Wednesday, February 24, 2021

The home of life

The history of life on Earth is truly one of the greatest stories ever told. Since its origin on our world some 3.5 billion years ago, life has been gradually evolving into multiple forms, yet it hasn’t been an easy path. Since the evolution of complex life some 600 million years ago, life has experienced five major extinction events that have managed to reverse most of what nature accomplished prior. 

Called mass extinctions, they are defined as any event wherein 75% or more of life is wiped out in a relatively short period of time. If you’ve ever been interested in dinosaurs, you likely first heard of these events from the famous Cretaceous extinction, which wiped out around 75% of life on Earth some 65 million years ago. Although this event is perhaps the most famous and well-known, it wasn’t the only extinction event, nor was it the worst. The worst day on planet Earth occurred some 250 million years ago during a time period called the Permian. It was during this period in Earth’s history that all the continents were joined together in a supercontinent called Pangea. The end of the Permian era was marked by a rapid decline in biodiversity, wherein over 90% of living species were wiped out in the largest and most widespread extinction event in the history of our planet. Although the exact cause of the event is still debated, the most likely explanation is that a chain of super-volcanoes in what is now modern day Siberia erupted, spewing massive amounts of aerosols and carbon dioxide into the atmosphere. The initial stages of the extinction were likely caused by a rapid increase in Earth’s temperature as the concentration of greenhouse gases in our atmosphere rose. Killer heat waves struck the supercontinent of Pangea, yet this was only the beginning. The ash cloud produced by the volcanic eruptions eventually blanketed the Earth and blotted out the sun. Temperatures rose for a time, yet eventually they began to plummet as the Earth was engulfed in a worldwide volcanic winter. Acid rain fell upon the surface of the Earth, wiping out plant life and marine organisms.

The rapid increase in temperatures for the oceans caused the amount of oxygen to plummet, and marine life suffered as a result. The extinction event occurred over the course of over ten thousand years, and by the end of it, life came closer than it ever has to complete annihilation. It’s no wonder the Permian extinction has been nicknamed “The Great Dying.”

Understanding past mass extinction events has become more important now than ever. Unfortunately for our time, the amount of biodiversity on Earth is declining rapidly, with current rates of extinction potentially 100 times higher than the background rate. Unlike in the past, these extinctions are not the result of a volcanic eruption or an asteroid impact. Rather, they are the direct result of humanity’s impact on the natural world. From habitat destruction to an unnatural change in Earth’s climate, we humans have wreaked havoc on our world and we now threaten the millions of other species that call this world home. If we do not act now to preserve ecosystems and the species they sustain, we will continue to lose what we can never get back.

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