What ancient pollen can tell us about climate change in future

Earth’s climate experienced a major climatic shift 56 million years ago. The ocean and atmosphere saw a huge release of carbon, which in turn raised atmospheric carbon dioxide (CO).₂) concentrations—which meant temperatures going up by 5 to 8°C and rising sea levels.

Do you sound familiar?

This event, called the Paleocene–Eocene Thermal Maximum (PETM), happened over the course of a few tens of thousands of years, but the causes and consequences of this transition are still widely debated.

The major causes of the large carbon release are, according to some theories, volcanic activity in North Atlantic, sudden release of methane at the ocean floor, and melting of permafrost in Antarctica.

The PETM is based mainly on evidence from ancient marine sediments. However, if we take these periods as a guide to what might happen in the future, it will be difficult to determine what they might have to do with our current knowledge. ClimateChange is a crisis. We need to understand the land.

There is not much information available about how the PETM climate has affected land life. Our research team used global distributed data sources to gather this information. fossil pollenThese ancient rocks have been preserved to reconstruct how terrestrial vegetation and climate changed during this period.

Our new research, which was led by me and Dr. Scott Wing at Smithsonian National Museum of Natural History’s Department of Paleobiology, was published in the journal Paleoceanography & PaleoclimatologyThis shows that the atmospheric CO concentration has increased.₂Played a major part in changing Earth’s climate.

As a result of human-caused increases in CO2, we could see a similar increase over the next century.₂.

We used a newly developed method based on fossil pollen found in ancient rock deposits to understand how terrestrial vegetation changed over this period. It uses the distinct appearance of pollen grains, which can be seen through a microscope.

The distinctive appearance of pollen was created to aid in the implementation of pollination strategies. Plants. Because each species has unique pollen, it means we can compare fossil pollen with modern pollen to find a match—as long as the plant familyIt hasn’t disappeared.

Fossil pollen can therefore be confidently assigned for many modern plant families. Each modern plant has its own climatic requirements. We assume that their ancient relatives had similar climates.

We did not collect data from any plant groups that we knew were evolving after the PETM in order to increase our confidence in this assumption. These species might not have settled in the same climate preferences as they do today.

We can reconstruct past climates and ancient floral communities by using pollen that has been preserved in rocks for tens or millions of years.

This is the first time that we have used this approach globally to fossil samples taken from 38 PETM sites across all continents, with the exception of Antarctica. This new pollen analysis reveals that PETM plant communities are different from pre-PETM plant communities at these same sites.

These changes in floral composition are a result massive plant migrations. However, the types of plants involved vary by region.

When we say plant migration we mean plant movement, as the seeds that are spread grow better in one place and climate than in another—in this case at higher, cooler latitudes over lower, warmer ones.

Plants can travel over 500m per year, so they can travel great distances over thousands of years.

In the Northern Hemisphere, for example, the bald cypress swamps of Wyoming, USA were suddenly replaced by subtropical palm-dominated, seasonally dry forests. Similar happened in the Southern Hemisphere where wet-temperate podocarp trees were replaced with subtropical palm forests.

We assigned each species a category based on climate, called a Köppen climate type. Examples of this are tropical rainforest, arid Desert, temperate summer, and polar tundra.

This shows that the PETM brought warmer and drier climates towards the poles of both hemispheres but a warmer and dryer climate to the mid-latitudes.

We worked with Dr. Christine Shields of the US National Centre for Atmospheric Research, and Dr. Jeffrey Kiehl of the University of California to explore the geographic extent of these shifts. Climate model simulations were also conducted.

These simulations were created using data from Community Earth System Model (version CESM1.2).

These simulations closely matched climate data we found in pollenThis includes the expansion and maintenance of temperate climates, at the expense of colder climate types towards the poles, as well as the expansion and maintenance of temperate or tropical climates in the mid-latitudes.

So, if your current CO₂As temperatures rise and melt permafrost, which could release more carbon to the atmosphere, as it did 56 million years ago. We will again see mass shifts in vegetation due to dramatic climate changes.

The ability of vegetation to migrate depends on many factors, including climate change speed and availability of suitable migration areas.

Where the plants go, so too will the animals that rely on them (if they can)—perhaps in some cases humans included.

Understanding the huge shifts in climate and our potential future gives us insight into our future. Are we ready to move out of our homes to adapt to climate change, as these ancient forests did? Or can we work together to mitigate the negative effects of a warming planet?