The Asteroid That Killed the Dinosaurs Created the Amazon Rain Forest

https://www.scientificamerican.com/article/the-asteroid-that-killed-the-dinosaurs-created-the-amazon-rain-forest/

Fossilized pollen and leaves reveal that the meteorite that caused the extinction of nonavian dinosaurs also reshaped South America’s plant communities to yield the planet’s largest rain forest

Dinosaur and fossil aficionados are intimately familiar with the meteorite strike that drove Tyrannosaurus rex and all nonavian dinosaurs to extinction around 66 million years ago. But it is often overlooked that the impact also wiped out entire ecosystems. A new study shows how those casualties, in turn, led to another particularly profound evolutionary outcome: the emergence of the Amazon rain forest of South America, the most spectacularly diverse environment on the planet. Yet the Amazon’s bounty of tropical species and habitats now face their own existential threat because of unprecedented destruction from human activity, including land clearing for agriculture.

The new study, published on Thursday in Science, analyzed tens of thousands of plant fossils and represents “a fundamental advance in knowledge,” says Peter Wilf, a geoscientist at Pennsylvania State University, who was not involved in the research. “The authors demonstrate that the dinosaur extinction was also a massive reset event for neotropical ecosystems, putting their evolution on an entirely new path leading directly to the extraordinary, diverse, spectacular and gravely threatened rain forests in the region today.”

These insights, Wilf adds, “provide new impetus for the conservation of the living evolutionary heritage in the tropics that supports human life, along with millions of living species.”

Carlos Jaramillo, a paleobiologist at the Panama-based Smithsonian Tropical Research Institute and co-lead author of the study, agrees that the meteorite’s evolutionary and ecological effects hold implications for today’s rapid, human-caused destruction of the Amazon rain forest and other key habitats across the planet. “We can relate this to nowadays,” he says, “because we’re also transforming landscapes, and that lasts forever—or at least a very long time.”

Modern-day rain forests are integral to life on Earth. The Amazon, in particular, plays a crucial role in regulating the planet’s freshwater cycle and climate. Yet Western European and North American paleontologists have paid little attention to tropical forests, focusing instead on temperate latitudes. Many academic and amateur fossil hunters have also tended to write off warm, wet locales as a lost cause for finds because they have assumed that conditions there would prevent organic materials from being preserved long enough to fossilize. “It’s this combination of factors that has led us to this absence of much data in the tropics,” says Bonnie Jacobs, a paleobiologist at Southern Methodist University, who co-authored a contextualizing essay that was published with the new study in Science.

Scientists already knew that the effects of the meteorite collision and its aftermath—at least in temperate zones—varied with local conditions and distance from the Chicxulub impact crater in Mexico’s Yucatán Peninsula. New Zealand forests, for example, escaped relatively unscathed. But researchers have had no idea how the event changed the tropical rain forests of Africa or, until now, those of South America. [ … ]

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Author: torpedo


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