The asteroid that kills dinosaurs probably created the Amazon rainforest

About 66 million years ago, a 12-kilometer asteroid hit Earth. The tremendous heat and shock probably set off tidal waves and clouded the sky with ash, The Washington Post reported. Scientists estimate that up to 75 percent of all life on land, including dinosaurs, has become extinct.

The space rock that triggered this mass extinction event is also a likely reason why we have the Amazon rainforest, new research suggests. Published in the prestigious journal Science, research shows that the same asteroid that killed the dinosaurs gave birth to all the tropical rainforests on Earth.

“A global catastrophe involving mass extinction creates a different world,” Bonnie F. Jacobs and Ellen D. Currano wrote in an article accompanying the study.

Mónica Carvalho, co-author of the study from the Smithsonian Institution for Tropical Research (STRI) in Panama, examined tens of thousands of fossils in Colombia to understand how plant life in Central and South America changed before and after the impact, Nerdist reported. Her team found that the type of vegetation consisting of the continent’s forests had changed drastically from before and after. Before the fall, widespread conifers and ferns filled the region, transmitting large amounts of light, The Post reported.

After an asteroid impact, many species became extinct, especially seed-bearing plants. The researchers found that plant diversity declined by about 45 percent after exposure. By researching more than 50,000 records of fossil pollen, the team found that flowering plants called angiosperms prevailed during forest recovery over the next six million years. They filled in where other species became extinct, leading to a “flower rule,” the STRI press release said.

The impact has also changed the spatial structure of forests, from widely distributed to densely packed. Leaf data from more than 6,000 fossils show that the dense, dense tropical canopy associated with today’s rainforests did not develop until after the impact. The data suggest that the spatial change from “relatively open to closed and layered … has led to increased vertical stratification and greater diversity of plant growth forms,” News18 reports. As the trees grew taller and closer, they partially blocked the sun, allowing different types of flowering plants to bloom, the Post reports. This is how the most diverse terrestrial ecosystem developed – tropical rainforests teeming with bright bromeliads and abundant orchids – the study suggests.

As to why, researchers have offered three theories: dinosaurs kept the forest open and sparse by feeding on plants and trampling them; ash-enriched soils, giving preference to faster-growing flowering plants; and the preferential extinction of conifers created an opportunity for plants to take over flowering plants.

Although scientists aren’t sure which theory, or combination of theories, created modern rainforests, Carvalho concluded with one key to take away: “The lesson learned here is that under rapid disturbances … tropical ecosystems don’t just bounce back, they’re replaced, and the process takes a really long time. “

Changes in plant species and tree density have also affected the past and present climate, the STRI statement added. Tropical rainforests, and especially the Amazon, are some of the most important abysses on the planet. By absorbing greenhouse gases, trees help combat the climate crisis and keep the Earth habitable.

“Less pre-impact forest canopies, with fewer flowering plants, would transfer less soil into the water into the atmosphere than those that grew up millions of years after,” STRI explained. This increased humidity and cloud cover, making the area much more productive, Wired reported.

Legume trees, the dominant feature of today’s tropical rainforests, also entered the fossil record after the impact. These trees, with the help of symbiotic bacteria at the root, fix nitrogen to the soil, Wired reported. Without these shifts in forest spacing and composition, today’s climate could develop differently.

Researchers hope the new study can help scientists understand how today’s rainforests will respond to the rapidly changing climate that currently threatens their existence.

According to Wired, Carvalho also warned, “The changes we are seeing today in relation to climate and deforestation are so rapid that we have not actually seen them in any other scenario in the history of the planet. Extinction is something that is happening very fast.”

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