A new method for assessing the sustainability of land-use systems (II): Evaluating impact indicators

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A new method for assystems (II): EvaluatiChristof Waltera,, Hartmut SaUnilever Colworth, Colworth Park, SharnbroobInstitute of Vegetable and Fruit Science, NatuA R T I C L E D A T AE C O L O G I C A L E C O N O M I C S 6 8 ( 2 0 0 9 ) 1 2 8 8 1 3 0 0ava i l ab l e a t www.sc i enced i rec t . comwww.e l sev i e r. com/ l oca te /eco l econprocedure introduced earlier.Finally, we explore the propagation of uncertainty (defined as a variable's 95% confidencelimits) throughout the standardisation procedure using a stochastic simulation approach.The uncertainty of the analysed standardised indicator was higher than that of the non-standardised indicators by a factor of 2.0 to 2.5.spinach production system inNorthwest Germany. Themethod highlightsmineral resourceconsumption, greenhouse gas emission, eutrophication and impacts on soil quality as themost important environmental effects of the studied system.We then explore the effect of introducing weighting factors, reflecting the differing societalperception of diverse environmental issues. Two different sets of weighting factors are used.The influence of weighting is, however, small compared to that of the standardisation Corresponding author. Unilever Colworth, SE-mail address: christof.walter@unilever.co0921-8009/$ see front matter 2008 Elsevidoi:10.1016/j.ecolecon.2008.11.017indicators with regard to sustainability.This methodology is then tested on an indicator set for the environmental impact of aIndicatorsSustainability assessmentStandardisationNormalisationSeverity factorLife cycle assessmentsessing the sustainability of land-useng impact indicatorsttzelbk, UKral Sciences, University of Hanover, GermanyA B S T R A C TIn the past decade, numerous indicators and indicator sets for sustainable agriculture andsustainable land management have been proposed. In addition to their interest incomparing different management systems on an indicator by indicator basis, landmanagers are often interested in comparing individual indicators against a threshold, or,in order to study trade-offs, against each other. To this end it is necessary to (1) transformthe original indicators into a comparable format, and (2) score these transformed indicatorsagainst a sustainability function.This paper introduces an evaluation method for land-use-related impact indicators, whichwas designed to accomplish these tasks. It is the second of a series of two papers, and assuch it links into a larger framework for sustainability assessment of land use systems.The evaluation scheme introduced here comprises (1) a standardisation procedure, whichaims at making different indicators comparable. In this procedure indicators are firstnormalised, by referencing them to the total impact they contribute towards, and then theyare corrected by a factor describing the severity of this total impact in terms of exceeding athreshold. The procedure borrows conceptually from Life Cycle Assessment (LCA) ImpactAnalysis methodology; (2) a valuation procedure, which judges the individual standardisedArticle history:Received 21 November 2005Received in revised form22 November 2008Accepted 23 November 2008Available online 20 January 2009Keywords:Sustainable agriculture 2008 Elsevier B.V. All rights reserved.ustainable Agriculture, Colworth Park, Sharnbrook, MK44 1LB, UK. Tel.: +44 1234 222 465.m (C. Walter).er B.V. All rights reserved.1. IntroductionAgriculture is one of the human activities most tightly con-nected with land (cf. Matson et al., 1997; Fields, 2001; Tilmanet al., 2001), but virtually any human enterprise is associatedwith land use or land occupancy.Numerous indicators and indicator sets for sustainableagriculture and sustainable land management have beenproposed in the past years (Niu et al., 1993; Izac and Swift,1994; Stockle et al., 1994; SmythandDumanski, 1995; Bockstalleret al., 1997; van Mansvelt, 1997; Smith and McDonald, 1998;Wackernagel and Yount, 1998; Halberg, 1999; Eckert et al., 2000;Sands and Podmore, 2000; Reganold et al., 2001; Stevenson andcomparable) and the actual sustainability valuation procedure(which assigns a sustainability value to each indicator value).Finally, during Stage 3 a strategy for improvement is developedand improvements are made visible.This paper focuses on Stage 2 of the assessment frame-work. The methodology presented here will address the twosteps that are involved: indicator standardisation and sustain-ability valuation.The method presented here includes elements inspired byLife Cycle Assessment (LCA) methodology. It was, however,extended to meet a number of specific requirements for landuse evaluation in the context of sustainability. In particular,the method was developed to:1289E C O L O G I C A L E C O N O M I C S 6 8 ( 2 0 0 9 ) 1 2 8 8 1 3 0 0Lee, 2001); for reviews see Hansen (1996), Christen (1999) andWalter (2005). Inaddition to their interest in comparingdifferentmanagement systems on an indicator by indicator basis, landmanagers are often interested in comparing individual indica-tors against a threshold (Syers et al., 1995), or, in order to studytrade-offs, against each other. To this end it is necessary, firstly,to transform the original indicators into a comparable format,and secondly, to submit these transformed indicators to asustainability scoring function (Walter, 2005).This paper presents an evaluation method for indicator setsthat describe the impact of land use systems on sustainability(or impact indicators). Impact indicators are here defined asmeasures of a land use system's contribution to certain threatsto sustainability (Smith and McDonald, 1998) or constraints tosustainability (Stockle et al., 1994). These are indicators thatwould be classified as Pressure/Driving Forces indicators in theOECD indicator classification scheme (OECD, 1998, 2000). Thisdefinition confines the method to indicator sets that describenegative impacts or bads, which, aswell asbeing less subject todiffering perceptions, are oftenmore salient and policy relevantthan positive impacts or goods (Costanza, 1993; Ludwig et al.,1993; Jamieson, 1998).The method presented here links into a broader frameworkof indicator based sustainability assessment (Walter, 2005),which can be conceptualised in three stages (as shown in Fig. 1).During Stage 1 the indicator set is determined by identifying thespecific problems that need to be assessed (also calledindicanda; Walter, 2005) and then attributing indicators thatadequately describe these indicanda. Stage 2 comprises twosteps: a standardisation procedure (tomake different indicatorsFig. 1 Stages of indicator-based sustai be appropriate for environmental, social and economicindicators alike, i.e. be suitable for all dimensions ofsustainability; allow for comparing very different land use systems, suchas agriculture and commerce; acknowledge the fact that sustainability issues emerge atvery different spatial scales, ranging from 1 m2 (or less) tohundreds of thousands of km2; separate the descryptive and normative elements ofsustainability evaluation as clearly as possible.The latter criterion keeping descriptive and normativeelements separate acknowledges the fact that science andscientists play a dual role in the sustainability debate. On theonehand they are a part of society andpolicydecisionsdoaffecttheir individual environments. On the other hand they areasked to informsocietal andpolitical decisionmakingprocessesin an impartial manner. The first role is connected to thenormative stratum of the sustainability debate, the second tothe descriptive. However, there is a fine line between these tworoles and they are not always easy to separate. In fact, they aremore like extreme poles of a broad continuum than clear-cutopposites, sinceanynormativedecision implies certaindescrip-tive elements and vice versa (Hoyningen-Huene, 1999).In order to assure the quality of scientific information, wehence hold that it is important to be explicit about normativeelements and about the limitations of descriptiveness(cf. Funtowicz and Ravetz, 1993; Tacconi, 1998). For the methodpresentedhere, thismeans that it doesnot engage innormativedebates with allegedly scientific arguments. It is meant tonability assessment (Walter, 2005).system S on issue i (any dimensionha1 yr1)I C SNFi Normalisation factor for issue i (dimension is reci-procal to that of ISi)SFi Severity factor for issue i (dimensionless).The normalisation factor, NFi, is the reciprocal of theindicator calculated for an average hectare of the spatialscale, on which the issue emerges:NFi =Itot iAtot i 12withItot i Indicator value describing the total impact, to whichland use system S contributes and which causesissue i ([same dimension as ISi]yr1)inform decisionmaking processes and fuel further debates, butnot to generate absolute facts.This paper adheres to the following structure: First thestandardisation and sustainability valuation procedures areintroduced. In order to enhance the transparency, we high-light and discuss underlying assumptions and implications ofthe method. We then apply the method to evaluate a set ofimpact indicators, which was developed to assess a spinachcropping system in the County of Borken, Northwest Ger-many. As the case study data are subject to large uncertain-ties, we also assess how these uncertainties are propagatedthrough the standardisation procedure and into the results byusing stochastic simulation. Finally, case study results arediscussed and main findings are summarised.2. The evaluation schemeAccording to the above framework, evaluation comprises twoseparate steps: Indicator standardisation and sustainabilityvaluation.2.1. Indicator standardisationThe standardisation procedure introduced here aims atmakingdifferent indicators comparable. It transforms each indicatorinto a dimensionless index bymultiplying it by two factors. Thefirst factor normalises the indicator by relating the impact ofthe system under investigation to the overall pressure causingthe issue that the indicator describes (e.g. it might relate thephosphate losses from agricultural fields to the total phosphateload discharged into the watershed that the fields are situatedin). The second factor describes the severity of the issue itself(e.g. the severity of eutrophication of the watershed caused byphosphate). The standardised indicator for any issue i is then:std IS i = IS i NFi SFi 1withstd ISi Standardised indicator for a particular issue i(dimensionless)ISi Indicator value describing the impact of land use1290 E C O L O G I C A L E C O N O MAtot i Total land area of the scale level, at which issue itypically emerges (ha).The severity ratio factor, SFi, is the ratio of an actual and acritical impact level (In Life Cycle Assessment, this is alsocalled a distance-to-target ratio):SFi =0 if Lact i=Lcrit ib1Lact i =Lcrit i if Lact i=Lcrit iz13withLact i Actual level of the impact causing issue i (anydimension)Lcrit i Critical level, beyond which impacts cause irrever-sible or severe damage (same dimension as Lact i).Must be0.Multiplication with the normalisation factor, NFi, meansdividing the average annual per ha impact of the land usesystem under investigation by the average total annual per haimpact it contributes to. The product ISiNFi can thus beinterpreted as the factor by which the total impact wouldchange if the particular land use under investigation wasextrapolated to the entire issue-specific area.The issue-specific area,Atot i, is the geographic extent of thespatial scale at which the particular issue emerges and isnormally assessed. It is here assumed to be predetermined byconventions of the pertinent scientific disciplines. Forinstance, the impact of pesticides on aquatic organismswould normally be assessed on a regional scale, whereas theemission of greenhouse gases affects the global level.Ideally, the actual and critical impact levels are assessedusing the same methodology as the indicator values. In thatcase Lact i= Itot i and Eq. (1) reduces tostd IS i = IS i Atot i=Lcrit i 4In practice it is, however, often difficult to find informationon critical impact levels that are methodologically consistentwith the data required for indicator calculation (e.g. due todifferences in base year or inventory method). In such cases isLact i Itot i.The severity factor, SFi, accounts for the fact that differentissues may be differently pressing. It can be interpreted as thefactor by which the actual impact level exceeds the criticalone. (This is similar towhat is referred to as distance-to-targetweighting in the Life Cycle Analysis literature; Brentrup et al.,2004; Mller-Wenk, 1996). If the actual impact level is belowthe critical impact level, this signals that there is not an issueand SFi is consequently set to zero.2.2. Sustainability valuationThe following valuation function then assigns the standar-dised indicators to three discrete sustainability classes:val IS i =sustainable for 0Vstd IS ibclcritical for clVstd IS ib1unsustainable for 1Vstd IS i8

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