66 million years ago an asteroid wiped out a little more than 75% of the population of living beings that inhabited the planet at that time. This story also became known because it led to the extinction of the dinosaurs. However, one of the enigmas that has surrounded this situation has been that of the plants.
Debate: K-Pg Extinction's Plant Impact
Although many years have passed, a debate still persists in the scientific world and that is how the Cretaceous-Paleogene (K-Pg) extinction affected plant life on earth, mainly plants. This is because, in part, global studies of the fossil record have shown that no major plant family went extinct.
However, a new analysis of fossil data points to another result. A group of researchers concluded that this asteroid did cause a true extinction in plant life on Earth, which reached 50% of the species.
They reached this conclusion based on new fossils from Colombia, Argentina and the United States, which provided a broader geographic range to study the severity, ecosystem effects and legacy of the event on plant life.
Peter Wilf, professor of geosciences at Pennsylvania State University and lead author of the study, noted in a statement that “there has been a tendency in the literature to say that maybe this event was bad for dinosaurs and a lot of marine life, but it was good for the plants because the main groups survived.”
For the geoscientist, understanding what happened to ancient plants during the extinction requires adequate collections of fossil plants. However, they were limited to the effects of this meteorite based on a few collections from areas in the United States. For this reason, the data found in Colombia, Argentina and the United States were decisive.
Solid sampling and rock layers needed
Wilf highlighted that “really solid sampling is needed and knowing where the rocks with plant fossils are,” adding that “differences in DNA between living plants will not tell us anything about species extinctions in deep time. You need plant fossils from before and after. You need rock layers that show extinction. And the more indicators you have, the more complete your story will be.”
Using this information as a starting point, the researchers reviewed emerging fossil data from North Dakota, Colorado and New Mexico in the United States and from Colombia and Argentina. In data published in the journal Cambridge Prisms: Extinction, they highlighted that they found that there was a significant loss of plant species, greater than 50% at each site.
But why was it not clear about the impact of this meteorite on plant species? The answer that the geoscientist has is that, for example, in the case of dinosaurs they were less diverse and abundant than plants and, therefore, it was much easier to exterminate almost all the main categories of them.
Real plant extinctions, significant evolutionary impact
In the case of plants, he added, “these species extinctions were real and very significant. “In every place we looked where the record is preserved, there were enormous losses of plant species, followed by an astonishing series of evolutionary events that made our modern world what it is.”
What Wilf is referring to is that the study found that this extinction marked the beginning of the emergence and dominance of flowering plants and helped establish the planet's rainforests that are home to most of its biodiversity.
One such example was explained by Mónica R. Carvalho, assistant professor at the University of Michigan and co-author of the study: “fossils show that post-extinction tropical forests were profoundly different from their predecessors in composition, structure and ecology.”
In other words, the researchers found that, in the places studied, the extinction event had a transformative impact on plant life and terrestrial ecosystems.
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