxicity dataare prepared to predict risks in the field. A retrospectivecomparison with field data yields knowledge gaps that lead tomore effective predictive models, such as refinements inexposure (e.g., equilibrium partitioning, bioavailability pre-dictors) and risk. A more holistic analysis may indicate thatsimply understanding one chemical may be insufficient toaccount for, predict, or achieve a desired ecological status.Hence, in an ERC, mixtures of chemicals are considered,which requires temporally and spatially explicit exposureassessments that can be overlaid with information on speciespresence based on known behaviors, typically requiringtools such as geographic information systems. A result ofthese analyses can be the probabilistic assessment of a suiteof chemicals within a specific geographical space andtime. When compared with appropriate biomonitoring data,these data determine the coherence of the ‘‘prospective’’tools. It is at this point where agencies focused on chemicalregulations must partner with agencies responsible forfactors important for ecological status. Multiple nonchemicalstressors and their relationship to species exposures and

responses are integrated into the chemical risk predictions.This then allows us to determine the relative risk or hazard ofeach stressor in terms of their contribution to ecologicalimpairment. Through interagency cooperation, each stressoris managed appropriately, which leads to achieving thedesired ecological status and in essence confirming thediagnosis. This process represents an Ecological RealityCheck.

Implementing a system of ERCs could condense disparateschemes from different regulatory fields, with the potential togrow it into an overarching regulatory paradigm. Such asystem could explicitly consider the role of chemical con-tamination in light of multiple stressors in human-alteredaquatic systems. An ERC is necessary because chemicals,whether singly or in mixtures, are just one class of stressorsthat affect aquatic biota and, in many cases, are no longer thechief cause of ecosystem impairments.

Complementary Approaches toEvaluating StressorsCurrently, protecting our waterways largely follows a chem-ical-specific approach (see sidebars, Single-Chemical Versus

FIGURE 1: How the Ecosystem Reality Check cycle has generically been implemented. From the center to the end, the color ramp represents theincrease in scientific inquiry, regulations, and intra- interagency involvement to confirm ecosystem diagnostics. EqP!equilibrium partitioning;GIS!geographic information systems.


The Single-Chemical Versus a Multi-Stressor Approach

The importance of a multiple-stressor perspective (the Environmental Reality Check [ERC]) in assessing and managingwatersheds is apparent in a case study performed for the Hocking River watershed (Ohio, USA). A general description ofthe Ohio data sources and the statistical method used for the second and third approaches can be found in Kapo et al. [11].

The case

Using several environmental data resources, three different approaches were applied to identify sites in the Hocking Riverwatershed at risk for impacts to their fish communities based on the environmental conditions present. The results of eachapproach were compared with real-world observations (sites with known biological impact) to determine how well eachapproach captured ecosystem reality (Fig. 2).

The investigations

The presence of ecological impacts was based on biomonitoring surveys in the watershed conducted by the OhioEnvironmental Protection Agency. Three approaches were applied to predict the real-world distribution of ecologicalimpacts in the watershed as a function of cumulative risks. First, the traditional single-chemical approach identified siteshaving one or more water quality criteria exceedances for metals. This approach demonstrated the weakest agreementwith ecosystem reality, because the vast majority of real-world impacted sites were left unaccounted for. Second, abiomonitoring and mixture toxicity approach, which incorporated cumulative metals (mixture) toxicity, fared significantlybetter at identifying impacted sites than the single-chemical approach, in part because it incorporated cumulative risks(here modeled by an ecotoxicological response addition model, applied to all metals present at the sites). This approachincorporated a retrospective component by using statistical relationships statewide between bio-monitoring data andmixture toxicity to identify sites where ecological impact was likely to occur. Third, the most successful identification ofimpacted sites was achieved using a multi-stressor approach in which a variety of stressor variables in addition tocumulative metals toxicity were evaluated. Significantly, the multi-stressor approach demonstrated that the specificinfluence of metals toxicity across the impacted sites was greatly outweighed by other sources of potential stress, such asaspects of general physical and chemical factors in the watershed.

The implications

The three assessment approaches correspond to potentially very differentmanagement strategies. Two of the approaches(the single- and refined-chemical approaches) focus only on reducingmetal emissions and exposures for a limited numberof sites with observed impacts. These two approaches are characterized by incomplete recovery as a result of neglectedstressors and neglected sites. Oneof the approaches—themulti-stressor approach—evaluates the ecosystem fromawiderperspective to identify the most important stressors and handle them accordingly. This approach to assessing stressorsbest reflects ecosystem reality and offers the most practical guidance for subsequent management actions.

FIGURE 2: A weight-of-evidence based geographical information system evaluation demonstrates how different lines of evidence yielddifferent conclusions regardingwhichwaters are impaired. The combination of habitat, water chemistry, and landscape yieldmore realisticassessments of stressor-response relationships [11].


a Multi-Stressor Approach and Tidal Surface Waters in TheNetherlands: Masking Nonchemical Stressors). Typically,water and sediment quality assessments are conducted inresponse to a regulatory directive, rely heavily on chemicalbenchmarks, and use standardized toxicity and bioaccumu-lation tests [2]. It is also well recognized, however, thatassessing ecosystem and sediment quality that integratesmultiple methods into a WoE-based approach can be moreaccurate and more useful from a resource managementperspective. Even these multiple-stressor approaches, how-ever, are often conducted in a disjointed or inconsistentmanner, such that they may fail to establish stressor causality[3]. For example, site characterizations of the quality ofphysical and chemical factors (e.g., suspended solids, sed-imentation, nutrients, toxicity), and biological status (struc-ture, function) may change throughout the year. Sampling foreach of these factors, though, may be relegated to convenientsampling periods (summer and fall, lower flows) and loca-tions (e.g., bridges) that are not necessarily relevant to thespatial and temporal dynamics of each factor. Hence, protect-ing biotic communities may be unsuccessful because deci-sions and actions have been based on data collected in timeand space that do not coincide with actual stressor events,whether they are single or multiple. Obviously, this hasmarked repercussions on how to improve, restore, or remedi-ate the ecosystem.

While the single-chemical management approach hasresulted in many success stories since the 1970s, continuedsuccesses appear to be partial and less common today; indeed,they are perhaps more coincidental than intentional. Still,chemical pollution has been tagged recently as one of ninemajor drivers of global concern in an exploration of safeplanetary boundaries of major stressors [4]. Methods arelacking, however, regarding how to determine the realityof these drivers’ significance alone or specifically whenconsidered in conjunction with the planetary boundary onbiodiversity loss [5]. In other words, a chemical focus isinsufficient because other factors need to be considered tomanage ecological status.

What Is Blocking the ERCProcess?In ecosystems for which environmental management deci-sions have been made to remediate and restore waterways, itis both surprising and disconcerting that few cases havedemonstrated improvements in ecosystem quality in recentyears. Most stream restoration or remediation efforts inurban-dominated watersheds have been unsuccessful becauseimportant stressors have not been removed or inadequaterefugia exist [6]. Indeed, 80% of benthic taxa decline in awide range of watersheds when impervious areas are only 0.5to 2% of the area [7]. Routine monitoring of chemicalstandard exceedances does little to account for impairmentsdue to urban runoff. In addition, chemical standards may beattained, but without source populations available, restorationefforts fail. Current management efforts are often focused on

restoring physical habitats or removing contaminated sedi-ment mass and fail to take a holistic approach to restoring thebiological integrity of our waterways. If an ERC approachhad been established to assess both baseline conditions andthe role of other stressors and their sources, then correctiveactions could have facilitated successful (and measurable)remedies and restorations [5]. So why don’t we apply ERCsyet? Is there a block in science, in policy, or both?

Crossing the Rubicon:The Stepping StonesBefore attempting to solve a problem, risk assessors com-monly frame the problem. A key issue is this: What are thecurrent regulations on which to establish an ERC? Whatstepping stones are in place to support or launch the ERCas a mindset or method?

In addition to chemical-oriented policies, such as the ToxicSubstance Control Act (TSCA) and Federal Insecticide Fun-gicide and Rotenticide Act (FIFRA), the U.S. EPA hasdivisions devoted to the safety of environmental compart-ments or species groups of concern, such as surface waters,ground water, and terrestrial organisms (for example, theOffice of Water, Office of Solid Waste and EmergencyResponse, and the Office of Research and Development).Their efforts are often relatively uncoordinated, and therebyunable to iteratively assess the aggregate and potentiallycumulative effects of multiple chemicals, let alone otherstressors. Although the U.S. EPA’s CADDIS methodologyis highly flexible and has, as mentioned, the potential to affectcorrective management, its connection to chemical and otherregulatory environmental policies and, more specifically,water regulatory programs in the United States, has not beendelineated clearly. Thus far, CADDIS has been used mostly inspecial cases within a regulatory or management context, forexample, certain Total Maximum Daily Loads [TMDLs]).While the U.S. EPA has jurisdiction over most chemicalmanagement policies in the United States, other agenciesmanage other stressors, such as the U.S. Department ofAgriculture (soil till management, forest management),the U.S. Food and Drug Administration (pharmaceuticals),and National Oceanic and Atmospheric Administration(marine ecological status). In essence, there is no coherentcoordination in the United States—let alone among regional,state, and local agencies—to avoid pitfalls and holisticallymanage relevant stressors that contribute to ecologicalstatus.

The situation in Europe is similar. The European Union hasenacted a suite of regulations, much like those in the UnitedStates, but there is room for improvement. A recent illustrationof this is provided in a cross-regulations evaluation ofhow chemical mixtures are handled in risk assessmentand management [8]. Many regulations handle mixturesdifferently and are based on different underlying scientificviews and arguments. Sometimes, a regulation looks at singlecompounds only because scientific methods for handling


mixtures were deemed absent at the time the regulation wasenacted. In other cases, subgroups of compounds are consid-ered on the basis of assumed similar mechanisms of action,which is then taken as justification for partial mixture

modeling and risk assessment. This evaluation concludedthat for Europe, ‘‘There is sufficient know-how [in termsof dealing with mixtures, yet]. . .the question as to howthis scientific knowledge might be best transferred into

Tidal Surface Waters in The Netherlands: Masking NonchemicalStressors

The importance of a multiple-stressor data analyses in assessing and managing national assessments is apparent in anassessment of chemical risk of Dutch sediments.

The case

A biomonitoring dataset was collected for sediments in Dutch surface waters. The acute toxicity of the local chemicalmixtures ranged from very low to 40% exceedence of species’ EC50 values. It was expected, therefore, that toxic effectswould be visible when samples were ranked according to increasing toxicity.

The investigations

To reveal these expected impacts, simple product-moment correlations were derived between mixture toxic pressures insediments and taxa abundance, for nearly 100 sediment taxa (per taxon). Thereafter, these correlation values were rankordered, starting with taxon with the most negative correlation to those with the most positive correlation. A significantcorrelation was found only for a low fraction of taxa (Fig. 3A). As expected, some impacts were negative (chemical loadsreduced abundance of these taxa, left), whereas some were positive (abundance increase at increased chemical loads,right). It could be (wrongly) concluded that no mixture impact was present for the remaining taxa (middle). Yet just theopposite is true. A statisticalmodel (generalized linearmodel) that describes a taxon’s abundance data in relation to a suiteof potentially relevant abiotic habitat characteristics (including the toxic pressure of mixtures) indicated that the fieldabundance of 74% of the species appeared to be significantly influenced by chemical mixtures. Again, both increasing anddecreasing impacts were found, as well as ‘‘optimum’’ abundance trends (bell-shaped abundance change with increasedchemical loads). The combination of generalized linear models with Monte Carlo simulation showed the sensitive,opportunistic, and optimum species (Fig. 3B).

The implications

The implication is that a predicted toxic pressure of 40% (for 40% of species the EC50 would be exceeded) apparently doesnot show up as clear abundance reduction for an equivalent percentage of species through simple correlation techniques;indeed, they remained masked by other stressors’ effects. The ERC that was applied—through the generalized linear modelsand the further data analyses—showed that systematic abundance changes associated with chemical mixtures occurred inmost species and were thus apparently masked by other stressors. The example suggests a high association betweenpredicted and observed fractions of species that were negatively affected (nearly 1:1), followed by major opportunistresponses. The Ecosystem Reality Check conducted here has policy relevance, such as via the European Water FrameworkDirective. In that directive, the policy aims are to reach Good Chemical Status as well as Good Ecological Status. DeviationsfromGood Ecological Status ask for evaluating the possible impacts ofmixtures of chemicals on local species assemblages. Inthe context of ERC, an approach such as a validated toxic pressure approach can be applied as a lower-tier approach toquantify the fraction of species affected by a local mixture, which expands the classical approach of evaluations via WaterQuality Criteria.

FIGURE 3: (A) Rank-ordered correlation between toxic pressure ofmixtures (msPAF-EC50) and taxon abundance for 103 taxa (279 sites)showedan indifferent responseformost taxa(blue). (B)Field-basedexposure-abundancepatterns forarandomsubsetof taxaderivedfromgeneralized linear models"Monte Carlo simulation showed that 74% of all taxa exhibit significant sensitive (negative), optimum, oropportunistic (positive) abundance changes with increased toxic pressure.


appropriate regulatory approaches is, however, not at alltrivial. . .’’. This evaluation stipulated that ‘‘. . .consistentand clear [policy] mandates are needed to take mixturetoxicity into account in the numerous pieces of legislationthat contribute to the protection of. . .the environment fromchemical risks. . .’’ [8]. These statements refer to 21 relevantEU substance- or product-oriented pieces of legislation. Thepicture in Europe thus becomes more entangled when onelooks at overarching regulations such as the Water Frame-work Directive, the Marine Strategy Directive, and the pro-posed Soil Directive. The Kortenkamp et al. report [8]suggested focusing on receptors experiencing multi-expo-sures rather than focusing on sources. Not all chemicalsco-occur in the field, however. Using an ERC approach,mixture risk assessments are needed only for those com-pounds that are likely to co-occur in realistic field settings.Notably, a similar conclusion was drawn more or less inde-pendently in the recent EU project named NoMiracle (http://nomiracle.jrc.ec.europa. eu/default.aspx), a project designedto increase knowledge on the transfer of pollutants betweendifferent environmental compartments and on the impact ofcumulative stressors, including chemical mixtures. In short,regulatory action—at least in the United States andEurope—is triggered along separate regulatory lines, inwhich scientific foundations vary and are not viewed inthe broader context. Nevertheless, there is a way forwardby using a growing focus on the final policy target: Theoverall impacts in aquatic systems.

This more holistic approach to environmental regulation ispossible through Registration, Evaluation, Authorisation,and Restriction of Chemical substances (REACH), theEU’s chemical-focused regulation. REACH starts fromthe chemical perspective, whereas the Water FrameworkDirective (WFD) focuses on the water body. REACH aimsto prevent and limit the emissions of the most toxic com-pounds. It refers to possible accumulation of compoundsthat are produced and used, such as specific mixtures thataccumulate at downstream locations. The regulationallows for the idea of addressing such sites of concernand specifically mentions a link to the WFD. Hence, thecrucial regulatory mandate is a very short portion of the law,but it is there to act as stepping stone. The WFD addsto REACH through the Good Chemical Status approach,which identifies selected priority and basin-specific com-pounds for phase out and the integral focus on the net effectsof all stressors. Water authorities are required to act, forexample, through River Basin Management Plans, to reachthe holistic goal of ‘‘Good Ecological Status.’’ What canand cannot be prevented in source-oriented policies iscaptured by the compartment-oriented policies, which arecross-linked.

Even so, mandating stepping stones in current regulations hasnot yet brought about adopted methods for ERCs. Althoughcrucial policy mandates do indeed exist, the regulatory needhas not yet been translated into validated, operational, andadopted methods of practice. Currently, we have simply a

library of methods—but they are ready to be used in ERCs.Unfortunately, how and when to implement such method isunclear as yet.

Defining the Ecosystem RealityCheckWe thus begin here to define the concept of routinely imple-mented ERCs, which we propose must be:

# Targeted. An ERC is meant to manage natural resourcesefficiently and effectively, thus minimizing costs and pro-vide the greatest benefits.

# A process. An ERC encompasses an iterative evaluation ofrisk assessment results and alternative risk managementoptions.

# Holistic. An ERC considers the dominant physical, chem-ical, and biological stressors and their links to ecosystemimpairments.

# Scientific. An ERC considers all issues along relevanthypothesized cause-to-effect chains, avoiding bias to eithersources or receptor.

# Pragmatic and practical. An ERC can consist of usingexisting, pragmatic, and practical approaches from variousscientific disciplines and is as simple or as complex asneeded in the context of a defined problem.

# Possible. ERCs are mandated by current regulations, butnot everywhere. Using the ERC productively is possibleimmediately by shifting the mindset of environmentalassessors and managers.

An ERC framework, illustrated in Figure 2, incorporatesthe complementary benefits of traditional preventativeapproaches. Typically, these approaches are used by linkingwhat are now often disjointed, overlapping, or competingregulatory programs, all of which are concerned with protect-ing and restoring aquatic systems. Notably, our focus here hasbeen on aquatic systems, but with the abundance of regulatorymechanisms and drivers, the ERC principles can and shouldalso be applied to terrestrial systems.

ERC Flexibility: Does One SizeFit All?The short answer is ‘‘no.’’ Commonly, various risk assess-ment schemes are conducted according to a tiered scheme.Simple and conservative methods are used initially withmore complex and realistic methods employed as neededin higher tiers. Chemical water quality criteria can becharacterized, for example, as a lower-tier approach, withrefinements possible in the United States only on a site-specific basis for the most part, because criteria are designedto protect aquatic ecosystems in general. Consideringmixtures, assessment approaches have appeared at varioustiers of the science, from the simplest to the most complex.For example, a simple approach to assess chemical mix-tures is to employ a Safety Factor (e.g., 1/10th of a risk


assessment-derived level to account for uncertainties,including mixtures). More complex approaches considerthe additivity of chemicals within a mechanism of action(e.g., Toxic Equivalence Factors for dioxin) or across mech-anisms via mixed-model approaches. The risk assessmentproblem defines the level of specificity and complexityneeded. Food web models, for example, represent a morecomplex, higher-tier approach. Recently, a suite ofexisting risk assessment methods have been comparedand combined in tiered frameworks [9]. The examplesprovided in this paper support our initial answer: An ERCis not a one-size-fits-all approach even when consideringchemical risks.

Examples in an ERC ContextMulti-stress conditions change chemicalsensitivity

Stress conditions for individuals and populations oftenincrease their sensitivity to toxicants. The environmentalcontext determines the causal link between the stressorand the biological community. How universal are chemicalcriteria for stressed environments? Are they sufficientlyprotective? Can chemicals be the focus in environs where

physical (habitat alteration) and biological stressors (invasivespecies) predominate? Do the stressors interact?

Case description. In this case, the ecological impact of anold waste site releasing heavy metal contamination intoAntarctic costal waters was assessed. Researchers identifiedthat the ultraviolet (UV) radiation present in Antarcticaincreased sensitivity of local invertebrates living in shorelinewaters by more than an order of magnitude. This relationshiphas been identified in the field and validated with in-situ andlaboratory investigations [10].

Implications for the ERC concept.In the case presented, thesource of contamination, a waste site was removed. Hence,assessing the combined action of chemical and a ubiquitousenvironmental stressor (UV radiation) triggered a manage-ment action. Future human activities in areas with high UVradiation may be affected by these results. The increase oforganism sensitivity due to UV is just a single example ofa wide range of stressors that increase mortality due totoxicants, including temperature, nutrients, siltation, oxygen,competition, predation and parasites [2].

The Clinch River: Managing multiple stressors

The Clinch River in southwest Virginia (USA) has one of themost diverse assemblages of freshwater mussels and native

FIGURE 4: In the Upper Clinch River Basin (Virginia, USA), traditional regulatory programs indicate impaired segments due to pathogen andsediment target exceedances. A multiple-stressor assessment resulted in more realistic conclusions of multiple stressor effects.


fish in the United States, both of which have been imperiled,although the cause of species declines has been elusive thusfar. Many stressors have been implicated, most of which falloutside the realm of current regulations (e.g., habitat impair-ment). The current regulatory approach identified that fecalcoliform bacteria and sediment were impairing water qualityin a small part of the watershed based on state standards andvisual inspections (Fig. 4). This approach identified animportant stressor (and its major sources), but it addressedonly a small part of the watershed and ignored other well-documented biological information available. Appropriatemanagement actions were left vague and little connectionwas made to an actual restoration strategy. The process thatwas initiated failed to result in restoration decisions andactions.

Case description.A watershed ecological risk assessmentwas conducted with multiple stakeholders involved (includ-ing a non-regulatory office of the state [Virginia] andthe U.S. EPA), using GIS and multivariate analyses. Theassessment identified not only sediment from agriculturalsources as an important factor, but also coal fine sedimen-tation from leaking coal slurry impoundments, toxicchemicals from recurring transportation and industrial spillstoxics, biochemical oxygen demand from urban runoff andCombined Sewer Overflows, and channel alterations fromriparian corridor degradation as important stressors(Fig. 4).

Implications for the ERC concept. Using a multiple-stressorframework, risk analyses demonstrated that proximity toseveral sources of stressors and multiple stressors werehighly related to the biological conditions. A single-stressorapproach could not provide the information needed to protector restore the valued aquatic resources in this system success-fully, because the cumulative mixture of stressors is a criticalfactor (Fig. 2). Using an ERC approach led to useful manage-ment strategies in this watershed.

Great Lakes: Interactions of multiple, non-toxicstressors

The Great Lakes (USA) have been undergoing dramaticchanges in the past 20 years, with changes becoming moredramatic during the past two years. This ecosystem contains21% of the world’s freshwater and 84% of the supply for theUnited States. As such, the scope and magnitude of theecosystem services the Great Lakes provide are likelyunmatched by any other freshwater system. Nevertheless,the salmonid fishery is collapsing in Lake Huron. Severalinvertebrate and fish species are at or near extinction in someof the lakes, including the amphipod Diporeia (a keystonespecies) and Daphnia sp. The southern basin of Lake Mich-igan and much of Lake Huron are nowmore oligotrophic thanLake Superior.

Case description. These dramatic food web changes canbe linked to the complex interactions of multiple stressors.Several recent papers (see Supplemental Data: SuggestedReading) have shown key stressor connections betweenspecies loss; increased and selective filtering by invasivespecies (the notorious zebra and quagga mussels); increasing

harmful algal blooms; increasing hypoxia; increasing benthicalgae (Cladophora); and subsequent beach ‘‘muck’’ andclosures due to pathogens, in addition to excessive phospho-rous runoff.

Implications for the ERC concept. Although the U.S.Clean Water Act has focused on maintaining the physical,chemical, and biological integrity of the Great Lakes viachemical regulations, it has done little to manage the combi-nation of these broad-scale and dominant stressors. Ourexamples have shown where an ERC approach would beuseful. While these are good examples, we need a deliberatepath forward.

The Path ForwardScience has matured sufficiently to provide regulators withmethods to develop and implement ERCs. As discussed,chemical-centric regulatory schemes have had a positiveimpact; however, they are limited in scope and cannotaccount for myriad other factors that may impair ecosystems.Because the science is ready and intentional regulatorysystems will be needed to maintain or improve the ecologicalstatus of human-affected systems, the time is right to developa path forward. We recommend that an Ecosystem RealityCheck framework be developed and adopted, building onexisting regulatory programs when needed.

The evidence and thoughts presented here should result in achanged mindset for all those involved in assessing risk andmanaging environmental issues. Furthermore, the ERCmind-set will reduce the negative connotations associated withbeing the messengers of bad news (‘‘The risk is. . ..’’ or‘‘We didn’t consider this. . .’’). Risk assessors with an ERCmindset will instead opt for solutions (‘‘Alternative manage-ment strategies are. . .’’).

In the long term, the ERC concept will require further steps.The Society of Environmental Toxicology and Chemistryhas conducted several ‘‘Pellston’’ workshops with the goalof providing integrated approaches (Fig. 2) to assess andthen develop prospective tools to positively affect ecologicalchange. It appears, however, that resource and regulatoryagencies have paid little attention to many of these tools.The result is the continued disuse of holistic approachesthat could lead to improved or restored ecological status.Just as there are internationally approved methods for testingphysical, chemical, and biological (e.g., biodegradation,toxicity) attributes to provide suitable data to assess thepotential risks of chemicals in the environment, it is time toelevate current methods used for assessing non-chemicalstressors and holistic integration systems via an inter-national effort with the goal of developing and promotingERCs. The step to be made would be to establish consensuson ERC via international, multi-stakeholder workshops.The output of these steps should be practical ERCapproaches for which it is clear that the benefits of managingresources effectively outweigh the costs mandating this newparadigm.


Call to ActionMake ERCs the status quo

Regulatory approaches to assessing and managing the qualityof ecosystems have tended to focus on a single stressor-centric approach and fail to ‘‘see the forest for the trees.’’While this has been and can be effective in rather simplisticsystems in which one stressor source dominates, it may bevery ineffective in complex, human-affected systems inwhich multiple stressors and sources occur. The exampleswe have presented illuminate our arguments. For our world’sincreasingly more complex and at-risk environments, weneed Ecosystem Reality Checks to be the status quo. Indeed,using several complimentary indicators simultaneously toaddress the numerous stressors and sources of ecologicalimpairment is critical if we ever hope to improve environ-mental management.

We recognize that it can be challenging to determine ERCs incomplex systems, because this requires knowledge of diverseissues such as selecting appropriate reference conditions,defining multiple spatial-exposure relationships, and assess-ing dominant versus cumulative stressors. Separate regula-tory approaches have identified and managed stressors,but have not linked approaches to manage multiple stressorseffectively in their appropriate contexts. Nevertheless, it isin human-affected systems that billions are being spenton remediation. An ERC would provide a predictiveevaluation of success. Despite the wide array of environ-mental disciplines and agencies that may be needed todetermine an ERC, the reality will be a more efficient useof scientific, regulatory, and financial resources to protect,conserve, or restore ecological status. Hence, we believethat the ERC mindset is productive and can be adopted hereand now.

The status quo of environmental regulatory actions executedvia disjointed, overlapping, and competing programs, all withthe noble mission of protecting and restoring the environ-ment, can no longer be justified. It is time for EcologicalReality Checks to be a routine procedure in all managementframeworks.

AcknowledgementD. De Zwart and L. Posthuma received financial support from the DutchNational Institute for Public Health and the Environment (RIVM) StrategicResearch Program (project S/607001), ‘‘Environmental Impact Assessment,’’under the auspices of CEO-RIVM and RIVM’s scientific Advisory Board.

Supplemental DataSuggested Reading (47K DOC).

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Making ecosystem reality checks the status quo

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