Asteroid that wiped out dinosaurs probably helped produce rainforests

“A global catastrophe involving a mass extinction produces a different

world.”

— Bonnie Jacobs and Ellen Currano

Sixty-six million years ago, a gigantic asteroid crashed into Earth, wiping out all kinds of life and changing the trajectory of the planet.

It was bad news for dinosaurs. But in the tropical rainforest, their loss was flowers’ gain, a new study in the journal Science suggests.

An international team of researchers used tens of thousands of fossils to explore what happened to plant life in what is now Colombia after the impact. Their work reveals that the crash was probably responsible for the modern makeup of tropical rainforests.

The fiery crash is thought to have generated massive heat, triggered tidal waves and clouded over the sky. In the aftermath, as much as 75% of land-based life went extinct.

To figure out what the area was like before the fiery extinction event, the researchers studied leaf and pollen fossils from the region. They tell a story of two different forests. Although the region was wet and warm before the crash, it teemed with conifers and ferns, and the widely spaced trees let in large patches of light.

Afterward, the researchers say, 45% of plants in the area became extinct. Flowering plants took over, and the canopy became denser. The rainforest became more diverse and stratified from top to bottom. In the shadier sections below, a rainbow of flowering plants flourished.

How was such a dramatic change possible after such a disruptive event?

The researchers have three potential explanations. Perhaps dinosaurs’ migration and snacking habits had been responsible for keeping the forests open before impact. Ash from the asteroid blast may have enriched tropical soils and helped foster faster-growing flowering plants. Maybe conifers were simply more prone to extinction in an era of environmental chaos. Or maybe it was a mix of all three.

“A global catastrophe involving a mass extinction produces a different world,” write Bonnie Jacobs and Ellen Currano in an accompanying article. In this case, it was a rich and diverse one. But it also laid waste to a forgotten ecosystem that only exists in fossils today. The study is available at bit. ly/sciencemag-rainforest.