Sixth Mass Extinction

Sixth Mass Extinction

Subject: Environment

Section: Biodiversity

Context- The ongoing sixth mass extinction may be one of the most serious environmental threats to the persistence of civilisation, according to new research.

Concept-

What is the mass extinction of species?

• Mass extinction 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.
• So far, during the entire history of the Earth, there have been five mass extinctions.
• The five mass extinctions that took place in the last 450 million years have led to the destruction of 70-95 per cent 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 or collision with an asteroid.
• After each of these extinctions, it took millions of years to regain species comparable to those that existed before the event.

What is the sixth mass extinction?

• The sixth, which is ongoing, is referred to as the Anthropocene extinction.
• Researchers have described it as the “most serious environmental problem” since the loss of species will be permanent.

 Why it is attributable to humans?

• The Global Assessment Report on Biodiversity and Ecosystem Services”, the first such by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) released in 2019, shows that the current rate and scale of extinction is unprecedented and is being caused majorly by humans.
• One of the reasons that humanity is an “unprecedented threat” to many living organisms is because of their growing numbers.
• The loss of species has been occurring since human ancestors developed agriculture over 11,000 years ago.
• Since then, the human population has increased from about 1 million to 7.7 billion.

Changes occurred and occurring:

• The IPBES assessment says that 1 million animal and plant species face extinction and thousands of these would become extinct within decades.
• About 40 per cent of the planet’s amphibian species are threatened with extinction.
• Since 1900, the number of native species in most of the land-based habitats has declined by 20 per cent.
• The World Wildlife Fund’s (WWF’s) “Living Planet Report 2020” says the Asia Pacific region lost 45 per cent of its vertebrate population in four-and-half decades, while the average global loss is 68 per cent.
• The biennial report, prepared jointly by WWF and Zoological Society of London, is based on the global dataset analysed between 1970 and 2016. The report has tracked almost 21,000 populations of mammals, birds, fish and reptiles globally to reach its conclusions. It showed the loss of vertebrate population was the highest in the Caribbean and Latin America (94 per cent), followed by Africa (65 per cent), with Europe and Central Asia showing the least loss (24 per cent).
• The loss could be higher than the global average in India, which has lost 12 per cent of its wild mammals, 19 per cent of its amphibians and 3 per cent of its birds over the past five decades.

Reasons for Extinction:

• The “Living Planet Report 2020” points out five major reasons behind the biodiversity loss across the planet:
  • changes in land and sea use (habitat loss and degradation),
  • overexploitation of species,
  • invasive species and disease,
  • pollution and
  • climate change.

Vulnerable regions:

• Tropical regions have seen the highest number of declining species.
  • In South and Southeast Asia, large-bodied species of mammals have lost more than four-fifths of their historical ranges.
• While fewer species are disappearing in temperate zones, the percentage is just as high or higher.
• As many as half of the number of animals that once shared our planet are no longer here, a loss described as “a massive erosion of the greatest biological diversity in the history of Earth”.
• In the Asia Pacific region, including India that is experiencing loss of species higher than the global average, habitat degradation is the biggest trigger, followed by species overexploitation and invasive species and disease. The role of pollution and climate change was proportionately higher at 16 per cent.

What happens when species go extinct?

• Impact can be tangible such as in the form of a loss in crop pollination and water purification.
• If a species has a specific function in an ecosystem, the loss can lead to consequences for other species by impacting the food chain.
• Effects of extinction will worsen in the coming decades as the resulting genetic and cultural variability will change entire ecosystems.