Climatic changes radically transformed European ecosystems during the Eocene-Oligocene transition
Postdoctoral researcher Aixa Tosal Alcobé, from the Sedimentary Geology research group and the Biodiversity Research Institute (IRBio) of the University of Barcelona, works on climate change during the Eocene-Oligocene Transition in Europe. She is leading a study that analyzes the causes paleoecological and paleoclimatic conditions that influenced the flora of Southwestern Europe during this critical period.
The Eocene-Oligocene Transition (TEO; 33.9-33.3 Ma) represents the greatest climate change of the last 65 Ma. On the continent, this climate change was characterized by a drop in global temperatures, an increase in seasonality and a general trend towards aridity: this climate change was transcendental for the ecosystems.
In this time interval, Europe sees a dispersal towards the south of plants tolerant to low temperatures such as oak, banana tree or maple. On the other hand, thermophilic plants (plants that do not survive low temperatures) that grew homogeneously throughout Europe had to be restricted in Southern Europe, where temperatures were mild. This fact, in Southern Europe, led to the appearance and diversification of a flora tolerant to a certain seasonality of precipitation, such as leguminous plants or jujubes, which would be the prelude to the Mediterranean flora.
The IBERINSULA project and the work of Dr. Tosal
The project that researcher Tosal is carrying out seeks to analyze the paleoecological and paleoclimatic causes that conditioned the flora of Southwestern Europe (Spain and France) during the Eocene-Oligocene transition (TEO) and better understand the influence of this climate change on the later origin of the Mediterranean flora. This project is part of a national project of the Ministry of Sciences and Innovation entitled Iberia in the Cretaceous and Paleogene: paleoisland and biogeographic bridge. Case studies in macroforaminifera, charophytes and vascular plants (IBERINSULA) where the main researcher is Carlos Martín-Closas, also a researcher at IRBio and the Faculty of Earth Sciences.
The project has three main objectives:
- Seeks to determine the distribution of flora before and after the TEO climate change in Southwestern Europe (France and Spain).
- Know what abiotic factors (climate, morphological characteristics of the basins, etc.) influenced the distribution of this flora.
- Understand what role the Iberian Peninsula played as a refuge for plant species, as a biogeographic bridge or as a focus for the emergence of endemism.
Changes in the distribution and composition of vegetation in the Eocene-Oligocene transition
Based on detailed analyzes of the basins of southern France and the Ebro Basin in Spain, the results obtained by Dr. Tosal together with other researchers have observed certain previously unknown differences in the plant communities between these areas, mainly attributed to climatic and geomorphological factors of the basins. “Theoretically, the basins of these two areas (Spain and France) should have great similarities because they were within the same climatic and vegetation zone. From the results we obtained we saw that, indeed, they shared some species, but that there were certain differences. For example, in the French area we find some species that are typical of Central Europe and that we do not find in the Iberian Peninsula” explains Aixa.
Before climate change, French basins exhibited greater plant richness, with wetlands that emerged as a result of higher rainfall and a topography that facilitated the formation of these environments. This great diversity contrasted with the more arid composition of the vegetation in the Ebro Basin: “This area, which today is located in the south of France, would represent the transition between the typical flora of Southern Europe and that of Central Europe. These differences would be due to the climate and the difference in the morphology of the basins: in the case of France, the morphology of the basin would allow the formation of wetland areas with a particular biodiversity and flora.” This, in turn, has led to the conclusion that the Iberian Peninsula could have acted as a refuge for various plant species during this critical period, as well as perhaps giving rise to endemism, as highlighted in the study of the plant Rhus asymmetrica.
During his stay in France at the Muséum national de Histoire naturelle in Paris he also worked with research groups from the Center Européen de Recherche and Enseignement des Géosciences del Environnement (CEREGE) with whom he continues to collaborate continuously: “With French research groups We have gotten along very well and my profile is quite complementary to yours. They are biologists and I provide all the geology, spatio-temporal changes of the basin's environments and also plant habitat, and they provide the experience in taxonomy, species attribution, and ecological adaptations of plants. We have open projects with two or three basins and in spring we do field campaigns together where each one with their pre-established work according to their training contributes their grain of sand. Really, we all contribute interesting ideas," says Aixa.
The next steps in this research field
Dr. Tosal identifies that there is still a long way to go in her field of work: “For example, it is necessary to characterize in detail what the climate change of the Eocene-Oligocene Transition was like, since until a few years ago it was thought to be gradual, but the results obtained show that this change was much more complex. Therefore, the future of my research is to study how it affected the dynamics of vegetation in other basins in southern Europe.”
With her discoveries, Dr. Tosal advances the field of paleoecology and paleoclimate, but she also paves the way for more research that delves into the complex climate changes that shaped Europe over millions of years.
What is it like to be a woman in the world of research?
Dr. Tosal highlights that, despite her scientific achievements, she has had to overcome several gender barriers throughout her career. From sexist comments at the beginning of her career to the constant perception of the need to demonstrate her competence as a female researcher: “Because I am a woman, I have to constantly demonstrate my worth and many times much more is demanded of me than a man with the same job position.”
Furthermore, she explains that the number of women in the faculty was and continues to be very low and with very few female historical references: “This situation worsened when I took the master's degree where there was only one female professor who taught us. At that moment I asked myself if there is room for a woman within this specialty. However, I wanted to continue doing research, in part thanks to the encouragement received from some professors I had during my Geology degree at the University of Barcelona.” Finally, Dr. Tosal's commitment to finding and overcoming gender barriers is an inspiration for future generations of scientists.