Climate And Biota Have Been Ecologically Connected For Millions Of Years

Rayshell Clapper for – Your Universe Online

According to Southern Methodist University paleontologists Timothy S. Myers, Louis L. Jacobs, and SMU sedimentary geologist Neil J. Tabor, the modern relationship between animals and vegetation is similar to millions of years ago.

In their study, the SMU scientists used fossil soils from the Late Jurassic age gathered from locations where animal fossils were previously found to determine the levels of carbon isotopes. The team used fossils gathered from North America, Europe, and Africa. The main problem with the study, though, is that few places in the world are well-sampled enough for terrestrial fossils, so Myers and his team discovered a new and creative use of an already existing method and already existing geological data.

To gather his results, Myers used a traditional method to estimate carbon dioxide in the ancient atmosphere, only he applied it to estimate the amount of carbon dioxide in ancient soils. To do this, the team took measurements from the nodules of calcite that take on the isotopic signature of the carbon dioxide gas around them. This comes from two sources: the atmosphere and the plants decaying in the soil.

Atmospheric carbon dioxide has a more positive isotope while the decaying plants have more negative isotopes. Therefore, more carbon dioxide from plants means a lusher, wetter environment, which is exactly what their research found.

Their method can be used for areas with pre-existing geological data, but it can also benefit areas where fossils are lacking. Through their comparisons of carbon dioxide in the fossil soils, the SMU team was able to determine what areas were lush with vegetation. In conjunction with vertebrate fossils, scientists would be able to determine the relationship between flora lushness and fauna.

As Tabor said, “Vertebrate paleontologists have been accumulating information about vertebrate fossils in Jurassic for well over 100 years.” So paleontologists could then use that to better understand the paleontology and geochemistry data to understand ancient ecosystems.

Myers and his team tested fossil data from the Upper Jurassic soil nodules gathered from the Morrison Formation in North America (spanning from Montana to New Mexico), Portugal, and a small sample from Central Africa. They predicted that they would see regional variations in plant lushness with the most in Portugal, followed closely by the Morrison Formation, and ending with the samples from Central Africa. They were correct in their hypothesis.

What they found based on these samples and their analysis was a more complete picture of the ancient ecosystems and landscapes including the climate. An interesting discovery through their research is that regional variability existed during the Late Jurassic in terms of the climate and the abundance of plants and animals across the planet. Prior to their findings, the Jurassic period was thought of as very warm and wet with lots of dinosaurs, and while that is true for some areas, it is not the absolute for the entire planet.

According to Myers, the result ““¦also illustrates that climate and biota have been ecologically connected for many millions of years and that future human-caused changes to global climate will have profound impacts on plant and animal life around the world.”

The findings from this research were reported in the article titled, “Estimating soil pCO2 using paleosol carbonates: implications for the relationship between primary productivity and faunal richness in ancient terrestrial ecosystems” published in Paleobiology, a publication of The Paleontological Society.

Image 2 (below): Nodules of ancient soil are fairly common in present day rock, forming as a result of seasonally dry conditions. They harden into mineralized clods, making them easy to spot and sample as they weather out of ancient soil profiles. Credit: Timothy S. Myers