Unraveling the Ordovician Mass Extinction: How 85% of Earth’s Life Vanished in an Extraordinary Event

When we think about mass extinctions, the K-Pg boundary comes to mind—a giant asteroid hit Earth, wiping out around 75% of life, including the dinosaurs. But there’s another significant extinction that predates this event by about 400 million years: the Late Ordovician mass extinction.

### Life in the Ordovician

Imagine a world very different from today. During the Ordovician period, around 485 to 443 million years ago, Earth had a warm climate and high CO₂ levels. Richard Twitchett, a researcher at the Natural History Museum in the UK, describes it as a time when the land was mostly void of recognizable animals or plants. Instead of trees and flowers, you’d find algae dominating the landscape. The lack of these plants also meant less food for animals.

While it may sound bleak, the oceans were bustling with life. The Great Ordovician Biodiversification Event (GOBE) marked this time, filled with unique marine animals evolving rapidly. Twitchett notes that this period was like evolution on fast-forward. Creatures such as starfish, sea urchins, and corals began to appear, diversifying and adapting to various ocean depths.

### End of the Ordovician

However, this thriving life faced challenges. The Late Ordovician extinction was not a single catastrophic event but a series of smaller ones, culminating in a significant loss of life. Unlike other mass extinctions that are often associated with warming climates, this extinction began with a dramatic cooling of the Earth.

Twitchett explains that this cooling might have been influenced by the earliest land plants. These primitive plants drew down CO₂, leading to glaciation. Additionally, at the time, all the continents were joined as one—Gondwana—and its shift toward the South Pole could have also contributed to the cooling trend.

After this initial chill, the Earth warmed again, but not without issues: the oceans became de-oxygenated, leading to another crisis for marine life. The fossil record indicates that this period led to the extinction of about 60% of genera and nearly 85% of species, making it one of the most significant extinctions in history, second only to the end-Permian mass extinction.

### The Forgotten Extinction

Interestingly, while the Late Ordovician mass extinction ranks high in terms of species loss, its long-term ecological impacts were minimal. Many groups that suffered extinction did not disappear entirely, allowing ecosystems to bounce back relatively quickly. In contrast, the end of the Cretaceous had far-reaching consequences for life on land, including the disappearance of dinosaurs.

Twitchett highlights that the mass extinction we remember most is often tied to relatable species. The public knows about the end of the dinosaurs but not as much about the oceanic changes of the Ordovician period.

With only a few relevant terrestrial components, it’s no wonder many people have little awareness of this extinction event. It’s a unique chapter in history, but its effects don’t resonate with our daily lives.

Understanding these extinction events is crucial. They remind us how environmental changes can drastically reshape ecosystems—something that feels all too relevant today as we face climate change and biodiversity loss.

### Recent Insights

Research shows that current biodiversity is on a decline, with recent statistics indicating that nearly one million species are at risk of extinction largely due to human activities. While the past can teach us about resilience and recovery, as Twitchett emphasizes, the nuanced impacts of mass extinctions remind us to tread carefully as we navigate our own ecological challenges.

In conclusion, the Late Ordovician mass extinction is a fascinating reminder of nature’s power and fragility. It stands as a significant yet often overlooked event that demonstrates how life can adapt, endure, and sometimes, fail to survive in the face of dramatic changes.



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