Ex·tinc·tion /ikˈstiNG(k)SH(ə)n/ noun

a situation in which something no longer exists

Editor's Note: At Outrider, we create in-depth content showcasing climate change impacts on our daily lives. In this Anthropocene series, we untangle the complex relationship between our species and our planet, the only home we have. Featuring a multi-discipline approach that contemplates the lessons of earth’s past and the solutions of earth’s present, we hope you can understand your individual role in our shared future. Here we discuss the consequences and lessons of past species extinctions so that we may come together to ensure the future of humanity.  

We need to begin with the end. Extinction is the end, nothing further—that's all. More than 95% of life that has ever inhabited our planet is extinct. Our Earth’s history is the record of a harsh, but simple truth: that life and death are inseparable. They serve as important counterbalances in the delicate natural tension that can push certain species forward and may pull certain species back. There are spectres haunting this delicate tension that throughout our earth’s timeline have tipped the scales in the direction of extinction and likewise in the direction of renewal. Fortunately, humanity can take collective action to tip the scales in favor of renewal and extend the age of humans, the Anthropocene.

Our Earth's history is a timeline of many naturally occurring extinction events. Many causes make these events possible including changing climates, sea level rise, and asteroid collisions. Moreover, these can occur in tandem—magnifying the effects of the loss of life resulting in mass extinction events. If the past is of any indication, species that once dominated the earth’s various ecosystems will crash down and ultimately disappear. However, nature has thus far, always found a way to grow and renew. The below graphic shows the Sepkoski Curve, which through the study of ancient marine organisms, establishes that biodiversity has grown throughout our planet's history following major extinction events.

We have tipped the scales towards extinctions—of both other species and ourselves.

This curve, shown through the fossil record establishes that biodiversity safeguards life from mass extinction events. Therefore, we need to heed history's warning bells as we have tipped the scales towards extinction—of both other species and ourselves. In fact, we may currently be in a sixth extinction event (see Elizabeth Kolbert's excellent work here) as human-caused climate change, human-induced habitat loss and pollution are the main catalysts for the loss of an alarming amount of species at an alarming rate. But, we have the guile and opportunity to forge the future of our earth, by positively modifying our behaviors and cultures to prolong the Anthropocene into the Earth's horizons.

Ordovician-Silurian Extinction

440 Million Years Ago

This event was the second in severity.

During this extinction event, 85% of species died out and it took millions of years. The species most affected were small marine organisms, most notably trilobites. The causes are thought to be the cooling of the climate, which led to glaciation and a drop in sea level. Then, rising temperatures melted the glaciers leading to higher sea levels, and possibly changing the ocean chemistry. Because of these drastic changes in environments and climates during a geologically short time, many species met their doom.

Devonian Extinction

365 million years ago

This event ranks fifth in severity.

During this extinction event 75% of species died out and it likely lasted millions of years. Unlike the Ordovician-Silurian event, the Devonian extinction was a series of five successive events. The species most affected were coral reefs, jawed fishes and sharks. While the causes are thought to be changing climates, sea level changes and trees thriving on the continents, there is no single cause that bridges all five of the events. Emerging and flourishing trees are the first signals that life on land was here to stay.

Permian-Triassic Extinction

250 million years ago

"The Great Dying" was first in severity.

During this extinction event, 96% of species died out and it lasted several million years. All current life sprang from this 4% of bottlenecked species. This event was also a successive extinction event spread over millions of years. Marine animals were particularly affected and insects suffered their only mass extinction. Volcanic eruptions, large methane releases, lowering oxygen levels, and changes in sea levels are thought to be the causes of "The Great Dying".

Triassic-Jurassic Extinction

200 million years ago

This event was fourth in severity.

During this event, 76% of all species died out and the event lasted for millions of years. Large amphibians, marine reptiles, and other vertebrate species on land disappeared. Extinction of these species allowed dinosaurs to adapt and later thrive, showcasing how life and death work together to propel change in our Earth's environment. Possible causes include the usual suspects: climate change, sea-level rise, atmospheric changes and possibly an asteroid strike.

 

Cretaceous-Paleogene Extinction

66 million years ago

This event was third in severity.

Perhaps the most well-known, this sudden extinction event led to the demise of the dinosaurs. In addition to turtles, snakes, and crocodilians—mammals started thriving to becoming widely distributed animals that they are today. The prevailing theory is that a giant asteroid impact caused this extinction. In addition, the impact led to widespread wildfires and an enormous tsunami which produced further loss of life and destruction. Another theory is that a large outpouring of lava and a significant release of greenhouse gases from volcanic traps were catalysts in turning dinosaurs from beasts to bones.

These extinction events yield a stark and severe reality: the earth spins forward, but species wind down. Unlike the great species of the past, we are uniquely capable of extending the age of humans, or the Anthropocene, into the foreseeable future. But, we must succeed where even the mightiest of species have failed as we must still overcome the historic spectres of changing climates, acidifying oceans and rising seas. Currently, at best we are ignoring these timeless hallmarks of species loss, and at worst we are downright denying them.

No doubt, we have the choice and the ability to create the future we want by learning from history's ghosts. However, our greatest challenges demand our greatest actions—embracing clean energy sources, developing sustainable infrastructure, and funding environmental conservation. Through these collective goals, we will secure our species well into the Anthropocene. It is up to us to determine if we are going to press forward into our planet's horizon or if we are going to fall back into our planet's history.