An ecological decision framework for environmental restoration projects

Ecological Engineering 9 (1997) 89–107

An ecological decision framework forenvironmental restoration projects

Robert A. Pastorok a,*, Anne MacDonald b, Jennifer R. Sampson a,Pace Wilber c, David J. Yozzo d, John P. Titre d

a PTI En6ironmental Ser6ices, 15375 SE 30th Place, Suite 250, Belle6ue, WA 98007, USAb PTI En6ironmental Ser6ices, 4940 Pearl East Circle, Suite 300, Boulder, CO 80301, USA

c National Oceanic and Atmospheric Administration Coastal Ser6ices Center, CCEH,1990 Hobson A6enue, Charleston, SC 29405, USA

d U.S. Army Corps of Engineers Waterways Experiment Station, En6ironmental Laboratory,3909 Halls Ferry Road, Vicksburg, MS 39180, USA

Received 30 December 1996; received in revised form 2 July 1997; accepted 9 July 1997

Abstract

Ecosystem restoration projects require planning and monitoring to maximize projectsuccess relative to costs, yet many projects completed thus far have been planned on an adhoc, consensus basis and are virtually ignored after revegetation at the site is complete. Wedescribe a formalized planning process geared specifically to the needs of ecological restora-tion projects (and ecosystem rehabilitation or management projects; National ResearchCouncil, 1992). This process emphasizes: 1) the importance of defining objectives related tothe appropriate ecosystem structure, function, and spatial scale; 2) the role of ecologicalmodels, restoration hypotheses, and key ecological parameters; 3) explicit consideration ofuncertainties in site processes and material performance in the restoration design; 4)guidelines for project design and feasibility analysis and the use of experimentation at thisstage; and 5) monitoring and adaptive management of restoration projects after implementa-tion of a design. This process was developed to integrate a fundamental understanding ofecological principles into the existing project planning framework used by the U.S. ArmyCorps of Engineers in their growing role in restoration of aquatic habitats, but it should beapplied to terrestrial habitats as well. © 1997 Elsevier Science B.V.

* Corresponding author. Tel.: +1 425 6439803; fax: +1 425 6439827; e-mail: [email protected]

0925-8574/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved.

PII S0925 -8574 (97 )00036 -0

R.A. Pastorok et al. / Ecological Engineering 9 (1997) 89–10790

Keywords: Habitat restoration; Ecological planning; Landscape design; Adaptive manage-ment

1. Introduction

Effective planning is critical for restoration projects to maximize the overallsuccess of restoration efforts and minimize costs (Garbisch, 1989; Wyant et al.,1995; Hobbs and Norton, 1996). Many restoration projects have not achieved theirpotential because project planning efforts have been too limited. At best, projects inthis category have succeeded on limited terms (e.g., a good project for the site butnot necessarily the optimum project for the region) and done as well as they haveonly because the professional judgment of the project planners was seasoned withyears of accumulated local ecological knowledge (e.g., Gog-Le-Hi-Te wetlanddescribed by Simenstad and Thom (1996)). At worst, projects have failed to providethe minimum ecological functions necessary for the site because of an inadequateunderstanding of the ecological system being manipulated (Westman, 1991). Smallto moderate-sized projects are particularly prone to this problem. Because they areoften considered simple (e.g., excavate and plant a pond, reseed a prairie), they arepoorly planned and result in nonfunctional ecosystems. For example, a ‘restored’riverine backwater may fill with sediment or become anoxic within a decade ofconstruction because watershed sediment routing and hydrology were poorlyunderstood (Westman, 1991).

Wyant et al. (1995) called for development of a decision framework to aid inselecting ecologically and economically robust restoration techniques on a site-spe-cific basis. We present here an ecological planning process that could serve as theecological portion of such a framework. In a companion paper, Thom (1997)describes a matrix model for analyzing ecosystem development that can be appliedin adaptive management of coastal ecosystem restoration projects.

2. Background

The Civil Works Program of the U.S. Army Corps of Engineers (Corps)recognizes habitat restoration as an important element in stewardship of ournation’s natural resources (e.g., Section 1135 of the Water Resources and Develop-ment Act of 1986, Section 204 of the Water Resources and Development Act of1992). To improve its role in planning and managing habitat restoration projects,the Corps initiated the Evaluation of Environmental Investments Research Pro-gram (EEIRP). Under this program, obstacles to effective planning of ecologicalrestoration projects were identified, and alternative guidance was developed. Thispaper is based on a section of a report (Yozzo et al., 1996) that addresses these

R.A. Pastorok et al. / Ecological Engineering 9 (1997) 89–107 91

issues from an ecological perspective. Yozzo et al. (1996) describe importantecological processes and key variables that should be considered when restoringspecific aquatic habitat types. The alternative guidance detailed in Yozzo et al.(1996) emphasizes characterizing site habitats early, understanding ecological mech-anisms that drive restoration, and adaptive management (sensu Holling, 1978) whileplacing less emphasis on a rigid project design than is usually the case in establishedengineering project planning performed by the Corps.

National Research Council (1992) distinguishes between three general restorationgoals. Restoration returns an ecosystem to a close approximation of its conditionbefore it was disturbed. Rehabilitation improves a system to a ‘good working order’.Management manipulates a system to ensure maintenance of one or a few func-tions. These concepts overlap and may be thought of as a continuum. Withoutdebating the relative merits of these goals (or, for that matter, what ‘restoration’ is[see Cairns, 1989 for a critique of the ‘pre-disturbance’ state as restoration end-point, and Hobbs and Norton, 1996 for a thorough current review of the purposeand scope of restoration ecology]), the term restoration throughout this paper refersto this entire continuum.

The following four key ecological perspectives should guide environmentalrestoration projects:1. Ecosystem Perspective—An understanding of ecosystem structure and function

at various spatial and temporal scales is essential to most restoration projects.The restoration site should be viewed in watershed and regional contexts, andobjectives should be defined at the relevant spatial scale(s) (e.g., Hobbs andNorton, 1996).

2. Key Species Functional Perspective—In addition to physical habitat factors, thepresence of certain organisms and their functional role drives the outcome of arestoration project. For example, seagrass species act as the foundation for theseagrass bed system, beaver act as engineer species in streams by modifyingphysical habitat and hydrology through pond building, and mycorrhizal fungiare key symbionts necessary for establishment of most conifers.

3. Bet-Hedging Design Perspective—Ecosystems consist of a mosaic of habitatsthat varies in space and time. Natural and anthropogenic disturbances affect thepattern of the mosaic and landscape-level processes. Although disturbances arenot always adverse (e.g., in many natural systems, high biodiversity is main-tained by disturbances), the unpredictability of system dynamics means thatrestoration project objectives are seldom met exactly. A bet-hedging strategy,which relies on spatial diversity and flexibility in the restoration design, isrecommended.

4. Adaptive Management Perspective—Restoration projects should be imple-mented in a tiered fashion that allows information about results from early tiersto be factored into the implementation of successive tiers. Adaptive managementrequires flexible goals and designs and a long-term commitment to detailedmonitoring and fine tuning after initial implementation.


3. Ecological planning framework

Restoration project planning starts with the definition of existing problems, aclear statement of project objectives, and an understanding of uncertainty. Recogni-tion of these fundamental concepts should continue throughout the planning,design, implementation, and monitoring phases of the project (Fig. 1). The successof the planning process depends on identifying key ecological processes within theecosystem of concern and understanding those processes in relation to the objec-tives of the project.

The primary steps in the ecological planning process proposed here are to:1. Define habitat of concern and existing problem(s) with quantitative statements

about physical, chemical, and biological conditions.2. Develop goals and objectives for restoration, including the time period over

which these should be met.3. Develop a conceptual model of the ecosystem to be restored.4. Develop restoration hypotheses regarding responses to specific habitat manipu-

lations or transplant efforts.5. Use the conceptual model to identify key ecological parameters to be manipu-

lated or monitored and to refine performance criteria.6. Evaluate and refine restoration hypotheses using ecological models or reference

site information. Use prior experience to evaluate whether the proposedmanipulations will support desired functions at sufficient levels or over thedesired time period.

7. Develop restoration design.8. Perform feasibility, cost, and impact analysis.9. Develop final restoration design and implementation plan.

10. Implement project.11. Perform monitoring and adaptive management including, but not limited to,

maintenance.Fig. 1 shows the relationships among these steps in the ecological planning

process and the supporting evaluations. Supporting evaluations involve review ofsite data, regional information, and case studies, as described by Garbisch (1989) orKentula et al. (1993). In planning exercises for major restoration projects, experi-mental manipulations may also be conducted on a microcosm (e.g., laboratory) ormesocosm (e.g., field) scale to aid in understanding key parameters, processes, andpotential pitfalls (e.g., feasibility study phase).

Several major elements of the ecological planning process are addressed below,including 1) defining goals and objectives, 2) ecological modeling and key parame-ters, 3) dealing with uncertainty, 4) restoration design, feasibility analysis, andexperimentation; and 5) implementation, monitoring, and adaptive management.

4. Defining goals and objectives

Defining project objectives is the most important single step in the planning


Fig. 1. Ecological planning process for environmental restoration projects.


process because it ensures that a ‘road map’ for the project is in place. To define theobjectives, the site ecosystem and its historical development must be understoodfirst. The depth of understanding necessary will vary by site, but the section on therelevant ecosystem type(s) in the Ecosystem and Restoration Profiles chapter ofYozzo et al. (1996) and Denbow et al. (1996) are good guides to what topics shouldbe evaluated in aquatic habitats. For example, hydroperiod (e.g., frequency,seasonal and multi-year distribution of water levels) and water quality are keyenvironmental parameters for all aquatic habitats, while a similar understanding ofthe spatial and temporal distribution of soil moisture regime and soil chemistry isan analogous key to restoring terrestrial habitats.

Ecological concepts that should be applied to each project include a landscapeperspective on habitats at the site (e.g., size, area, connectedness of patches at thesite and in the surrounding landscape); an understanding of species–substrateinteractions; and an assessment of both natural and anthropogenic disturbanceprocesses, frequencies, and magnitudes. In most instances, baseline studies of therestoration site will be required along with the professional judgment of a scientistwith experience at the site or in similar habitats.

Second, the problem at a site must be adequately understood from both ascientific perspective and a broader ‘stakeholders’ perspective. The scoping processused for environmental impact statements is a good analog to this problemdefinition process, although the specific stakeholders may differ. At this point,restoration objectives can be defined that specify:1. Target species, biological communities, or abiotic functions to be restored.2. Site or habitat characteristics to be enhanced.3. Spatial and temporal scale of restoration.4. Performance criteria.

Objectives of the restoration project should be as specific as possible whilerecognizing natural variability. Although an initial statement of a general narrativeobjective (or goal; National Research Council, 1992) may be useful, specificobjectives are needed to maximize project success. For example, a goal for a lakerestoration project could be ‘to enhance water quality’, and the objectives related tothis goal would specify the exact characteristics of water quality to be achieved,such as ‘increase water clarity by 20%’. Other quantitative objectives may relate tomeeting water and sediment quality criteria and achieving desired levels of speciesabundance, biomass, or species richness. Specific objectives should define a suite ofhabitat conditions beneficial to the desired biological community and the timeperiod over which they may be achieved. Objectives should recognize seasonal andinterannual variability. Quantitative approaches include performance curves (Ken-tula et al., 1993) or the combination of resemblance functions (used to quantifystatic similarity with a reference site) and resilience indices (used to quantify thetemporal aspects of recovery) (Westman, 1991). The process of defining objectivesis discussed in more detail in Thom (1997) and Thom and Wellman (1997).

Target species for restoration may include foundation species, such as kelp orseagrass, which provide the key structural component of habitat for a variety of


other species. Rare, threatened, or endangered species may be addressed in somerestoration projects (e.g., in cooperation with the U.S. Fish and Wildlife Service). Ifan entire biological community is targeted for restoration, indicator species thatreflect the status of the community would typically be specified in the objectives.

In some cases, habitat conditions may be enhanced primarily for human aestheticor cultural reasons, with detrimental consequences for certain ecosystem compo-nents. For example, increased water clarity in a lake may be desirable from ahuman aesthetic perspective, but this habitat change may be related to a reductionin primary productivity and fish biomass. In addition, introduction of harvestablespecies, such as largemouth bass, bullfrogs, or crayfish, for recreational uses maycause declines in native fish, amphibian, or invertebrate populations or restructur-ing of ecological communities. Any restoration objective that is related primarily tohuman aesthetics or consumptive uses should be evaluated carefully to determinethe risk of adverse ecological effects.

U.S. Environmental Protection Agency (1990) provides specific guidance onselection of indicators of ecological health in their environmental monitoring andassessment program, which is equally applicable to restoration objectives. Criteriafor selecting ecological indicators include the following:1. Indicators should be physical, chemical, or biological elements of ecosystem

structure and function.2. Indicators should be socially relevant, clearly connected to environmental

values, and responsive to individual or cumulative effects of stressors.3. Indicators should be sensitive to various levels of stress, but not overestimate

impacts resulting from natural variation.4. Indicators should require limited sampling effort and be cost effective and have

precedent in other, successful monitoring projects.U.S. Environmental Protection Agency (1990) notes that using community

process and rate measurements (primary production, respiration, and nutrientcycling) in monitoring studies does not help identify ecological alterations in theirearliest stages, although they contribute to understanding the longer-term ‘trajec-tory’ of the system (Kentula et al., 1993; Simenstad and Thom, 1996).

The level of detail of the objectives and their attainability (i.e., as indicated by theeffort and costs required to meet the objectives) are determined by the size of theproject, the complexity of the ecosystem, and the nature of environmental degrada-tion. Thus, the project scale in terms of area to be restored, the time period overwhich restoration efforts should be effective, and the extent of the biologicalcommunity targeted for restoration should be defined while developing objectives.Factors to be considered in defining the project scale include the influence of thesurrounding landscape, the size of the area of existing degradation or disturbance,the area required for adequate monitoring of results, and the available budget(National Research Council, 1992).

In defining the objectives of a restoration project, available site data on thecurrent status of habitats (e.g., measures of habitat quality) and fish and wildlifespecies should be reviewed in a regional context using reference areas (Fig. 1).Reference area characterization is used to define the current status of the site, the


potentially attainable conditions for the habitat to be restored, and as a point ofreference for evaluating project success The behavior of natural reference ecosys-tems and their regional variation based on available monitoring data is also used todevelop restoration hypotheses (Fig. 1). For example, hypotheses about the popula-tion dynamics of a target species in restored systems may be based on predictionsderived from available data on that species in regional reference systems.

Selection of reference sites and development of reference databases can be mademore efficient with careful planning. First, ecological regions must first be delin-eated (or selected from existing databases) based on geologic, geomorphic, andclimatic factors to ensure equivalence of physiochemical properties (e.g., hydroge-omorphic setting (Brinson, 1993); substrate texture and chemistry). Water bodieswithin the same watershed or in nearby watersheds with the same geologic settingand climatic influences as the restoration site will provide the most appropriatereference sites. The intersection of ecoregion and major watershed should beemphasized, although the larger subregions of McNab and Avers (1994) should beconsidered as well, particularly if the restoration target is a rare ecotype. Referenceareas should represent the desired habitat quality and functions. The varioustopical/regional HGM guidebooks being developed (e.g., Brinson et al., 1995) areimportant tools in defining these critical properties for wetland projects, forexample.

Anthropogenic influences on a potential reference site should be evaluated priorto its use as a reference site. Evaluation of potential influences of human activitieswill facilitate selection of appropriate sites and ecological indicators. For example,what initially appears to be an undisturbed lake may be receiving large amounts ofsediment from erosional processes occurring as a result of large-scale slope failureaccelerated by land-clearing activities. While the slope failure may be far upstreamfrom the lake, changes in sediment accretion rates within the lake could changebiological communities, making this site unreliable as an reference area. Anhistorical perspective on anthropogenic disturbance is frequently required. Forinstance, restoration planners should at least consider the possibility of landscapemodifications by indigenous peoples prior to European settlement (Westman, 1991).At a minimum, moderate anthropogenic disturbance tends to structurally simplifyhabitats (McIntosh et al., 1994).

The regional perspective is also important for evaluating the influence of thelandscape on a project and the consequences of restoration within a landscapecontext. Lake and stream ecosystems are strongly influenced by their watersheds(e.g., nutrient and sediment inputs), and unique biological communities maydevelop as a result of landscape influences. The spatial distribution and dynamics ofhabitat patches within a landscape affect the distribution and abundances of mostwildlife species, especially wide-ranging species (e.g., birds, large terrestrial mam-mals, and marine mammals) that depend on landscape-scale resources (Turner andGardiner, 1991; Dunning et al., 1992). Thus, the status of a restored ecosystem (i.e.,patch within a landscape) may contribute to or benefit from landscape-levelresources and influence the distribution and abundance of regional species.


5. Ecological models, restoration hypotheses, and key parameters

The objectives of a restoration project and information from site-specific surveysor case studies provide the basis for developing a conceptual model of theecosystem (Fig. 1). The conceptual model shows the relationships among targetspecies (or communities), performance indicators, and key ecological parameters.Such a model forms the basis for developing restoration hypotheses, which arepostulates that describe causal mechanisms that lead to changes in target species (orcommunities). The model can be based initially on information provided in therelevant ecosystem profile(s) section of Yozzo et al. (1996), with the addition ofsite-specific information. Restoration hypotheses state the expected changes inperformance indicators in relation to key ecological parameters, including thoseparameters that are manipulated in the restoration effort (e.g., Table 1).

Key ecological parameters are the driving variables that determine communitystructure and function and, by definition, influence performance indicators. Somevariables, such as the abundances of foundation and keystone species, may be bothperformance indicators and key ecological parameters.

To the extent practical, ecosystem restoration projects should address the causesof degradation, not just the symptoms. The use of models aids in understandingecological processes and in identifying key parameters that drive observed changesin ecological systems. Conceptual models may be used to identify foundationspecies, keystone species, and engineer species; identify key ecological parameters;and develop quantitative ecological models.

The components of a conceptual ecosystem model may include the following:1. Key abiotic processes or habitat characteristics (e.g., nutrient loading, water or

substrate chemistry).2. Food web structure and key resource species.3. Foundation, keystone, and engineer species that may affect the restoration goal

(if known; see discussion of models below).4. Optimal physical characteristics to satisfy restoration goal.5. Successional sequences resulting from natural or anthropogenic disturbance.6. Spatial and temporal heterogeneity in habitats that may affect restoration goal.7. Natural disturbance regime that affects the restoration goal.8. Landscape influences that support or inhibit the restoration goal.

If possible, the conceptual model should be summarized in a diagram or series ofdiagrams that illustrates basic relationships among ecosystem components, includ-ing key processes. Such diagrams may include flow charts that illustrate ecosystemcompartments and processes, relatively detailed food webs, and fault-trees thatshow mechanisms of environmental degradation or enhancement (e.g., Suter, 1993).Fault-trees may also be used to evaluate potential failures of restoration actionsand to perform uncertainty analyses.

The restoration hypotheses and the identification of key ecological parametersleads to the design of restoration actions (Fig. 1). Quantitative ecological modelsare valuable for refining hypotheses and ranking key ecological parameters. Forexample, model sensitivity analysis may aid in identifying parameters that most


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influence performance indicators. Quantitative uncertainty analysis and failureanalysis are useful for evaluating alternative restoration actions and for avoidingpitfalls.

Bench-scale, plot-scale, or demonstration-scale experiments may be valuable forvalidating models and for performing empirical sensitivity analysis to identify keyecological parameters. Tanner et al. (1994) illustrate the use of a combination ofempirical community-level studies, modeling, and sensitivity analysis to characterizeecological systems and identify keystone species.

6. Dealing with uncertainty and failure

Planning for potential failure of a project is perhaps the best strategy formaximizing project success. Random variability in space and time is an inherentpart of ecosystems. Moreover, uncertainty in our basic understanding of ecologicalparameters and processes increases the risk of failure. Characterizing variability anduncertainty during project planning can lead to better predictions about ecosystemdevelopment, chances of project success, and potential mechanisms for failure.Quantitative uncertainty analysis of any ecological model used during restorationplanning helps to define the limits of our understanding. Project objectives maytherefore account for alternative outcomes or ecosystem structure that cannot beprecisely defined because of uncertainty. This ‘safe-fail’ approach to restorationdesign contrasts with the traditional ‘fail-safe’ approach of standard engineeringdesign.

Assuming the project design is properly implemented, failure of a restorationproject is generally related to inadequate objectives or a poor functional design(National Research Council, 1992). For example, restoration projects may fail forthe following reasons:1. Poor definition of the initial problem or inadequate understanding of undesir-

able ecosystem characteristics.2. Vague or overly ambitious project objectives.3. Inadequate understanding of nutritional requirements and tolerance limits of

target species.4. Attempts to stabilize the physical–chemical environment (i.e., problem of

overcontrol) when the target species requires environmental variation.5. Insufficient colonizers or transplants of inappropriate genetic stock.6. Lack of understanding or control of exotic or other undesirable species that

invade and out-compete the target species.7. Unpredicted species interaction.8. Unpredicted natural or anthropogenic disturbances.

The three strategies recommended for avoiding pitfalls and recovering fromrestoration project setbacks are the appropriate setting of objectives (describedabove) to allow a ‘safe-fail’, ‘bet-hedging’ during restoration project design, andadaptive management during implementation and monitoring (see Thom, 1997 fordiscussion of this latter topic). The uncertainty inherent in forecasting future


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environmental conditions for a specific restoration project precludes selection of asingle set of values for design parameter as the ‘optimal design’. Thus, part of theplanning of an optimal design should incorporate heterogeneity in the physical,chemical, and biological design factors as a bet-hedging strategy.

Fig. 2 demonstrates a mix between the horticulturally driven and ‘self-designed’strategies of Mitsch and Wilson (1996), where the restoration area may be dividedinto spatial modules and several restoration subdesigns may be spatially distributedacross the entire area. For example, multiple microhabitats which foster ecosystemdiversity are easily obtained by providing microtopographic diversity throughrough grading the site and allowing the plant growth medium to vary in thickness,texture, or other physiochemical properties. For some habitats, such as forestedwetlands, this microtopographic diversity is a crucial and often overlooked designcomponent (Barry et al., 1996). Encouraging colonization by more than onedesirable species with similar functions reduces the risk inherent in relying entirelyon the success of one element. The important point is to build in heterogeneity andopportunity for colonization by desired species, enhancing the desired successionalprocesses where possible. Finally, the appropriate level of heterogeneity in thedesired (target) system can only be judged against reference area conditions.

Spatial variation in design accomplishes two things. First, it increases theprobability that at least one of the subdesigns is successful, creating a viable habitat‘island’. Propagules may then spread from this habitat island. Excluding keypredators from some areas of a site is one way to encourage desirable species. Forexample, fish exclusion cages in restored hypereutrophic lakes allow the expansionof herbivorous zooplankton, thereby creating ‘islands’ of improved habitat withreduced phytoplankton populations and greater water clarity. Many foundationspecies modify their environment in such a way that colonization by additionalindividuals and expansion of the habitat is enhanced (e.g., in establishing a seagrassbed, the presence of seagrass dampens wave action, increases sediment deposition,and favors further colonization at the edge of the bed). In terrestrial systems, a widevariety of species can be introduced (e.g., companion species plantings) or thehabitat manipulated to encourage the establishment of biodiversity by naturalprocesses.

Second, even if most of the subdesigns fail initially, this strategy results ininformation on which series of subdesigns are most effective. Such information iskey to using an adaptive management approach. If most of the subdesigns succeedinitially, future environmental variations may still lead to failure or disturbance ofsome of the subdesigns or of a portion of the restoration area. Spatial variation inthe design may confer some resistance to unforeseen natural disturbances as well asresilience following disturbance.

7. Restoration designs, feasibility, and experimentation

Restoration designs may be developed from conceptual models, quantitativemodels, and data from previous case studies or restoration experiments. Confidence


in the restoration design will generally be higher as more data from experimentsand case studies are used to support the initial design and the evaluation ofalternatives in the feasibility study (Fig. 1). Experiments may also be conductedspecifically to support the cost and impact analysis, especially tests of alternativedesigns at the larger scales. Such experiments may also be used to refine (orvalidate) ecological models and restoration hypotheses (e.g., feedback loops in Fig.1).

Local and regional ecological constraints on restoration efforts must be consid-ered in the evaluation of feasibility, cost, and impacts of each alternative. Thequantitative objectives of the project should be realistic relative to these constraints.Assuming that a design is properly implemented, restoration efforts may still haveadverse effects on nontarget species. There is also some risk of project failure, withadverse consequences for the target species. Thus, risks to both target and non-target species should be evaluated for each restoration alternative.

Multi-attribute decision techniques may be useful for evaluating the benefits andrisks of restoration alternatives (Brown et al., 1980; Edwards and Newman, 1982;Brown and Valenti, 1983; Tetra Tech, 1986). These techniques allow evaluationfactors for projects to be differentially weighted and scaled to a common relativeunit. For example, the benefit of increased abundance of a target wetland species(e.g., sawgass in the Everglades water conservation areas) as a result of reducingphosphorus loading to a given level can be weighed against the risk of furtherincreases in populations of undesirable species (e.g., cattails) and compared to thepredicted consequences of choosing a different level of phosphorus loading.

Technical factors that should be considered in evaluating restoration alternativesor combinations of alternatives include:1. Expected benefits to target species and nontarget species within the project area

and other systems in the local landscape and region.2. Risk of adverse impacts on nontarget species (e.g., effects on threatened or

endangered species).3. Past successes and failures with restoration design or similar efforts (i.e., case

study analysis and experimental studies; fault-tree analysis).4. Initial ecosystem manipulation and degree of maintenance needed (i.e., ability of

restored ecosystem to be self-sustaining).5. Projected time until specific target conditions are attained, in the context of

other local projects (e.g., housing development, road construction).Mesocosm-scale (e.g., plot- or enclosure-scale) tests of restoration designs or

subdesigns may provide experimental verification that a design will work, at leastfor some portion of the restoration area. The choice of spatial scale for mesocosmtesting depends on a balance between making the mesocosm large enough toprovide realistic results that are not confounded by scale effects and small enoughto be feasible and cost-effective. Moreover, repetition of smaller experiments indifferent areas of a heterogeneous site may provide more information than a singlelarge-scale experiment. Voshell (1989) and Graney et al. (1994) discuss pastexperiences with aquatic mesocosms in ecological research and recommendationsfor mesocosm design. Field experiments are widely used in planning terrestrialrestoration projects (Bradshaw and Chadwick, 1980).


8. Implementation, monitoring, and adaptive management

A ‘final’ restoration design is developed from the results of the feasibility, cost,and impact analysis (Fig. 1). Chance events, in the form of physical or biologicaldisturbance, may modify restoration projects after construction, and uncertaintiesin design decisions cannot be entirely overcome with either detailed site and contextunderstanding or variable design approaches. Therefore, contrary to the perspectiveof Garbisch (1989), we believe that restoration projects are not ‘fully formed’ at theend of the revegetation phase, or successful if the ‘as built’ project matches design.To deal with these realities, adaptive management, as a way of learning from ouractions, is the capstone of the proposed planning process (National ResearchCouncil, 1992; U.S. GAO, 1994). Adaptive management, as described by Holling(1978) formally requires that the site be considered a long-term experiment. Itinvolves:1. Monitoring of the site relative to the project objectives (including pre-project

baseline or reference areas)2. Analysis of the monitoring data to determine the effectiveness of specific

restoration methods and techniques, and3. Incorporation of ‘experimental’ results in further site manipulation and, as

applicable, in other similar projects.Adaptive management may involve iteration of any of the planning steps shown

in Fig. 1.This form of ‘after care’ is now required for mine reclamation in the United

Kingdom, and is substantially more rigorous than most monitoring required inClean Water Act Section 404 mitigation projects (Kentula et al., 1993) or surfacemine reclamation bond release in the United States (Toy and Hadley, 1987; Officeof Surface Mining, 1996). It must explicitly incorporate the temporal perspective onrestoration (i.e., 15–20 years rather than 5 years) advocated by Mitsch and Wilson(1996). It also requires a more formal analysis of post-project manipulation than istypical of maintenance programs for engineering (i.e., abiotic) projects such as floodcontrol channels or highways. Active long-term adaptive management is increas-ingly being called for in large-scale ecosystems management in the United States(e.g., Lee and Lawrence, 1986; FEMAT, 1993; Hennessey, 1994), which shouldincrease its acceptance in a restoration setting (e.g., Thom, 1997).

The key purpose of monitoring with respect to adaptive management is twofold.First, monitoring guides further selective manipulations of the project that improvethe outcome relative to stated objectives. Second, monitoring allows evaluation ofthe effectiveness of specific restoration methods or techniques. Design of monitor-ing programs is a complex topic that has been addressed by many authors (e.g.,Green, 1979; Mar et al., 1986; U.S. Environmental Protection Agency, 1990; Loeband Spacie, 1994). For example, the discussion in Kentula et al. (1993) providesuseful advice on selection of wetland ecosystem characteristics to be monitored (i.e.,performance indicators; also termed ‘assessment criteria’ by National ResearchCouncil, 1992).


The performance indicators (i.e., the structural or functional elements of theecosystem that are to be used to judge the success of the project) (NationalResearch Council, 1992) should be linked to project objectives within the context ofknown attributes of regional reference ecosystems. Multiple performance indicatorsshould be used to minimize the risk of missing important ecological effects of theproject (National Research Council, 1992).

9. Conclusion

The planning framework described in this paper, while recognizing that restora-tion actions focus on replacement of ecosystem structure, requires that a thoroughunderstanding of site-specific ecological processes guide all phases of a restorationproject. For example, one must not only understand important physical andchemical factors (e.g., hydrological regime, substrate composition, and chemistry)that control vegetation communities, but also recognize the roles of key species anddisturbances in maintaining a diverse habitat mosaic. Furthermore, site construc-tion, while not trivial, becomes only one of several equally important phases in thisprocess by virtue of detailed planning, feasibility studies, and post-constructionmonitoring. Only by approaching projects in this way can we fulfill the twin goalsof advancing the science of restoration and avoiding further ecosystem damage byeither trivial tinkering or over-engineering.

Acknowledgements

This paper was adapted from a chapter in Yozzo et al. (1996), and benefited fromdiscussions with the technical work group members responsible for the report: DanWillard (originator of the ‘safe-fail’ concept), Ron Thom, Barry Vittor, Dick Pratt,Dave Gettleson, Don Rhoads, John Lunz, and Jane Sexton. Comments by anony-mous reviewers and William Mitsch also considerably strengthened this paper.Development of this framework was funded by the U.S. Army Corps of EngineersEEIRP Objectives and Outputs Work Unit (J. Titre, Principal Investigator, andD.G. Nolton, Institute for Water Resources, Co-Principle Investigator) underContract No. DACW39-93-0006. Ms. Michaele Reynolds provided editorial sup-port. The views presented in this paper are those of the authors and not those ofthe U.S. Army Corps of Engineers.

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An ecological decision framework for environmental restoration projects