What are the limits to oil palm expansion? Global Environmental Change

What are the limits to oil palm expansion?

Johannes Pirker*, Aline Mosnier*, Florian Kraxner, Petr Havlík, Michael Obersteiner

InternationalInstituteforAppliedSystemsAnalysis(IIASA),Laxenburg,Austria

ARTICLE INFO Articlehistory:

Received3December2015

Receivedinrevisedform30May2016 Accepted7June2016

Availableonlinexxx Keywords:

Oilpalmproduction Suitabilitymap Sustainabilitycriteria Landavailability

ABSTRACT

Palmoilproductionhasboomedoverthelastdecade,resultinginanexpansionoftheglobaloilpalm plantingareafrom10to17Millionhectaresbetween2000and2012.Previousstudiesshowedthata significantshareofthisexpansionhascomeattheexpenseoftropicalforests,notablyinIndonesiaand Malaysia,thecurrentproductioncenters.Governmentsofdevelopingandemergingcountriesinall tropicalregionsincreasinglypromoteoilpalmcultivationasamajorcontributortopovertyalleviation,as wellasfoodandenergyindependence.However,beingunderpressurefromseveralnon-governmental environmentalorganizationsandconsumers,themainpalmoiltradershavecommittedtosourcing sustainablepalmoil.Againstthisbackdropweassesstheareaofsuitablelandandwhatarethelimitsto futureoilpalmexpansionwhenseveralconstraintsareconsidered.Wefindthatsuitabilityismainly determined by climatic conditions resulting in 1.37 billionhectares of suitable landfor oil palm cultivationconcentratedintwelvetropicalcountries.However,weestimatethathalfofthebiophysically suitableareaisalreadyallocatedtootheruses,includingprotectedareaswhichcover30%ofoilpalm suitablearea.Ourresultsalsohighlightthatthenon-conversionofhighcarbonstockforest(>100tAGB/

ha)wouldbethemostconstrainingfactorforfutureoilpalmexpansionasitwouldexcludetwo-thirdsof globaloilpalmsuitablearea.Combiningeightcriteriawhichmightrestrictfuturelandavailabilityforoil palmexpansion,wefindthat234millionhectaresor17%ofworldwidesuitableareaareleft.Thismight seemthatthelimitsforoilpalmexpansionarefarfrombeingreachedbutoneneedstotakeintoaccount thatsomeofthisareamightbehardlyaccessiblecurrentlywithonly18%ofthisremainingareabeing under2htransportationtotheclosestcityandthatgrowingdemandforotheragriculturalcommodities whichmightalsocompeteforthislandhasnotbeenyettakenintoaccount.

ã2016TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).

1.Introduction

Palmoilproductionhasboomedoverthelastdecadesdrivenby increasinguseasfryingoil,asaningredientinprocessedfoodand non-edible products (detergents and cosmetics), and more recentlyinbiodieselproduction(Thoenes,2006).Mostobservers expectthistrendtocontinuein thecomingyears,eventhough probablyata slowerpacethanthelastdecade (OECDand FAO, 2013).Theshareofpalmoilinglobalvegetableoilproductionhas morethandoubledoverthelasttwentyyears,todayrepresenting morethan30%,outstrippingsoyaoilproduction(OECDandFAO, 2013).Reasonsforthisstrongexpansionincludethesubstantially higheroilyieldofpalmoilcomparedtootheroilseeds–overfour and seven times greater than rapeseed and soy, respectively (ProductBoardMVO,2010)–anditslowerprice,whichhasmadeit theprimarycookingoilforthemajorityofpeopleinAsia,Africa

andtheMiddleEast(Carteretal.,2007;USDA-FAS,2011).Schmidt andWeidema(2008)estimatethatpalmoilistodaythe“marginal oil”, i.e. future increases in demand for vegetable oils will be primarilysatisfiedbypalmoilratherthanbyothervegetableoils.

Thisresultedinanexpansionof theglobaloilpalmplanting areafrom6to16Millionhectaresbetween1990and2010,anarea whichnowaccountsforabout10percentoftheworld’spermanent cropland.MalaysiaandIndonesiahavebeentheepicenterofthis dynamic development:in thesetwocountriesplantedareahas increasedby150%and40%,respectively,overthelastdecade,and togethertheycurrentlyrepresentover80%oftheglobalpalmoil production(FAO,2016).Asglobaldemandincreasesandavailable land becomes increasingly scarce in the traditional production centers(KongsagerandReenberg,2012;USDA-FAS,2011),govern- mentsofdevelopingandemergingcountriessuchasBrazil,Peru and Central and Western Africa increasingly promote oil palm cultivationasamajorcontributortopovertyalleviation,andfood and energy independence (Carrere, 2010; Feintrenie, 2014;

Gutiérrez-Vélez andDeFries, 2013; Pacheco,2012; Villelaet al., 2014).

* Correspondingauthors.

E-mailaddresses:pirker@iiasa.ac.at(J.Pirker),mosnier@iiasa.ac.at(A.Mosnier).

http://dx.doi.org/10.1016/j.gloenvcha.2016.06.007

0959-3780/ã2016TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).

ContentslistsavailableatScienceDirect

Global Environmental Change

j o u r n al h o m ep a g e: w w w . el s e v i e r . c o m / l o c at e / g l o e n vc h a

Itisestimatedthat17%ofthenewplantationsinMalaysiaand 63% of those in Indonesia came at the direct expense of biodiversity-rich tropical forests over the period 1990–2010 (Gunarso et al., 2013; Koh et al., 2011)and up to 30% of this expansionoccurredonpeatsoils,leadingtolargeCO2emissions (Carlsonet al.,2012; Miettinen et al.,2012; Omaret al.,2010).

Thesepotentialnegativeeffectsofoilpalmcultivationhavegiven risetocloserscrutinyfromconsumers(GreenpeaceInternational, 2012).Asaconsequence,thepalmoilsectordevelopedin2004its own sustainable certification standard, the Roundtable on SustainablePalmOil(RSPO;vonGeibler,2013),andtheEuropean UnionaswellastheUnitedStateshavealsoset-upsomespecific sustainabilitycriteriaonfeedstockimportsforbiofuelproduction (Environmental Protection Agency, 2012; European Comission, 2010).However,RSPO-certifiedpalmoilcontinuestobeaniche product,holdingaboutonly15% ofthemarket,halfofwhich is marketedasconventionalpalmoil,sincedemandforcertifiesoilis still toolow (Balch, 2013; Roundtableon sustainablepalm oil (RSPO),2011).In2014,fivemajoroilpalmgrowersinitiatedthe SustainableOilPalmManifestowhichispreparingthegroundfor theestablishmentofasetofclearlydefinedandgloballyapplicable thresholdstothedefinitionofsustainablepalmoil(Raisonetal., 2015).

Thebroadobjectiveofsustainabledevelopmentisto“meetthe needsofthepresentwithoutcompromisingtheabilityoffuture generationstomeettheirownneeds”(Brundtland,1987).Some palmoilcertificationschemesliketheRSPO,tacklethethreepillars of sustainable development i.e. the environmental, social and economic dimensions while someother initiatives,like theEU directive onbiofuels, focus oncarbon savings and biodiversity protection(Franketal.,2013).Thereisnotanalignmentamongthe differentcertificationschemesonthemostappropriateoruseful setofindicatorsandtherearedifferentapproachesfordeveloping andusingthem (Pavlovskaia, 2014).However,two schemesare widelyusedinordertopreventemissionsfromtheconversionof landwithhighcarboncontentorthedestructionofbiodiversity- richnaturalhabitatsfrompalmoilproduction:theHighCarbon Stocks(HCS)andtheHighConservationValueindicator(HCV).

Inthecontextofacontinuedboominpalmoildemandandthe increasingsustainabilitycommitmentofthepalmoilsector,the objectiveofthispaperistoidentifythepotentialavailableareafor future expansion of palm oil plantations globally and more especially,howthismightbeaffectedbytheimplementationof some environmental sustainability criteria which are currently discussedbythesector.Wefirstassessoil palmlandsuitability fromabio-physicalperspectivetakingintoaccountclimate,soil andtopography.Subsequently,weremovefromthesuitablearea thelandwhereconversioniscurrentlynotpossiblebecausebeing alreadyunderuseorprotection.Then,weexcludelandwhichisof special value for biodiversity conservation or carbon storage.

Finally, we assess the accessibility of the resulting potentially available land for future oil palm plantations expansion, as remotenessmightreducetheprofitabilityofpalmoilproduction.

2.Materialsandmethods

2.1.Bio-physicalsuitabilityforoilpalm 2.1.1.Climate

Oilpalmtreesgrowinwarmandwetconditions.Fourclimatic factorsare crucial for oil palm cultivation:the average annual temperature,theaveragetemperatureofthecoldestmonthofthe year,theannualprecipitationandthenumberofmonthswhich receive less than 100mm of precipitation (Corley and Tinker, 2008). Optimal temperature conditions range between 24 and 28C,andtheaveragetemperatureofthecoldestmonthoftheyear

shouldnotfallunder15C(CorleyandTinker,2008).Further,the length of the growing period (LGP) for oil palm is mainly determinedbythelengthoftheperiodwithsufficientmoisture supply. Optimal conditions for palm cultivation are 2000– 2500mmrainfallperyearwithaminimumof100mmpermonth.

Onwelldrainedsoils,i.e.soilswhichareclassifiedasotherthan poorlydrainedaccordingtotheHarmonizedWorldSoilDatabase (HWSD;Nachtergaeleetal.,2012)annualrainfallupto4000mmis well supported, above this threshold diseases become more frequentand5000mmisconsideredthedefiniteupperlimitto oilpalmcultivation.Itisreportedtobegrownunderprecipitation conditionsaslowas1000mmperyear(YaoandKamagate,2010) and up tofive months of dry period. We present a review of suitability factors used by other studies in SM C. We do not consider irrigation schemes as a potential management option because for oil palm cultivation these schemes are still in the experimental phase.WeusedatafromtheWorldClimdatabase (Hijmansetal.,2005)tocomputeclimatesuitabilityatthe30arc secondsresolutionlevelanddatafromtheHWSD(Nachtergaele etal.,2012)todeterminethedrainagestatusofasite.

2.1.2.Soil

Oil palm is not very demanding in its requirements of the chemicalandphysicalpropertiesofthesoil:itgrowsonawide range of tropical soils, many of which are not suitable for the productionof othercrops.Constraining soilfactorsforoilpalm cultivationcan beeither chemical(e.g.nutrientdeficiencies) or physical (e.g. low water holding capacity) in nature. Optimal conditionsareprovidedbyfinelystructuredsoilswithhighclay content,thoughfairlygoodyieldscanalsobeachievedonloamand silt-dominatedsoils.Oilpalmisalsoverysensitivetoinsufficien- cies inwater provisionwhich arefrequent onsand-dominated soils. We distinguish between those soil features that can be overcomebyappropriateagronomicmanagementandthosethat are unsuitable regardless of management (see SM A for more details).Wemaketheassumptionthatappropriatesoilmanage- mentmeasuresareappliedinagro-industrialoilpalmplantations and therefore non-permanentproblematic soil features can be overcome and are not considered in the analysis. For soil information werely ontheHWSD(HWSD;Nachtergaele et al., 2012),asitprovidesgloballyconsistentdataandhasbecomethe standardsoildatasetforglobalapplicationsinrecentyears.The databaseis,however,incompleteconcerningsignificantareasin AfricaandAsiaandtobeconservativeweclassifiedtheseareasas notsuitable.However,sincethesepatchesarelocatedinaridareas unsuitableforoilpalmcultivation,thepartiallackofsoildatadoes notaffectourassessment.

2.1.3.Topography

Steepslopesrestrictoilpalmcultivationindifferentways.They increaseplanting,maintenanceandharvestingcosts,andshallow soilsmeanweakanchorage of theplants and surfacerunoff of fertilizers. Topsoil erosion of exposed sites is also commonly associatedwithslopingland,whichisanexclusioncriterioninan assessment of High Conservation Values (HCVs; HCV Resource Network,2015).Idealconditionscanbefoundonflatareaswith0– 4 slope inclination – but palmscan successfully begrown on slopesofupto16.Thecommonopinionatpresentisthatslopes above25 shouldnotbeplantedatall.Furthermore,intropical regions, elevationis strongly correlated totemperature, witha lapseratebeingaround 6C per1000mandelevationis also oftenassociatedwithslopeinclination.WeusedatafromtheNASA Shuttle Radar Topography Mission(SRTM;http://srtm.usgs.gov) witha90minitialrastergridcellsizeresampledto1kmusinga nearest neighbor technique as this source provides a globally consistentdatasetathighresolutionandfreeofcharge.

2.1.4.Overallsuitabilityindicator

Soilandclimatearethebasicresourcesforgrowthofanycrop whereastopographyis agood proxyforthemanageability ofa mechanizedproductionsystem,withthelatterbeingparticularly truefortheoilpalm.Wedefinedanoptimalrangeandminimum andmaximumsuitabilityvaluesforoilpalmgrowingconditions accordingtofourclimatic,threesoilandtwotopographycriteria and classified suitable land from 1 – marginally suitable to 5–perfectlysuitable.Theapproachtocombinecriteriaintoone overallsuitabilitypresentedhereisbasedonLiebig’sfundamental

“LawoftheMinimum”,whichstatesthat“agivenfactorcanexert itseffectonlyinthepresenceofand inconjunctionwithother factors”(Rübel,1935).Forinstance,asoilmayberichinnutrients butthesesubstancesareuselessifnecessarymoistureislackingto sustainplantgrowth.Consequently, theoverallsuitabilityscore reflects the score of that bio-physical variable which is least suitableforoilpalmcultivation,e.g.overallsuitabilityiszeroifone or more variables are zero. In the following we use the term

“suitable land” for all land that is suitable from a purely bio- physical viewpoint based on the criteria described in Table 1.

Detailedinformationofthethresholdsconsideredtoclassifybio- physicaldataintosuitabilitybinsisprovidedintheSupplementary material(SMA).

2.2.Landpotentiallyavailableforoilpalmexpansion

Wedistinguishthreetypesoflimitstooilpalmexpansion:(i) landthatispreventedfrombeingconvertedtootherusessuchas built-upland,(ii)landwhichisalreadyusedsuchascroplandand pasture and (iii) non-protected areas which are nevertheless importantforbiodiversityconservationand carbonstorage.The datasetsusedareavailableatvaryingspatialresolutions,inraster or polygon format. To allow for a consistent assessment, we convertedthedatasetstorasterformatatthespatialresolutionof 30Arcseconds,correspondingtoca.1kmusinganearestneighbor technique.

2.2.1.Landthatcannotbeconvertedtootheruses

Wefirst excludeprotectedareas (PAs) fromland potentially availableforoilpalmexpansionsincethelawusuallypreventsland conversionintheseareas.WeoptedtousePAsofallstatusclasses fromtheWorldDatabaseonProtectedAreas(WDPA,versionJune 2015)toidentifylocationandextentofprotectedareas.PAsofany statuswerepickedinordertoadoptaconservativeapproachand toensure we didnot omit PAs that might bedelivering some conservationonthegrounddespitenotbeinglegallyrecognizedas PAbythejurisdictioninplace(Juffe-Bignolietal.,2015).Generally,

informationaboutbothlocationandextentofPAswasavailableas polygons.Insomecases,pointdatawasavailablefromtheWDPA indicatingtheapproximatecenterandthereportedareaofeachPA only. In those cases we calculated a circular shape of the PA correspondingtothereportedsizeofeachPAassuggestedbyJuffe- Bignolietal.(2015)andaddedthesecircularpolygonsasaproxyof theactualextentofPAstothedataset.

Weconsiderthatthetimescaletoconvertbuiltareatoother usesgoesbeyondthescopeofthisstudy.Consequently,wealso excludeurbanareasfromthelandbeingpotentiallyavailableforoil palmexpansion. Weusedthecrowdsourcing-basedhybrid land covermapconstructedbySeeetal.(2014)toidentifyurbanareas (Table2).

2.2.2.Landalreadyunderuse

Suitablelandforoilpalmcultivationcanbealreadyusedfor food,animal feedortimberproduction.Substitutionofpalmoil plantationstothesedifferentusesisusuallynotforbidden,butthis couldpotentiallycreatesomeconflictswithotherneedsincluding foodforlocalpopulations.Followingaconservativeapproach,we decidedtoexcludethislandfromtheavailablelandforoilpalm plantationsexpansion.

Existingcropland,pastureandcropland-forestmosaicareawas identifiedbased ontheSeeetal.(2014) globallandcover map.

Furthermore, we also excluded existing industrial oil palm plantationsforIndonesia,theCentralAfricanRepublic,Equatorial Guinea, Cameroon, Democratic Republic of the Congo, Gabon, Liberia (World Resources Institute (WRI), 2013a), Cameroon (Nkongho et al., 2015), the Republic of the Congo (MEFDDE, 2015)andGuatemala(IARNA,2012),forwhichwehadaccessto spatial data.Thisapproach allowedus tocaptureca.15Mhaof concessionarea.Spatialdatawerenotavailableforimportantpalm oilproducingcountrieslikeMalaysiaandColombia.

Finally, forest concessions are usually attributed to timber harvestsduringaperiodlongerthan25yearsinthetropics.We excludethemfromavailablelandforsevencountriesworldwide wherewehadaccesstospatialdata:Indonesia,theCentralAfrican Republic, Equatorial Guinea, Cameroon,DemocraticRepublic of theCongo,Gabon(WorldResourcesInstitute(WRI),2013a,b)and theRepublicofCongo(MEFDDE,2015).

2.2.3.Landwithahighvalueforbiodiversityandcarbonstorage High Conservation Values (HCV) dominate the discussion aroundsustainablepalmoilandconductingassessmentsagainst HCV standards are obligatory for a number of certification schemes. However, HCV is a concept developed for local and case-to-caseapplicationandhencethere isnoglobaldatasetof

Table1

Criteriausedfortheconstructionofthebio-physicalsuitabilitymap.

Criterion Unit/description Suitablerange Originalspatial

resolution

Datasetused

Climate AnnualPrecipitation mm/m² 1000–5000 30arcseconds(ca.

1km)

WorldClim(Hijmansetal., 2005)

Numberofdrymonths Monthlyprecipitationlessthan100mm/m² 0–4

AverageAnnualTemperature Celsius 18–38

Temperatureofthecoldest month

Celsius >15

Soil Predominantsoiltexturetype Soiltextureclassification Sand–Clay- loam

30arcseconds(ca.

1km)

HWSD(Nachtergaeleetal., 2012)

Otherproblematicsite features

Permanentlywaterloggedzonesconsidered unsuitable

– MODIS(Friedletal.,2010)

Topography Slope Slopingdegrees 0–25 3arcseconds(ca.

90m)

NASASRTM(NASA,2010)

Elevation Metersa.s.l 0–1500

HCVs.InanattempttofindsubstitutesforHCVdata,weidentified areaswhereatleastfourofthesixglobal,terrestrialbiodiversity priorityareasoverlap,followinganapproachputforwardbyKapos etal.(2008)tocoverHCV1and3(HCVResourceNetwork,2015).

The six priority areas include Conservation International’s Hotspots(Mittermeieretal.,2004),WWF’sGlobal200terrestrial andfreshwaterecoregions(OlsonandDinerstein,2002),Birdlife International’sEndemicBirdAreas(BirdlifeInternational,2008), WWF/IUCN’s Centers ofPlant Diversity (Davis etal.,1998)and AmphibianDiversityAreas(Duellman,1999).

Thedraftversionofthesustainabilitycommitmentofthemajor oil palm growers mentions that “old-growth forests without evidenceofrecenthumandisturbance”shouldnotbeconverted (Raisonetal.,2015p.9),whichisrelatedtoHCV2.Forthispurpose,

weusetheIntactForestLandscapedatasetthatmapsoldgrowth forestswithaminimumareaof20,000ha(Potapovetal.,2008).

Thesustainabilitycommitmentofthepalmoilsectorsetsout veryclearguidelinesforthedefinitionofwhatistobeconsidered landwithhighcarbonstock(HCS)–includingbothaboveground andbelowgroundcarbon –thatshouldbepermanentlyspared fromconversiontooilpalmplantations.Theproposalistoconsider asHCSanyforesttypewithanabovegroundbiomass(AGB)greater orequalto100t/haandpeatsoilwithathicknessofitspeatlayer exceeding12.5cm(Raisonetal.,2015).Tothatend,weusethepan- tropicalAGBmapproducedbyBaccinietal.(2012)toidentifyHCS forests, and thehistosolssoilcategory fromtheHWSD(HWSD;

Nachtergaeleetal.,2012)asaproxyfortropicalpeatlands.

Table2

Criteriausedtoexcludelandfromavailablelandforoilpalmexpansion.

Description GenericDefinition Definition Original spatial resolution

Datasource

Landalready underuseor protection

Landnot possibleto convert

Urbanareas Allurbanareas 10arc seconds (ca.300m)

Seeetal.(2014)

Protectedareas Allprotectedareas n.a. UNEP-WCMCandIUCN(2015) Landalready

underuse

Croplandand pasture

Cropland,pasture, agriculture-forest mosaic

10arc seconds (ca.300m)

Seeetal.(2014)

Oilpalm concessions

Existingplantations whenspatialdata available

n.a. Indonesia,DRC,Gabon,Liberia(WorldResourcesInstitute(WRI),2013a), Cameroon(Nkonghoetal.,2015),theRepublicofCongo(MEFDDE,2015) andGuatemala(IARNA,2012)

Logging concessions

Existingforest concessionswhen spatialdataavailable

n.a. Indonesia,DRC,Gabon,Liberia,Cameroon(WorldResourcesInstitute (WRI),2013a,b),RepublicofCongo(MEFDDE,2015)

Sustainability criteria

Biodiversity- richareas

Globalterrestrial biodiversity priorityareas

4overlappingpriority areas

15arcsec (ca.500m)

Kaposetal.(2008)

Intactforest landscapes

20,000haof continuousforest

500m Potapovetal.(2008) Carbon-rich

areas

Aboveground biomass

100tAGB/ha 930m Baccinietal.(2012)

Peatlands Allhistosols 30arc

seconds (ca.1km)

Nachtergaeleetal.(2012)

Note:Noscaleorspatialresolutioncouldbedeterminedforthedatasetsmarkedas“n.a.”inthecolumn“Originalspatialresolution”.

Fig.1.Globalsuitabilitymapandzoomintothreeoilpalmfocusareas(fromlefttoright):TheAmazonregion;thecoastofCentralAfricaandtheislandofBorneo.

2.2.4.Marketaccessibility

Finally,weoverlaythepotentiallyavailablelandforsustainable oilpalm cultivationthatweobtainfromthecombinationofall previouslymentionedcriteria,withthetimetoaccesstheclosest city above 50,000 inhabitants based on current infrastructure network(Nelson,2008).Thisallowsustoestimatehowaccessible and therefore economically attractive are the remaining areas identifiedforsustainableoilpalmproductionandhenceprovidesa firstglimpseoftheeconomicdimensionofthisassignment.The spatialresolutionofthisdatasetis30arcseconds(ca.1km).

3.Results

3.1.Landsuitableforoilpalmcultivation

Wefind thatsome 1.37billion hectaresof land globallyare suitableforoilpalmcultivation.Suitablelandisconcentratedin twelvetropicalcountries,whichtogetherencompass84%ofthe globalsuitablearea(Fig.1).AlmosthalfofthelandareaofBrazil– essentiallylocatedintheAmazon–istosomeextentsuitablefor oilpalmplanting,whichcorrespondstoatotalsuitableareaof417 Mha,makingitthenumberonecountryintermsofsuitableland.

Thesheersizeofthecountrydeterminesthehugepotentialforoil palmexpansion,infactothercountrieshaveahigherproportionof suitablelandrelativetotheirtotal.TheSupplementarymaterial (SMDandE)providesanoverviewofthebio-physicallysuitable areaforalltropicalcountries.

Suitabilityisessentiallydrivenbyclimate.Hightemperatures overtheyearalongwithsufficientandsteadyrainfallarecrucialto oilpalmcultivation.OptimalclimaticconditionsarefoundinSouth East Asia and especially in Indonesia and Malaysia, with consistentlyhightemperaturesandprecipitationthroughoutthe year.However,whenmovingnorthtocontinentalSouthEastAsia awayfromtheequator,amarkeddryseasondiminishesclimatic suitabilityforoilpalmcultivationincountriessuchasThailand, IndiaandCambodia.

InSouthAmerica,largetractsoftheAmazonregioninBrazil, Colombia,PeruandEcuadorexhibitgoodclimaticconditionsforoil palmgrowthandsodopartsofCentralAmericaandtheCaribbean.

The main limiting factor here is the Andean mountain chain stretchingNorth-Southandtheclimatewhich inadditiontothe equatorialgradient istoodrytobearoilpalmsinagoodportion ofthenorthofBrazil.

InAfrica,thebiggestareaofsuitablelandislocatedintheCongo basin, essentiallyinDRC,but alsothegulf of Guineaand West Africaharborarelativelynarrowstretchofsuitablelandalongthe coast.However,severalmonthswithlessthan100mmandlower annual precipitations than in the other tropical regions partly reducethesuitabilityforoilpalmintheregion.

Undulatingslopesandelevatedareasposefurtherconstraints inmountainous areassuchastheAndes inSouth America, the AlbertineRiftinEasternDRCandtheNewGuineaHighlandsonthe islandofPapua.

About70%ofthepotentiallysuitablecultivationareaforoilpalm accordingto climatic conditions couldbe negativelyaffected by problematicsoilgrowingconditions,themostprominentproblem- atic soil type being weathered and leached soils (Acrisols and Ferralsols)whicharewidespreadoverthewholetropicalarea,and especiallyinAfrica.Poorlydrainedsoilsarecommonindepression zonesofIndonesia,whichareoftenidenticaltopeatareasandother soilswithhighorganicmatter.Thesecanalsobeobservedalong majorriversinSouthAmerica.However,mostoftheseconstraints couldbeovercomebyapplyingoptimalmanagement,evenifitwill entailsomeadditionalproductioncosts.

3.2.Landavailableforoilpalmcultivation

Startingfromthetotalsuitableareaforoilpalmcultivation,we firstexcludeonebyonethelandwhichfallsundereachindividual criterion to determine how each of them impacts the land availabilityforoilpalmexpansion.Inasecondstep,wecombineall thecriteria todeterminetheirjointimpactonland availability, since it is important to notethat many of the criteria overlap (Fig.3).

3.2.1.Suitablelandalreadytaken

Ofthetotalof1370Mhaofsuitableland,urbanareasreduce availablelandforoilpalmexpansionby5Mhawhichisequivalent to 0.38% of total suitable area. Conversely, 30% of the globally suitableareaforoilpalmproductioniscurrentlyoccupiedbyPAs, reducingtheavailablelandforoilpalmplantationsexpansionby 417Mha worldwide. PA coverage of suitable land for oil palm productionrangesfromlessthan2%inPapuaNewGuinea(PNG)to asmuchas67%inVenezuela,withthemajorityofthecountries covering15-20%oftheirsuitablearea.

About216Mhaofagriculturallandislocatedonsuitableareas.

Thisnumbercomprisescroplandandpasture(47Mha)aswellas areascoveredwithcropland-forestmosaic(168Mha).Oilpalmis currentlygrownonatotalareaof18Mhaaccordingtoavailable spatial information, among which 20% is already classified as agriculturalland.Thismeansthatabout14Mhaofcurrentoilpalm concessionshavetobeaddedtotheagriculturalareatoaccountfor theareaalreadyunderagriculturaluse.Forthecountrieswhere data was available – basically the Congo basin countries and Indonesia – logging concessions could furtherreduce oil palm plantationsexpansionbyalmost70MhawithIndonesiaholding thelargestareawitha totalof 24.9Mhaof suitable landbeing underforestconcession.

Sincetheoverlapsbetweentheabovecriteriaarequitelimited (exclusiveuse),wecalculatethat723Mhaofsuitableareaforoil palmexpansionisalreadytakenbyotheruses,reducingtheland availabilityforfutureexpansionbyhalfcomparedtothebiophysi- callysuitablearea.

3.2.2.Suitablelandwithhighenvironmentalvalue

Highlybiodiverseareascover125Mhaofsuitablelandforoil palmcultivation andarerelativelyconcentrated inahandful of countrieswithIndonesia(22.3Mha),Peru(16Mha),Brazil(9Mha) and Venezuela (8Mha) makingup foralmost 45% ofall highly biodiverseareasinsuitableareasforoilpalmcultivation.Wealso notethathighlybiodiverseareaswouldalmostcompletelyprevent oil palm plantation expansion in some countries, such as Madagascar(99%) andLiberia(92%). Asimilarconcentrationon afewcountriesistrueforintactforests,whereBrazil(227Mha), DRC (62Mha)and Peru (48Mha) accountfor two thirdsof the globalsuitablearea,whichamountstoatotalof507Mha.Forest storingmorethan100tonsAGBperhaisthemostconstraining criterion in terms of land availability for oil palm expansion, covering about 1 billion ha i.e. leaving 370Mha suitable for potentialexpansionworldwide.Thesuitableareaforoilpalmis stronglycorrelatedwiththiscriterionas83%ofcarbon-richforests are located in the twelve countries that also have the largest suitable area. This criterion would especially reduce land availabilityinBrazil,withmorethan300Mhadroppedfromthe suitablearea.Peatlands,bycontrast,areverymuchconcentrated on South-East Asia with Indonesia (16.7Mha) and Malaysia (2.4Mha) harboring almost all the world’s known peatlands (21.7Mha).

3.2.3.Totalpotentiallyavailablelandforoilpalmplantations expansion

Thecombinationofallabovementionedcriteriaandsuitable landforoilpalmcultivationyieldsanestimateofavailablelandfor oilpalmplantationsof233.82Mhaworldwide,only17%ofwhat wehaveestimatedasthetotalsuitablearea(Fig.3andSME).

Brazil,with43.4Mha,hasbyfarthelargestareaofavailable land for oil palm expansion followed by the DRC (38.4Mha), Colombia(21.1Mha)andIndonesia(18.2Mha).Thatbeingsaid,the applicationofsustainabilitycriteriawillrestrictoilpalmcultiva- tioninsomecountriesmorethaninothers(SeeSMDandE).There are countries which could develop as much as 49% (Nigeria, 9.5Mha), 53% (Cote d’Ivoire, 9.3Mha) and even 69% (Uganda, 5.1Mha) oftheirsuitable landwhile adheringtothefullsetof sustainabilitycriteria.Ontheotherendofthespectrumcountries suchas Peru,Guyana, Surinameand FrenchGuyanacouldonly developamarginalshareoflessthan4%ofthecountries’suitable area for sustainable palm oil production. The extensive and biomass-richforestcover isbyfarthesinglemostconstraining factorinthesecountries.

Whereasoverallpotentialavailabilityofsuitablelandisca.17%

(233.82Mha)globally,only5%ofthe‘verysuitable’areasremain (suitabilityclasses4and5–darkandlightgreeninFigs.2and3).In absoluteterms,thiscorrespondsto19.3Mhaofverysuitableland whichcouldbeavailableforsustainableoilpalmcultivationinthe future,a number which would still allow doubling thecurrent extentof18.1Mhaofoilpalmworldwide.Onceoverlapofcriteriais takenintoaccount,thecombinationofexistingagriculturalland and 100t/ha aboveground biomass cover wouldbe enough to cover 88% of the total excluded area globally based on the combination of the eight criteria considered in this study.

However,thiscouldnotbethecaselocally,whereothercriteria, likebiodiversityhotspots couldsignificantlyreduceareafor oil palmexpansionbeyondcarbonandagriculturalland.

3.2.4.Marketaccessibility

Analysisofaccessibilityofpotentiallyavailablelandsyieldsthe resultspresentedinFig.4.Justlessthan1/5th(18%)oftheareaisin reachinlessthan2hfromtheclosestcityand50%areaccessiblein less than 5h. On theotherhand, 20%of allavailable areas are locatedat10hormore fromcities.Variationamong suitability classesisminor,yetlandinthehighestsuitabilityclasstendstobe somewhatmoreremotethanlandinotherclasses.

4.Discussionandconclusion

We have generated a new global bio-physical oil palm suitability map which differentiates between five suitability classes.Thisdatasetcouldbeoneusefullayerofinformationto guidefutureoilpalmexpansionaccordingtodifferentobjectives.

Ourresultsindicatethattencountriesencompass75%oftheglobal suitablearea.CountriesinSouthEastAsia–thecurrentcenterof palmoilproduction–havethehighestshareofsuitablelandin relation to the size of the countries, while countries in Latin AmericaandCentralandWesternAfricahavethelargesttractsof potentially suitable land. Suitability is essentially driven by climate,andinparticularhightemperatureswithsufficientand steadyrainfallovertheyear.Thechoiceofthresholdstocategorize categoricaldata(soil)anddiscretedata(climate,topography)to formsuitabilityclasseshasbeenmadeuponadetailedliterature review.However,thiscouldremainapotentialsourceofdebate.

Thesuitabilitymapproducedforthisstudyiscomparablewith previousstudies,yetregionallystrongdifferencesexistbetween theproductswhichmainlyrelatetodifferencesinthewaywater availabilityinparticularduringdryseasonsarebeingtakeninto account.Wethinkthat thisstudybettercapturestheimpactof seasonalitybyusingthenumberofdrymonthsovertheyearand the lowest temperature in the coldest month rather than the lowest mean monthly relative humidity (RHlow) of the driest monthof theyearwhich isusedin theGAEZstudy,wheredry

Fig.2.Exclusionofsuitableareaforfutureoilpalmexpansionaccordingtodifferentcriteria(blackdiagonalhatching)andremainingpotentiallyavailableareabysuitability class(green,yellow,red)onaglobalscale.(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderisreferredtothewebversionofthisarticle.)

spellsarenotreflectedexplcitly.Thisstudyalsotendstoconsidera widerareatobesuitablethantheWRIstudybecauseweusea lowerminimum annual rainfall:1000mm insteadof 1400mm.

Sincethereisempiricalevidenceofoilpalmbeingcultivatedunder lessfavorableclimaticconditions(Corley,2009;PALMCI,2011;Yao andKamagate,2010),weareconfidentinusingalowerminimum thresholdvalue.WepresentacomparisonoftheboththeGAEZ product and our new suitability map in the Supplementary material (SM G). One limiting factor to the reliability of the suitability map is the quality of input data. As we assessed suitabilityon a global scale, thedata is often theresult of an interpolation process from in situ measurements. Climactic informationiscollectedinanetworkofclimatestationsaround theglobe,however,intropicalareasthisnetworkisparticularly

thinandthequalityofthefinalproductisthusdiminished(see http://www.worldclim.org/methods).Bothavailabilityandquality ofsoildataalsovarygreatlyamongregions.Theauthorsofthe HarmonizedWorldSoilDatabaseacknowledgethatsoildatafor WestAfricaandSouthAsiaisespeciallylessreliable(Nachtergaele etal.,2012).

Thesuitabilitymaphasbeenrealizedunderoptimalmanage- menti.e.assumingthatmostofthesoilconstraintsareovercome by betterpractices includingfor instance ploughing,soil water managementtechniques,mulchingorfertilization.Consequently, suitability area on problematic soils is higher than without management but the total suitable area is not affected by assumptions made about themanagement. In fact the suitable areacouldbeexpandedifirrigationcouldbeusedtoovercome Fig.3.Locationsofremainingpotentiallyavailableareaforoilpalmexpansionbysuitabilityclass(green,yellowandred)onceareasalreadyusedorprotectedandwhichdo notmeetenvironmentalsustainabilitycriteriahavebeenexcluded(inblue).(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderisreferredtotheweb versionofthisarticle.)

Fig.4.Accessibility(inhanddays)ofpotentiallyavailablelandseparatedbysuitabilityclasses.

waterdeficit.However,thereiscurrentlyalmostnoagro-industrial plantationwhich uses irrigation sowe decidedto notuse this managementoption.Yet,analternativesuitabilitymapcouldbe builtin the future to allowfor irrigation.Ultimately, all these management options should not only be considered through increaseinthepotentialyieldperhectarebutalsothroughhigher productioncosts.Thiswouldallowexploringwhichpalmoilprice levelwouldbenecessarytoadoptcertainmanagementoptions.

Oneofthelimitsoffutureoilpalmexpansionisthecompetition forlandwithotheruses.Wehaveshownthatbyremovingthearea under current use or protection, we reduce by half the total suitableareapotentiallyavailableforfutureoilpalmexpansion.In reality,animportantshareofplantationhasbeendevelopedon agriculturallandinthepast(Gunarsoetal.,2013).Butsincethe globalpopulationisexpectedtocontinuegrowinguntilatleast 2050(Lutzetal.,2001),welikelyunderestimatetheareawhich willbeallocatedtootherusesandoverestimatetheavailablearea forfutureoilpalmcultivation.Weenvisagetoinvestigatethisissue ofincreasingcompetitionforlandinthefuturebetweenoilpalm and other commodities by using an economic model with a detailed representation of land-based activities and market interactionssuchasGLOBIOM(Valinetal.,2014).Ourresultsalso highlighttheneedtoreinforcecontrolinexistingprotectedareas as30%ofcurrentprotectedareasarelocatedinareassuitableforoil palm.

Majorpalmoilproducingcompaniesandcountriesaremore andmorecommittedtoreducetheirenvironmentalimpacts.From 1.37billionhectaresoflandbeingsuitableforoilpalmcultivation, only17%remainswhenlandcurrentlyallocatedandenvironmen- tal sustainability criteria are taken into account, including 19 millionhectaresofhighlysuitablearea.Highcarbonstockscriteria alonereducesby73%thesuitableareaforoilpalmexpansionand encompasses88%of thelandexcluded bythe sumofallother environmentalcriteria.Thissuggeststhatthiscriterioncouldbe prioritizedinfuturestudiesifdataonothercriteriaisnotavailable (Raison et al., 2015). However, if several global datasets on abovegroundbiomassareavailable(Avitabileetal.,2016;Baccini et al., 2012; Saatchi et al., 2011), there is a high uncertainty associatedwiththebiomassinformationwhich isderivedfrom satelliteimages(Mitchardetal.,2013).

The remainingsuitable, sustainableand potentiallyavailable landthatweestimateinthisstudyisstilllargeifwecomparewith thecurrent17millionhectaresunderoilpalmcultivationglobally.

AstudycommissionedbytheIndonesiangovernmentfinds18Mha ofavailableland foroil palmexpansionwhich issimilartoour results(TheJakartaPost,2009).FortheBrazilianAmazon,Ramalho Filhoetal.(2010)identified31.2Mhawhichisabout12Mhaless thanourstudyandfortheRepublicoftheCongoFeintrenieetal.

(2014)foundavailablelandof1.28Mhaasopposedto6.3inour study.ThiscanpartlybeexplainedbytheexplicitfocusofRamalho Filhoetal.onpreviouslydeforestedsitesandthefactthatbuffer zonesaroundvillages,rivers,andprotectedareasarealsoexcluded in Feintrenie’s assessment. It should also be noted that the biodiversitysustainabilitycriteriausedinthisstudyarelikelyless rigorousthanadetailedHCVassessment.Inourassessmentwe explicitly cover HCV 1-3 by considering global terrestrial biodiversitypriorityareas and intact forestlandscapes. Butwe lackcriteriaonecosystemservices,socialandculturalwell-being oflocalcommunitiesorindigenouspeoples(HCV4-6)whichcan onlybeidentifiedthroughengagementatthelocallevel.

However,ourresultsalsoshowthatthepotentiallyavailable landforoilpalmexpansionusinga limitednumberofenviron- mental sustainability criteria becomes quite scarce in some countries,especiallyforhighlysuitablearea.There isalmostno arealeftforthedevelopmentofoilpalmplantationsinLiberiaand Madagascar. Moreover, diverting oil palm production to lower

suitableareaswillalsoleadtolowereconomicprofitabilitywhich couldbepartlyoffsetbyhigherplantationsarea.Acarefulcost- benefit analysis must be done to ensure that new oil palm plantations meet thethree dimensions of sustainabledevelop- ment.

Finally,theoilpalmbusinessmodelhasverymuchfocusedon expansionasthemeanstosatisfyincreasingdemandandyields have stagnatedover thelast decade in Malaysia and Indonesia (Murphy, 2007). However, novel breeding technologies are expectedtoallowforattaininghigheryieldsandlongerproductive rotationperiods,whichmightcontributetoareductioninfuture expansionofplantations.Furtherresearchshouldthereforealso addressthepossibleroleofagronomic intensification andyield increases.

5.Implicationsoftheresults

Focusing on the current centers of oil palm production, Indonesia with available land in the order of 18.2Mha and currentlyplantedareaof10Mhamightfaceloominglandscarcity forsustainableoilpalmproductionandMalaysiawith2.1Mhaof availablelandand4.6Mhaofcurrentlyplantedareahasalready exceededitssustainablearea(FAO,2016).Ontheotherhand,our findings also support the feasibility of a number of countries’ futureoilpalmexpansionplans(SMF),althoughtheyshouldbe consideredasanupperboundarytosustainableoilpalmexpansion asfine-scaleeconomicandsocialcriteriamustalsobetakeninto account.

Acknowledgements

This work was supported by the REDD+ Policy Assessment Center (www.redd-pac.org) which is part of the International ClimateInitiative(IKI),supportedbytheFederalMinistryforthe Environment,Nature Conservation,Building and Nuclear Safety (BMUB)basedonadecisionadoptedbytheGermanBundestagand theImprovingForestGovernancethroughindependentmonitor- ingprojectintheDemocraticRepublicoftheCongosupportedby theNorwegianAgencyforDevelopmentCooperation(NORAD).We wouldliketothankPaulChatterton(WWFREDD+Landscapes)for hisconstructivecommentsonthedraftarticle.

AppendixA.Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound,in the online version, at http://dx.doi.org/10.1016/j.

gloenvcha.2016.06.007.

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