Congratulations! You belong to one percent of the species on Earth that are not extinct yet! During the entire existence of our planet – 4.5 billion years – five billion species lived on it. Among them were giant placoderms, dinosaurs, and Tasmanian tigers.
Many scientists believe that the sixth extinction is coming. Today, species are disappearing hundreds of times faster than before, due to human activities.
Scientists have linked extinctions to carbon dioxide (CO2) levels. CO2 acts as a greenhouse gas in the atmosphere. As the concentration of carbon dioxide increases, the global temperature increases – and vice versa.
Changes in temperature lead to the destruction of the habitat, and this, in turn, triggers the extinction process.
There have been five mass extinctions in the past five hundred million years.
Ordovician-Silurian extinction – 443 million years ago
During the Ordovician period, most of life developed underwater. In addition to life in water, the first primitive plants, mosses, appeared on land.
The extinction was due to two successive events. Rapid warming followed the extreme ice age.
The marine plants absorbed all the carbon dioxide in the air and caused a global cooling, with the rapid formation of glaciers, which, in turn, lowered sea levels, reducing the habitat of marine species.
Twenty million years later, the Ice Age was followed by rapid warming. Those species that have adapted to low temperatures have not been able to adapt to warmer climates.
Global extinction rate: 86%
Devonian extinction – 358 million years ago
The Devonian period was marked by the first appearance of amphibian species. It was then that the animals first came out of the water onto land.
However, most of life continued to develop in the seas. There was such a great variety of fish that we call this era “the age of fish.”
Terrestrial plants have developed roots and branches. The trees grew up to thirty meters in height. The earth turned green.
The Devonian extinction was due to a number of factors: oxygen depletion, cooling and volcanic activity.
Land plants enriched the water with a large amount of nutrients that caused overgrowth of algae. The bacteria decomposed the algae, absorbing all the oxygen. Because of this, aquatic animals suffocated.
In addition, the plants reduced carbon dioxide levels and caused a cold snap. In Siberia, meanwhile, there was a lot of volcanic activity.
Global extinction rate: 75%
Massive Permian extinction – 252 million years ago
In the Permian period, the first land reptiles appeared. Some of them had canvas-like formations on their backs that allowed them to receive more sunlight and warm their bodies.
Some reptiles have become warm-blooded. This meant that their bodies had developed the ability to store heat as a result of the chemical breakdown of food.
The Permian extinction, dubbed the “great death,” was the deadliest extinction in history. Only four percent of the species survived.
Volcanic activity in Siberia ignited huge coal deposits. Burning coal gave off a large amount of carbon dioxide into the atmosphere. In addition, the bacteria produced a lot of methane, which is another greenhouse gas. The gases increased the temperature of the planet and made the water acidic.
Global extinction rate: 96%
Triassic-Jurassic extinction (201 million years ago)
During the Triassic period, the first dinosaurs and mammals appeared. Reptiles called pterosaurs were able to fly. In addition, the first coral reefs formed and phytoplankton developed.
The collapse of the supercontinent Pangea caused a massive eruption of lava in the Atlantic Ocean. Volcanoes emitted huge amounts of carbon dioxide, which absorbed heat, which triggered global warming and acidification of the oceans.
Global extinction rate: 80%
Cretaceous-Paleogene extinction – 65 million years ago
During the Cretaceous, dinosaurs dominated the air, land, and seas. On top of that, birds, sharks, rays, turtles, snakes, and crocodiles bred successfully. With the help of bees, ants, and other pollinating insects, the flowers spread throughout the land.
The abundance of life was drastically disrupted when an asteroid hit Earth. He created a crater with a diameter of 145 kilometers in Mexico. The impact caused many volcanic eruptions. The dust covered the sun and the Earth suddenly began to cool down.
The Cretaceous extinction is marked by the extinction of the dinosaurs.
Global extinction rate: 76%
The sixth extinction?
Scientists believe that we are currently experiencing the middle of the sixth extinction – the Holocene.
It began with the extinction of huge land mammals such as mammoths 12,000 years ago.
Anthropogenic impact is believed to be the main reason for this extinction. Currently, one million species are threatened with complete extinction over the next several decades.
Deforestation, overpopulation, over-hunting and mining are all possible causes of the sixth extinction. Every day we emit more and more carbon dioxide into the atmosphere. The global temperature is rising. Glaciers, which reflect most of the sun’s heat back into space, are melting.
However, unlike the previous five extinctions, we have the ability to slow down or even stop this extinction. We have several solutions at our disposal, such as containing population growth, switching from fossil fuels to renewable energy sources, and a plant-based diet.
We are not only the cause of the sixth extinction, we can also become its victims.
What happens next depends on each of us.