These were the unlikely survivors after the dinosaurs became extinct

    Abdulaziz Sobh

    When an asteroid struck Earth 66 million years ago, it unleashed a violent force millions of times more massive than an atomic bomb. Known as the fifth mass extinction event of the Cretaceous-Paleogene, it annihilated three-quarters of all plant and animal life on Earth, including dinosaurs. A new study suggests that the impact also decimated the Earth's forests, leading to the extinction of all the birds that lived in the trees. But in a twist, the valiant survivors in the fiery aftermath turned out to be ferns and resistant birds, living on the ground. The study was published Thursday in the journal Current Biology. Scientists also refer to the event as the impact of K-Pg Chicxulub because it created the Chicxulub crater in what is now Mexico. During the initial impact, shockwaves swept the trees in massive waves within a radius of almost 1,000 miles. But what followed was probably even worse for the initial survivors of this apocalyptic event. The intense heat generated by the impact would have caused global forest fires, devastating what was left of the forests. Steam, rich in sulfates, triggered the acid rain. The soot obstructed the atmosphere, which affected the photosynthetic activity that the plants needed to survive or grow back. This lasted for years, which prevented the global climate from cooling. Not only did the forest canopy collapse, they could not grow back. Any bird that landed or landed on a tree would have been left homeless. The chances of surviving the asteroid were already slim for the birds that live in the trees; the elimination of their habitat guarantees extinction. Researchers from the United States, England, and Sweden studied the fossil record from North America to New Zealand, closely observing carbon debris from trees, fossilized pollen and fern spores, and bird fossils. The combination of samples provided a broader picture of what the world was like after the impact. "For me, it is really exciting to see that the combination of knowledge from the fossil record of birds and the fossil record of plants allows us to reconstruct a large macroevolutionary history that took place more than 66 million years ago," Daniel Field, lead author of the studio and evolutionary paleontologist at the Milner Center for Evolution at the University of Bath, he wrote in an email. "He talks about the power of collaborative science and the importance of the fossil record to understand life in the modern world." A dangerous life on the ground The land birds that survived would not have had an easy existence. It is likely that the smallest birds that live in the soil experience a catastrophic loss. They probably lived on the toughest grains and seeds that survived the impact, as well as the insects. Many small-bodied birds today eat insects, and this trait can be traced back to surviving birds 66 million years ago. "I think any surviving bird would have been pretty skinny for a few years immediately after the impact of the asteroid," Field said. Their fossils reveal that the birds that lived on the ground had long, sturdy legs, like those of a kiwi or an emu, nothing like the delicate legs of the birds that perch. They can be compared to the current relatives of ostriches and emus that live in Central and South America, they are small, corpulent, flying and living on the ground. Being small, flying and living on the ground were probably all the features that would have favored survival through the mass extinction event, Field said. But the land birds that survived had a lasting legacy beyond the tinamús. "Today, birds are the most diverse and globally widespread group of terrestrial vertebrates: there are almost 11,000 living species," Field said in a statement. "Only a handful of ancestral lineages of birds managed to survive the mass extinction event 66 million years ago, and all the amazing diversity of living birds today can be traced back to these ancient survivors." The ferns were also the great survivors, unlike the trees, because their tiny unicellular spores dispersed quickly. Spores are much smaller than seeds, and can easily grow in a damp area. Ferns are usually among the fastest plants to return after a natural disaster."The spores are very small: I could place four in a single strand of hair," study co-author Regan Dunn, a paleontologist at the Field Museum in Chicago, said in a statement. So how long would it take for the ferns to thrive? They can colonize an area quickly, but it still takes time. "It may have taken about 100 years for the 'fern peak' to begin, and about 1,000 years for forest communities to recover," Field said. "Once the forests returned, the ancestors of the modern birds that live in the trees could, and did, move to the trees." In a couple of million years after the impact of the asteroid, we have direct evidence of birds tree fossils. " The past could reflect the future Studying complete paleoecosystems shows how life on Earth has evolved through all the trials and tribulations of the past, Dunn said in an email. But it is also incredibly important to study what happened during the fifth mass extinction because many scientists believe that we are entering the sixth mass extinction. "Human activity is causing deforestation on a massive scale," Field said. "We know that the diversity of bird communities is affected by the availability of forests: when forests are cut down in favor of, for example, palm oil monoculture, bird diversity is reduced. This type of deforestation continues without decreasing, it will leave an indelible signature on the evolution of the life of the birds. " Dunn added, "By studying this event, we learn about what happened to biodiversity in the past after the destruction of Earth's ecosystems and how long it took for biodiversity to recover." On a human time scale, recovery is very long. Take these lessons seriously and act now to preserve today's profound biodiversity. "

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