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AlittleafternoononSunday26June2011,strongwindstoppledanaspentreeontoapowerlineintheJemezMountainsofnorthernNewMexico.Theyearhadbeenextra?ordinarilydry,andthetemperaturesthatweekhadsoaredwellabovenormal.Whenasparkfromthepowerlineignitedafire,windgustsspreadtheflamesintonearbydensestandsoffirandpine.Withinanhour,ecologistCraigAllen,55?kilometresawayathishomeinSantaFe,learnedaboutthefireinane?mailfromaUSForestServicefiremanager.“Ihopeyouguyscatchthis,”Allenwroteback.“Wedon’tneedanotherbigfireintheJemez.”ButAllencouldalreadyseeaplumeofgreysmokerisingtothewest.Byearlythenextmorning,theLasConchasfirehadburned17,500hectares—aboutahectareeverythreeseconds.Withinfivedays,ithadgrownto42,000hectaresandbecomethelargestfireinNewMexico’shistory.Bythetimethefirewascontainedweekslater,ithadburnedmorethan60,000hectaresofforestandscrubland,inmanyplacesroastingthevegetationsothor?oughlythatonlycharredstumpsandbaredirtremained.ForAllen,whoworksfortheUSGeologicalSurvey(USGS)inLosAlamos,NewMexico,andhasbeenstudyingtheforestsoftheJemezMountainsformorethan30years,alargefirewasnotunexpected,butitsspeedandinten?sitycaughthimoffguard.Laterthatyear,whenAllenandotherforestscientiststouredtheburnedarea,theywereallstunnedintosilence.Thesizeoftheareasscorchedbarebythefiredwarfedthepatternsofpastburns,judgingfromstudiesoffirescarsintreeringsreachingbackto1600.Thistime,saysAllen,theforestmaynotrecover.AcrosstheAmericanwest,theareaburnedeachyearhasincreasedsignificantlyoverthepastseveraldecades(see‘BiggerBlazes’),atrendthatscientistsattributebothtowarminganddryingandtoacenturyofwildfiresup?pressionandotherhumanactivities.Allensuggeststhattheintertwinedforcesoffireandclimatechangewilltakeecosystemsintonewterritory,notonlyintheAmericanwestbutalsoelsewherearoundtheworld.IntheJemez,forexample,itcouldtransformmuchoftheponderosapine(Pinusponderosa)forestintoshrubland.“We’relosingforestsaswe’veknown
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