Wildlife & Biodiversity

Sixth mass extinction more severe than estimated, 73 genera vanished since 1500: Study

Human actions fuel surge of genus extinctions; extinctions due in 18,000 years happened in last 5 decades

By Rohini Krishnamurthy
Published: Tuesday 19 September 2023
An illustration of a male and female Dodo birds in a forest. Dodos went extinct in the 17th century. The new study has found birds have suffered the heaviest losses of genus extinctions. Photo: iStock_

Human actions are compounding the severity of the ongoing sixth mass extinction, according to a new study. The current rate at which entire genus of vertebrates, or animals with spinal cords, are going extinct is 35 times greater than the last million years.

A genus is a group of animals or plants which share some common characteristics. For example, dogs and wolves are in the same genus, Canis.

Between 1500 and 2022 AD, 73 genera (plural of genus) of vertebrates (excluding fish) went extinct, the study published in journal PNAS stated.

Read more: Sixth Extinction? Over 150,000 species vanished in last 500 years

Humans are putting a big dent in the evolution of life on the planet in the long term, Gerardo Ceballos, senior researcher at the Institute of Ecology at the National Autonomous University of Mexico and one of the authors of the paper, said in a statement.

“But also, in this century, what we’re doing to the Tree of Life [representing the evolutionary relationships among groups of plants, animals and all other forms of life] will cause a lot of suffering for humanity,” Ceballos added.

Previous studies have focused on the extinction of species and found thousands of species and myriad populations have vanished. For example, around 10,000,000 African elephants roamed Earth at the beginning of the 20th century. Now, only about 450,000 remain.

To gain insights into patterns of extinction beyond the species level, researchers from the United States and Mexico studied how the current extinction crisis is impacting land vertebrates at the generic level.

The team first gathered information on species’ conservation statuses from the International Union for the Conservation of Nature, Birdlife International and other databases. Overall, they examined 5,400 genera of land-dwelling vertebrate animals.

Their analysis showed that 73 genera of land-dwelling vertebrates have vanished since 1500 AD. 

Read more: Living Planet Report 2022: Wildlife populations decline by 69% in 50 years

Birds, they found, suffered the heaviest losses with 44 genus extinctions, followed by mammals (21 genus extinctions), amphibians (five extinctions) and reptiles (three extinctions).

Humans have fuelled a surge of genus extinctions in the last five decades, which otherwise would have taken 18,000 years to occur.

Most extinctions were recent. The years between 1800 and 2022 saw 55 total extinctions. Birds ranked the highest with 36 extinctions, followed by mammals (12), amphibians (five) and reptiles (two). 

Without humans, the researchers estimated that Earth would likely have lost only two genera between 1500-2022. 

“This mass extinction is transforming the whole biosphere, possibly into a state in which it may be impossible for our current civilisation to persist,” the researchers wrote in their paper.

Losing a genus could impact the functioning of an entire ecosystem. For example, when the passenger pigeons went extinct, it narrowed human diets in northeastern North America and altered ecosystem structure over wide areas. It also triggered population declines of cougars and wolves, leading to shifts in rodent communities.

Read more: Oceans Great Dying 2.0: Mass extinction haunts oceans

The region, according to the paper, became more conducive to outbreaks of infectious diseases that jump from animals to humans. An example is Lyme disease, a bacterial infection spread to humans by infected ticks.

Then, there is also climate change.

“Climate disruption is accelerating extinction and extinction is interacting with the climate because the nature of the plants, animals, and microbes on the planet is one of the big determinants of what kind of climate we have,” Paul Ehrlich, co-author of the study and Bing Professor of Population Studies, Emeritus, in the Stanford School of Humanities and Sciences, explained.

Read more:

Subscribe to Daily Newsletter :
Related Stories

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.