【未来能源研究所】塑造荒地-城市界面的土地利用模式：州和地方政府在减少野火风险中的作用-2025.5

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernmentsinReducing

ExposuretoWildfireRisks

MargaretWallsandMatthewWibbenmeyer

Report25-11May2025

AbouttheAuthors

MargaretWallsisaseniorfellowanddirectoroftheClimateRisksandResilience

Program,aswellascohostofResourcesfortheFuture’s(RFF’s)podcast,

Resources

Radio

.Walls’sresearchfocusesontheimpactsofextremeweather,floods,hurricanes,andwildfiresonpeopleandcommunitiesandthedesignofprogramsandpoliciesto

equitablyenhanceresiliencetosuchevents.

MatthewWibbenmeyerisafellowatRFF.Wibbenmeyer’sresearchstudiesclimate

impactsandmitigationwithintheUSlandsector,withaspecialemphasisonwildfire

impactsandmanagement.USwildfireactivityhasacceleratedinrecentyears,leadingtoincreasesinpropertydamages,carbonemissions,andhealthimpactsduetosmoke.

Acknowledgements

ThisresearchwasfundedbyagrantfromtheGordonandBettyMooreFoundation.We

appreciatehelpfulcommentsandsuggestionsfromDavidWear,KateDargan,Carlos

Martín,andJimBoyd.Wealsoappreciatehelpfulconversationswithmanystateand

localgovernmentofficialsandothers,whoareacknowledgedintheAppendix.

AboutRFF

ResourcesfortheFuture(RFF)isanindependent,nonprofitresearchinstitutionin

Washington,DC.Itsmissionistoimproveenvironmental,energy,andnaturalresource

decisionsthroughimpartialeconomicresearchandpolicyengagement.RFFis

committedtobeingthemostwidelytrustedsourceofresearchinsightsandpolicy

solutionsleadingtoahealthyenvironmentandathrivingeconomy.

Theviewsexpressedherearethoseoftheindividualauthorsandmaydifferfromthose

ofotherRFFexperts,itsofficers,oritsdirectors.

SharingOurWork

OurworkisavailableforsharingandadaptationunderanAttribution-

NonCommercial-NoDerivatives4.0International(CCBY-NC-ND4.0)license.You

cancopyandredistributeourmaterialinanymediumorformat;youmustgive

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ResourcesfortheFuturei

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernmentsii

inReducingExposuretoWildfireRisks

Abstract

Developmentinthewildland-urbaninterfaceisincreasingexposuretowildfirerisksinthewesternUnitedStates.Yet,amongthecomponentsofrisk—hazard,vulnerability,andexposure—mitigatingexposurehasarguablybeenmostdifficult.Inthisreport,wedescribethesetofinterconnectedstateandlocalpoliciesthataffectdevelopmentandriskexposure,includinglocallanduseplanningandzoning,statepoliciesgoverning

insurance,buildingcodes,andinfrastructurespending,aswellastheroleofstates

asintermediariesbetweenthefederalgovernmentandlocalities.Wediscussvariousplansthatlocalgovernmentsdevelop,includingComprehensivePlans,Hazard

MitigationandCommunityWildfireProtectionPlans,andComprehensiveEconomic

DevelopmentStrategies,andwearguethatinmostcommunities,theseplansdonotadequatelyaddresstheexposurecomponentofthewildfireriskproblemorprovide

potentialresiliencesolutionsthataddressexposure.Wesuggestanumberofpolicy

directions,includingchangestoplanningrequirements,creativezoningoptionslike

wildfireresilienceoverlays,andincentivesthatstatesandthefederalgovernmentmaybeabletousetodirectgrowthtowardlowerriskareas.

ResourcesfortheFutureiii

Contents

1.Introduction1

2.WildfireRisksandtheWildland-UrbanInterface3

2.1.WhyDoPeopleLiveintheWUI?3

2.2.ContributionofPopulationGrowthtoWildfireCosts4

2.3.ExternalitiesfromDevelopmentinHighWildfireHazardAreas5

2.4.PotentialFutureWildfireCosts5

3.LocalPlanningandZoning7

3.1.ComprehensivePlans7

3.2.Zoning8

3.2.1.ZoningHistoryandSingle-familyHomes8

3.2.2.NaturalHazardsandZoning9

3.2.3.TheRoleofStatesinLocalPlanning/Zoning10

3.3.AdditionalPlanningDocuments11

3.3.1.HazardMitigationPlans11

3.3.2.CommunityWildfireProtectionPlans13

3.3.3.ComprehensiveEconomicDevelopmentStrategies13

3.4.LocalFiscalPolicy13

4.State-levelPolicies14

4.1.WildfireHazardMapping14

4.2.InsuranceRegulation15

4.3.InfrastructureSpending16

4.4.BridgingFederalandLocalGovernance16

5.DiscussionandSuggestedPolicyDirections17

5.1.TransferofDevelopmentRights18

5.2.TheRoleofStates20

5.3.TheRoleoftheFederalGovernment21

6.Conclusion22

References23

Appendix29

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernments1

inReducingExposuretoWildfireRisks

1.Introduction

WildfirecostsareontheriseintheUnitedStates,andincreasingexposurefrom

populationgrowthinhigh-hazardareasisasignificantcontributor.Thenumber

ofpeoplelivinginthewildland-urbaninterface(WUI),theareawheredeveloped

landsmeetforestsandothernaturallands,roughlydoubledbetween1990and2010

andgrewby160percentinareaswiththehighestwildfirehazard(Raoetal.2022).

AlthoughWUIgrowthappearstohaveslowedinrecentyears,anestimated40percentofUShomesintheinteriorWestandtheSoutheastareintheWUI(Radeloffetal.

2023).Inarecentstudythatlookedatgrowthinjobsandwageincome,Joineretal.(2025)foundthatjobgrowthinthewesternUnitedStatesoverthe1990–2020timeperiodwashighestinthehighestwildfireriskareas.

Reducingexposuretowildfirerisksiscriticalforcontainingwildfirecosts,butexposureisarguablythemostchallengingpartofthewildfireproblem.Multiplefactorsaffect

wherepeoplechoosetolive,anddisentanglingtheminawaythatprovidesguidanceforpolicyisdifficult.Inaddition,localgovernmentsplayacentralroleinmanaging

landusebutareoftendisinclinedtousethetoolsattheirdisposal—namelyzoning

codes—tocurtaildevelopmentorshiftdevelopmentpatternsforseveralreasons.First,theyrelyheavilyonpropertytaxrevenuestopayforpublicservicesandareconcernedaboutstagnatingorfallingrevenuesifdevelopmentisrestricted.Second,theyworry

aboutbeingexposedtotakinglawsuitsfromdevelopmentrestrictions.Third,ahousingaffordabilitycrisishasmanycommunitieslookingforwaystoincreasehousingsupplyhowevertheycan.Finally,evenwhentheseproblemscanbeovercome,itishardfor

communitiestoknowwhentheirlanduserulesarestrikingtherightbalancebetweenmanagementofrisksandotherimportantaspectsofqualityoflife.

Whilestatepolicyalsoinfluencesdevelopmentpatterns,itdoessoindirectly.Statesregulateinsurance,makedecisionsaboutinfrastructurespending,providefunding

tocommunitiesforhazardmitigation,approvelocalhazardmitigationplans,and

sometimesestablishbuildingcodesandhomeriskdisclosurerequirements.Theyalsoplayimportantintermediaryrolesbetweenthefederalgovernmentandlocalities.Allthesethingsmatterinwayslargeandsmallforhousingdemandandsupplyandtheextentofexposuretorisk,butfullyunderstandingtheimpactsischallengingand

researchinthisareaisscarce.

Inthisreport,wereviewthecomplexsystemofstateandlocalpoliciesandprograms,fundingstreams,andlocalactionsthatdirectlyandindirectlyaffectlanduseinhigh

wildfirehazardareas.ThissystemisillustratedinFigure1.Arrowsshowhowfederal,stateandlocalpolicies,plans,andactionsaffectriskthroughthreechannels:hazard—thelikelihoodofawildfireoccurring;exposure—thedegreetowhichpeopleand

propertyareinharm’sway;andvulnerability—thetendencyofpeopleandthebuilt

environmenttosustainharm.Statepolicies(showninblueboxes)includevarious

regulations,suchaswildfirehazarddisclosuremandatesandinsurancerequirements,infrastructurespending,andbuildingcodes,andstateplanningframeworksthat

guidelocalcomprehensiveplans.Localgovernmentsareresponsiblefordeveloping

comprehensiveplans,HazardMitigationPlans(HMPs),CommunityWildfireProtection

ResourcesfortheFuture2

Plans(CWPPs),and,sometimes,inconjunctionwithregionalplanninggroups,

ComprehensiveEconomicDevelopmentStrategies(CEDS).Thoseplansprovidethe

foundationforvariouslocalprogramsandregulations.Comprehensiveplansprovideavisionthatguideszoningregulations,whichdetermineexposure.CEDSguidebusinessandjobgrowth,alsoafactorinexposure.HMPsandCWPPsarethefoundationsfor

localhazardmitigationandemergencypreparednessactivitiesandareprerequisitesforseveralstateandfederalfundingprograms,depictedbytheblueandreddollar

signsinthediagram.Theseplansandfundingstreamsaffecthazardandvulnerability.Theplansandfundingalsogotowardemergencyresponseprograms,whichimpactpost-disasterrecovery.Weusethisfigureasaguideforourstudyanddiscussthe

elementsofitinmoredetailinthefollowingsections.

Figure1.ConnectionsBetweenStateandLocalPoliciesandWildfireRisk

Hazard

mapping

Infrastructurespending

State

planning

frameworks

Regulation

(e.g.,insurance,

disclosure)

Buildingcodes

Statepolicy

HazardMitigationPlans

andCommunityWildfire

ProtectionPlans

Comprehensive

EconomicDevelopment

Strategies

Compplans

Localplans

$

$$$$$$

Zoning

Hazard

Emergencypreparedness

Emergencyresponse

Localactions

mitigation

Development

Postdisaster

Risk=

Exposure

xVulnerabilityxHazard

Outcomes

recovery

$Denotesstatespending$Denotesfederalspending

Greenboxesarelocalactions;blueboxesarestateactions

Ourreporthighlightsthewaysinwhichpoliciesandprogramscurrentlyfallshortinaddressingriskexposureandoffersomechangesthatcouldpotentiallyaddresstheproblem.Wereviewlocaloptionsforshiftingdevelopmentpatternsincommunities,encouragingrelativelymoredevelopmentinlow-riskareasandlessinhigh-riskones,andwediscussleveragepointsthatstategovernmentsandthefederalgovernmentcanusetoencourageactionatthelocallevel.Wealsoidentifygapsinknowledgeandsuggestfurtheranalysisthatcouldhelpmovethesechangesforward.

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernments3

inReducingExposuretoWildfireRisks

Populationgrowthinhigh-riskareascreatesacompoundingproblemforcommunities.Inadditiontoincreasingignitionsandstructure-to-structurefirespread,population

growthraisesthecostoffiresuppressionandhasrippleeffectsinhousingand

insurancemarkets.Ourreportemphasizestheimportanceofthispieceofthewildfireriskpuzzle,discusseshowithasreceivedlessattentioninthepolicyworldthanhazardmitigation,andofferssomewaystoimprovecurrentpoliciesandprograms.

2.WildfireRisksandtheWildland-UrbanInterface

Inrecentdecades,wildfirehazardshaveincreasedduetothecombinedeffectsof

climatechange(Abatzoglou&Williams2016),increasesinhuman-causedignitions(Balchetal.2017),and,insomeregions,heavyfuelloadsresultingfromdecadesoffireexclusion(seee.g.Tayloretal.2016,Wuetal.2023).MoreandlargerfiresinthewesternUnitedStateshaveledtoaroughlythreefoldincreaseinannualareaburnedovera20-yearperiod—fromamedianofjustunder1millionacresperyearbetween1984and1998toapproximately3.5millionacresperyearbetween2005and2018

(Iglesiasetal.2022).

Thesetrendshaveoccurredagainstthebackdropofanexpandingwildland-urbaninterfacethathasincreasedexposure.Wildfirehazardisnotadefinitionalfeature

oftheWUI;however,inregionswherewildlandsarecharacterizedbyregularor

intermittentwildfires,theWUIiswherepeopleandpropertyfacethemostimminentthreat.BothWUIareaandthenumberofhomesintheWUIhaveincreasedoverthepastfourdecades.A2023ForestServicereportshowsthatbetween1990and2020,theWUIareagrewby31percent,andthenumberofhomesintheWUIgrewby47

percent(Mockrinetal.2023).

2.1.WhyDoPeopleLiveintheWUI?

UnderstandingthefactorsthataffectpopulationgrowthandhousingdevelopmentintheWUIischallenging.Ingeneral,peoplemakedecisionsaboutwheretolivebasedonhousingcosts,income,preferences,andaccesstojobs.Theymayhavepreferences

foramenitiesthatarecorrelatedwithwildfirerisk,suchasproximitytopubliclands

andviewsofforestedlandscapes.Manyeconomicstudieshavefoundthatproximitytoopenspace,parks,andpubliclandsishighlyvaluable(McConnellandWalls2005;Wallsetal.2015),affectswherepeoplelive(Walsh2007),andcontributestomeasuresofqualityoflife(AkhundjanovandJakus2023).

Inareaswithnaturalhazards,householdstypicallyweightheselocationalattractionsagainstrisks.Onlyafewstudieshaveanalyzedthesetradeoffsinsystematic,data-informedways.BakkensenandMadothisinaresidentialsortingmodeloffloodrisks(BakkensenandMa2020),andMaetal.(2024b)takeasimilarapproachinamodelofwildfirerisks.UsingdatafromCalifornia,theyfindthathouseholdsareaverseto

ResourcesfortheFuture4

wildfireriskswhenchoosingwheretolive—i.e.,higherrisksreduceahousehold’swillingnesstopayforahouseinaparticularlocation,allelseequal—andthathigh-incomehouseholdsaremoreresponsivetorisksthanarelow-incomehouseholds,whichhintsatsomepotentialequityconcerns.

2.2.ContributionofPopulationGrowthtoWildfireCosts

ThegrowthoftheWUIhaslikelycontributedtoheavylossesfromrecentwildfires.

NineofthetoptenmostdestructivewildfiresinUShistoryhaveoccurredsince20171InCalifornia,hometomostofthesecatastrophicfires,theaverageannualvalueof

structurelossesrosefrom$30millionperyearonaverageinthe1979–1989periodtonearly$1billionperyearonaveragein2009–2018(Buechietal.2018).

Studiesdifferoverhowmuchoftheincreaseinlossesowestoincreasesinthesize

andintensityofwildfiresandhowmuchisduetoincreasedexposuretoriskdue

toexpansionoftheWUI.Higueraetal.(2022)findthatthenumberofstructures

destroyedperunitareaburnedincreasedby160percentbetween1999–2010and

2010–2020,suggestiveofincreasingencroachmentofdevelopmentintohazardous

areasorincreasingfireintensity(orboth).Radeloffetal.(2023)estimatethatout

ofthe84,000additionalhomesthatwerewithinwildfireperimetersinthe2010sas

comparedtothe1990s,47percentwereduetohousinggrowth,while53percent

wereduetoexpansionofwildfireactivity.Incontrast,ModaresiRadetal.(2023)findthatmost(93percent)ofthegrowthinpopulationexposuretowildfirefrom2000to2019wasduetoincreasingwildfireactivity.GrowthoftheWUIsloweddowninthe

2010s;therefore,someofthedifferencesinfindingsacrossstudiescouldbeduetothedifferingtimeperiods.However,thestudiesalsousedifferentpopulationdatasets,sothesourceofdifferencesisunclear.2

2.3.ExternalitiesfromDevelopmentinHighWildfireHazardAreas

Theexpansionofdevelopmentinwildfirehazardareascanimposecostsonthose

livingelsewhere.Fourtypesofexternalitiescanbeatplay.First,humansarealeadingsourceofwildfireignitions,andstudieshaveshownthatincreaseddevelopment

withinhighhazardareasincreasesthelikelihoodoffireignitions(Balchetal.2018;

ChenandJin2022).Second,airpollutionfromwildfiresmokecanaffectpeopleliving

1ThisstatisticisasofJanuary2024andisbasedondatafromtheInsuranceInformationInstitute(availableat

/fact-statistic/facts-statistics-wildfires

)andanestimatethatthe2023wildfireinLahaina,Hawaiicausedinsuredlossesof$3.2billion.ItdoesnotincludethecatastrophicfiresinLosAngelesinJanuary2025.

2Radeloffetal.(2023)useblock-levelCensusdata,whereasModaresiRadetal.(2023)use

100mgriddedpopulationdatafromtheWorldPopGlobalProject.

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernments5

inReducingExposuretoWildfireRisks

hundreds,eventhousands,ofmilesfromthesourceofawildfireignition(Gellman

andWibbenmeyer,2025).Third,increasingdevelopmentinhighhazardareasinducesfederalandstatefireprotectionagenciestospendlargerandlargersumsofmoneyonfiresuppression(BaylisandBoomhower2023).Last,inpartduetoinsurance

regulationsthatmakeithardertoraiseratesinsomestates,thecostsofinsuring

householdsinhigh-riskstatesarepartiallybornebyhouseholdsinlowerriskstates

(Oh,Sen,andTenekedjieva2022).Thiscross-subsidizationcanalsoplayoutwithinastate;recentresearchfindsevidenceofcrosssubsidiesinCalifornia,whichhasannuallimitsontheamountthatinsurancecompaniescanincreaserates(Boomhoweretal.2023;Tayloretal.2023).

2.4.PotentialFutureWildfireCosts

Ifunabated,developmentwithinhighwildfirehazardareaswillcontinuetoincrease

propertydamageandothercostsassociatedwithwildfires.Box1presentsasimple

analysis,similartothosebyRadeloffetal.(2023)andModaresiRadetal.(2023),whichillustratespotentialfuturewildfireimpactsifpopulationsinwesternstatesgrowas

projectedinofficialforecasts.Ouranalysisaskshowmanypeoplewouldbeimpactedbythesamewildfiresthatoccurredoverthe2015–2021periodifthefiresweretooccurin2050andpopulationsweretogrowasforecastedbystateagencies.

Accordingtoourcalculations,thefireswouldbeapproximately15percentmore

damaging,i.e.,theywouldaffect15percentmorepeoplethantheydidintheyears

theyoccurred.Importantly,our2050countyprojectionsassumenewpeopleare

geographicallydistributedwithincountiesproportionaltotheirdistributionwhenthepastfiresoccurred,i.e.,thesameshareofacounty’sfuturepopulationfallsinsidethefireperimeters.Ifrelativelymorepeoplelocateinhigh-riskareas,thenumberscouldbehigher.Butimportantly,ifpoliciesencouragegrowthinlessriskyareasanddiscourageitinmoreriskyareas,thenumberscouldbelower.

ResourcesfortheFuture6

Box1.NumberofPeopleImpactedby2015–2021Wildfires

AccordingtotheMonitoringTrendsinBurnSeverity(MTBS),1,962wildfiresoccurredinthe9statesinthewesterncontinentalUnitedStatesoverthe7-yearperiodbetween2015and2021.WeoverlaidgeospatialfireperimeterdatafromMTBSwithCensusblockgrouppopulationdatatoestimatethenumberofpeopleaffectedbythesefires.

Toestimatehowmanypeoplecouldpotentiallybeaffectedinthefuturewiththesesamefires,weusedcountypopulationforecastsfor2050for8ofthe9states(wecouldnotfindcountypopulationforecastsforIdaho).*Weassumedthesamefractionoftotalcountypopulationwouldbelocatedwithinthefireperimetersaswerelocatedtherewhenthesehistoricalfiresoccurredtoyieldaforecastofpopulationaffectedin2050.Thegraphbelowshowsresultsforeachstate.

Figure2.NumberofPeopleImpactedby2015–2021Wildfires,byState

PeopleImpactedinMillions

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

PopulationafectedForecasted2050populationafected

Arizona

California

Colorado

Idaho

Montana

NewMexico

Nevada

Oregon

Utah

Washington

Wyoming

Intotal,acrossallstates,4.7millionpeoplewereaffectedbythese1,962wildfires;ifthesamefiresoccurin

2050,approximately5.3millionpeoplewouldbeaffected.Clearly,themagnitudeoftheprobleminCaliforniadwarfsthatinotherstates,bothwhenthefiresoccurredandwithfuturepopulationprojections.Butthe

percentageincreaseinpopulationaffectedishigherinotherstates:Utah,Arizona,andColoradoseeincreasesofpeopleaffectedbyfiresof86%,39%,and36%,respectively,comparedto9%forCalifornia.

*Countypopulationforecastsarefromofficialgovernmentsources;referencesavailablefromtheauthorsuponrequest.

ShapingLandUsePatternsintheWildland-UrbanInterface:TheRoleofStateandLocalGovernments7

inReducingExposuretoWildfireRisks

3.LocalPlanningandZoning

Localgovernmentsplayadirectroleindeterminingcommunitylandusepatterns

throughplanningandzoning.VirtuallyeverylocalgovernmentintheUnitedStates

producesacomprehensiveplan.Theseplansprovideasnapshotofcurrentcommunitylanduse,housing,transportation,andtheenvironment,andavisionforthefuture

underpopulationandeconomicgrowthprojections.Thefrequencywithwhich

comprehensiveplansareupdatedvariesacrosscommunities,asdoesthelevelof

detailtheycontainandtheextentofcommunityengagementindevelopingtheplan.

Comprehensiveplansprovidetheconceptualunderpinningforlocalzoningordinances,whichestablishtherulesandregulationsfordevelopment:howmuch,whattype,andwhere.

3.1.ComprehensivePlans

Allstateshavelawsthatenableorrequiredevelopmentoflocalcomprehensiveplans(AmericanPlanningAssociation2022).However,statesvarytoasignificantdegreeintheirengagementwiththedevelopmentoftheseplansandwhatrequirements

theyplaceonlocalities.Statesalsovaryinthedegreetowhichtheyrequirelocal

jurisdictions’zoningrulestobeconsistentwiththeirownplans;amongwestern

states,sixhavethisrequirement(California,Oregon,Washington,Idaho,and

Arizona;AmericanPlanningAssociation,2022).Ahandfulofstatesrequirethatlocalcomprehensiveplansbeconsistentwithastatewideplanninglaw;amongwesternstates,onlyWashingtonandOregonhavethisfeature.Somestatessetguidelines

forwhatcomprehensiveplansshouldincludeorrequireplanstocontainspecific“elements”—sectionsoftheplanthatdealwithaparticulartopic.

States’requirementsforcomprehensiveplanscanhaveimportantimplicationsfor

whetherandhowcommunitiesconsidernaturalhazardsintheirplanningandzoning

decisions.Forexample,inColorado,localcomprehensiveplansarerequiredtoincluderecommendationsregardinglanddevelopmentwithinwildfirehazardareas(ColoradoRevisedStatutes[CRS]§31-23-206).However,a1974law,knownas“1041regulations,”explicitlygrantslocalgovernmentstheauthoritytomakeplanningdecisionsthataffectissuesof“statewideinterest,”includingwildfirehazard.3Thelaw’sintentionistoallowlocalgovernmentstomaintaintheircontroloverdevelopmentprojectsevenwhere

developmenthasstatewideimpacts.Itthusgivessignificantlicensetocommunitiestoplanforwildfirehazardshowevertheyseefit,andasaresult,planningapproachesacrosslocalitiesvarythroughoutthestate(MoweryandPunchard,2021).

StandardsforcomprehensiveplanninginCaliforniaandOregonaremorerigorous.Inthosestates,citiesandcountiesarereq