A recent study published in Science reveals that the asteroid that wiped out the dinosaurs 66 million years ago also triggered the formation of tropical rainforests in Colombia and across South America.
At the end of the Cretaceous period, a 12-kilometer-wide asteroid struck Earth in what is now Mexico’s Yucatán Peninsula. The impact caused one of the most significant mass extinctions in the planet’s history, wiping out 75% of all life on Earth.
This cataclysmic event not only brought an end to the non-avian dinosaurs but also radically reshaped terrestrial ecosystems—ultimately giving rise to the dense tropical rainforests that now define regions like Colombia.
The asteroid that killed the dinosaurs and transformed open forests into rainforests in Colombia
Before the impact, the tropical forests of what is now South America were open and luminous, dominated by conifers, ferns, and sparsely distributed flowering plants.
The asteroid strike drastically altered this landscape. According to the study led by scientists from the Smithsonian Tropical Research Institute, 45% of plant species in what is now Colombia went extinct after the impact.
This catastrophic event paved the way for flowering plants (angiosperms) to proliferate, transforming the forests into the dense, shadowy jungles we know today.
The research team analyzed over 50,000 fossil pollen samples and 6,000 fossil leaves from Colombia, covering a period spanning 10 million years before and after the impact.
Subsequently, the team assessed overall forest plant diversity, dominant species, insect-plant interactions, and tracked how these factors evolved over time.
These fossils reveal a significant shift in tropical forest composition and structure. Following the event, jungles became denser and more humid, with increased diversity of flowering plants and the emergence of new ecological interactions such as insect pollination and seed dispersal by animals.
The reasons for this transformation aren’t entirely clear. The region’s climate at the end of the Cretaceous, 66 million years ago, was similar to today’s—warm and humid. But other factors likely played roles.
The study states that enormous herbivorous sauropods (long-necked dinosaurs) would have helped maintain open clearings, allowing light to penetrate.
After the asteroid impact, these dinosaurs disappeared. The extinction of certain plant families due to the impact may also have contributed, the paper adds.
A third probable factor was a change in the chemical composition of forest soil. Frequent rains during the warm, humid Cretaceous period leached many nutrients from the soil, which would have favored gymnosperms like conifers.
The formation of the Amazon rainforest
This ecological shift didn’t only affect what is now Colombia; it had implications across all of South America. The transformation of open woodlands into dense rainforests laid the foundation for the formation of the Amazon rainforest, the planet’s most biodiverse terrestrial ecosystem.
The evolution of these rainforests has been crucial for regulating the global climate and conserving a vast number of species.
Studying how a catastrophic event gave rise to modern tropical rainforests offers valuable lessons about ecosystem resilience and transformation.
In the context of climate change and biodiversity loss, understanding these historical processes can inform strategies for conservation and sustainable management of tropical forests.
“A single historical accident changed the ecological and evolutionary trajectory of the tropical rainforests,” states Carlos Jaramillo, a paleopalynologist (specialist in ancient pollen) at the Smithsonian Tropical Research Institute in Panama City.
“The forests we have today are actually the byproduct of what happened 66 million years ago,” the scholar stated.
The asteroid impact that wiped out the dinosaurs didn’t just mark the end of an era; it also initiated another one, characterized by the exuberance and diversity of tropical rainforests. Colombia, with its rich biodiversity and vast rainforests, is a living testament to how life can re-emerge and adapt after large-scale events.
Colombia’s participation in the study on the consequences of the asteroid impact
Finding traces of the asteroid impact in Colombia and answering how this event affected the tropics, the planet’s most biodiverse region, was a task undertaken by Colombian scientists Felipe de la Parra and Carlos Jaramillo since the early 2000s.
“In the Northern and Southern Hemispheres, it had been documented that about 35% of plants went extinct, but we didn’t know what had happened in the tropics. We were interested in understanding whether extinction levels were higher or lower and how tropical vegetation had responded,” explains De la Parra.
The study also examined insect feeding marks on fossil leaves, revealing that after the impact, ecological interactions changed significantly. Herbivorous insects shifted from being specialists to generalists, adapting to the new plant diversity.
“When the extraterrestrial body impacted the Yucatan Peninsula, it melted the rocks it struck, and many fragments were ejected at high speeds into the atmosphere. As these fragments fell, they solidified and formed millimeter-sized, rounded or oval structures known as impact spherules. These have been found in many parts of the world,” explains De la Parra.
This finding highlights Colombia’s importance as a natural laboratory for understanding the evolution of tropical ecosystems and how catastrophic events can give rise to new forms of life.
Furthermore, it provides valuable insights into the capacities of tropical forests in the face of extreme climatic and environmental changes, such as those occurring during the planet’s current evolution.