Introduction

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Resources,ConservationandRecycling64 (2012) 1–2

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Resources,

Conservation

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Recycling

j o u r n al hom ep ag e :w w w . e l s e v i e r . c o m / l o c a t e / r e s c o n r e c

Introduction

Climatechangemaybeseenasthelargesteconomic,political, developmentaland environmentalchallengetheworldhasever faced.IPCCreportshaveshownthathumanactivitiesarealtering theatmosphere,andthatitiscrucialnowfordecision-makersat alllevelstotakeurgentaction.

Atthesametime,urbanizationiscreatingagrowingchallenge forcitiesandurbanpopulationcentersbothasenginesofeconomic activityandassourcesofgreenhousegasemissions.Accordingto theUnitedNationsPopulationFundthenumberofpeopleliving incitiesexceedstheworld’sruralpopulationsince2008andthis trendisexpectedtocontinue.Thewayinwhichwebuildand oper-atecitiesstronglyaffectsenergyuseandemissions.Forexample, theso-called‘urbanheatislandeffect’affectsenergyuseforspace conditioningandgreenhousegasemissions,whereassimple mea-surescanbeappliedtocontrolthiseffect.Citiesarealsovulnerable toclimatechange,sincemanyarelocatedincoastalareasordepend onimportedresourcessuchaswaterandfood.Urbancentersare alsoimportantusersofresources,andpotentialfuturestocks. Cli-mateprooﬁngcitieswillhenceaffectresourceuseglobally.Many citiesareintheforefrontofinitiativesformitigatingandadapting toclimatechangeandtrytodevelopcreativesolutions.

TheSymposium‘ClimateProofingCities’,organizedDecember 1st 2009 by ‘SENSE’ (the Netherlands Research School for Socio-Economic and Natural Sciences of the Environment, http://www.sense.nl),providedaplatformtodiscusskey develop-mentsforcitiesintheclimatedebate.TheSENSEnetworkisnotonly aresearcher’snetworkforpromotingtheintegratedand interdisci-plinaryenvironmentalsciences,butalsoagraduateschoolforsome 500PhDstudentsinthesocio-economicandnaturalsciencesof theenvironment.Organizinganexploringsymposiumon‘Climate ProofingCities’fitswellinSENSE’smissionofdevelopingbridges betweenscienceandsocietyforsustainablesolutionsaroundthe globe.

ThisSpecialIssuepresentshighlightsfromthepresentations. WhilemostarticlesrelatetotheDutchsituation:anafﬂuent, urban-izedsocietyinacoastalarea,withamoderateclimateatpresentand withawelldevelopedwatermanagementsystem,lessonslearned maybeapplicabletosimilar(delta)areasaroundtheworld.

UndertheheadingofBalancingadaptationandmitigation, sym-posium participants discussed conceptual approaches tourban climate management. Bergsma et al. (2012) focus on adaptive capacitytowaterstressofdifferentDutchlocalities.Whatshould be handled publicly, what can be handled individually? Using an‘AdaptiveCapacityWheel’,thearticlecomparesstrengthsand weaknesses of adaptive capacity in two urban areas and one ruralarea. In general,they concludethat cities requirea more

top-down approach, while rural areas require a more group-centredapproach.Leadership shouldﬁt thesedifferent require-ments.Foreffectivepolicies,thearticlelistsgenericaccountability demandsandinformationneeds.

Under the headingof Future CityDesign, symposium partic-ipants discussed design challenges for Climate Prooﬁng Cities.

Agudelo-Veraet al.(2012)presenttheUrbanHarvestapproach, a novel design tool that maps resource potentials of urban areas. Based on urban metabolism, Urban Harvest aims for better resource management by closing urban cycles and har-vesting urban resources. The ‘urban tissue’ concept is used to map harvestingpotentials forenergy and water foran average Dutch city hectare. Atneighbourhood level, ‘urbantissues’ are applied to develop harvesting scenarios. The article concludes that urbandesign shouldfocusonsynergiesof urbanfunctions and facilitiestocascade and recycleresourceswithinthesame area.

ThreearticlesdiscusstheUrbanHeatIslandEffect,warmer tem-peratureswithinurbansettlementscomparedtosurroundingrural areas.Afirststepistomeasureandmonitorthiseffect.Kloketal. (2012)usedsatelliteimagestoquantifythesurfaceheatislandof Rotterdam.Theyfindthattemperaturedifferencesbetween Rotter-damandnon-urbanareascanbealargeas10◦C.Thedataalsoshow theinfluence ofurbanvegetationoncity districttemperatures, urbanmaterialsandbuildingdensity.Howtousesuch measure-mentsforurbandesign?Lenzholzer(2012)presentsa ‘research fordesign/researchbydesign’ projectthat generatedguidelines for thermally comfortable squares in Dutch cities. The project combinedpeople’s microclimateperceptions withmicroclimate simulation tests.Urban shelterbeltsof trees offeroptimalwind andsunprotection.Achallengingconclusionisthat‘themanin thestreet’intuitivelyknowsmoreaboutmicroclimatethanDutch cityplanners.Kleerekoperetal.(2012)discusstoolsandstrategies tocombatheatinoutdoorspaces.Nexttovegetationandsurface water(ponds,fountains,flowingwater),theystresstheimportance ofmaterialuse(permeablematerials,colours)andbuiltform (opti-maldensity,greenwalls).Applyingtheseprinciplestocitydistricts inDenHaagandUtrecht,thearticleshowsthatrenovationof exist-ingneighbourhoodsofferssufficientopportunitiestocombatthe accumulationofheat.

Greening the city canbe seenas a speciﬁc design challenge. Twoarticlesdiscussthepossibilitiestocombineclimatepolicies withbiodiversityconservation.Metselaar(2012)discussoptions and dilemmas of green roofs. Increasing biodiversity requires matching natural vegetation types to growing conditions on roofs. They contrast water demands of vegetation types with

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2 Introduction/Resources,ConservationandRecycling64 (2012) 1–2

construction requirements, which determine roof costs.

Vermondenetal.(2012)startwiththenotionthatmoreextreme rainfalldemandsanincreaseinstorageanddischargecapacityof surfacewatersystems.Whatopportunitiesdoesthisprovideto increasebiodiversityinurbanareas?Urbansurfacewatersystems cansustainabiodiversitycomparabletothatofman-madeditches and(semi)naturalstreamsinruralareasandcanevenbeahabitat forseveralendangeredspecies.Ecologyofurbandrainagesystems showsthatkeyfactorsforbiologicaldiversityarenutrients, sedi-mentcomposition,transparencyandhabitatstructure.Reducing thenutrientloadappearstobetheoverarchingrequirementfor increased biodiversity, while difﬁcult to achieve in delta areas withhighnutrient load of riversby communal discharges and agriculture.

TheClimateProoﬁngCitiesSymposiumshowedpromisingtools todevelopandassesssustainablecities.Atthesametime,practical applicationsareintheirinfancy.Thereisanurgentneedtocollect experiencebasedevidence.Thisisevenmorepressingbecausethe reconstructionofourexistingurbanfabricswillbemore compli-catedandmoretimeconsumingthanconstructionofnew,climate proof,urbanareas.

References

Agudelo-VeraCM, Leduc WRWA,Mels AR, Rijnaarts HHM. Harvesting urban resourcestowardsmoreresilientcities.Resources,Conservation&Recycling 2012;64:3–12.

BergsmaE,GuptaJ,JongP.Doesindividualresponsibilityincreasetheadaptive capacityofsociety?ThecaseoflocalwatermanagementintheNetherlands. Resources,Conservation&Recycling2012;64:13–22.

KlokL,ZwartS,VerhagenH,MauriE.ThesurfaceheatislandofRotterdamand itsrelationshipwithurbansurfacecharacteristics.Resources,Conservation& Recycling2012;64:23–9.

KleerekoperL,vanEschM,SalcedoTB.Howtomakeacityclimate-proof,addressing theurbanheatislandeffect.Resources,Conservation&Recycling2012;64:30–8. LenzholzerS.ResearchanddesignforthermalcomfortinDutchurbansquares.

Resources,Conservation&Recycling2012;64:39–48.

MetselaarK.Waterretentionandevapotranspirationofgreenroofsandpossible naturalvegetationtypes.Resources,Conservation&Recycling2012;64:49–55. VermondenK,van-der-VeldeG, LeuvenRSEW.Keyfactorsforbiodiversityof surfacewatersinclimateproofcities.Resources,Conservation&Recycling 2012;64:56–62.

FransvanderWoerd∗ VUUniversityAmsterdam,IVMDeBoelelaan1085, 1081HVAmsterdam,TheNetherlands ArjenHoekstra CTW,TwenteUniversity,TheNetherlands KristinKern WageningenUniversity,TheNetherlands RobLeuven RadboudUniversityNijmegen,TheNetherlands HenkMoll IVEM,RijksuniversiteitGroningen,TheNetherlands

∗_{Corresponding}_author._Tel.:₊₃₁₂₀_5989533;

fax:+31205989553. E-mailaddress:frans.vander.woerd@vu.nl