Science of the Total Environment 886 (2023) 163947 Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv A recent Cannabis pollen increase on the Iberian Pyrenees ⁎ Valentí Rull a,b, , Teresa Vegas-Vilarrúbia c a Botanic Institute of Barcelona, Spanish National Research Council (CSIC), Pg. Midgia s/n, 08038 Barcelona, Spain b Catalan Institute of Paleontology Miquel Crusafont, Universitat Autònoma de Barcelona, ICTA-ICP Bld., C. Columnes s/n, 08193 Cerdanyola del Vallès, Barcelona, Spain c Department of Evolutionary Biology, Ecology and Environmental Sciences, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona, Spain H I G H L I G H T S G R A P H I C A L A B S T R A C T • A recent (1980s) characteristic peak of Cannabis pollen in a high resolution lake record • The peak coincided with a general in- crease in hemp production fostered by EU subsidies. • The contribution of illegal cannabis crops to the pollen increase remains unknown. • The varved record could be a potential candidate for the definition of the “Anthropocene”. A R T I C L E I N F O A B S T R A C T Editor: Fernando A.L. Pacheco The continuous, varved and absolutely dated sedimentary record of Lake Montcortès (Iberian Pyrenees) has provided evidence for a distinct and characteristic 20th century (1980s) increase in Cannabis pollen (20C) that persists today. Keywords: This event was coeval with the geographical shift of the hemp production center in the Iberian Peninsula from east Cannabis to northeast (where Lake Montcortès lies), which was accompanied by a significant production increase. This increas- Hemp ing trend was fostered by the renewed interest of the paper industry in hemp and was promoted by the onset of Pollen Cultivation European Union subsidies to hemp cultivation. Illegal cannabis crops could have also contributed to the Cannabis pol- Retting len increase, but sound evidence is still lacking. These preliminary conclusions should be reinforced by increasing the 20th century resolution of the current palynological record and modeling the dispersal of Cannabis pollen around the Montcortès Pyrenees region. More similar high-resolution records are needed to verify the geographical extent of the 20C event. Addition- Iberian Peninsula ally, Lake Montcortès varved sediments are proposed as a suitable candidate to characterize the onset of the “Anthropocene” epoch (mid-20th century), as currently defined by the Anthropocene Working Group. 1. Introduction tional, ritual, aesthetic and educational materials, among others (Clarke and Merlin, 2013, 2016; Gray et al., 2016). A database on the traditional uses of Cannabis is among the earliest human domesticates and has been an inte- Cannabis (CANNUSE) is available at http://cannusedb.csic.es/ (last visited gral part of human life for millennia (Rull, 2022). Almost every part of this 24 March 2023) (Balant et al., 2021). Taxonomically, the genus Cannabis plant is able to provide a variety of products and services, such as textiles, has a single species, Cannabis sativa, subdivided into two subspecies, cordage, fuel, paper, medicine, oil, food, drugs or biofuel, along with recrea- C. sativa subsp. sativa and C. sativa subsp. indica. However, as usual in plants intensively used by humans, a number of new varieties have been created ⁎ Corresponding author at: Botanic Institute of Barcelona, Spanish National Research by artificial selection to adapt the plant to a diversity of biogeographical fea- Council (CSIC), Pg. Midgia s/n, 08038 Barcelona, Spain. tures and cultural needs (Barcaccia et al., 2020; Kovalchuk et al., 2020). Due E-mail address: vrull@csic.es (V. Rull). to the illegal condition of this plant in most Western countries, the scientific http://dx.doi.org/10.1016/j.scitotenv.2023.163947 Received 3 April 2023; Received in revised form 30 April 2023; Accepted 30 April 2023 Available online 7 May 2023 0048-9697/© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). V. Rull, T. Vegas-Vilarrúbia Science of the Total Environment 886 (2023) 163947 study of Cannabis underwent a significant decline in the mid-20th century cementing compounds to separate the fiber from the stalk (Akin, 2013). The (Duvall, 2014; Warf, 2014). However, the last decade has witnessed a revival immersion of male hemp plants in lakes caused the pollen to be released of interest in Cannabis, especially in relation to the genetic and phytochemical and incorporated into sediments in larger amounts than expected if the only characteristics of its different varieties, as well as its evolutionary origin, do- source of this pollen was wind transport from local and/or regional crops. mestication and further diffusion. This resurgence is linked to a renewed inter- The dramatic Modern-Age hemp pollen increase in Montcortès has been est in crop improvement, especially for medical purposes but also for other linked to the general increase in the hemp industry to meet the needs (mainly applications (Gray et al., 2016). sails and ropes) of the Spanish navy, between the Columbian discovery of The Iberian Peninsula (IP) has been considered a keystone area for the America (1492 CE) and the decadence of the Spanish empire, with the ensuing natural and anthropogenic diffusion of Cannabis due to its peculiar biogeo- dismantling of its royal navy (1834 CE) (Rull and Vegas-Vilarrúbia, 2014). In graphical position and its diverse and dynamic cultural history (Rull, 2022). Lake Montcortès, hemp-retting activity during this ~350-y period was demon- According to the recent meta-analysis of a database (CHIP, for Cannabis- strated not only by Cannabis pollen values over 20 % (Fig. 1) but also by the Humulus Iberian Peninsula) with nearly 60 pollen records widespread identification of sedimentary RNA from bacteria actually responsible for the across the IP (Rull et al., 2023), Cannabis would have entered the IP in its retting process (Rull et al., 2022). wild form by the Late Pleistocene (150–12 kyr BP). Domesticated forms During the first half of the 20th century, hemp retting ceased in Lake would have arrived later in two main dispersal waves, the first in the Neo- Montcortès (Rull et al., 2022), and Cannabis pollen dropped to minimum lithic (7–5 kyr BP) and the second in the Middle Ages (500 CE onward), via historical values, coinciding with a major depopulation (60 % reduction) continental (Europe) and maritime (Mediterranean) pathways. Maximum of the Pallars region, where the lake lies, caused by the crisis of the subsis- cultivation and hemp retting activities were recorded during the Modern tence economy and the massive emigration to industrial cities (Farràs, Age (16th–19th centuries). A unique Cannabis record was obtained in the 2005). The Cannabis pollen suddenly increased again to values close to annually-laminated (varved) sediments of Lake Montcortès, situated in the retting threshold during the second half of the 20th century (Fig. 1). the northeastern sector (Fig. 1), which contains the longest (last However, bacterial RNA (bRNA) analyses show that local hemp retting 3000 years), continuous (gap-free) and high-resolution (bidecadal) abso- never returned (Rull et al., 2022), and therefore, the source for this pollen lutely dated pollen sequence available for the Mediterranean region (Rull rise – called here the 20th century Cannabis increase (20C) – should be et al., 2021). In this record, Cannabis appeared in the early Middle Ages sought in other activities. Although some potential causes for the 20C (~600 CE) and has continued until today, showing significant variations, event have been suggested (Trapote et al., 2018; Rull et al., 2022), the which have been correlated with historical sociocultural developments. issue has not yet been addressed in depth. This paper analyzes the trends In the Middle Ages, Cannabis was below 20 % of the pollen assemblages, of the last century and the patterns of pollen deposition in recent years to which is considered the threshold for hemp retting (Rull et al., 2022). There- discuss the potential causes of the 20C in relation to the main developments fore, the Cannabis pollen deposited in the lake would have been wind- of the hemp industry in the IP. transported from small-scale domestic hemp crops (Rull et al., 2021). The sit- uation changed in the Modern Age, when hemp retting for fiber extraction 2. Material and methods seems to have been the main activity around the lake. By those times, hemp fiber extraction was accomplished by immersion of plants in lakes and The raw data used in this study are from Rull et al. (2017, 2021, 2022) ponds, where autochthonous pectinolytic bacteria naturally degraded the and Trapote et al. (2018) and are available at https://data.mendeley.com/ Fig. 1. Left. Map of the Iberian Peninsula and the Balearic Islands (left), indicating the localities with published pollen records (white dots) (Carrión et al., 2022) and those containing Cannabis pollen (red dots) (Rull et al., 2023). Yellow dots indicate the sites with Cannabis records in the 20th century (AD, Alcúdia; CE, Cueto Espina; EN, Estanyons; ET, Estanya) (Rull et al., 2023). The location of Lake Montcortès (LM) is indicated by a yellow star. Blues boxes are the cities with aerobiological studies on Cannabis pollen mentioned in the text (CO, Córdoba; MA, Málaga; MU, Murcia). Blue circles are the main areas of hemp production, as explained in the text (AL, Alicante; CT, Catalonia). Right. Cannabis pollen curve (blue) and RNA from retting bacteria (bRNA) (blue) in percentage with respect to the total bacterial flora (Rull et al., 2021, 2022). CDA, Columbian discovery of America; DSN, dismantling of the Spanish navy; 20C, mid-20th century Cannabis increase. 2 V. Rull, T. Vegas-Vilarrúbia Science of the Total Environment 886 (2023) 163947 datasets/mr4h3x7x35 (pollen) and the Supplementary Material of Rull 1920s and 1980s. The first was a decline that signified the end of the et al. (2022) (bRNA). In this analysis, Cannabis has been excluded from hemp retting decline initiated in the late 19th century, as manifested in the pollen sum because the parent plant is not part of the local/regional the bRNA curve. This Cannabis decline is only evident in percentage vegetation (Carreras et al., 2005-2006; Mercadé et al., 2013). Pollen per- units, whereas influx values show that this pollen was virtually absent centages have been recalculated and the diagrams have been redrawn, from the beginning of the century. The second increase is the 20C event, with a focus on the 20th century (1896–2013) and a 2-year modern- when Cannabis increased and attained values over 30 % in the 1990s, analog study (2014–2015) using sediment traps submerged in the lake. De- which is beyond the threshold for hemp retting (Rull et al., 2022). Influx tails on the study site and the methods used are available in former papers. values confirm that this increment was actually an increase in the amount The age-depth model was based on varve counting (Corella et al., 2014, of Cannabis pollen reaching the lake, rather than a percentage artifact. 2016), the palynological methods are described in detail in Trapote et al. The 20C persists today, as indicated by a study of modern pollen sedimen- (2018) and Rull et al. (2017, 2021), and the methods for bRNA analysis tation using sediment traps submerged in the lake (Rull et al., 2017). In- are available at Rull et al. (2022). deed, the average amount of Cannabis pollen settled during 2014 and 2015 was slightly above 11 %, with maxima over the retting threshold in 3. Results winter and fall (Fig. 2). However, retting practices are no longer developed in the lake. The pollen trends of roughly the last century (1896–2013) are shown in Fig. 2, where it can be seen that the regional vegetation, consisting mainly 4. Discussion of a mosaic of Pinus and Quercus forests intermingled with grasslands and crops, has experienced little variation. The main vegetation shift occurred As mentioned above, wild or cultivated Cannabis plants have not been in the second part of the 20th century, when a conspicuous expansion of co- reported in Montcortès local and regional vegetation surveys (Carreras nifer forests coincided with a significant decline in olive groves, paralleled et al., 2005-2006; Mercadé et al., 2013), and hemp retting has not been by a meaningful increase in total plant cover, as manifested in pollen accu- practiced in the lake since the late 19th century, as indicated by historical mulation rates (PAR). Regarding Cannabis, the main shifts occurred in the records and supported by the absence of bRNA (Rull et al., 2022). Fig. 2. A) Percentage pollen diagram (core MON013-0713-G05) corresponding to the 20th century at subdecadal (~5-year) resolution. Influx values (grains/particles cm−2 y−1) for Cannabis and pollen accumulation rates (PAR) are also provided. RNA from retting bacteria (bRNA) is represented in percentage with respect to the total bacterial flora (Rull et al., 2022). Solid lines are x10 exaggeration. Red arrows represent the major shifts in Cannabis pollen percentage. ΣP, pollen sum. B) Seasonal distribution of sedimentary Cannabis pollen in Lake Montcortès during 2014 and 2015 (Rull et al., 2017). The hemp retting threshold (20 %) is indicated by a red dashed line. Wt. winter; Sp, spring; Sm, summer; Fl, fall. 3 V. Rull, T. Vegas-Vilarrúbia Science of the Total Environment 886 (2023) 163947 Therefore, a reasonable explanation for the 20C event seems to be long- higher precipitation (600–700 mm per year), thus avoiding the need for con- distance pollen dispersal mediated by wind (anemophily). However, the pos- tinuous irrigation (Gorchs and Lloveras, 2003; Gorchs et al., 2017). This geo- sibility of local or regional illegal crops cannot be disregarded (Munuera et al., graphical shift coincided with a considerable production increase (<1000 tons 2002). In both cases, a conspicuous increase in these activities would be in 1980 to >8000 tons in 1998) favored by the onset of EU subsidies to hemp needed to explain the 20C. Therefore, pollen dispersal patterns and historical cultivation, which started in 1985 (40 € ha−1) and significantly increased trends of Cannabis cultivation are critical points to be addressed. (~780 € ha−1) in 1996–97 (Fig. 3). This production increase was centered The high productivity and dispersal power of anemophillous Cannabis on the southern Pyrenees, where Lake Montcortès (slightly above 1000 m el- pollen are well known (e.g., Small and Antle, 2003; Li et al., 2017). On evation) lies, under wet climates, as a spring crop in rotation with winter the IP, several studies have documented relatively high amounts of air- wheat. This rotation significantly increased wheat yields, which has been at- borne Cannabis pollen in areas far from known plant sources. For example, tributed to the improvement of soil structure and the contribution of hemp a northern African origin for the airborne Cannabis pollen found in some lo- to control pests, diseases and particularly weeds, as its rapid early growth out- calities from the southeastern IP has been proposed by several authors after competes most weed species, thus reducing the weed burden for the ensuing detailed aerobiological studies including the use of long-distance dispersal winter crops (Gorchs et al., 2017). modeling tools. These localities include the cities of Murcia (Munuera et al., The 20C event, as recorded in Lake Montcortès was coeval with this 2002; Aznar et al., 2022), Málaga (Cabezudo et al., 1997; Aboulaich et al., 1980s hemp production acceleration, which strongly suggests a causal rela- 2013) and Córdoba (Cariñanos et al., 2004) (Fig. 1), which are situated tionship (Fig. 3). Due to its high dispersion power, hemp pollen could have 150–300 km north of the African coasts. Pollen from northern Africa easily reached Lake Montcortès from adjacent regional pre-Pyrenean hemp comes primarily from illegal crops (Aboulaich et al., 2013). The possibility crops, which could be confirmed by modeling the Cannabis pollen dispersal of nearest sources, such as illegal local/regional crops, was suggested by around the lake area. Hemp cultivation declined again shortly after the Munuera et al. (2002). Recently, Aznar et al. (2022) found a significant in- 1990s and was abandoned by 2006, due to the relocation of the hemp crease in airborne Cannabis pollen between 2017 and 2020 in the region of straw processing industry (Gorchs et al., 2017). This decline was also Murcia (Fig. 1), which coincided with the predominance of local/regional paralleled by pollen trends (Fig. 2), thus reinforcing the potential causal re- wind patterns, and attributed this increase to the spread of illegal crops in lationship. However, Cannabis pollen remained close to the retting thresh- the region rather than to long-distance dispersal from Africa. The occur- old until at least 2015 (Figs. 2 and 3), which deserves an additional rence of high Cannabis pollen percentages in modern sediments near crop explanation. Additional hemp pollen sources from illegal crops cannot be fields of this plant has recently been documented (Boutahar et al., 2023). disregarded, although the available evidence is less robust. In recent de- A typical feature of these crops is their high mobility and spatial turnover, cades, a relevant rise in large-scale Cannabis plantations has been recorded which is a strategy to avoid detection and makes their identification diffi- in the IP, especially along the Mediterranean coasts, in a trend to increas- cult (Aboulaich et al., 2013). These studies come from the southernmost ingly replace hashish imports from northern Africa (Alvarez et al., 2016; part of the IP, and no comparable information exists for other regions. How- Belackova et al., 2016). The potential manifestation of this peninsula- ever, it is expected that the dispersal of Cannabis pollen follows similar spa- wide rising trend in the Montcortès region remains to be documented, tial patterns. Similar surveys should be conducted in the Montcortès region and is worth to be addressed in future studies. to evaluate the potential contribution of long-distance vs. local/regional The geographical extent of the 20C event remains unknown, as it has pollen sources. These studies could also contribute to the detection of illegal not been recorded in other IP localities. This lack of evidence could suggest cannabis crops in the area. that this event could be a local/regional phenomenon, but methodological Regarding production, hemp cultivation almost disappeared from Spain in constraints should not be dismissed. On the one hand, only 23 of the 56 re- the early 1970s, but a renewed interest in this crop began in 1972. Until the cords included in the peninsular-wide CHIP database (Rull et al., 2023) con- 1960s, hemp was cultivated mainly on irrigated semiarid areas from the east- tain the 20th century, and of them, Cannabis pollen occurs in only four ern IP (Alicante) (Fig. 1) to provide thread, ropes and fabric. In 1972, however, (Fig. 1), excluding Lake Montcortès. Of these four sites, Cannabis pollen is the paper pulp industry started using hemp as a raw material instead of worn abundant (maximum of 25 %) in only one (ET), whereas in the others textiles, and in the early 1980s, the main production center shifted from the this pollen has maxima of only 5 % (CE) or shows single scattered occur- east to the northeast (Catalonia) in lowland areas (400–900 m elevation) of rences (AD, EN). On the other hand, the resolution of these records, usually Fig. 3. Hemp production in NE Spain (HP) and European Union subsidies to hemp cultivation (EU) (raw data from Gorchs and Lloveras, 2003) compared with the Cannabis pollen percentage curve from Lake Montcortès sediments (CP) (Fig. 2). 4 V. Rull, T. Vegas-Vilarrúbia Science of the Total Environment 886 (2023) 163947 centennial to millennial, is not enough to resolve eventual changes that oc- References curred within the 20th century. For example, in ET, which is the most sim- ilar to Montcortès regarding pollen abundance, the record ends in 1991, Aboulaich, N., Trigo, M.M., Bouziane, H., Cabezudo, B., Recio, M., El Kadiri, M., et al., 2013. and only a couple of samples are available for the whole 20th century Variations and origin of the atmospheric pollen of Cannabis detected in the province of tetouan (NW Morocco): 2008-2010. Sci. Total Environ. 443, 413–419. (Riera et al., 2004). Therefore, the lack of high-resolution records including Akin, D.E., 2013. Linen most useful: perspective on structure, chemistry and anzyme for ret- the 20th century is a major handicap to assessing the spatial patterns of the ting flax. ISRN Biotechnol. 2013, 1–23. 20C across the IP. Alvarez, A., Gamella, J.F., Parra, I., 2016. Cannabis cultivation in Spain: a profile of planta- tions, growers and production systems. Int. J. Drug Policy 37, 70–81. Another interesting observation is that the major vegetation shift Aznar, F., Negral, L., Moreno-Grau, S., Elvira-Rendueles, B., Costa-Gómez, I., Moreno, J.M., documented above and the 20C occurred at or shortly after the onset of 2022. Cannabis, an emerging aeroallergen in southeastern Spain (region of Murcia). Sci. the “Anthropocene”, as currently defined by the Anthropocene Working Total Environ. 833, 155156. Balant, M., Gras, A., Gálvez, F., Garnatje, T., Vallès, J., Vitales, D., 2021. CANNUSE, a database Group (AWG) (Waters et al., 2023). Indeed, the AWG proposes that this of traditional Cannabis uses – an opportunity for new research. Database baab024 2021. boundary should be situated in the mid-20th century, coinciding with the Barcaccia, G., Palumbo, F., Scariolo, F., Vannozzi, A., Bona, S., 2020. Potentials and challenges Great Acceleration, when the Earth System underwent a global transforma- of genomics for breeding cannabis cultivars. Front. Plant Sci. 11, 573299. Belackova, V., Tomkova, A., Zabransky, T., 2016. Qualitative research in Spanish cannabis so- tion overcoming the range of variability of the Holocene (Steffen et al., cial clubs: “the moment you enter the door, you are minimising the risks”. Int. J. Drug 2015). Our results, together with the very high resolution (seasonal) Policy 34, 49–57. of the Montcortès record, suggest that the sediments of this lake could Boutahar, A., Cariñanos, P., Picone, R.M., Crisafulli, A., Molero, J., Zahrae, F., et al., 2023. be a suitable candidate to identify and precisely date an eventual Modern pollen-vegetation relationships in the Rif mountains (northern Morocco). Rev. Palaeobot. Palynol. 310, 104828. “Anthropocene” GSSP (Global Stratotype Section and Point) (Waters Cabezudo, B., Recio, M., Sánchez-Laulhé, J.M., Trigo, M.M., Toro, F.J., Polvorinos, F., 1997. et al., 2018). The proxies identified by the AWG as the best suited strati- Atmospheric transportation of marihuana pollen from north Africa to the southwest of graphic markers (radioisotopes, fly ash, stable carbon and nitrogen iso- Europe. Atmos. Environ. 31, 3323–3328. Cariñanos, P., Galán, C., Alcázar, P., Domínguez, E., 2004. Analysis of the particles topes) have not yet been analyzed in the Montcortès record, but efforts in transported with dust-clouds reaching Cordoba, Sotheastern Spain. Arch. Environ. this direction are worth doing, especially after the detection of significant Contam. Toxicol. 46, 141–146. Hg and Pb increases during the Industrial Revolution and the Great Accel- Carreras, J., Vigo, J., Ferré, A., 2005-2006. Manual dels Hàbitats de Catalunya. vols. I-VIII. Dep. Medi Ambient Habitatge, Generalitat de Catalunya, Barcelona. eration in these sediments (Corella et al., 2017). Carrión, J.S., Munuera, M., Ochando, J., López-Sáez, J.A., Casas-Gallego, M., González- Sampériz, P., et al., 2022. Paleoflora y Paleovegetación Ibérica III: Holoceno. Min. Ciencia 5. Conclusions and future prospects Innovación & Fund, Séneca, Murcia. Clarke, R.C., Merlin, M.D., 2013. Cannabis: Evolution and Ethnobotany. Univ. California Press, Los Angeles. A distinct and characteristic increase in Cannabis pollen during the Clarke, R.C., Merlin, M.D., 2016. Cannabis domestication, breeding history, present-day ge- 1980s has been recorded in the unique varved record of Lake Montcortès, netic diversity, and future prospects. Crit. Rev. Plant Sci. 35, 293–327. Corella, J.P., Benito, G., Rodríguez-Lloveras, X., Brauer, A., Valero-Garcés, B., 2014. Annually- which has been related to the significant increase in hemp production doc- resolved lake records of extreme hydro-meteorological events since AD 1347 in NE Ibe- umented by the same time in the southern Pyrenees, fostered by the incom- rian Peninsula. Quat. Sci. Rev. 93, 77–90. ing EU subsidies to this crop. Additional sources for this pollen type, Corella, J.P., Valero-Garcés, B., Vicente-Serrano, S.M., Brauer, A., Benito, G., 2016. Three notably illegal cannabis plantations, cannot be disregarded but sound evi- millennia of heavy rainfalls in Western Mediterranean: frequency, seasonality and atmo- spheric drivers. Sci. Rep. 6, 38206. dence is still lacking. The geographical extent of this palynological event, Corella, J.P., Valero-Garcés, B., Wang, F., Martínez-Cortizas, A., Cuevas, C.A., Saiz-Lopez, A., called here 20C (20th century Cannabis increase), remains unknown due 2017. 700 years reconstruction of mercury and lead atmospheric deposition in the Pyre- to the lack of similar continuous and absolutely dated high-resolution re- nees (NE Spain). Atmos. Environ. 155, 97–107. Duvall, C., 2014. Cannabis. Reaktion, London. cords for the 20th century. A number of future studies are proposed to com- Farràs, F., 2005. El Pallars contemporani. In: Marugan, C.M., Rapalino, V. (Eds.), Història del plement this preliminary assessment, including (i) increasing the resolution Pallars. Dels Orígens als Nostres Dies, Pagés, Lleida, pp. 121–144. of the available pollen record from subdecadal (~5 years) to annual, (ii) Gorchs, G., Lloveras, J., 2003. Current status of hemp production and transformation in Spain. J. Ind. Hemp. 8, 45–64. modeling the Cannabis pollen dispersion in the region around Montcortès, Gorchs, G., Loveras, J., Serrano, L., Cela, S., 2017. Hemp yields and its rotation effects on (iii) surveying the occurrence of illegal plantations as potential local wheat under rainfed Mediterranean climates. Agron. J. 109, 1551–1560. sources for Cannabis pollen, (iv) increasing the number and geographical Gray, D.J., Clarke, R.C., Trigiano, R.N., 2016. Introduction to the special issue on Cannabis. Crit. Rev. Plant Sci. 35, 425–426. extent of 20th century high-resolution records similar to Montcortès, and Kovalchuk, I., Pellino, M., Rigault, P., van Velzen, R., Ebersbach, J., Ashnest, J.R., et al., 2020. (v) evaluating the Lake Montcortès record as a potential candidate for the The genomics of Cannabis and its close relatives. Ann. Rev. Plant Biol. 71, 713–739. identification of the current AWG “Anthropocene” prospect. Li, F., Gaillard, M.-J., Sugita, S., Mazier, F., Xu, Q., Zhou, Z., et al., 2017. Relative pollen pro- ductivity estimates for major plant taxa of cultural landscapes in central eastern China. Veget. Hist. Archaeobot. 26, 587–605. CRediT authorship contribution statement Mercadé, A., Vigo, J., Rull, V., Vegas-Vilarrúbia, V., Garcés, S., Lara, A., et al., 2013. Vegeta- tion and landscape around Lake Montcortès (Catalan pre-Pyrenees) as a tool for palaeo- Both authors contributed equally to the research and the manuscript. ecological studies of lake sediments. Collect. Bot. 32, 87–101. Munuera, M., Carrión, J.S., Navarro, C., 2002. Seasonal fluctuations of the airborne pollen spectrum in Murcia (SE Spain). Aerobiologia 18, 141–151. Riera, S., Wansard, G., Julià, R., 2004. 2000-year environmental history of a karstic lake in the Data availability Mediterranean pre-Pyrenees: the Estanya lakes (Spain). Catena 55, 293–324. Rull, V., 2022. Origin, early expansion, domestication and anthropogenic diffusion of Cannabis, Data are available in public databases with emphasis on Europe and the Iberian Peninsula. Persp. Plant Ecol. Evol. Syst. 55, 125670. Rull, V., Vegas-Vilarrúbia, T., 2014. Preliminary report on a mid-19th century Cannabis pollen peak in NE Spain: historical context and potential chronological significance. Holocene Declaration of competing interest 24, 1378–1383. Rull, V., Trapote, M.C., Safont, E., Cañellas-Boltà, N., Pérez-zanón, N., Sigró, J., Buchaca, T., et al., 2017. Seasonal patterns of pollen sedimentation in Lake Montcortès (Central Pyre- The authors declare that they have no known competing financial inter- nees) and potential applications to high-resolution paleoecology: a 2-year pilot study. ests or personal relationships that could have appeared to influence the J. Paleolimnol. 57, 95–108. work reported in this paper. Rull, V., Vegas-Vilarrúbia, T., Corella, J.P., Trapote, M.C., Montoya, E., Valero-Garcés, B., 2021. A unique Pyrenean varved record provides a detailed reconstruction of Mediterranean vegeta- tion and land-use dynamics over the last three millennia. Quat. Sci. Rev. 268, 107128. Acknowledgments Rull, V., Sacristán-Soriano, O., Sànchez-Melsió, A., Borrego, C.M., Vegas-Vilarrúbia, T., 2022. Bacterial phylogenetic markers in lake sediments provide direct evidence for historical This work has been funded by the Ministry of Economy and Competi- hemp retting. Quat. Sci. Rev. 295, 107803. Rull, V., Burjachs, F., Carrión, J.S., Ejarque, A., Fernández, S., López-Sáez, J.A., et al., 2023. tiveness, projects CGL 2012-3665 and CGL 2017-85682-R. The comments Historical biogeography of Cannabis in the Iberian Peninsula: a probabilistic approach by two anonymous reviewers are greatly acknowledged. using palynological evidence. Persp. Plant. Ecol. Evol. Syst. 58, 125704. 5 V. Rull, T. Vegas-Vilarrúbia Science of the Total Environment 886 (2023) 163947 Small, E., Antle, T., 2003. A preliminary study of pollen dispersal in Cannabis sativa in relation Waters, C.N., Zalasiewicz, J., Summerhayes, C., Fairchild, I.J., Rose, N.L., Loader, N.J., et al., to wind direction. J. Ind. Hemp 8, 37–50. 2018. Global boundary stratotype section and point (GSSP) for the Anthropocene series: Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., Ludwing, C., 2015. The trajectory of the where and how to look for potential candidates. Earth-Sci. Rev. 178, 379–429. Anthropocene: the great acceleration. Anthr. Rev. 2, 81–98. Waters, C.N., Turner, S.D., Zalasiewicz, J., Head, M.J., 2023. Candidate sites and other refer- Trapote, M.C., Rull, V., Giralt, S., Corella, J.P., Montoya, E., Vegas-Vilarrúbia, T., 2018. High- ence sections for the Global boundary stratotype section and point of the Anthropocene resolution (sub-decadal) pollen analysis of varved sediments from Lake Montcortès series. Anthr. Rev. https://doi.org/10.1177/20530196221136422. (southern Pyrenean flank): a fine-tuned record of landscape dynamics and human impact during the last 500 years. Rev. Palaeobot. Palynol. 259, 207–222. Warf, B., 2014. High points: an historical geography of Cannabis. Geogr. Rev. 104, 414–438. 6