Ancient pollen research provides insight into future climate change

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A new research study of Earth’s dramatic climate transition around 56 million years ago has provided evidence of its dramatic impact on Earth’s vegetation and climate, as well as insights into Earth’s future in the future. as a result of ongoing climate change. The study demonstrated that an increase in atmospheric CO2 concentration plays a major role in changing Earth’s climate and plant life.

The research was led by Vera Korasidis of the University of Melbourne and Dr Scott Wing of the Smithsonian’s National Museum of Natural History Department of Paleobiology, and published in the journal Paleoceanography and Paleoclimatology.

According to Korasidis, this event – called the Paleocene-Eocene Thermal Maximum (PETM) – witnessed a huge release of carbon into the ocean and atmosphere, which increased atmospheric concentrations of carbon dioxide (CO2). and resulted in an increase in temperatures of 5 to 8°. C and sea level rise.

While the PETM unfolded over a few tens of thousands of years, the causes and consequences of this transition remain hypothetical with evidence based on ancient marine sediments. With little information about how the PETM’s climate changed life on earth, the research team used globally distributed fossil pollen preserved in ancient rocks to reconstruct how terrestrial vegetation and climate changed. during this period, allowing them to reconstruct both ancient floral communities and past climates.

“To understand how terrestrial vegetation changed and moved during this time, we used a recently developed approach based on fossil pollen preserved in ancient rock deposits. It uses the distinct, species-specific appearance of pollen grains seen through a microscope,” Korasidis explained.

“Pollen’s distinct appearance evolved to aid the pollination strategies employed by plants. Because each species has unique pollen, this means we can compare fossil pollen with modern pollen to find a match – as long as the family of plants has not disappeared.

“As a result, fossil pollen can be confidently assigned to many modern plant families. Each of these modern plants has specific climatic requirements, and we assume that their ancient relatives needed a similar climate.

The research team collected fossil samples from 38 PETM sites on every continent except Antarctica. Analysis of pollen samples showed that PETM plant communities were distinct from pre-PETM plant communities at the same sites.

These changes in floral composition caused by mass plant migrations indicated that the changes in vegetation resulting from climate change were global. Plants can migrate more than 500 meters each year, which means they can move great distances for thousands of years.

The study found that in the northern hemisphere, the bald cypress swamps of Wyoming in the United States were suddenly replaced by seasonally dry subtropical forests dominated by palm trees. Similarly, in the southern hemisphere, humid temperate podocarp forests have been replaced by subtropical palm forests.

This meant that the PETM brought warmer and wetter climates towards the poles in both hemispheres, but seasonally warmer and drier climates at mid-latitudes.

The research team worked with Dr. Christine Shields of the US National Center for Atmospheric Research and Dr. Jeffrey Kiehl of the University of California to run climate model simulations and determine the geographic extent of these changes. These simulations closely matched the climate data the researchers had found in their pollen study.

Applying the findings to the current climate crisis, Korasidis said rising CO2 levels today could lead to the release of more stored carbon into the atmosphere, leading to mass changes in vegetation.

“Understanding this massive change to our planet that has occurred as a result of global warming gives us insight into our potential future. Are we ready to physically leave our homes, as these ancient forests did, to adapt to climate change or can we work together now to avoid the adverse consequences of a warming world?” Korasidis concluded.

Image: The research uses the distinct, species-specific appearance of pollen grains seen through a microscope. Credit: University of Melbourne

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