How a Two-Million-Year Rainstorm Set the Stage for the Reign of Dinosaurs

Life usually evolves under the least expected circumstances, but always finds a way

I once told a good friend that I got migraines right before the rain was about to hit. She looked at me in disbelief; she thought that wasn’t even possible.

However, a few years later, something strange happened that made us reconsider her take. I was at work when a strange feeling hit me. My brain was foggy, and I started feeling this urge to get into bed immediately. It was 2 p.m., and I wasn’t supposed to finish work until 5 p.m. By 3 p.m., the feeling was unbearable, so I just left. Maybe I was coming down with some virus.

As soon as I got home, I closed all the curtains and curled in bed as if it was 10 p.m. Two hours later, I was awakened by the craziest storm I had ever seen. Streets looked like rivers, and thunders overlapped. I couldn’t see the houses across the street. Had I stayed at work, it would have hit me on my way home and trapped me in a metro station for hours. Did I know this was coming? Are our instincts tuned to these events?

Whatever the answer, something is certain: I wouldn’t enjoy living in a place where it rains almost every day. However, what if Earth was in that place with heavy rain? Well, it happened for two million years. As a result, life on Earth changed forever.

This prolonged wet period, known as the Carnian Pluvial Episode (CPE), occurred around 230 million years ago during the Late Triassic period (between 237 and 201.4 million years ago). The most important thing? It brought significant changes to the planet’s climate and ecosystems, setting the stage for the age of the dinosaurs.

But why? Before this event, Earth was a different place. The supercontinent Pangaea dominated the landscape, with extensive deserts stretching across its interior. The climate was arid and inhospitable, with little room for the kind of lush environments we often associate with the Mesozoic era’s giant reptiles.

Life was rebounding from the Permo-Triassic mass extinction, the most severe extinction event in Earth’s history. It had wiped out about 80–90% of species, and the few survivors struggled to fill the empty ecological niches.

Then came the rain. The CPE was marked by a dramatic shift in climate, where a prolonged period of increased rainfall transformed the arid landscapes into more humid environments. This wasn’t just a series of heavy showers; it was a major, long-term change that lasted for a couple of million years. Yes, you read it right: a rainy season of 2 million years.

This wet phase led to the expansion of lush, green forests and the creation of new, diverse habitats, offering a wealth of opportunities for life to adapt and evolve.

However, this rainy period was crucial for the early dinosaurs and their close relatives. Here’s why.

At the time, dinosaurs were just one of many groups of reptiles living on Earth. Yes, many other dinosaur-looking creatures roamed the Earth alongside them. In fact, dinosaurs were not yet the dominant force they would become later in the Mesozoic.

However, the increase in rainfall and the subsequent changes in vegetation created new niches for these creatures to explore. As forests expanded, early dinosaurs began to diversify, exploiting these new environments and resources.

Interestingly, the rain didn’t just benefit the dinosaurs. It also helped shape the ecosystems that supported their evolution. The increased moisture led to the flourishing of plant life, particularly ferns and other primitive plants that thrived in wet conditions.

This growth of vegetation not only provided food for herbivorous dinosaurs but also helped to stabilize the soil and create more complex habitats. With these changes, the dinosaurs had the opportunity to evolve into various forms, from small, agile hunters to large herbivores and everything inbetween.

However, one of the most fascinating aspects of CPE is how it sets the stage for what comes next. The changes in climate and vegetation during this period didn’t just create a temporary boom for the dinosaurs; they helped establish the conditions that would allow these reptiles to evolve and diversify during the Jurassic and Cretaceous periods. So, by the time the CPE ended, dinosaurs were well on their way to becoming the dominant terrestrial vertebrates.

What’s also interesting is how the CPE acted as a sort of evolutionary pressure cooker. The sudden influx of rain and the resulting environmental changes created a dynamic and ever-changing landscape. Species had to adapt quickly to survive, leading to rapid diversification and the emergence of new characteristics.

For dinosaurs, this meant developing new ways of moving, feeding, and interacting with their environment. These adaptations would later give them the edge over other groups and help them thrive for the next 170 million years. Can you think of more prominent butterfly effects?

However, it’s important to note that the rise of the dinosaurs wasn’t just about outcompeting other groups. In recent years, the traditional view of dinosaurs as evolutionary conquerors, outpacing their rivals because, well, they simply were superior, has been challenged.

Instead, their success seems to have been a combination of being in the right place at the right time and having the right set of adaptations to take advantage of new opportunities. The CPE provided those opportunities, reshaping the environment in ways that favored the dinosaurs and allowed them to flourish.

So, the next time you think about dinosaurs (which, in my case, is more often than I want to admit), remember that their story began with a period of relentless rain.

This two-million-year wet spell was a turning point in Earth’s history, creating a world where dinosaurs could not just survive but thrive. It was a game-changer that transformed arid landscapes into thriving ecosystems, setting the stage for one of the most successful groups of animals the planet has ever seen.

Oh, are you curious about what caused these 2 million years of increased rainfall? Read this fresh-out-the-press story to learn more!

What Triggered the Two-Million-Year Rain That Made Dinosaurs Possible?

And what lessons can we learn from that event?