Dinosaurs and fossil lovers are very familiar with meteorite attacks, which wiped out Tyrannosaurus and all non-avian dinosaurs, about 66 million years ago. But people often ignore this impact and wipe out the entire ecosystem. A new study shows how these casualties led to another particularly profound evolutionary result: the emergence of the Amazon rainforest in South America, which is the most spectacular environment on earth. However, due to the unprecedented destruction of human activities (including land clearing for agriculture), the rich tropical species and habitats of the Amazon are now facing their own survival threats.
Peter Wilf, a geoscientist at Pennsylvania State University, said that the new study, published in the journal Science on Thursday, analyzed thousands of plant fossils and represented “a fundamental advancement in knowledge.”
Wilf added that these insights “provide new impetus for the protection of the tropical biological evolutionary heritage and millions of biological species that support human life.”
Carlos Jaramillo, a paleontologist at the Smithsonian Tropical Research Institute in Panama, is a co-author of the study. He believes that the evolution and ecological effects of meteorites have an impact on the current man-made Amazon rainforest and other major habitats. The rapid destruction of the land is of great significance. On the whole earth. He said: “We can connect it to the present, because we are also changing the landscape and it can exist forever, or at least it can last for a long time.”
Analysis of approximately 50,000 pollen grains and 6,000 fossil leaves shows that meteorites that wiped out non-avian dinosaurs also created the Amazon rainforest.
Read | The world’s first well-preserved dinosaur fossil found in China, with fossilized embryos on it
The modern rainforest is an indispensable part of life on earth. In particular, the Amazon River plays a vital role in regulating the earth’s fresh water circulation and climate. However, paleontologists in Western Europe and North America paid little attention to tropical forests, and only focused on temperate regions. Many academic and amateur fossil hunters also tend to log off warm and humid places because they believe that the conditions there will prevent organic matter from being preserved long enough to be fossilized, thus becoming a reason for people to look for lost objects. Bonnie Jacobs, a paleontologist at Southern Methodist University, said: “It is the combination of these factors that has caused us to lack a lot of data in the tropics.”
Scientists already know that, at least in temperate regions, the impact of meteorite collisions and their consequences varies with local conditions and the distance from the Chicxulub impact crater on the Yucatan Peninsula of Mexico. For example, the forests of New Zealand escaped relatively loosely. But researchers don’t know how this event changed the tropical rain forests in Africa, or until now, it has changed the tropical rain forests in South America.
Jaramillo and most of his co-authors are from Colombia, and he particularly wants to study the origin of the tropical forests in his native country. He conceptualized the new research as an undergraduate student, representing nearly 12 years of hard work. He said: “It took us a long time because we had to start from scratch.”
The entire tree is almost never preserved in the fossil record, so Jaramillo and his colleagues turned to fossil pollen and leaves for insight. Pollen is well preserved over time and is widely spread in the fossil record. Just like leaves, there are differences in morphology between species, which helps researchers determine which plants lived in ancient habitats.
Jaramillo and his colleagues searched for rocks formed in the late Cretaceous period (before meteorite impact) in 53 locations in Colombia, and other rocks formed in the subsequent 10 million years (Paleogene). rock. The research team gathered and analyzed about 50,000 fossil pollen grains and 6,000 fossil leaves from these rocks to characterize the types of plants that make up them. The latest independent findings indicate that plant leaves that receive more light have a higher vein density and a higher proportion of the natural isotope carbon 13. Researchers studied these characteristics in these fossils to sort out the past structural forests in the area.
Also read | Comet from the edge of the solar system killed dinosaurs: study
Their discovery portrays the sudden, catastrophic death of life after the impact, but it also portrays the phoenix-like rebirth millions of years later. The author determined that before the meteorite occurred, there were many coniferous trees and bright open canopies in the forests of South America, supporting dense fern forests. Dinosaurs may play a key role in maintaining these Cretaceous forests by knocking down trees and clearing vegetation. However, at the moment of the impact of the Chicxulub meteorite, this ecosystem has undergone irreversible changes. The fire, which may have been burning for several years, engulfed the southern forests of South America. According to the authors’ calculations, along with many of the animals they supported, a total of 45% of tropical plant species on the continent have disappeared.
It took six million years for the forest to return to its pre-meteorite diversity, and the slow-growing species is completely different from before. Leguminous plants-plants that form a symbiotic relationship with bacteria that can make them fix the nitrogen in the air-appear first, and they enrich the originally poor soil. The influx of nitrogen and the phosphorus in the limestone allowed other flowering plants to thrive beside legumes and replaced conifers. When flowering species competed for light, they formed a dense leaf canopy and created the layered Amazon rainforest as we know it today, characterized by a productive mulch at the top and a dark underforest at the bottom.
Regan Dunn, a paleoecologist at the La Brea Tabet Pit and Museum in Los Angeles who was not involved in the new study, agreed that his discovery is not only the key to revealing the past, but also bringing current man-made threats into perspective. The essential. She specifically pointed out the author’s calculation that 45% of plant species will become extinct after the meteorite impact, because “current estimates indicate that in the next 30 years, at least so many plant species will be affected only by human activities in the Amazon River Basin. Global threats.”
“The question remains: How will human influence permanently change the composition and function of the Amazon forest?” Dunn said.
Jacobs said the new findings show how mass extinctions can change “every process.” She added that today we are in another such event, but this event is driven by a species, and likened to volcanic crater “everywhere” “because humans are everywhere”.
Jacobs said that unlike previous mass extinctions, this time “we are not powerless to stop it.”