If you sneeze this spring, you are not alone. Every year, plants release billions of pollen grains in the air, particles of male reproductive material that many of us only perceive when our eyes cry and moquet our nose.
However, pollen grains are much more than allergens: they are capsules of the time of nature that preserve clues about the past environments of the earth for millions of years.
The resistant external layer of the pollen allows him to survive long after his progenitor plants have disappeared. When pollen grains are trapped in the sediments of the Lagos, Oceans and river beds, fossil pollen can provide scientists with a unique story of the environments in which these pollen producing plants were born.
The types and amounts of pollen found in a deposit help researchers rebuild old forests, track changes at sea level and identify significant events, such as asteroid impacts or collapse of civilizations.
A team of palinologists, studied these old pollen fossils worldwide. Here are some examples of what can be learned from these microscopic pollen grains:
Missuri: Pollen and asteroid
It is believed that when an asteroid impacted the earth about 66 million years ago, which attributes the extinction of dinosaurs, caused a tidal that hit North America.
The marine fossils and rock fragments found in the southeast of Missuri seem to have been deposited there by a massive wave generated by the impact of the asteroid on what is now the Yucatan Peninsula, in Mexico.
Between the rocks and the marine fossils, the scientists found fossilized pollen of the upper cretaceous and the lower paleocene that reflects changes in the surrounding ecosystems. Pollen reveals how ecosystems were instantly altered at the time of asteroid impact, before gradually recovering throughout hundreds or thousands of years.
Gymnosperms pollen, such as pine trees, as well as that of ferns and flowers with flowers, such as grasses, aromatic herbs and palm trees, records a clear pattern: part of the forest pollen disappeared after the impact, which suggests that the vegetation of the region changed. Subsequently, pollen began to resurface slowly as the environment stabilized.
Gulf Coast of Mexico: Secuoya pollen and increased sea level
Fosylized pollen grains also helped scientists track slower, but equally drastic changes, along the mississippi and alabama states, on the east coast of the Gulf of Mexico.
During the early oligocene, between 33.9 and 28 million years ago, the sea level rose and flooded the low coniferous forests of the region. The researchers identified a distinctive change in the pollen released by seduoya trees, giant conifers who once dominated the coastal plains.
Scientists were able to use these pollen records to reconstruct the distance to the coast of Earth inland, tracing the proportion of pollen grains in the geological record with respect to the emergence of marine microfossils.
The evidence shows how the sea flooded terrestrial ecosystems hundreds of kilometers from the current coast. Pollen is a biological marker and a geographical tracker of this ancient change.
We recommend: scientists seek to claim the Romance languages in dinosaurs research
Western Australia: From swamps to salinity
In Western Australia, the sediment nuclei of the Aerodrome Lake, Lake Gastropod and Lake Prado reveal how long -term drought can change the ecology of a region.
During the Eocene, a period between 55.8 and 33.9 million years, leafy swampy forests surrounded freshwater lakes. This is reflected in the abundance of tropical trees pollen, moisture loving shrubs and ferns of ferns of the time. However, the vegetation changed dramatically as the Australian tectonic plate moved north and the weather became more arid.
The upper layers of the sediment nuclei, which capture more recent data, contain pollen mainly of winds pollinated by the wind and tolerant of salt and drought, which evidences the evolution of the vegetation under a growing environmental stress.
The presence of Dunaliella, a green algae that thrives in very salty waters, along with the low pollen of plants that could survive in dry environments, confirms that the lakes that once housed forests became highly saline.
Guatemala: Mayan history and forest recovery
Closer to the tropics, Lake Izabal in Guatemala offers a more recent file that covers the last 1,300 years. This sediment record reflects both natural climatic variation and the deep impact of human use of the earth, especially during the rise and fall of Mayan civilization.
Between 1,125 and 1,200 years, the pollen of crops such as corn and opportunistic herbs increased, at the same time that trees pollen decreased, which reflects generalized deforestation. Historical records show that the political centers of the region collapsed shortly after.
Only after demographic pressure decreased, the forest began to recover. The pollen of tropical tough wood trees increased, indicating that the vegetation recovered even with the decrease in rainfall during small ice age, between the fourteenth and mid -nineteenth centuries.
The fossil pollen shows how ancient societies transformed their landscapes and how ecosystems responded, providing more evidence and explanations for other historical stories.
Modern pollen also tells a story
These studies were based on the analysis of fossil pollen grains according to their shape, superficial characteristics and structure of the walls. By counting the grains (from hundreds to thousands per sample), scientists can build statistical images of ancient vegetation, the present species, their abundance and how the composition of each varied with the climate, changes in sea level or human activity.
Therefore, modern pollen also tells a story. As the current climate is heated, the behavior of pollen producing plants is changing. In temperate regions such as the United States, pollen seasons begin before and last more due to the increase in temperatures and carbon dioxide in the atmosphere from vehicles, factories and other human activities.
All this is registered in the fossil pollen record in the layers of sediments of the Lagos Fund around the world.
So, the next time I suffer from allergies, remember that the tiny grains that float in the air are biological time capsules that one day could inform future inhabitants about the environmental changes of the earth.
*Francisca Oboh Ikuenobe is a professor of Geology and Geophysics at the University of Science and Technology of Missouri; Linus Víctor Anyanna is a postgraduate research assistant in Geology, University of Missouri Science and Technology.
This text was originally published in The Conversation
Subscribe to our YouTube channel and do not miss our content
