TheSERI nternati onal Pri mero nEcol ogi cal Restorati onSociety for Ecological Restoration International Science & Policy Working Group (Version 2: October, 2004)*Section 1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Section 2: Definition of Ecological Restoration . . . . . . . . . . . . . . . . . . . . . . 3Section 3: Attributes of Restored Ecosystems . . . . . . . . . . . . . . . . . . . . . . 3Section 4: Explanations of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Section 5: Reference Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Section 6: Exotic Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Section 7: Monitoring and Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Section 8: Restoration Planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Section 9: Relationship Between Restoration Practice and Restoration Ecology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Section 10: Relationship of Restoration to Other Activities. . . . . . . . . . . . 12 Section 11: Integration of Ecological Restoration into a Larger Program. . 13This document should be cited as: Society for Ecological Restoration International Science & Policy Working Group. 2004. The SERInternational Primer on Ecological Restoration. www.ser.org & Tucson: Society for Ecological Restoration International. The principal authors of this Primer were Andr Clewell (Quincy, FL USA), James Aronson (Montpellier, France), and Keith Winterhalder(Sudbury, ON Canada). Clewell initially proposed thePrimer and wrote its first draft. Aronson and Winterhalder, in collaboration withClewell, revised the Primer into its present form.Winterhalder, in his capacity as Chairperson of SERs Science & Policy Working Group,coordinated this effort and invited other Working Group members to participate. Eric Higgs (Victoria, BC Canada) crafted the Overview sec-tion. Dennis Martinez (Douglas City, CA USA) contributed a position paper that became the basis for text pertaining to cultural ecosystems.Other Working Group members provided critiques and suggestions as the work progressed, including Richard Hobbs (Murdoch, WAAustralia), James Harris (London, UK), Carolina Murcia (Cali, Colombia), and John Rieger (San Diego, CA USA). The SPWG acknowledgesEric Higgs, former Chairperson of SER Internationals Board of Directors, for his encouragement and for bringing the Primer before SERInternationals Directors for its official adoption as an SER International document on 6 April, 2002, by unanimous vote.This document supercedes SER Internationals Project Policies that were initially published in Restoration Ecology 2(2):132-133, 1994, and thatwere later posted on SER Internationals website. This document also supercedes the policy on Project Evaluation that was posted on the SERInternational website. SER International environmental policies, initially published in Restoration Ecology 1(3):206-207, 1993, remain in effect.*The content of the second version is exactly the same as the first version published in 2002, except that International has been appended toSER's name, photos have been added, and the graphics redesigned. Version 2 was published simultaneously in print and on the internet atwww.ser.org.OverviewEcological restoration is an intentional activitythat initiates or accelerates the recovery of anecosystem with respect to its health, integrity andsustainability. Frequently, the ecosystem that requiresrestoration has been degraded, damaged, trans-formed or entirely destroyed as the direct or indirectresult of human activities. In some cases, theseimpacts to ecosystems have been caused or aggravat-ed by natural agencies such as wildfire, floods,storms, or volcanic eruption, to the point at whichthe ecosystem cannot recover its predisturbance stateor its historic developmental trajector y.Restoration attempts to return anecosystem to its historic trajec-t o ry. Historic conditions aret h e re f o re the ideal start i n gpoint for re s t o r a t i o ndesign. The re s t o re decosystem will not nec-essarily re c over its for-mer state, since contem-p o r a ry constraints andconditions may cause itto develop along ana l t e red trajectory. The his-toric trajectory of a seve re l yimpacted ecosystem may be dif-ficult or impossible to determinewith accuracy. Ne ve rtheless, the generald i rection and boundaries of that trajectory canbe established through a combination of know l e d g eof the damaged ecosystems pre-existing stru c t u re ,composition and functioning, studies on compara-ble intact ecosystems, information about re g i o n a le n v i ronmental conditions, and analysis of otherecological, cultural and historical re f e rence infor-mation. These combined sources allow the historict r a j e c t o ry or re f e rence conditions to be chart e df rom baseline ecological data and pre d i c t i ve mod-els, and its emulation in the restoration pro c e s sshould aid in piloting the ecosystem tow a rd si m p roved health and integrity. Restoration represents an indefinitely long-termcommitment of land and resources, and a proposalto restore an ecosystem requires thoughtful delibera-tion. Collective decisions are more likely to be hon-ored and implemented than are those that are madeunilaterally. For that reason, it behooves all stake-holders to arrive at the decision to initiate a restora-tion project by consensus. Once the decision torestore is made, the project requires careful and sys-tematic planning and a monitored approach towardsecosystem recovery. The need for planning intensifieswhen the unit of restoration is a complex land-scape of contiguous ecosystems.Interventions employed inrestoration vary widelyamong projects, dependingon the extent and dura-tion of past disturbances,cultural conditions thathave shaped the land-scape, and contemporaryconstraints and opportu-nities. In the simplest cir-cumstances, restorationconsists of removing ormodifying a specific distur-bance, thereby allowing ecolog-ical processes to bring about anindependent recovery. For example,removing a dam allows the return of anhistorical flooding regime. In more complex circum-stances, restoration may also require the deliberatereintroduction of native species that have been lost,and the elimination or control of harmful, invasiveexotic species to the greatest practicable extent.Often, ecosystem degradation or transformation hasmultiple, protracted sources, and the historical con-stituents of an ecosystem are substantially lost.Sometimes the developmental trajectory of a degrad-ed ecosystem is blocked altogether, and its recoverythrough natural processes appears to be delayedindefinitely. In all of these cases, however, ecologicalrestoration aims to initiate or facilitate the resump-www.ser.org SER International Primer on Ecological Restoration 1Section 1:tion of those processes which will return the ecosys-tem to its intended trajectory.When the desired trajectory is realized, the ecosys-tem under manipulation may no longer requireexternal assistance to ensure its future health andintegrity, in which case restoration can be consideredcomplete. Nevertheless, the restored ecosystem oftenrequires continuing management to counteract theinvasion of opportunist species, the impacts of vari-ous human activities, climate change, and otherunforeseeable events. In this respect, a restoredecosystem is no different from an undamagedecosystem of the same kind, and both are likely torequire some level of ecosystem management.Although ecosystem restoration and ecosys-tem management form a continuumand often employ similar sorts ofintervention, ecological restora-tion aims at assisting or initi-ating recovery, whereasecosystem management isintended to guarantee thecontinued well-being ofthe restored ecosystemthereafter.Some ecosystems, partic-ularly in developing coun-tries, are still managed bytraditional, sustainable cultur-al practices. Reciprocity exists inthese cultural ecosystems betweencultural activities and ecologicalprocesses, such that human actions reinforceecosystem health and sustainability. Many culturalecosystems have suffered from demographic growthand external pressures of various kinds, and are inneed of restoration. The restoration of such ecosys-tems normally includes the concomitant recovery ofindigenous ecological management practices, includ-ing support for the cultural survival of indigenouspeoples and their languages as living libraries of tra-ditional ecological knowledge. Ecological restorationencourages and may indeed be dependent uponlong-term participation of local people. Culturalconditions in traditional cultures are currentlyundergoing unprecedented global change. To accom-modate this change, ecological restoration mayaccept and even encourage new culturally appropri-ate and sustainable practices that take into accountcontemporary conditions and constraints. In thisregard, the North American focus on restoring pris-tine landscapes makes little or no sense in places likeEurope where cultural landscapes are the norm, or inlarge parts of Africa, Asia and Latin America, whereecological restoration is untenable unless it manifest-ly bolsters the ecological base for human survival.What makes ecological restoration especially inspir-ing is that cultural practices and ecological processescan be mutually reinforcing. Accordingly, it is notsurprising that interest in ecological restoration isgrowing rapidly worldwide and that, in most cases,cultural beliefs and practices are drawn uponto help determine and shape of what isto be performed under the rubricof restoration.The definition presented onthe next page, the one offi-cially endorsed by theSociety for EcologicalRestoration International,is sufficiently general toallow a wide variety ofapproaches to restoration,while giving prominence tothe historically rich idea ofrecovery. T2 SER International Primer on Ecological Restorationwww.ser.orgDefinition ofEcologicalRestorationEcological restoration is the process of assistingthe recovery of an ecosystem that has beendegraded, damaged, or destroyed. TAttributes ofRestoredEcosystemsThis section addresses the question of what ismeant by recovery in ecological restoration.An ecosystem has recovered - and is restored - whenit contains sufficient biotic and abiotic resources tocontinue its development without further assistanceor subsidy. It will sustain itself structurally and func-tionally. It will demonstrate resilience to normalranges of environmental stress and disturbance. Itwill interact with contiguous ecosystems in terms ofbiotic and abiotic flows and cultural interactions.The nine attributes listed below provide a basis fordetermining when restoration has been accom-plished. The full expression of all of these attributesis not essential to demonstrate restoration. Instead, itis only necessary for these attributes to demonstratean appropriate trajectory of ecosystem developmenttowards the intended goals or reference. Some attrib-utes are readily measured. Others must be assessedindirectly, including most ecosystem functions,which cannot be ascertained without research effortsthat exceed the capabilities and budgets of mostrestoration projects.1. The restored ecosystem contains a characteristicassemblage of the species that occur in the refer-ence ecosystem and that provide appropriatecommunity structure.2 . The re s t o red ecosystem consists of indigenousspecies to the greatest practicable extent. Inre s t o red cultural ecosystems, allowances canbe made for exotic domesticated species andfor non-inva s i ve ruderal and segetal speciesthat presumably co-evo l ved with them.Ruderals are plants that colonize disturbedsites, whereas segetals typically grow inter-m i xed with crop species.3. All functional groups necessary for the contin-ued development and/or stability of the restoredecosystem are represented or, if they are not, themissing groups have the potential to colonize bynatural means.4. The physical environment of the restoredecosystem is capable of sustaining reproducingpopulations of the species necessary for its con-tinued stability or development along thedesired trajectory.5. The restored ecosystem apparently functionsnormally for its ecological stage of development,and signs of dysfunction are absent.6. The restored ecosystem is suitably integratedinto a larger ecological matrix or landscape,with which it interacts through abiotic andbiotic flows and exchanges.7. Potential threats to the health and integrity ofthe restored ecosystem from the surroundinglandscape have been eliminated or reduced asmuch as possible.8. The restored ecosystem is sufficiently resilient toendure the normal periodic stress events in thelocal environment that serve to maintain theintegrity of the ecosystem.www.ser.org SER International Primer on Ecological Restoration 3Section 2:Section 3:9. The restored ecosystem is self-sustaining to thesame degree as its reference ecosystem, and hasthe potential to persist indefinitely under exist-ing environmental conditions. Nevertheless,aspects of its biodiversity, structure and func-tioning may change as part of normal ecosystemdevelopment, and may fluctuate in response tonormal periodic stress and occasional distur-bance events of greater consequence. As in anyintact ecosystem, the species composition andother attributes of a restored ecosystem mayevolve as environmental conditions change.Other attributes gain relevance and should be addedto this list if they are identified as goals of therestoration project. For example, one ofthe goals of restoration might be toprovide specified natural goodsand services for social benefitin a sustainable manner. Inthis respect, the restoredecosystem serves as natu-ral capital for the accrualof these goods and serv-ices. Another goal mightbe for the restoredecosystem to providehabitat for rare species orto harbor a diversegenepool for selectedspecies. Other possible goalsof restoration might include theprovision of aesthetic amenities orthe accommodation of activities of socialconsequence, such as the strengthening of a commu-nity through the participation of individuals in arestoration project. TExplanations of TermsVarious technical terms are introduced through-out this document. Some of these terms maybe unfamiliar to readers who are not ecologists,while others have multiple connotations from differ-ential usage. To reduce the potential for misunder-standings, key terms are explained in the manner inwhich they are used in this document.An ecosystem consists of thebiota (plants,animals, microorganisms) within agiven area, the environment thatsustains it, and their interac-tions. Populations of speciesthat comprise the biota arecollectively identified asthe biotic community.This community is fre-quently segregated on thebasis of taxonomic status(e.g., the insect commu-nity) or life form (e.g.,the tree community).Assemblages of organismscan also be recognized bytheir functional roles in theecosystem (e.g. primary producers,herbivores, carnivores, decomposers,nitrogen fixers, pollinators), in which casethey are known asfunctional groups. The physicalor abiotic environment that sustains the biota of anecosystem includes the soil or substrate, the atmos-pheric or aqueous medium, hydrology, weather andclimate, topographic relief and aspect, the nutrientregime, and the salinity regime. Habitat refers to thedwelling place of an organism or community thatprovides the requisite conditions for its life processes.An ecosystem can be recognized in a spatial unit ofany size, from a microsite containing only a fewindividuals to an area showing some degree of struc-tural and taxonomic homogeneity such as a small-scale and community-based wetland ecosystem, or4 SER International Primer on Ecological Restorationwww.ser.orgSection 4:a large-scale and biome-based tropical rainforestecosystem. Ecological restoration can be conductedat a wide variety of scales, but in practice all ecosys-tem restoration should be approached with a spatial-ly explicit landscape perspective, in order to ensurethe suitability of flows, interactions and exchangeswith contiguous ecosystems. A landscape consists ofa mosaic of two or more ecosystems that exchangeorganisms, energy, water and nutrients. A legitimateand indeed important object of much ecologicalrestoration is the reintegration of fragmented ecosys-tems and landscapes, rather than focusing on just asingle ecosystem. A natural landscape or ecosystem is one that devel-oped by natural processes and that is self-organizing and self-maintaining. Acultural landscape or ecosystemis one that has developedunder the joint influence ofnatural processes andhuman-imposed organiza-tion. Many grasslandsand savannas are main-tained in large part bythe human activitiessuch as the regular igni-tion of surface fires forhunting, gathering or ani-mal husbandry. In Europe,many of the species-richmeadows are cultural ecosys-tems that arose following forestremoval in the Bronze Age, and havebeen maintained through mowing and seasonalgrazing by livestock. The repair of a damaged mead-ow qualifies as ecological restoration, even thoughthe meadow ecosystem that is selected as the land-scape of reference derives from human activities. Inanother example, a dense coniferous forest currentlyoccupies large parts of western North America. Inthe 19th century, much of this forest was open andpark-like with copious herbaceous cover, owing tothe frequent use of fire and plant species utilizationby indigenous tribal people. This woodland seemednatural and its condition was sustainable under theregime of tribal land usage. The return of thisecosystem to an open, park-like woodland, occupiedand utilized in the traditional tribal manner, quali-fies as ecological restoration. Sustainable culturalpractices are traditional human land uses that main-tain biodiversity and productivity. In this context,the biota is valued as much for its importance toecosystem stability as it is for its shortterm worth ascommodities. Perhaps all natural ecosystems are cul -turally influenced in at least some small manner, andthis reality merits acknowledgement in the conductof restoration.The terms degradation, damage, destruction andtransformation all represent deviations from the nor-mal or desired state of an intact ecosystem. The mean-ings of these terms overlap, and their application isnot always clear. Degradation pertains to subtle orgradual changes that reduce ecological integrityand health. Damage refers to acute andobvious changes in an ecosystem.An ecosystem is destroyed whendegradation or damageremoves all macroscopic life,and commonly ruins thephysical environment aswell. Transformation isthe conversion of anecosystem to a differentkind of ecosystem or landuse type.A reference ecosystem canserve as the model for plan-ning an ecological restorationproject, and later serve in the evalu-ation of that project. In instances wherethe object of restoration consists of two ormore kinds of ecosystems, the reference can be calledthe reference landscape or, if only a portion of alocal landscape is to be restored, the reference land-scape unit. The designated ecosystem, landscape orunit can simply be called the reference. Typically,the reference represents a point of advanced develop-ment that lies somewhere along the intended trajec-tory of the restoration. In other words, the restoredecosystem is eventually expected to emulate theattributes of the reference, and project goals andstrategies are developed in light of that expectation.The reference can consist of one or several specifiedlocations that contain model ecosystems, a writtendescription, or a combination of both. Informationwww.ser.org SER International Primer on Ecological Restoration 5collected on the reference includes both biotic andabiotic components. A more comprehensive discus-sion of the reference ecosystem appears in Section 5.An ecological trajectory is one that describes thedevelopmental pathway of an ecosystem throughtime. In restoration, the trajectory begins with theunrestored ecosystem and progresses towards thedesired state of recovery that is expressed in the goalsof a restoration project and embodied in the refer-ence ecosystem. The trajectory embraces all ecologi-cal attributes - biotic and abiotic - of an ecosystem,and in theory can be monitored by the sequentialmeasurement of coherent suites of ecological param-eters. Any given trajectory is not narrow and specif-ic. Instead, a trajectory embraces a broad yetconfined range of potential ecologicalexpressions through time, asmight be described mathemat-ically by chaos theory, orpredicted by various eco-logical models. A fullyempirical description ofa trajectory is impededin two ways. First, thenumber of ecosystemtraits that can be meas-ured far exceeds thosethat can be reasonablymonitored, and thedescription of the trajectoryover time is necessarily incom-plete. Second, the monitoringdata lend themselves to the plottingof trajectories for individual parameters, buttheir combination into a single trajectory represent-ing the entire ecosystem requires highly complexmultivariate analysis of a kind that has yet to bedeveloped. This represents a critical research chal-lenge for the future.Biodiversity refers to biota in terms of taxonomicand genetic diversity, the variety of life forms presentand the community structure thereby created, andthe ecological roles performed. Thebiota is organ-ized hierarchically from the level of the genome upto individual organisms, species, populations, andcommunities. Two related aspects of biodiversity arespecies composition, i.e. the taxonomic array ofspecies present, and species richness, i.e. the numberof different species present. The importance of anample recovery in species composition cannot beoverstated in restoration. All functional species-groups must be represented if a restored ecosystem isto maintain itself. Species redundancy, i.e. the pres-ence of multiple species that play similar roles inecosystem dynamics, provides assurance that ecosys-tem health is maintained in response to stress, dis-turbance or other environmental changes.In order for an ecosystem to be well adapted to localsite conditions and to display resilience in responseto a stressful or changing environment, the species-populations that comprise it must possess geneticfitness. An ecosystem containing geneticallyfit populations is one that is not onlyadapted to the current environmen-tal regime, but possesses somegenetic redundancy, wherebythe gene pool contains adiversity of alleles that maybe selected in response toenvironmental change.Under normal circum-stances, the reintroductionof local ecotypes is suffi-cient to maintain geneticfitness. Nevertheless, insites that have suffered sub-stantial damage and conse-quent alteration to their physicalenvironment, the introduction ofdiverse genetic stock may be the pre-ferred strategy, thereby allowing recombina-tion and the eventual development of novel, moreadaptive ecotypes.By community structure is meant the physiognomyor architecture of the community with respect to thedensity, horizontal stratification, and frequency dis-tribution of species-populations, and the sizes andlife forms of the organisms that comprise those com-munities.Ecological processes or ecosystem functions arethe dynamic attributes of ecosystems, includinginteractions among organisms and interactionsbetween organisms and their environment.6 SER International Primer on Ecological Restorationwww.ser.orgEcological processes are the basis for self-mainte-nance in an ecosystem. Some restoration ecologistslimit the use of the term ecosystem functions tothose dynamic attributes which most directly affectmetabolism, principally the sequestering and trans-formation of energy, nutrients, and moisture.Examples are carbon fixation by photosynthesis,trophic interactions, decomposition, and mineralnutrient cycling. When ecosystem functions arestrictly defined in this manner, other dynamic attrib-utes are distinguished as ecosystem processes suchas substrate stabilization, microclimatic control, dif-ferentiation of habitat for specialized species, pollina-tion and seed dispersal. Functioning at larger spatialscales is generally conceived in more general terms,such as the long-term retention of nutrients andmoisture and overall ecosystem sustainability.Ecosystem functions and processes, along with thereproduction and growth of organisms, are whatcause an ecosystem to be self-renewing or autogenic.A common goal for the restoration of any naturalecosystem is to recover autogenic processes to thepoint where assistance from restorationists is nolonger needed. In this regard, the central role of arestoration practitioner is to initiate autogenicprocesses. Restoration practitioners commonlyassume that autogenic processes will commence oncethe appropriate species composition and structurehave been re-established. This is not always a validassumption, but it is a reasonable starting point forecosystem restoration.Some dynamic processes are external in origin, suchas fires, floods, damaging wind, salinity shock fromincoming tides and storms, freezes, and droughts.These external processes stress the biota and aresometimes designated as stressors. The biota of anygiven ecosystem must be resistant or resilient to thenormal stress events that periodically occur in thelocal environment. These events serve to maintainecosystem integrity, by preventing the establishmentof other species that are not adapted to those stressconditions. For example, the tidal influx of salinewater is essential to maintain a salt marsh ecosystemand prevent its conversion to a freshwater ecosystem.In cultural ecosystems, human-mediated activitiessuch as burning or grazing qualify as stressors. Theterms disturbance or perturbation are sometimesused interchangeably for stressor or stress event.However, the term disturbance is restricted hereinto impacts on ecosystems that are more severe oracute than normal stress events.Resistance is the term describing an ecosystems abil-ity to maintain its structural and functional attrib-utes in the face of stress and disturbances. Resilienceis the ability of an ecosystem to regain structural andfunctional attributes that have suffered harm fromstress or disturbance. Ecosystem stability is the abil-ity of an ecosystem to maintain its given trajectoryin spite of stress; it denotes dynamic equilibriumrather than stasis. Stability is achieved in part on thebasis of an ecosystems capacity for resistance andresilience.The terms ecosystem integrity and ecosystem healthare commonly used to describe the desired state of arestored ecosystem. Although some authors use theterms interchangeably, they are distinct in meaning.Ecosystem integrity is the state or condition of anecosystem that displays the biodiversity characteristicof the reference, such as species composition andcommunity structure, and is fully capable of sustain-ing normal ecosystem functioning.Ecosystem health is the state or condition of anecosystem in which its dynamic attributes areexpressed within normalranges of activity relative toits ecological stage of development. A restoredecosystem expresses health if it functions normallyrelative to its reference ecosystem, or to an appropri-ate set of restored ecosystem attributes such as thosethat are listed above in Section 3. A state of ecosys-tem integrity suggests, but does not necessarily con-firm, a concurrent state of ecosystem health and asuitable abiotic environment. Twww.ser.org SER International Primer on Ecological Restoration 7ReferenceEcosystemsAreference ecosystem or reference serves as amodel for planning a restoration project, andlater for its evaluation. In its simplest form, the ref-erence is an actual site, its written description, orboth. The problem with a simple reference is that itrepresents a single state or expression of ecosystemattributes. The reference that is selected could havebeen manifested as any one of many potential statesthat fall within the historic range of variationof that ecosystem. The referencereflects a particular combination ofstochastic events that occurredduring ecosystem develop-ment.In the same manner, anecosystem that undergoesrestoration can developinto any of a potentiallylarge array of states. Anystate that is expressed isacceptable as restoration,as long as it is comparableto any of the potential statesinto which its reference couldhave developed. Thus, a simple ref-erence inadequately expresses the con-stellation of potential states and the historic range ofvariation expressed by the restored ecosystem.Therefore, a reference is best assembled from multi-ple reference sites and, if necessary, other sources.This composite description gives a more realistic basisfor restoration planning.Sources of information that can be used in describ-ing the reference include:I ecological descriptions, species lists and maps ofthe project site prior to damage;I historical and recent aerial and ground-level pho-tographs; remnants of the site to be restored, indi-cating previous physical conditions and biota;I remnants of the site to be restored, indicating pre-vious physical conditions and biota;I ecological descriptions and species lists of similarintact ecosystems;I herbarium and museum specimens;I historical accounts and oral histories by personsfamiliar with the project site prior to damage;I paleoecological evidence, e.g. fossil pollen,charcoal, tree ring history, rodent mid-dens.The value of the referenceincreases with the amountof information it contains,but every inventory iscompromised by limita-tions of time and fund-ing. Minimally, a baselineecological inventorydescribes the salient attrib-utes of the abiotic environ-ment and important aspectsof biodiversity such as speciescomposition and communitystructure. In addition, it identifiesthe normal periodic stress events thatmaintain ecosystem integrity. Descriptions ofthe reference for cultural ecosystems should identifythe cultural practices that are critical in restoring andlater in managing that ecosystem.The description of a reference is complicated by twofactors that should be reconciled to assure its qualityand usefulness. First, a reference site is normallyselected for its well-developed expression of biodiver-sity, whereas a site in the process of restoration typi-cally exhibits an earlier ecological stage. In such acase, the reference requires interpolation back to aprior developmental phase for purposes of both proj-ect planning and evaluation. The need for interpre-tation diminishes where the developmental stage at8 SER International Primer on Ecological Restorationwww.ser.orgSection 5:the restoration project site is sufficiently advancedfor direct comparison with the reference. Second,where the goal of restoration is a natural ecosystem,nearly all available references will have suffered someadverse human-mediated impacts that should not beemulated. Therefore, the reference may require inter-pretation to remove these sources of artifice. Forthese reasons, the preparation of the description ofthe reference requires experience and sophisticatedecological judgement.Written restoration project goals are critical fordetermining the detail that is needed in the descrip-tion of the reference. For large, landscape-scalerestoration for which only general goals are pre-scribed, the description of the reference canbe equally general. In such instances,aerial photographs may representthe most important source ofinformation for the prepara-tion of the reference.Restoration at a finerscale may require muchmore detailed referenceinformation, such asdata that are collectedon-site in small plots.TExotic SpeciesAn exotic species of plant or animal is one thatwas introduced into an area where it did notpreviously occur through relatively recent humanactivities. Since ecological restoration of naturalecosystems attempts to recover as much historicalauthenticity as can be reasonably accommodated, thereduction or elimination of exotic species at restora-tion project sites is highly desirable. Nonetheless,financial and logistical constraints often exist, and itis important to be realistic and pragmatic inapproaching exotic species control. In cultural land-scapes, exotic species are frequently anintegral part of the ecosystem, partic-ularly as crops and livestock, andeven as ruderals or segetals thathave presumably co-evolvedwith these domesticatedspecies. Such exotic speciesare acceptable for culturalrestoration.In natural ecosystems,invasive exotic speciescommonly compete withand replace native species.However, not all exoticspecies are harmful. Indeed,some even fulfill ecological rolesformerly played by the native speciesthat have become rare or extirpated. Insuch instances, the rationale for their removal maybe tenuous. Some exotic species were introducedcenturies ago by human or non-human agents andhave become naturalized, so that their status as anexotic is debatable. Other species have migrated inand out of the region in response to climatic fluctua-tions during the Holocene, and can scarcely beregarded as exotics. Even if all exotic species areremoved from a restoration site, the opportunity forreinvasion may remain high. Therefore it becomesessential for a policy to be developed for each exoticspecies present, based upon biological, economic andlogistical realities. Highest priority is best reservedfor the control or extirpation of those species whichwww.ser.org SER International Primer on Ecological Restoration 9Section 6:pose the greatest threats. These include invasiveplant species that are particularly mobile and pose anecological threat at landscape and regional levels, andanimals that consume or displace native species.Care should be taken to cause the least possible dis-turbance to indigenous species and soils as exoticsare removed.In some instances, non-indigenous plants are usedfor a specific purpose in the restoration project, forexample as cover crops, nurse crops or nitrogen fix-ers. Unless these are relatively short-lived, non-per-sistent species that will be replaced in the course ofsuccession, their eventual removal should be includ-ed in restoration plans. TMonitoring andEvaluationAproperly planned restoration project attemptsto fulfill clearly stated goals that reflect impor-tant attributes of the reference ecosystem. Goals areattained by pursuing specific objectives. The goalsare ideals, and the objectives are concrete measurestaken to attain these goals. Two fundamental ques-tions should be asked with respect to the evaluationof a restored ecosystem. Were the objectives accom-plished? Were the goals fulfilled? Answers to bothquestions gain validity only if the goals and objec-tives were stated prior to implementation of restora-tion project work.Ecosystems are complex, and no two intact ecosys-tems are ever identical, at least not when examinedin fine resolution. For that reason, no restoredecosystem at a project site can ever be identical toany single reference. The number of ecosystem vari-ables that can be used in an evaluation is too greatfor all to be measured within a reasonable period oftime. The selection of which variables to assess andwhich to ignore requires pragmatism and value judg-ment by the evaluator.Objectives are evaluated on the basis of perform-ance Standards, also known as design criteria orsuccess criteria. These standards or criteria are con-ceived in large part from an understanding of thereference ecosystem. Performance standards providean empirical basis for determining whether or notproject objectives have been attained. Objectives,performance standards, and protocols for monitoringand for data assessment should be incorporated intorestoration plans prior to the start of a project. Ifinterpretation of the data collected during monitor-ing shows that performance standards have beenmet, there can be no doubt that project objectiveswere achieved, and the restored ecosystem is likely tobe sufficiently resilient to require little or no furtherassistance from the restoration practitioner.It is assumed that project goals are, or soon will be,fulfilled once the objectives are attained. The validityof this assumption is not guaranteed, since theobjectives and performance standards that were des-ignated may prove to be inadequate, and unantici-pated environmental vicissitudes can deflect therestoration trajectory. For that reason, and sincegoals are ideals that resist strict empirical measure-ment, an element of professional judgment and sub-jectivity is inevitable in the evaluation of goals.Three strategies exist for conducting an evaluation:direct comparison, attribute analysis and trajectoryanalysis. In direct comparison, selected parametersare determined or measured in the reference andrestoration sites. If the reference description is thor-ough, as many as 20 or 30 parameters can be com-pared that include aspects of both the biota and theabiotic environment. This can lead to ambiguity ofinterpretation when the results of some comparisonsare close and others are not. The question arises -how many parameters must have similar values andhow close must the values be before restoration goalsare satisfied? The most satisfactory approach may beto carefully select a coherent suite of traits that col-lectively describe an ecosystem fully yet succinctly.In attribute analysis, attributes are assessed in rela-tion to the list provided in Section 3. In this strategy,quantitative and semi-quantitative data from sched-uled monitoring and other inventories are useful injudging the degree to which each goal has beenachieved.10SER International Primer on Ecological Restorationwww.ser.orgSection 7:Trajectory analysis is a promising strategy, stillunder development, for interpreting large sets ofcomparative data. In this strategy, data collected peri-odically at the restoration site are plotted to establishtrends. Trends that lead towards the reference condi-tion confirm that the restoration is following itsintended trajectory. Evaluations include the assessment of any stated goalsand objectives that pertain to cultural, economic andother societal concerns. For these, the techniques ofevaluation may include those of the social sciences.The evaluation of socio-economic goals is importantto stakeholders and ultimately to policy-makers whodecide whether or not to authorize and financerestoration projects. TRestorationPlanningPlans for restoration projects include, at a mini-mum, the following:I a clear rationale as to why restoration is needed;an ecological description of the site designated forrestoration;I an ecological description of the site designated forrestoration;I a statement of the goals and objectives of therestoration project;I a designation and description of the reference; I an explanation of how the proposed restorationwill integrate with the landscape and its flows oforganisms and materials;I explicit plans, schedules and budgets for sitepreparation, installation and post-installationactivities, including a strategy for making promptmid-course corrections; I well-developed and explicitly stated performancestandards, with monitoring protocols by whichthe project can be evaluated;I strategies for long-term protection and mainte-nance of the restored ecosystem.Where feasible, at least one untreated control plotshould be included at the project site, for purposesof comparison with the restored ecosystem. TRelationshipBetweenRestorationPractice andRestorationEcologyEcological restoration is the practice of restoringecosystems as performed by practitioners at spe-cific project sites, whereasrestoration ecology is thescience upon which the practice is based. Restorationecology ideally provides clear concepts, models,methodologies and tools for practitioners in supportof their practice. Sometimes the practitioner and therestoration ecologist are the same person-the nexus ofpractice and theory. The field of restoration ecology isnot limited to the direct service of restoration practice.Restoration ecologists can advance ecological theoryby using restoration project sites as experimental areas.For example, information derived from project sitescould be useful in resolving questions pertaining toassembly rules of biotic communities. Further,restored ecosystems can serve as references for set-aside areas designated for nature conservation. Twww.ser.org SER International Primer on Ecological Restoration 11Section 8:Section 9:Relationship ofRestorationto OtherActivitiesEcological restoration is one of several activitiesthat strive to alter the biota and physical condi-tions at a site, and are frequently confused withrestoration. These activities include reclamation,rehabilitation, mitigation, ecological engineering andvarious kinds of resource management, includingwildlife, fisheries and range management, agro-forestry, and forestry. All of these activities can over-lap with and may even qualify as ecological restora-tion if they satisfy all criteria expressed in Section 3of this document. Relative to other kinds of activi-ties, restoration generally requires more postinstalla-tion aftercare to satisfy all these criteria.Rehabilitation shares with restoration a fundamen-tal focus on historical or pre-existing ecosystems asmodels or references, but the two activities differ intheir goals and strategies. Rehabilitation emphasizesthe reparation of ecosystem processes, productivityand services, whereas the goals of restoration alsoinclude the re-establishment of the pre-existing biot-ic integrity in terms of species composition andcommunity structure. Nonetheless, restoration, asbroadly conceived herein, probably encompasses alarge majority of project work that has previouslybeen identified as rehabilitation.The term reclamation, as commonly used in thecontext of mined lands in North America and theUK, has an even broader application than rehabilita-tion. The main objectives of reclamation include thestabilization of the terrain, assurance of public safety,aesthetic improvement, and usually a return of theland to what, within the regional context, is consid-ered to be a useful purpose. Revegetation, which isnormally a component of land reclamation, mayentail the establishment of only one or few species.Reclamation projects that are more ecologicallybased can qualify as rehabilitation or even restora-tion.Mitigation is an action that is intended to compen-sate environmental damage. Mitigation is commonlyrequired in the USA as a condition for the issuanceof permits for private development and public worksprojects that cause damage to wetlands. Some, butperhaps relatively few, mitigation projects satisfy theattributes of restored ecosystems listed in Section 3,and thus qualify as restoration.The term creation has enjoyed recent usage, particu-larly with respect to projects that are conducted asmitigation on terrain that is entirely devoid of vege-tation. The alternate term fabrication is sometimesemployed. Frequently, the process of voiding a sitecauses sufficient change in the environment torequire the installation of a different kind of ecosys-tem from that which occurred historically. Creationthat is conducted as supervised engineering or land-scape architecture cannot qualify as restorationbecause restoration initiates ecosystem developmentalong a preferred trajectory, and thereafter allowsautogenic processes to guide subsequent develop-ment with little or no human interference.Ecological engineering involves manipulation ofnatural materials, living organisms and the physical-chemical environment to achieve specific humangoals and solve technical problems. It thus differsfrom civil engineering, which relies on human-madematerials such as steel and concrete. Predictability isa primary consideration in all engineering design,whereas restoration recognizes and accepts unpre-dictable development and addresses goals that reachbeyond strict pragmatism and encompass biodiversi-ty and ecosystem integrity and health. When pre-dictability is not at issue, the scope of many ecologi-cal engineering projects could be expanded untilthey qualify as restoration. T12SER International Primer on Ecological Restorationwww.ser.orgSection 10:Integration ofEcologicalRestorationinto a LargerProgramEcological restoration is sometimes only one ofmany elements within a larger public or privatesector enterprise, such as development projects andprograms for watershed management, ecosystemmanagement and nature conservation. Project man-agers of these larger undertakings should be aware ofthe complexities and costs involved in planning andimplementing ecological restoration. Cost savingscan be realized by careful coordination of restorationactivities with other aspects of a large program. Forthis reason, project managers will benefit by recog-nizing ecological restoration as an integral compo-nent of a program. If this is done, the restorationistcan contribute substantively to all aspects of the pro-gram that impinge on restoration. Moreover, therestorationist will be in a position to ensure that allecological restoration is well conceived and fully real-ized. In this manner, the public good is served. Twww.ser.org SER International Primer on Ecological Restoration 13Section 11:Our mission is to promote ecological restoration as a means of sustaining the diversity of life on Earth andreestablishing an ecologically healthy relationship between nature and culture.SER International is a non-profit organization infused with the energy of involved members individuals andorganizations who are actively engaged in ecologically sensitive repair and management of ecosystems.Our members live and work all over the planet and draw on an unprecedented breadth of experience, knowledgesets and cultural perspectives. We are scientists, planners, administrators, ecological consultants, First Peoples,landscape architects, philosophers, teachers, engineers, natural areas managers, writers, growers, communityactivists, and volunteers.SER International serves the growing field of ecological restoration by facilitating dialogue among restorationists;encouraging research; promoting awareness of, and public support for, restoration and restorative management;contributing to public policy discussions; recognizing those who have made outstanding contributions to the fieldof restoration; and promoting ecological restoration around the globe.Founded in 1987, SER International now has members in 37 countries, with 14 chapters worldwide.Recognized by public and private organizations as the source for expertise on restoration science, practice and pol-icy, SER International achieves its objectives through cooperation with partner organizations and the work of itsglobal membership.We're a growing world community of practitioners dedicated to restoring damaged and disturbed ecosystems ...shouldn't you be a member of SER International? You can join online by visiting www.ser.org or call, write, emailor fax us for a membership application.Society for Ecological Restoration International285 West 18th Street, Suite 1Tucson, Arizona 85701 USAPhone: 520-622-5485Fax: 520-622-5491E-mail: info@ser.org I www.ser.org