I am stuck in the past. But why am I stuck there, when most therapists suggest letting go and moving on? I work in the field of paleoecology, the ecology of the past, which is a branch of paleontology, and try to understand and imagine ancient landscapes, along with the factors that drove their evolution, using the pollen fossil as my main tool. Yes, pollen from flowers; the microscopic yellowish-whitish particles that make you sneeze when you smell a flower. The same dust spread through the air by the wind, and the reason for your red eyes and itchy nose when passing through a grassland. And the thing that turns your white clothing yellow at weddings.
Biologically speaking, pollen is responsible for carrying the male gametes that lead to fertilization to flowering plants (Edlund et al., 2004). All this is pollen and, more importantly, at least for me, is that it can be preserved for millions of years. Pollen, despite its tiny size, is composed of one of the strongest biopolymers on Earth: sporopollenin (Grienenberger and Quilichini, 2021), which enables preservation of those particles for long periods of time. Pollen grains also have specific shapes and ornaments that help us to classify them (Figure 1). One could say that every plant has a pollen signature, which means that a paleoecologist like me can translate the pollen found buried in sediments and interpret it as past vegetation. You might say that I am interested in dead material that brings snapshots of ancient environments back to life.
Figure 1. Pollen grains found in Colombian Andean ecosystems seen under light microscope. From left to right: Espeletia grandiflora (frailejón, or Big Monk) pollen grains (400x). Espeletia grandiflora (frailejón, or Big Monk) (1000x). Quercus humboldtii (Andean oak) (1000x). Alnus acuminata (Adler) (1000x).
Our dynamic planet has survived a number of transformations during its lifetime (see,
for example, Jaramillo and Oviedo’s Hace tiempo, published in 2017, free digital access
in Colombia); everything from geological and extraplanetary events, such as plate tectonics and meteorite impacts, to the drastic climatic changes observed during the recent quaternary glaciations (last 2.58 million years; Head et al. , 2021). These forces triggered many biotic
and abiotic interactions (i.e., mass extinctions, mountain uplifting, sea level changes, etc.), which led to the current state of our planet. But why is it important to learn about our planet’s past climate and environmental conditions? Simply put, we are dynamic beings and our planet has never been static, thus a knowledge of the Earth’s different phases over time can help to assess the current state of the spaces we inhabit.
Variations in environmental, climatic, and geological conditions are to be expected over time. Likewise, one would expect organisms to react differently to these conditions. Understanding the Earth’s processes and the way that ecosystems function along different time scales can help us to properly manage and use our resources. This information can, in the end, help to infer and project plausible scenarios for the future of our planet. The real challenge is to determine how living organisms will cope with the extreme transformations that our planet will face –and is indeed already facing– in the future (IPCC, 2021), including the negative effects induced by anthropogenic activities such as increases in CO2 levels and land surface and ocean transformations, bearing in mind that vast changes are already occurring and have exceeded natural geological processes (Tierney et al. , 2020).
In Colombia, one example might be the role of the páramo and its ecosystem services. Páramos, which cover only 1.7% of Colombian territory (Hofstede et al. , 2014), supply water to 70% of the country. What will happen, then, if we continue to apply the same agro-industrial processes to these ecosystems (i.e. expanding potato fields to higher altitudes)? What about the temperature increases that add to the effects of these harmful practices? They are certain to lead to catastrophe, as millions of people depend on these very vulnerable ecosystems. Not to mention their floristic composition, which may disappear in the next few decades if we fail to act now (Diazgranados et al. , 2021 and literature therein). The current diversity and endemism observed in the páramos is the result of the isolation and expansion that took place during the glaciations of the past ca. 2.6 million years (Flantua et al. , 2019) and what we see today is a mere remnant of those processes. A knowledge of the past ecological states of these ecosystems, in conjunction with recent ecological data, can help us to assess the effects of climate and humans on future scenarios (Diazgranados et al. , 2021).
Since we possess no photographic archives or movies, or even perceptions, of our planet from the past hundreds to millions of years, geological records are our main source for assessing the former conditions of the Earth, through the analysis of sediment records. There are many tools to evaluate geological records and scientists from many fields contribute to these findings (geology, paleontology, paleoclimatology, archeology etc.). Perhaps the best known is paleontology, a field which in Colombia is increasing exponentially (Jaramillo and Oviedo, 2017). It is also important to point out here the enormous value of historians, and other disciplines, who work to disentangle the past by other means and timescales. In the end, all our work is aimed at the same goal, keeping the past present.
Before we can discuss past vegetation, however, we need to choose a time frame and scale. The history of the plants on our planet is quite long –as old as ca. 300 million years (Morris et al. , 2018)– so specialists work on specific periods; in my case, the Quaternary (last 2.58 million years), a choice which seemed as good as any other. Having once chosen a period, in order to be able to reconstruct the past vegetation at a given place in the world, we need to locate the pollen deposits that have been accumulating consistently over time with few disturbances. Lakes are the best place to find not only well preserved pollen but other types of proxies (diagnostic tools) such as diatoms, sediments (sand, clay, silt, etc.), and charcoal, to name only a few. Pollen, transported by wind, animals, or water currents, is deposited in the water and accumulates next to sediments of varying provenance, and then begins its fossilization process. One therefore expects that pollen deposited in deeper sediments will be older than that closer to the water column.
After characterizing these sediments, we can reconstruct their past. It is worth mentioning that the more tools used to study the past, the better our characterization and understanding. Pollen fossils are just one of many tools. You may also wonder how we retrieve the pollen stored in the lakes. This is done by using coring systems that help to extract the sediments. Afterwards, we use meshes and chemicals to extract the pollen (Faegri and Iversen, 1989). After removing 0.5 cm3 of sediment at a specific depth, we basically clean the sample of everything and keep only the preserved pollen. Next, samples are counted using a microscope. Generally, we find a universe of thousands of particles with different shapes and sizes, which in the end will tell us what type of plants were growing in the past. This routine is quite straightforward; you count and separate the different pollen shapes (pointing to different types of vegetation) for every depth that you sampled. In the end, we build “pollen diagrams” that help us to understand the dynamics over time (see, for example: Gómez et al., 2007; Muñoz et al., 2017; or Jaramillo et al., 2021, using other tools). Nevertheless, as I mentioned before, for a more precise history we use additional tools, known as proxies. One of these tools, dating, is crucial in order to determine the time frame, and can be performed using different approaches. Depending on the time scale that you are working on, different dating techniques such as radiocarbon dating, luminescence dating, Pb dating, etc. may be used. Application of these approaches gives us the age of lake sediments at specific depths and, therefore, the age when those plants were growing in the studied area.
Plenty of palaeoecological studies have been done in Colombia already, and it is not my intention to explain them here –I hope you’ll be inspired to dig further! I will, however, point out that much more research is needed, especially research by Colombians, to fully understand our ecosystems.
Strangely enough, after I began writing this text, and started on the journey of explaining the past through pollen and geological records, I realized that I had no idea about the past of the place where I was born. I have been exploring the pasts from other tropical regions, but never that of my homeland, Colombia, a country of forgotten history and lives (#nosestanmatando). So I began thinking about Sogamoso, the city where I was born, and wondered how it became the place it is now, and what will happen to it in the future.
Located in Colombia’s Boyacá department, Sogamoso lies in a valley of the eastern Andean cordillera choked by the industrial dust and smoke from chircales (Figure 2), the ovens used to make bricks. Interestingly, the term chircales comes from the tree that was cut to produce the fire in these ovens during colonial times (Molina Prieto, 2010). The plant (Baccharis latifolia) is also known as chilco (see common names of Colombian flora in Bernal et al., 2017: http://www.biovirtual.unal.edu.co/nombrescomunes/) and is rarely seen in the area nowadays. The Sogamoso where I grew up was industrial. For better or for worse, the hills surrounding it were full of minerals that attracted the brick-making, cement and iron industries. Not to mention that the area is dominated by non-endemic species such as eucalyptus, acacias, and pines, originally planted during the colonial period. The continued presence of these trees in the landscape indicates the local population’s extremely limited awareness of the native flora. (Although I can hardly complain about people not being aware of their own surroundings; I was one of them!)
The streets of Sogamoso are, for the most part, full of pot holes and the city’s parks are paved with cement and littered with the excrement of stray dogs. If asked to describe the city, I would simply say, “dust”. Like pollen fossils, dead dust. However, as with the pollen, Sogamoso could be re-imagined, rebuilt, and deconstructed. What we need is for people to become more aware of their surroundings. There are several páramo complexes near Sogamoso with small lakes just waiting to “speak up”, not to mention Lake Tota, the country’s largest lake, which has been highly impacted by humans and harmful agricultural practices (Figure 3).
Suamox, or the Dwelling of the Sun, was the name given to this place by the Muisca people, ancient inhabitants of the region. Although I know little about that indigenous settlement,
I do know that it was built, unlike its modern counterpart, on the hills surrounding the valley, as a religious center (Langebaek, 2019; Museo Arqueológico Eliecer Silva Celis-Sogamoso). Nowadays, you can visit a reconstruction of a “sun temple” at the Sogamoso Archeological Museum; however there is little information about the climate, environment and vegetation that grew in the mountains and valley at that time. Were there Quercus (oak) or Alnus (alder) forests in the area, or did something entirely different grow there? When was maize planted for the first time in this region and what were the main agricultural products? Was the valley a swamp, a lake or an alluvial plain at some point?
Figure 3. Panoramic View of Lake Tota
View of Sogamoso city.
Figure 2. Sogamoso Valley. In the background of photos in the top row, the mountains are being actively mined for minerals. Photos in the second row show vegetation and chircales on the outskirts of the city.
Although many of these questions remain unanswered, archeologists and geologists working in the region may have already addressed some of them and their work needs to be reviewed in order to begin an evaluation of this Andean region’s past. In any case, I imagine a less disturbed, less contaminated place than the one we live in today. One where it was possible, at the very least, to breathe more oxygen than smog, for example. I don’t, however, mean to imply that past human societies were more careful with nature; indeed, prior to the Spanish conquest, the social and cultural practices of humans also impacted the territory (i.e. , Aceituno et al. , 2013).
I would merely draw attention to the increase in the human footprint, especially during the last decades, and wonder how climate influenced the vegetation dynamics in Suamox and Sogamoso, and whether it is possible to understand how climate affected past societies in the region. Likewise, it is important to study the effects of disturbances caused primarily by human transformations. Of course, many other questions could also be answered in a study of this nature and it is therefore important to involve more people, civil society in particular. The work should be approached from a synergistic perspective.
It is difficult at this point to project the future of Sogamoso based only on studies of the past, since they have yet to be done. However, given the pace at which we are currently living and using the city’s resources, we are certain to be struggling soon with a loss of diversity, poor
air quality (already a problem), and limited water resources. The city will doubtless be affected by temperature increases, as green areas are steadily being paved over or replaced with cement. However pessimistic this may seem, these things can be drastically reduced by increasing our awareness of the environment.
As you may have guessed from reading the introductory part of this text, I believe now is the time to search for lakes or lacustrine systems containing the dynamics of those ancient landscapes. Hopefully, what we find will help to build a better future for the region (Figure 3). There are many cities, villages, and towns like Sogamoso that need to be rediscovered (and not only environmentally, as I usually do). I hope that this text has made you more familiar with pollen, but also a bit more aware of your surroundings, and that you have begun to wonder about the past of wherever you are reading this.
Acknowledgements
Historian Ricardo Plazas, for sharing literary references related to Sogamoso and the Muisca people. Camilo Saldaña, for his linguistic advice and discussions.
References
Aceituno, J. , Loaiza, N. , Delgado-Burbano, M.E. , Barrientos, G. (2013). The initial human settlement of Northwest South America during the Pleistocene/Holocene transition: Synthesis and perspectives. Quaternary International 301, 23-33.
Bernal, R. , G. Galeano, A. Rodríguez, H. Sarmiento y M. Gutiérrez. 2017. Nombres Comunes de las Plantas de Colombia. http://www.biovirtual.unal.edu.co/nombrescomunes/.
Diazgranados, M. , Tovar, C. , Etherington, T.R. , Rodríguez-Zorro, P.A. , Castellanos-Castro, C. , Galvis Rueda, M. , Flantua, S.G.A. (2021). Ecosystem services show variable responses to future climate conditions in the Colombian páramos. Peer J 9: e11370.
Edlund, A.F., Swanson, R., Preuss, D. (2004). Pollen and Stigma Structure and Function: The Role of Diversity in Pollination. The Plant Cell 16, S84–S9.
Faegri, K. , Iversen, J. , 1989. Textbook of Pollen Analysis, fourth ed. Wiley, New York.
Flantua, S.G.A. , O'Dea, A. , Onstein, R.E. , Giraldo, C. , Hooghiemstra, H. (2019). The flickering connectivity system of the North Andean páramos. Journal of Biogeography 46:1808–1825.
Grienenberger, E. , Quilichini, T.D. (2021). The Toughest Material in the Plant Kingdom: An Update on Sporopollenin. Front. Plant Sci. 12: 703864.
Gómez, A., Berrío, J.C., Hooghiemstra, H., Becerra, M., Marchant, R. 2007. A Holocene pollen record of vegetation change and human impact from Pantano de Vargas, an intra-Andean basin of Duitama, Colombia. Review of Paleobotany and Palynology 145, 143-157.
Head, M.J. , Pillans, B. , Zalasiewicz, J.A. , TISOQS. (2021). Formal ratification of subseries for the Pleistocene series of the Quaternary system. Episodes 44, 241-247.
Hofstede, R. , Calles, J. , López, V. , Polanco, R. , Torres, F. , Ulloa, J. , Vásquez, A. , Cerra, M. (2014). Los Páramos Andinos ¿Qué sabemos? Estado de conocimiento sobre el impacto del cambio climático en el ecosistema páramo. UICN Quito Ecuador.
IPCC, 2021: “Summary for Policymakers”, in Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan,
S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press.Jaramillo, C. , Oviedo, L.H. (Eds.). (2017). Hace tiempo. Un viaje paleontológico ilustrado por Colombia. Instituto Alexander von Humboldt and Smithsonian Tropical Research Institute. Bogotá, D.C., Colombia. 124 p. free Access book: http://www.humboldt.org.co/es/i2d/item/1198- hace-tiempo-libro.
Jaramillo, D. , Vélez, M.I. , Escobar, J. , Pardo-Trujillo, A. , Vallejo, F. , Villegas, J.C. , Acevedo, A. , Curtis, J. , Rincón, H. , Trejos-Tamayo, R. (2021). Mid to late Holocene dry events in Colombia’s super humid Western Cordillera reveal changes in regional atmospheric circulation. Quaternary Science Reviews 261, 106937.
Langebaek, C.H. 2019. Los Muiscas, la historia milenaria de un pueblo chibcha. Penguin Random House. p. 309.
Molina, L.F. (2010). Alfarería y urbanismo. Los chircales de Santafé (hoy Bogotá) y su impronta en la arquitectura y el desarrollo urbano de la ciudad colonial. Revista nodo 8, 4: 31-58.
Morris, J. L. , Puttick, M. N. , Clark, J. W. , Edwards, D. , Kenrick, P. , Pressel, S. , Wellman, C. H. , Yang, Z. , Schneider, H. , & Donoghue, P. C. J. (2018). The timescale of early land plant evolution. Proceedings of the National Academy of Sciences of the United States of America, 115 (10), E2274-E2283.
Muñoz, P. , Gorin, G. , Parra, N. , Velásquez, C. , Lemus, D. , Monsalve-M, C. , Jojoa, M. (2017). Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high- resolution record unravels the dual influence of ENSO and ITCZ. Quaternary Science Reviews 155, 159–178.
Tierney, J. E. , Poulsen, C. J. , Montañez, I. P. , Bhattacharya, T. , Feng, R. , Ford, H. L. , Hönisch, B. , Inglis, G. N. , Petersen, S. V. , Sagoo,N. , Tabor, C. R. , Thirumalai,K. , Zhu, J. , Burls, N. J. , Foster, G. L., Goddéris, Y., Huber, B. T., Ivany, L. C., Turner, S. K., Lunt, D. J., McElwain, J. C., Mills, B. J. W., Otto-Bliesner, B. L. , Ridgwell, A. , Zhang, Y. G. 2020. Past climates inform our future. Science 370, eaay3701.