Explained: What is the ongoing sixth mass extinction?

News: According to researchers at National Academy of Sciences of the United States of America(PNAS), the ongoing sixth mass extinction may be one of the most serious environmental threats to the persistence of civilisation.

Facts:

• Mass extinction: It refers to a substantial increase in the degree of extinction or when the Earth loses more than three-quarters of its species in a geologically short period of time. 
• Earlier Extinctions: There have been five mass extinctions that have taken place in the last 450 million years.This have led to the destruction of 70%-95% of the species of plants, animals and microorganisms that existed earlier.
  • These extinctions were caused by catastrophic alterations to the environment such as: Massive volcanic eruptions, Depletion of oceanic oxygen, Collision with an asteroid among others.
• Sixth Extinction: The sixth mass extinction which is ongoing is referred to as the Anthropocene extinction or Holocene extinction.
  • The research has claimed that this extinction is human-caused and is more immediate than climate destruction.The rate of extinction of species is also estimated at 100 to 1,000 times higher than natural background rates.