About 56 million years ago, Earth already experienced major climate change. The release of large amounts of carbon into the ocean and atmosphere caused a 5° to 8°C increase in global temperatures and a rise in sea level. This event, called the Paleocene-Eocene Thermal Maximum (PETM),occurred over several tens of thousands of years, but the causes and consequences of this transition are still the subject of much debate.
Among the most likely causes of this massive release of carbon into the atmosphere and oceans are, Massive volcanic activity in the North Atlantic, as well as the melting of Antarctic permafrost or the sudden release of methane from the bottom of the ocean.
The main evidence of this ancient climate change comes mainly from ancient marine sediments, but we also need to understand what happened on land to deepen our understanding of this period and predict what might happen from current climate change.
for him, To reconstruct how terrestrial vegetation and climate have changed, a research team analyzed fossil pollen scattered across the planet and preserved in ancient rocks. During this time.
Research led by Vera Korasidis of the University of Melbourne and Scott Wing of the Smithsonian Institution’s National Museum of Natural History and published in the journal Science Paleoceanography and Paleoclimatology, It shows that an increase in atmospheric CO2 concentration plays an important role in changing Earth’s climate and life. vegetable.
The study authors believe we may see a similar increase in the coming centuries as a result of anthropogenic (human-induced) increases in CO2 emissions.
Conserved in rocks for tens of millions of years, pollen makes it possible to reconstruct both ancient flower communities and past climates. “We have applied this approach all over the world, Fossil samples from 38 Paleocene-Eocene Thermal Maximum (PETM) regions from all continents, Except for Antarctica. This new pollen analysis shows that PETM plant communities differ from those that existed before PETM in the same regions,” says Korasidis.
These changes in flower composition due to large plant migrations suggest that climate change is causing global transformations in vegetation, but plant species involved vary by region.
Plants move, and with them animals
“When we talk about plant migration, we mean Movement of plants, as scattered seeds grow better in one place or climate than others. In this case, they perform better at higher, colder latitudes than at lower, warmer latitudes,” he added.
Plants can migrate more than 500 meters each year, so they can travel great distances over thousands of years.
In the northern hemisphere, for example, the bald cypress swamps of Wyoming in the USA were suddenly replaced by subtropical seasonal dry palm forests. Similarly, in the southern hemisphere, humid temperate podocarp forests have been replaced by subtropical palm forests.
These factory displacements show: PETM brought warmer, wetter climates towards the poles and seasonally drier climates towards the mid-latitudes in both hemispheres.
Climate model simulations were also run to explore the geographic extent of these changes. These simulations closely matched the climate data obtained in the pollen study, including the expansion of temperate climates towards the poles at the expense of cold climate types, as well as the expansion of temperate and tropical climates in the mid-latitudes.
HE IS allows to draw lessons for the time being“If current CO2 levels continue to rise, warming and thawing of permafrost could release more stored carbon into the atmosphere, just as it did 56 million years ago, and we will again see these massive changes in vegetation in response to dramatic changes in local climate. conditions”, drew the attention of the researcher.
The migratory ability of vegetation will depend on many factors, including the pace of climate change and the availability of suitable migration sites for these plants.
However Wherever plants go, the animals that depend on them will go, and in many cases this includes humans.scientists remind This has implications for the ability to grow or grow crops in certain regions as agriculture and global warming progress.
Understanding this global change occurring on our planet as a result of a warmer climate provides insight into our future potential. Vera Korasidis, “Are we ready to physically move from our homes to adapt to climate change, as these ancient forests have done, or can we work together now to avoid the negative consequences of global warming?” he asks.
Reference work: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021PA004325
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