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sixth mass extinction

What is the Sixth Mass Extinction?

August 5, 2020 - earthorgkids

When a species disappears permanently, we say that it has gone ‘extinct’. Extinction is a natural process and happens when a species cannot adapt to a change in its environment. Those species that can change are less likely to go extinct. While extinction is nothing to be worried about in itself, humans are making species go extinct much faster than the natural rate. The planet has seen five mass extinction events, and scientists are worried that we are going through a sixth mass extinction. What does this mean and can we stop it?

What Kinds of Extinction Are There?

There are two kinds of extinction events– ‘background’ and ‘mass’.  Background extinctions happen as a result of environmental factors and are part of the natural cycle of life on Earth. We can expect 10- 100 species to go extinct every year. These can happen because of habitat loss, changes in the food supply, the introduction of a new predator or an invasive species or extreme weather events like droughts, flooding or hurricanes. They usually affect one or several species that inhabit a small area, such as a forest or a lake. 

Mass extinctions happen on a much larger scale! They result in the extinction of many different species over a very large geographic area, even globally. They can happen as a result of massive events like an asteroid strike or ice age. Fossils show that the Earth has experienced five mass extinction events over the past 600 million years. They are:

  1. The Permian Extinction- This was the worst one and it happened about 266 million to 251 million years ago. About 95% of marine species and 70% of land species were lost!
  2. The Ordovician- Silurian Extinction- This happened about 444 million years ago. About 85% of marine species were lost.
  3. Cretaceous- Tertiary Extinction- This happened about 66 million years ago. This is the most famous event because this one killed the dinosaurs! Overall, about 80% of all animal species were lost. Some scientists think that one or more large asteroids striking the Earth killed them, but some think that there were changes in the global climate from volcanic activity.
  4. End-Triassic Extinction- This happened about 200 million years ago and may have been caused by rapid climate change or an asteroid. This event caused 20% of marine species and 76% of all species living at that time to die out within 10 000 years. 
  5. Devonian Extinctions- These extinctions took place 407 million to 359 million years. 70-80% of all animal species became extinct during this time. No one is sure what caused the events, but scientists think it was a combination of several factors, including rapid global warming or cooling and asteroid or comet impacts. 

In each event, it took millions of years to regain the numbers of species as before the extinction event. Because of this, only 2% of the species that ever lived are alive today! The losses that we are seeing have mostly happened since our ancestors developed agriculture 11 000 years ago. 

Nowadays, many species have become extinct because of human activities, particularly the destruction of natural environments. Current rates of extinction are about 1 000 times greater than past natural background rates of extinction! Because of this, some scientists call modern times the sixth mass extinction. 

The high extinction rate is due to the massive growth in human population, which went from about 1 billion in 1850, to 2 billion in 1930 and more than 6 billion in 2000. It is expected to reach about 10 billion by 2050. It is also due to increasing levels of greenhouse gases in the atmosphere that have changed the Earth’s climate. Finally, endangered animals are killed because of the illegal wildlife trade, where their body parts are used in food, objects or medicine.

If we keep living as normal, up to 50% of all species in the world could go extinct by the year 2050- that’s only 30 years away!

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Why Are Extinctions Bad for The Planet?

A mass extinction event would greatly affect human beings because the diversity of species in an ecosystem provides us all types of services that we can’t live without. For example, trees provide us with oxygen to breathe and they remove carbon dioxide from the air, plants make the air and water cleaner, bacteria breaks down waste and animals spread seeds that helps to keep forests alive. Nature also provides us with food, shelter and medicine. 

When the number of animals in a population drops too low, the species can no longer provide ecosystem services and it is unable to reproduce. 

The sixth mass extinction is happening faster but there is still time to save species! We must learn to use natural resources better and protect the extinctions that we rely on to live.