Drought as a possible contributor to the Visigothic Kingdom crisis and Islamic expansion in the Iberian Peninsula

A icle h ps://doi.o g/10.1038/s41467-023-41367-7 D ough as a possible con ibu o o he Visigo hic Kingdom c isis and Islamic expansionin heIbe ianPeninsula Jon Camue a 1 , F ancisco J. Jiménez-Espejo 1 , José So o-Chica 2 , Gonzalo Jiménez-Mo eno 3 , An onio Ga cía-Alix 3 , Ma ía J. Ramos-Román 4 , Leena Ruha 5,6 & Manuel Cas o-P iego 7 TheMuslimexpansionin heMedi e anean basin was one he mos ele an and apid cul u al changes in human his o y. This expansion eached he Ibe ian Peninsula wi h he eplacemen o he Visigo hic Kingdom by he Muslim Umayyad Calipha e and he Muslim Emi a e o Có doba du ing he 8 h cen u y CE. In his s udy we made a compila ion o wes e n Medi e anean pollen eco ds o gain insigh abou pas clima e condi ions when his expansion ook place. The pollen s ack esul s, oge he wi h o he paleohy- d ological eco ds, a chaeological da a and his o ical sou ces, indica e ha he s a is ically significan s onges d ough s be ween he mid-5 h and mid- 10 h cen u ies CE (450–950CE)occu eda 545–570, 695–725, 755–770 and 900–935 CE, which could ha e con ibu ed o he ins abili y o he Visigo hic and Muslim eigns in he Ibe ian Peninsula. Ou s udy suppo s he g ea sensi i i y o he ag icul u e-based economy and socio-poli ical un es o Ea ly Medie al kingdoms o clima ic a ia ions. Th oughou human his o y, ises and alls o empi es, kingdoms, and coun ies ha e been con olled by economic, social, and poli ical ac- o s, some o hem pa ially condi ioned by clima e changes1,2, including he ecen conflic s in he Middle Eas 3,4. The s udy o pas en i onmen al changes in a specifica eaisessen ial ounde s and how clima e could ha e a ec ed he poli ical s abili y o a egion. Nowadays, clima e is becoming a cen al elemen in explaining his- o ical c ises in he Medi e anean a ea, as has occu ed in ecen decades a ound he Da k Age Cold Pe iod and i s ela ionship wi h he appea ance o he Jus inian´s plague5, o wi h he c isis ha a ec ed u al se lemen s in some pa s o Eu ope du ing hose cen u ies6.One o he mos in e es ing pe iods, and one ha emains ela i ely unknown om a clima ic poin o iew, is he pe iod o Islamic expansioninNo hA ica 7, culmina ing in he conques o he Ibe ian Peninsula. The o ma ion o al-Andalus (Muslim- uled a ea in he Ibe ian Peninsula) om 711 CE led o he apid disappea ance o he Visigo hic Kingdom, in a p ocess ha combined mili a y conques , poli ical c isis, e i o ial agmen a ion, and pac s8,9.TheVisigo hic Kingdom uled he Ibe ian Peninsula o a ound 300 yea s (5 h–8 h cen u ies CE), eplacing he Roman Empi e ule, un il he beginning o he Islamic expansion in Ibe ia du ing he ea ly-8 h cen u y CE. This decline was ma ked by a ci il wa and he in asion o he Muslim Umayyad Calipha e (Islamic dynas y) in 711 CE un il he final conques in 726 CE. Al hough he a cheological si es s udied du ing he las decades o he Visigo hic pe iod p o ide use ul in o ma ion abou a ming s a egies, u banisms, e i o ial con ol o social o ganiza ion10, he apid all o he Visigo hic Kingdom is s ill unde deba e, and he hypo hesis o clima e igge ing he Islamic expansion om he no he n A ica o he no he n Ibe ia has no been in es i- ga ed ye 11,12. Recei ed: 8 No embe 2022 Accep ed: 1 Sep embe 2023 Check o upda es 1 Andalusian Ea h Sciences Ins i u e (IACT), Spanish Na ional Resea ch Council - Uni e si y o G anada (CSIC-UGR), G anada, Spain. 2 Depa men o Medie al His o y and His o iog aphic Sciences and Techniques, Uni e si y o G anada, G anada, Spain. 3 Depa men o S a ig aphy and Paleon ology, Facul y o Science, Uni e si y o G anada, G anada, Spain. 4 Facul y o Educa ion, Mid-A lan ic Uni e si y, Mad id, Spain. 5 Na u al Resou ces Ins i u e Finland, Oulu, Finland. 6 Resea ch Uni o Ma hema ical Sciences, Uni e si y o Oulu, Oulu, Finland. 7 Uni o A chaeology, Depa men o His o y and Philosophy, Uni e si y o Alcalá, Alcalá de Hena es, Spain. e-mail: Jcamue [email protected];F [email protected] Na u e Communica ions | (2023) 14:5733 1 1234567890():,; 1234567890():,; To da e, he sca ci y o bo h high- esolu ion paleoclima e eco ds and s udies ocusing on he impac o clima e changes in Ea ly Medie al kingdoms du ing he 5 h–10 h cen u ies CE has p e en ed an assess- men o whe he clima e changes con olled he decline o he Visi- go hic Kingdom and he Islamic expansion in Ibe ia. P e ious Holocene paleoclima ic s udies a decadal- o cen ennial scale showed ha he main clima e ac o a ec ing he en i onmen al a iabili y in he Med- i e anean egion is he amoun o p ecipi a ion, which has s ongly a ec ed he human popula ion and dispe sal in his a ea13,14.He ewe used a high- esolu ion pollen s ack based on 107 pollen eco ds om Ibe ia and Mo occo (Fig. 1) along wi h o he paleohyd ological eco ds, a cheological da a and his o ical sou ces o show how he pe sis en d ough s, iden ified unde he Scale-no malized Significan Ze o c ossing (SnSiZe ) s a is ical analysis, could ha e influenced he eco- nomic, social and poli ical condi ions du ing he Visigo hic Kingdom and al-Andalus be ween he 5 h and 10 h cen u ies CE. Resul s and discussion Recons uc ion o d ough pe iods om Ibe ian/Mo occan paleoen i onmen al p oxies The s acks o he a id-adap ed A emisia and xe ophy e axa display an o e all inc easing end o e he las 5000 yea s, indica ing a p o- g essi e a idifica ion o e ime (Fig. 2e, ). In addi ion, he esul s o A emisia a subdecadal-scale esolu ion allow he iden ifica ion o 23 d ough e en s du ing he las 5000 yea s (black a ows in Fig. 2e). Inc eases in A emisia and xe ophy e da a, indica i e o a id condi ions in he Ibe ian Peninsula, occu ed a ca. 4900, 4550, 4150, 3900, 3650, 3450, 3200, 2900, 2650, 2400, 2300, 2100, 1950, 1750, 1500, 1400, 1250, 1150, 1000, 850, 700, 500 and 200 cal y BP. Compa ison o pollen da a wi h iso opic analysis o speleo hems p o ides a mo e de ailed insigh in o local en i onmen al and egional paleoclima e changes in he s udy egion15,16. In addi ion, since human influence on speleo hem eco ds is lowe han on he ege a ion eco ds, he compa ison be ween hese wo p oxies allows us o co - obo a e whe he he a idi y pe iods obse ed in pollen eco ds a e p edominan ly na u al o no . Changes in speleo hem ca bon and oxygen iso opes can be d i en by di e en ac o s16, including ege- a ion densi y17, ca e empe a u es18, o he amoun o p ecipi a ion, among o he s19. The co ela ion analyses be ween he d ough e en s eco ded by he pollen da a and he high- esolu ion oxygen and ca - bon iso opic eco ds om ca es in no he n Mo occo (Chaa a ca e, composi e δ18O)20 and no he n Spain (Cob e, Kai e, and Mayo ca es, s acked ela i e δ13C)21 show high posi i e co ela ion ( = 0.80 be ween A emisia and δ18O, p= 0.007; = 0.76 be ween A emisia and δ13C, p= 0.010; o u he de ails, see Me hods) (Fig. 2c–e). This posi i e co ela ion sugges ha he Mo occan and Ibe ianca es could ha e been con olled by simila paleohyd ological condi ions. The inc easing δ18Oandδ13C speleo hem alues om Mo occo and Spain sugges a educ ioninp ecipi a ion, which al hough subjec ed o small age unce ain ies, coincides wi h he d ough pe iods eco ded by he s acked A emisia eco d. Simila δ18O-palaeohyd ological pa e ns ha e been obse ed in speleo hems and in ecen me eo ic wa e eco ds om Ibe ia, showing inc easing δ18O alues du ing dec easing p ecipi a ion condi ions22,23. The high δ13C alues du ing d ough pe iods could eflec a lowe con ibu ion o he ligh ca bon iso ope in he speleo hem as a consequence o dec easing ege a ion densi y su ounding he ca e19,24. These pe iods o spa se ege a ion would ag ee wi h inc easing A emisia, and he e o e, mo e s eppe axa (Fig. 2c, e, ). Howe e , o he e ec s esul ing in high δ13Cdu inga id condi ions canno be uled, such as he inc ease o CO 2 degassing o he d ipwa e du ing low ain all pe iods (low infil a ion) and low ca e d ip a es25, o a educ ion o he soil biogenic CO 2 p oduc ion ia mic obial ac i i y and plan espi a ion, which we e also ela ed o low humidi y condi ions16. IBERIAN IBERIAN PENINSULA PENINSULA AFRICA AFRICA MEDITERRANEAN SEA MEDITERRANEAN SEA ATLANTIC OCEAN ATLANTIC OCEAN CANTABRIAN SEA CANTABRIAN SEA ALBORAN ALBORAN SEA SEA 600 km3000 N 34ºN 36ºN 38ºN 40ºN 42ºN 44ºN32ºN 12ºW 10ºW 8ºW 6ºW 4ºW 0º2ºW 2ºE 4ºE14ºW Ele a ion (m a.s.l.) -5000 -4000 -2500 -2000 -3000 -1000 -1500 -500 0 -200 50 200 400 600 800 1000 1200 2000 2500 3000 1 2345 6 789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27-28 29 30 31 32 33 34 35 36 37 38 3940 4142 43 44 45 46 47 48-50 51 52-54 55 60 56-59 61-62 63 64 65 66 67 68-70 71-72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 Cob e, Kai e and Mayo ca es Asiul ca e Bu aca Glo iosa ca e G o e de Pis e ca e Chaa a ca e Fig. 1 | Loca ion o he 107 ossil pollen eco ds (black do s) compiled and used in his s udy. Yellow do s show he Ibe ian and Mo occan ca e eco ds ci ed in he manusc ip and used o compa ison wi h he pollen esul s. Fo de ailed in o ma ion o he ossil pollen eco ds, see Supplemen a y Da a 1. A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 2 The pe iod be ween 450 and 950 CE (1500–1000 cal y BP) dese es special a en ion, as i p esen s ou a id e en s, one o hem p esen ing he maximum a idi y peak o he las 5000 yea s a ~700 CE (1250 cal y BP), shown by he maximum abundance o A emisia and xe ophy es (Fig. 2e, ). The pe o med SnSiZe s a is ical analysis o he s acked A emisia eco d be ween mid-5 h and mid-10 h cen u ies CE (450–950 CE, 1500–1000 cal y BP) iden ified ou s a is ically sig- nifican ex eme d ough pe iods a : (I) 545–570, (II) 695–725 CE, (III) 755–770 CE, and (IV) 900–935 CE (Fig. 3a, b), co esponding o he d ough e en s8,7,6,and5o helas 5000yea s(Fig.2e). The p e iously men ioned δ18O (N Mo occo) and δ13C(NSpain) eco ds also showed ou e en s o clima ic de e io a ion be ween 450 and 950 CE (Fig. 2c, d). Global-scale dend oclima ological s udies showed ha he coldes clima e condi ions o he las wo millennia occu ed a 536–565 CE26 in connec ion wi h h ee main olcanic e up ions a 536, 540, and 547 CE27, ma ching wi h ou s a is ically significan d ough pe iod I (Fig. 3a, b). In addi ion, he speleo hem eco ds om Asiul (N Spain)28 and Bu aca Glo iosa (Po ugal)29 ca es p esen ed sig- nifican inc eases in δ18O alues a ca. 540–580 and 700–750 CE and a ca. 500–600 and 700–770 CE, espec i ely, consis en wi h he mos a id condi ions iden ified in he pollen da a du ing he d ough pe iods IandII(Fig.3a, b and Supplemen a y Fig. 1c–e). Ano he speleo hem 1 3 4 5 6 7 8? 9 10 11? 12 13 15? 17 20 21 2 16 18 19 22 14 23 -6.5 -6 -5.5 -5 -4.5 Composi e δ18O (‰ VPDB) (in e ed axis) d Chaa a ca e (N Mo occo) Age (cal y BP) 01500 50010002500 20004000 3500 30005000 4500 Age (y CE/BCE) 500 1000-500 0-2000 -1500 -1000-3000 -2500 20001500 0 -2 2 In e ed NAO index HumidA id a 0.8 0.4 b 0 -0.4 -0.8 To al Sola I adiance (Wm-2) 2 1 0 -1 S ack Xe ophy es (in e ed axis) ( his s udy) This s udy (1500-1000 cal y BP) (450-950 y CE) 2 1 0 -1 S ack A emisia (in e ed axis) ( his s udy) e 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 16 18 19 20 21 22 23 (II) (III) (IV) (I) Humid A id -3 -2 -1 0 1 S acked ela i e δ13C (in e ed axis) c 2 3 1 2 3 4? 4? 5 6 7 8 9 10 11 12 13 14 15 17-16? 18 20-19 Cob e, Kai e and Mayo ca es (N Spain) Humid A id Fig. 2 | Compa ison o clima e p oxies/mechanisms o he las 5000 yea s. aNAO index econs uc ion (in e ed axis)83.bTo al Sola I adiance (W/m2)84. cS acked ela i e δ13C eco d (in e ed axis) om Cob e, Kai e, and Mayo ca es (N Spain)21.dComposi e δ18Ospeleo hem eco d(‰VPDB, in e ed axis) om Chaa a ca e (N Mo occo)20. In g aphs cand d, he g ay lines show he aw ela i e δ13Cand δ18O alues, and he black lines he 5-poin mo ing a e ages. e– S acks o A emisia and xe ophy es (in e ed axes) om his s udy, wi h black lines ep esen ing he 45-poin mo ing a e ages, and he o ange (A emisia) and yellow (xe ophy es) lines he 15-poin mo ing a e ages. The ex eme d ough s eco ded by he A emisia da a, and obse ed in he Spanish δ13C and Mo occan δ18O eco ds, a e indica ed wi h black a ows. In g aph e, he d ough s I, II, III, and IV occu ing du ing he pe iod o in e es o his s udy (450–950 CE, 1500–1000 cal y BP, yellow e ical shade) co espond o he d ough e en s 8, 7, 6 and 5 o he las 5000 yea s. The sou ce da a om g aphs eand a e a ailable in Supplemen a y Da a 2. A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 3 eco d om Mo occo, he GP5 speleo hem eco d om G o e de Pis e ca e30, which eco ded he en i onmen al condi ions be ween 600 and 2010 CE, p esen ed wo hia us su aces linked o a id condi ions a ca. 620–750 and 900–940 CE. These wo e en s o s alagmi e g ow h cessa ion ma ch ela i ely well wi h h ee s a is ically significan d ough pe iods shown by he s a is ical analysis o he s acked A e- misia, hefi s hia us coinciding he d ough s a 695–725 and 755–770 CE (d ough pe iods II and III), and he second hia us wi h he one a 900–935 CE (d ough pe iod IV). A ecen quan i a i e p ecipi a ion econs uc ion om he Ibe - ian Peninsula31 eco ded an annual p ecipi a ion decline o 0–100 mm/ y a 700–800 CE o no he n Ibe ia and o 200 mm/y a 680 CE o sou he n Ibe ia (Supplemen a y Fig. 1 ). Mo eo e , he palynological s udy om Medina lake32 and he lake le el econs uc ion o Zoña lake33, bo h si es loca ed in sou he n Ibe ia, showed simila se e e d ough condi ions du ing he la e-7 h and ea ly-8 h cen u ies CE. The analysis o non-pollen palynomo phs om Medina lake o he las 5000 yea s eco ded he highes abundance o Gelasinospo a spo e a ca. 710 CE, which has been linked o d y lake condi ions34,35,andis coe al wi h he p esence o A emisia h oughou he en i e eco d, ein o cing he in e p e a ion o low ain all condi ions du ing he ea ly-8 h cen u y (Supplemen a y Fig. 1g). In Zoña lake he lowes lake le el o he las 2500 yea s occu ed a ca. 650–750 CE, which could also indica e ha he lowes p ecipi a ion condi ions o he las wo and a hal millennia we e eco ded du ing he la e-7 h and ea ly-8 h cen u ies CE (Supplemen a y Fig. 1h). Rela ionship be ween he ou s a is ically significan d ough pe iods and his o ical sou ces be ween mid-5 h and mid-10 h cen u ies CE (450–950 CE, 1500–1000 cal y BP) In he ollowing sec ions, we show he ela ionship be ween he ou SnSiZe s a is ically significan d ough s obse ed in he A emisia pollen eco d a (I) 545–570, (II) 695–725, (III) 755–770 CE and (IV) 900–935 CE, and he di e en his o ical e en s collec ed om his o ical sou ces be ween mid-5 h and mid-10 h cen u ies CE (Fig. 3a, b). In ecen yea s, he con ibu ions o w i en his o ical sou ces o he Visigo hic pe iod (5 h–8 h cen u ies CE) ha e been suppo ed by a cheological da a and, in pa icula , by s udies on inhabi ed u al a eas and subsis ence esou ces36. Some a cheological esul s ha e also allowed us o dis inguish di e en o ms o peasan habi a s ( illages, a ms) and hei pe manence o disappea ance o e ime37,whe eas o he s udies ha e p o ided new da a abou he ag icul u al p oduc ion s a egies38, including esea ch on he expansion o sheep and goa a ming, and changes in c op managemen 39,40. All his ook place in a changing poli ical con ex , especially om 633 CE onwa ds, and wi h a econfigu a ion o p oduc ion sys ems and land owne ship, which would ha e been closely linked o clima e and en i onmen al changes. D ough pe iod I (545–570 CE)/E up ions, plagues, and Visi- go hic ci il wa The fi s d ough pe iod eco ded by he Ibe ian and Mo occan A e- misia and xe ophy e da a be ween 450 and 950 CE, and s a is ically significan unde he SnSiZe , occu ed a 545–570 CE (Figs. 2e, and 3a, b). The his o ical sou ces, such as he Byzan ine his o ian P ocopius, no ed ha du ing 536–538 CE in he I alian peninsula, inclemen wea he caused se e e c op damages and unusually ha sh and long win e s ha las ed h ough he sp ings and summe s, as well as cases o cannibalism due o amine41.TheRomans a esmanCassiodo us w o e ha “The hea om he sun was eeble”and “A win e wi hou s o ms, a sp ing wi hou mildness, and a summe wi hou hea ”42, leading o p olonged os s and d ough s. This clima ic si ua ion, which seems o ha e been igge ed by he abo e-men ioned olcanic e up ions27, could ha e p omo ed ood sho ages and amine, he ARIDITY Age (cal y BP) 1150 11001250 12001400 1350 13001500 1450 1050 1000 Age (y CE) 800 850700 750550 600 650450 500 950900 -1 0 1 2 3 S ack A emisia (3-poin mo . a e .) a + - 2 1.5 1 0.5 0 log10(h) 0.50 0.25 0 -0.25 -0.50 b (I) D oug h pe iods (II) (III) (IV) 545 570 695 725 755 770 900 935 + a idi y + a idi y + a idi y + a idi y 418 CE c His o ical sou ces Visigo hic Kingdom Umayyad Calipha e Independen Emi a e o Có doba Calipha e o Có doba 1031 CE 929 CE756 CE711 CE Ci il wa Visigo hic c isis Ci il wa s Muladi / Moza abic io s 579549 E up ions and plagues 536 585 680 713 750 772 880 928 Fig. 3 | The SnSiZe analysis o he A emisia s ack be ween 450 and 950 CE (1500–1000 cal y BP) o iden i y he s onges d ough pe iods along wi h he e en s collec ed om his o ical sou ces. a,bThe s ack o A emisia (3-poin mo ing a e age, in e ed axis) and he SnSiZe g aph wi h h ee smoo hing le els ( ed, blue, and yellow lines in bo h panels). In he SnSiZe g aph (b), ed and blue colo s sugges s ong inc easing and dec easing ends o A emisia, espec i ely. The numbe s I, II, III, and IV (bo om o b) indica e he ou s a is ically significan d ough pe iods iden ified by he SnSiZe (age anges included). cE en s and du a ion o he compiled his o ical sou ces (black s a s and ho izon al lines). The sou ce da a om g aph aa e a ailable in Supplemen a y Da a 2. A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 4 onse o he La e An ique Li le Ice Age (LALIA), and he ou b eak o he Jus inian plague in 541–543 CE h ough he Medi e anean2,26,43.The ch onicle o Vic o o Tunnuna s a ed ha his plague a ec ed His- pania in 542 CE44. La e on, he Gallo-Roman his o ian G ego y o Tou s w o e ha du ing 580/581 CE he ambassado s o he king o Neus ia e u ned om Hispania wi h news abou plagues and amine ha we e a aging Ca pe ania ( egions su ounding he Tagus alley) and sp eading o Sep imania (SE o p esen -day F ance)45. The his o ian also w o e ha du ing 580–585 CE Hispania su e ed s ong os s and d ough s, coinciding wi h he Visigo hic ci il wa (580–584 CE) (Fig. 3c). Conside ing hese his o ical sou ces and he pollen esul s, he s a is ically significan d ough pe iod I eco ded a 545–570 CE (Fig. 3a, b), which oughly coincides wi h he onse o he LALIA and p obably linked o he olcanic e up ions and he cold clima e condi ions2,27, could be conside ed an impo an ac o o he sp ead o he amine and plagues du ing he mid-6 h cen u y CE in Ibe ia. A e he d ough pe iod I (545–570 CE), he Visigo hic s a e unde king Leo igild (Visigo hic king, eign 568/569–586 CE) was able o consolida e a policy o cen aliza ion, e i o ial expansion, and s eng hening o he fiscal sys em a e a long pe iod o mone a y de alua ion46. I is likely ha he clima e amelio a ion could ha e con ibu ed o an imp o emen o ag icul u e and, he e o e, o he kingdom adminis a ion and s abili y, which could also ha e con- ibu ed o a be e economic condi ion o he cons uc ion o new u ban cen e s, such as Reccopolis (578 CE), Vic o iaco (581 CE) and Oligicus (621 CE). D ough pe iod II (695–725 CE)/Visigo hic Kingdom c isis and Umayyad Calipha e expansion The A emisia and xe ophy e s acks om Ibe ia and Mo occo show ha he maximum d ough condi ions o he las 5000 yea s occu ed a 695–725 CE, indica ed by he highes A emisia alues and iden ified by he SnSiZe analysis (Figs. 2eand3a, b). The ege a ion eco ds om he Spanish Cen al Sys em showed dec easing ee co e , especially in mon ane a eas, and inc easing fi e ac i i y, which was ela ed wi h he e ec o human ac i i y o ob ain new pas u es and lands o a ming47,48. Howe e , he changing clima e condi ions o ced he cul i a ion o cold-adap ed ye (S. ce eale)a high al i udes, sugges ing ha al hough some ege a ion changes in pollen eco ds we e a ec ed by human ac i i y47, hese a ia ions could ha e been o ced a he same ime by cold and d ough condi- ions. Ac ually, du ing he Visigo hic pe iod, di e en echniques we e de eloped in u al a eas o adap o d ough condi ions. In sou he n Ibe ia (Sie a Ne ada ange) hey buil he oldes aqui e echa ge sys ems in Eu ope, da ed a 636 ± 80 CE49, and popula ion mo ed o highe ele a ions wi h he consequen inc ease in popula ion in moun ain egions o sou he n Ibe ia50. This popula ion displacemen o highlands ook ad an age o he highe al i udinal ain all condi- ions compa ed o lowlands51. In addi ion, he a cheological e idence om he Visigo hic ci y o Reccopolis (cen al Ibe ia), such as he cons uc ion o e aces and he eo ganiza ion o he ag icul u al sys em, ha e also been ela ed o o es decline and d y condi ions du ing his pe iod52. His o ical sou ces sugges he beginning o pe sis en d ough condi ions a a ound 680 CE in he Ibe ian Peninsula. This is coe al wi h he inc easing a idi y a e ca. 670 CE in Ana olia and he Le an , which caused he abandonmen o ag icul u al land and he collapse o he majo se lemen s53. The XII Council o Toledo, o ganized in cen al Ibe ia by he king E igio (Visigo hic king, eign 680–687 CE), ook place in No embe 681 CE “ o suppo a wo ld in collapse”54. Th ee yea s la e , in No embe 684 CE, Ti le III o he Minu e Book o he XIV Council o Toledo eco ded: “This no e, wi h all ha has happened, was p esen ed in he wo s momen o a e ible wea he , when all lands, in he wo s win e momen , a e co e ed by hea y snow all and glacial empe a u es”55, poin ing in o ha sh win e condi ions du ing he Au umn season. In addi ion, he Moza abic ch onicle o 754 CE s a ed ha du ing his pe iod: “E i- gio was consec a ed in he kingdom o he Go hs. He uled o se en yea s, and Hispania su e ed a huge amine”56. Du ing he nex eign o king Egica (Visigo hic king, eign 687–702/703 CE), in pa icula du ing he yea s 691–692 CE, a bubonic plague ha a ec ed he Ibe ian Peninsula56 was ela ed o long pe iods o cold/d ough condi ions, low ood p oduc i i y and amine57–59 (Fig. 3c). The Moza abic ch onicle also eco ded ha du ing 702–703 and 710–713 CE “The s a a ion and plague a aged Hispania”56. Mo eo e , he ch onicles poin o pe iods o se e e amine (707–709 CE) imme- dia ely p io o he pe iod o conques (711 CE)60 and he A abic Akhbā majmūʿa ch onicle (mid-11 h cen u y) indica ed ha a ound hal o he popula ion o Hispania died o s a a ion be ween 706 and 710 CE61,62 (Fig. 3c). These ch onicles poin o a clima e change owa ds mo e a id and colde condi ions du ing la e-7 h and ea ly- 8 h cen u ies CE. The dea h o king Wi iza (Visigo hic king, eign 700–710/711 CE) in 710/711 CE, he consequen ci il wa , and he Muslim in asion o he Visigo hic Kingdom (711 CE) ook place du ing he iden ified pe sis en A emisia pollen d ough pe iod II (695–725 CE) (Fig. 3b, c). In his ega d, bo h he ch onicle o king Al onso III (Ch is ian king, eign 866–910 CE) and he Moza abic ch onicle o 754 CE coincided abou he decline o he kingdom du ing he in asion: “The Go hs pe ished pa by hung y and pa by he swo d”(ch onicle o Al onso III)63 and “Wi h swo d, amine and cap i i y, no only Hispania Ul e io bu also Hispania Ci e io was de as a ed”(Moza abic ch onicle)56. No e ha he inc ease in A e- misia a 695–725 CE shows a delay wi h espec o he fi s his o ical sou ces on ha sh clima e condi ions a 680–684 CE. This 15-yea delay could be ela ed wi h age model limi a ions and/o he esi- lience o ege a ion biomes p io o he expansion o a id-adap ed A emisia in he egion. Despi e he desc ibed ha sh clima e condi ions, he a cheological eco ds do no show massi e de as a ion o des uc ion o ci ies o se lemen s du ing he in asion64. In he Ea ly Medie al kingdoms a leas 60% o he ichness was based on ag icul u al p oduc s. Ag i- cul u al labo employed a ound 80% o he popula ion65,and he e- o e, ha sh and a id clima e condi ions would ha e a ec ed he s abili y o kingdoms. Howe e , in he case o he Visigo hic Kingdom, he e is no unanimous posi ion on he main ac o s ha could ha e led o he collapse o he Visigo hic s a e66. The decline o he Himya i e kingdom and he eme gence and expansion o Islam du ing he 6 h cen u y CE ac oss he A abian Peninsula has ecen ly been ela ed wi h a id clima e condi ions and s ong d ough s67. This d ough eco ded in A abia as well as he one we eco ded in Ibe ia du ing la e-7 h and ea ly-8 h cen u ies CE mus also ha e a ec ed he No h A ican egions. These a id condi ions cons i u e a new elemen in poli ical, economic, and mili a y mo i a ions ha led o he Islamic expansion o he Ibe ian Peninsula om 711 CE onwa ds. Fo se e al decades, he e has been a consensus ha Islamic expansion om he Middle Eas and No h A ica o he Ibe ian Peninsula may ha e been a o ed by he in oduc ion and di usion o new echnologies, ag icul u al p ac ices, and p oduc s be e adap ed o d ylands and a id en i onmen al condi ions68. Howe e , he e is inc easing e idence o he di usion o p e-Islamic ag icul u al echniques, ools, and c ops adap ed o semi- a id egions, sugges ing ha he p e- and pos -Islamic Nea Eas and Medi e anean a eas we e mo e simila o each o he han p e iously assumed69. Al hough he Visigo hic social and poli ical c isis could ha e s a ed p io o he d ough pe iod II eco ded by he pollen da a, we can conclude ha he ex eme and pe sis en d ough du ing he la e- 7 h and ea ly-8 h cen u ies CE in he Ibe ian Peninsula may ha e had a nega i e impac on ood p oduc ion, damaging he p ima ily ag icul u e-based economy and pas o al ac i i ies70, igge ing (a leas pa ially) he social and poli ical ins abili y ha could ha e A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 5 a ec ed he decline o he Visigo hic Kingdom, and he fi s phases o he consolida ion o al-Andalus. D ough pe iods III and IV (755–770 and 900–935 CE)/Islamic io s and ci il wa s The d ough pe iod e ealed by he SnSiZe analysis du ing he inc ease in A emisia a 755–770 CE due o enhanced a idi y in he egion (d ough pe iod III, Fig. 3a, b), coincides wi h he fi s Muslim poli ical des abiliza ion a e he es ablishmen o he Umayyad Cali- pha e in 711 CE. Muslims a emp ed o expand no hwa d, bu we e s opped by he F anks a he Ba le o Poi ie s (F ance, 732 CE)71.La e on,in740 CE, he Be be up ising ha s a ed in he No h A ica and in al- Andalus/Hispania gene a ed se e al ci il wa s, amine, and depopula- ion o ce ain a eas, p omo ing he up u e o al-Andalus wi h he Abbasid Calipha e (Islamic dynas y) and becoming an independen Emi a e (Emi a e o Có doba) in 756 CE72. Acco ding o he Moza abic ch onicle, du ing he yea s 748–750 CE “Aho ible aminedesola e he en i e al-Andalus/Hispania”, simila o ha eco ded by he Akhbā majmūʿa ch onicle o he 750–754 CE “The yea o he Hegi a 132 / 750 CE, God sen a majo d ough and amine o he en i e al-Andalus/His- pania”and hech onicleo Moissac(11 hcen u y) o he771-772CE“A de as ing amine a ec all Hispania”73 (Fig. 3c). Bo h he s acked A emisia eco d and he ch onicles show d ough condi ions du ing he mid-8 h cen u y CE. The beginning o Abd al-Rahman’s ule (Muslim king, eign 756–788 CE) was cha ac e ized by se e al socio- poli ical c ises, which could ha e been a consequence o he d ough and subsequen amines, and only om 783-784 CE onwa ds shows an inc ease in mone a y and expanding e i o ial con ol, linked o he s abiliza ion o axa ion74. The las s ong d ough pe iod iden ified by he SnSiZe analysis o pollen da a occu ed a 900–935 CE (d ough pe iod IV, Fig. 3a, b). This las episode coincides in pa wi h he fi s fi na (Muslim ci il wa ), a long p ocess o poli ical c isis ha began wi h he mos powe ul ebellion led by Oma Ibn Ha sun om 880 o 928 CE75 (Fig. 3c). These con on a ions ha e been linked o he expansion o he p ocess o con e sion o Islam and he inc ease o he poli ical and e i o ial con ol o he Emi a e o Có doba76. The wo s a is ically significan inc eases in he s acked A emisia eco d and his o ical sou ces sugges ex eme d ough condi ions du ing he mid-8 h cen u y and he ea ly-10 h cen u y CE. These d ough s could ha e a ec ed ag icul u e, con ibu ing o low ood p oduc ion and amines, and hus p omo ing he economic and socio- poli ical des abiliza ion o al-Andalus. Howe e , his p ocess o mac o analysis canno igno e he ac ha communi ies esponded o cli- ma ic and en i onmen al condi ions. In his ega d, he Andalusian socie y was cha ac e ized by he expansion o new ag icul u al ech- niques, including i iga ion77. D ough s in he wes e n Medi e anean egion and possible clima e mechanisms Nume ous paleoclima e s udies ha e demons a ed a s ong ela ion- ship be ween in e nal a mosphe ic dynamics, such as he No h A lan ic Oscilla ion (NAO), and ex e nal sola ac i i y, including To al Sola I adiance (TSI)78,79. The NAO index con ols he s eng h and di ec ion o he wes e lies o e Eu ope and hus he amoun and sou ce o p ecipi a ion en e ing he wes e n Medi e anean80. Al hough he NAO econs uc ion o he Ibe ian Peninsula81 does no ma ch well wi h he pollen da a be ween 450 and 950 CE (Supple- men a y Fig. 1a, c), he mos a id condi ions shown by he inc ease in A emisia and xe ophy es a he end o he 7 h and he beginning o he 8 h cen u ies CE occu ed du ing he highes posi i e No h A lan ic NAO index econs uc ion82,83 and he lowes TSI84 o he las 5000 yea s (Fig. 2a, b, e, ). The low sola i adiance gene a es cold and esh No h A lan ic Cu en condi ions, a ec ing he s a e o he NAO85. Howe e , his ela ionship has been a opic o deba e o e he las decade. Some s udies ha e shown ha a educed sola i adiance du ing he Holocene may ha e modula ed he nega i e NAO phases20,86, whe eas o he p oxy eco ds ha e e idenced a ela ionship be ween low sola i adiance and a id condi ions in he Medi e anean87–89, which could be ela ed o posi i e decadal- o cen ennial-scale NAO phases. In his la e case, a low sola i adiance could ha e p oduced a sou hwa d mo emen o he pola on and a educ ion in he ad ec ion o wa e masses in he A lan ic, educing he s o m ac i i y o e he Medi e anean and esul ing in a id clima e and d ough condi ions88. An excep ion occu ed du ing he cold and d ou h pe iod o he mid-6 h cen u y CE, in e p e ed as a possible consequence o h ee olcanic e up ions occu ing in a sho ime pe iod (536, 540, and 547 CE)27 and coe al wi h he Jus inian plague. Me hods Fossil pollen da a This s udy syn hesized pollen and a cheological da a om Spain, Po - ugal, Ando a, and Mo occo. Wi h espec o he pollen da a, we ocused on he analysis o A emisia and o he xe ophy e pollen axa om lacus ine con inuous sedimen a y eco ds o gain insigh in o he a idi y c ises o he las 5000 yea s and, in pa icula , o he las 1500–1000 cal y BP (450–950 CE). The ossil pollen da a acquisi ion was pe o med using he Neo oma da abase (www.neo omadb.o g)and he Eu opean Pollen Da abase (EPD, www.eu opeanpollenda abase.ne ), whe eas o he pollen eco ds no included in hese da abases we e ob ained by p i a ely con ac ing he au ho s o he co esponding s u- dies (see Re e ences in Supplemen a y Da a 1). We selec ed all he con- inen al pollen eco ds om Spain, Po ugal, Ando a, and Mo occo con aining da a-samples du ing he las 5000 yea s, which esul ed in 107 pollen eco ds (Fig. 1). In o de o make he s udy as objec i e as possible, none o hese eco ds ha e been fil e ed acco ding o he numbe and/o p ecision o da es. We conside ha fil e ing he da a based on he numbe o da es and/o hei p ecision would cause sub- jec i i y in he da a acquisi ion and, he e o e, esul s would lose c edibili y. The s acked A emisia eco d is based on 3977 samples whe eas he xe ophy e eco d is based on 4115 samples. No e ha he numbe o samples in he A emisia and xe ophy e eco ds is di e en due o he absence o A emisia in se en eco ds. The de ailed in o ma ion (Si e no. map,Si ename,Da abase,Si e ID,Da ase ID,La i ude,Long- i ude,Al i ude,Ch onology sou ce, Da ing and dep hs, Age model de ails, and Re e ences) o he 107 pollen eco ds a e included in Supplemen- a y Da a 1, and he s acked A emisia and xe ophy e da a in Supple- men a y Da a 2. Age ch onologies Age ch onologies o he pollen eco ds we e ob ained om da a- bases, including he ch onologies om he o iginal s udies and he ch onologies p oduced by he Mapping and Da a Accu acy wo king g oup (MADCAP) o he EPD90,91. As he calib a ed age di e ence be ween he di e en calib a ion cu es o he pe iod o in e es (450–950 CE, 1500–1000 cal y BP) is negligible (<20 calib a ed yea s, see Supplemen a y Fig. 2), we decided o use he o iginal calib a ion cu es (i.e., In Cal98, In Cal04, In Cal09, In Cal13 and In Cal20) p o- ided by he da abases and he au ho s (Supplemen a y Da a 1). Since each o he ossil eco ds collec ed o he s acked A emisia pollen cu e has i s own age model, i is no possible o p o ide specificage unce ain ies o his composi e eco d. This p oblem has been mi i- ga ed by collec ing a la ge numbe o ossil eco ds (107 eco ds), which educes he age unce ain ies. Pollen as a p oxy o p ecipi a ion Al hough he inc easing abundance o A emisia and o he xe ophy e axa (such as Ama an haceae and Ephed a) a e well known as A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 6 indica o s o a idi y pe iods in he wes e n Medi e anean du ing he Qua e na y92–94, we made a calib a ion using he Eu asian Mode n Pollen Da abase (EMPD 2)95 and he Wo ldClim 2.1 da a (www. wo ldclim.o g)96 o obse e he ela ionship be ween high pe cen- ages o A emisia and low p ecipi a ion condi ions. The e o e, he ecen mean annual p ecipi a ion (mm/y ) and A emisia pe cen ages om 8217 mode n pollen si es we e used o analyze he ela ionship be ween he abundance o A emisia and he p ecipi a ion alues (Supplemen a y Fig. 3). The mode n pollen da abase shows ha si es wi h p ecipi a ion alues below ca. 400 mm/y p esen mean A emisia pe cen ages o e 7%, whe eas he mean A emisia pe cen ages dec ease below 3% wi h p ecipi a ion alues abo e ca. 400 mm/y , sugges ing ha he A emisia pollen genus is a good p oxy o in e - p e ing a id clima e condi ions in his egion. The e o e, pe sis en d ough s in pas pe iods caused an expansion o he as -g owing and a id-adap ed he b/g ass species, such as A emisia, esul ing in a highe p opo ion o hese axa in he ossil eco ds. The limi a ions o he pollen analysis in paleoclima e in e p e a- ions ha e o be aken in o accoun , since modifica ions in he ege- a ion co e caused by human impac could also ha e a ec ed pollen abundances. Howe e , i is mo e likely ha he human e ec on ege a ion could ha e had an impac du ing a gi en pe iod in a pa - icula a ea o he Ibe ian Peninsula and/o Mo occo, bu i is less likely ha his e ec would ha e a ec ed di e en la ge Ibe ian/Mo occan a eas a he same ime. The e o e, in o de o educe he human e ec on ege a ion, we ha e collec ed a la ge numbe o pollen eco ds o e a la ge e i o y, educing he noise o human dis u bance ha could ha e a ec ed some pollen eco ds du ing specificpe iods. Da a no maliza ion A z-sco e no maliza ion (x–mean/s de ) was pe o med on he ossil A emisia and xe ophy e da a (indi idually o each eco d) be o e s acking he da a, esul ing in high- esolu ion A emisia and xe ophy e s acks o he las 5000 yea s (Fig. 2e, ). A 45-poin and 15-poin mo ing a e ages we e pe o med on he A emisia and xe ophy e s acks (black lines and o ange/yellow lines in Fig. 2e, ) o an easie compa ison wi h o he paleoclima ic eco ds. The no malized s acked A emisia and xe ophy e eco ds a e included in Supplemen a y Da a 2. Co ela ion analyses A Pea son co ela ion analysis was pe o med be ween ou s acked A emisia, he composi e δ18O om Chaa a ca e (Cha1 and Cha2 speleo hems, N Mo occo), and he s acked ela i e δ13C om Cob e, Kai e and Mayo ca es (C11, LV5, and SLX1 speleo hems, N Spain). The s acked A emisia (las 5000 cal y BP), composi e δ18O (las 5000 cal y BP), and s acked ela i e δ13C(las 3900caly BP) eco ds p esen a da a esolu ion da a o 1.3, 4, and 4.5 yea s, espec- i ely. Be o e pe o ming he co ela ion analyses, A emisia and composi e δ18O da a we e in e pola ed (linea in e pola ion) o he lowes da a esolu ion o he δ18O eco d, i.e., 4 yea s, whe eas A e- misia and s acked ela i e δ13C we e in e pola ed o he lowes da a esolu ion o he δ13C eco d, i.e., 5 yea s. The esul s show a high posi i e co ela ion, wi h =0.802 (p= 0.007104) o he s acked A emisia s composi e δ18O eco ds,and =0.768 (p=0.01058) o he s acked A emisia s s acked ela i e δ13C eco ds. The co ela ion analysis was de eloped unde he Pas 4.12b s a is ical so wa e97. Scale-no malized Significan Ze o c ossing (SnSiZe ) analysis The Significan Ze o c ossing (SiZe ) analysis is a use ul ool in paleoecology o assess he ele an h esholds in he da a and o define whe e s a is ically significan changes occu in a da a se 98.In his analysis, nonpa ame ic smoo hing is applied o da a using a sequence o smoo hing le els in o de o e eal salien ea u es in he signal a all equencies. The Scale-no malized Significan Ze o c oss- ing (SnSiZe ) analysis99, based on he o iginal SiZe analysis100,has been used o obse e ends and anomalies in he da a, allowing he iden ifica ion o s a is ically significan inc eases and dec eases in he da a. In addi ion, he SnSiZe uses scale-no malized de i a i es101 o de ec he s a is ically significan changes in he signal and highligh he in ensi y o inc easing and dec easing changes ( ed and blue), esul ing in mo e o less in ense colo s in he g aph. Thus, in he SnSiZe g aph, eading om pas o p esen (i.e., om le o igh ), ed and blue a eas indica e inc eases and dec eases o A emisia, espec- i ely (no e he in e ed axis in Fig. 3a), and he e o e, ele an inc easing and dec easing a idi y ends. Da k g ay a eas ep esen no significan changes, whe eas he ligh g ay a eas indica e ha he sampling esolu ion is oo low (Fig. 3b). When a ce ain le el o smoo hing ( ed, blue, o yellow ho izon al lines in he e ical axis, Fig. 3b) cu s he ele an inc ease ( ed) o dec ease (blue) in A emisia, i means ha hose changes a e s ong unde ha smoo hing le el. The ecen ly de eloped SnSiZe was implemen ed by modi ying he sou ce code o he size R-package102.Theda awasp ep ocessedusinga 3-poin mo ing a e age smoo he o educe backg ound noise in he s acked A emisia eco d and he e o o he age ch onologies. Howe e , such p e-smoo hing may p oduce au oco ela ion in he da a and cause alse posi i es in he SnSiZe analysis. In o de o mi iga e he au oco ela ion e ec , he SnSiZe analysis was un unde he 95% confidence le el. To define he age anges o d ough pe iods, we ook he onse s o he A emisia inc eases ( ed a eas in he SnSiZe g aph, Fig. 3b), which indica e he beginning o he d ough s, un il he onse s o he dec eases (blue a eas in he SnSiZe g aph), indica ing he end o d ough con- di ions. The maximum esolu ion o de e mining he onse s/ends o d ough s is 5 yea s. Since he end o he hi d s ong d ough pe iod (d oug h pe iod III) is no cha ac e ized by an ab up dec ease in A emisia (and he e o e, no obse ed in he SnSiZe g aph a he selec ed smoo hing le els — ed, blue, and yellow lines—), his d ough was delimi ed by he s ong inc ease in A emisia iden ified by he SnSiZe analysis be ween 755 and 770 CE (Fig. 3b). The e o e, his me hodology be ween 450 and 950 CE esul ed in ou s a is ically significan d ough s a 545–570 (1405–1380 cal y BP), 695–725 (1255–1225 cal y BP), 755–770 (1195–1180 cal y BP) and 900–935 CE (1050–1015 cal y BP). Al hough he s a is ical significance o hese e en s canno be wa an ed due o he abo e-men ioned isk o alse posi i es, hey can be conside ed as s onge d ough s in he da a. His o ical and a cheological sou ces His o ical sou ces unde annual/bi-annual esolu ion we e collec ed and compa ed wi h he pollen and paleoclima e p oxy da a o unde s and he clima e impac on he Visigo hic and Muslim socie ies. The his o ical sou ces we e selec ed acco ding o he geog aphical and ch onological c i e ia and he eliabili y o he sou ce, including he Roman s a eman Cassiodo us (6 h cen u y), he Gallo-Roman his o ian G ego y o Tou s (6 h cen u y), he Roman-Byzan ine his o ian Vic o o Tunnuna (6 h cen u y), he Minu e Books o he XII and XIV Councils o Toledo (7 h cen u y), he Moza abic ch onicle o 754 CE (8 h cen u y), he Ch is ian ch onicle o king Al onso III (9 h cen u y), he A abic Akhbā majmūʿa ch onicle (11 h cen u y) and he ch onicle o Moissac (11 h cen u y). In addi ion, a e iew o he mos significan a cheological da a has been ca ied ou . Special emphasis has been placed on u al si es o he Visigo hic pe iod. Da a om u ban si es om he pe iod be ween he 6 h and 8 h cen u ies CE ha e also been analyzed. Repo ing summa y Fu he in o ma ion on esea ch design is a ailable in he Na u e Po olio Repo ing Summa y linked o his a icle. Da a a ailabili y The da a om his s udy, including he de ailed in o ma ion on all he Ibe ian and Mo occan ossil pollen eco ds and he A emisia and A icle h ps://doi.o g/10.1038/s41467-023-41367-7 Na u e Communica ions | (2023) 14:5733 7 xe ophy e s acks a e a ailable in Supplemen a y Da a 1 and 2, espec i ely. The A emisia and xe ophy e s acks (Supplemen a y Da a 2) a e also a ailable a he Pangaea da a eposi o y (www. pangaea.de). The aw ossil pollen da a we e ob ained om he open- access Neo oma da abase (www.neo omadb.o g)and heEu opean Pollen Da abase (www.eu opeanpollenda abase.ne ), and by con ac - ing he au ho s p i a ely (Viñuelas, B ezoso, Medina, Zoña , Padul, Río Seco and Honde a eco ds, see Re e ences in he Supplemen a y Da a 1). The se en pollen eco ds a e no a ailable in open da abases, can be ob ained by con ac ing he ollowing au ho s: C. Mo ales- Molina (Viñuelas and B ezoso), T. Sch öde (Medina), C. Ma ín- Pue as and P. González-Sampé iz (Zoña ), J. Camue a (Padul), R.S. Ande son and G. Jiménez-Mo eno (Río Seco), and J.M. Mesa-Fe nández (Honde a). The sou ce da a om his s udy ha we e used o Figs. 1–3 and Supplemen a y Fig. 1 a e a ailable in Supplemen a y Da a 1 and 2. Code a ailabili y The SnSiZe code is a modified e sion o he o iginal SiZe code published by Chaudhu i and Ma on (1999)100, and de eloped by modi ying he sou ce code o he size R-package (Sonde egge , 2020)102. Since he new SnSiZe code has no ye been published, he code will be a ailable p i a ely upon eques . Re e ences 1. Fagan, B. The g ea wa ming: clima e change and he ise and all o ci iliza ions (Bloomsbu y Publishing, New Yo k, 2008). 2. Bün gen, U. e al. Cooling and socie al change du ing he La e An ique Li le Ice Age om 536 o a ound 660 AD. Na . Geosci. 9, 231–236 (2016). 3. Selby, J., Dahi, O. S., F öhlich, C. & Hulme, M. Clima e change and he Sy ian ci il wa e isi ed. Poli ical Geog . 60,232–244 (2017). 4. Ide, T. Clima e wa in he Middle Eas ? 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