The Earth has seen five mass extinction events over the last half-billion years. Now, researchers claim that a sixth mass extinction is unfolding and humans are largely to blame.

Biological Annihilation Of Thousands Of Species

In a new study published in the Proceedings of the National Academy of Sciences on Monday,  July 10, scientists claim that the world is facing a biological annihilation of thousands of species.

For the research, Gerardo Ceballos, from Universidad Nacional Autónoma de México, and colleagues mapped 27,600 species of birds, amphibians, mammals, and reptiles, which represent nearly half of the world's known terrestrial vertebrate species, and found evidence suggesting that the Earth's sixth mass extinction event is more severe than previously believed.

Nearly one-third of the studied species were found shrinking in numbers and in territorial range. The number of individual animals that used to live alongside humans also dropped by as much as 50 percent. Ceballos and colleagues also found that the temperate regions lose species at an equal or even higher rates than the tropics.

The researchers found what is described as "extremely high degree of population decay" among vertebrate species including those considered at low risk of extinction.

"We describe this as a 'biological annihilation' to highlight the current magnitude of Earth's ongoing sixth major extinction event," the researchers wrote in their study.

Sixth Mass Extinction Largely Due To Humans

Ceballos and colleagues noted that their findings were conservative given that the drivers that cause the extinction and population loss of species such as habitat loss, over-exploitation, pollution, invasive organisms, climate change and toxification, were taking increasing trajectories.

The researchers also noted that while previous mass extinctions were often linked to sudden and catastrophic natural events such as meteor strikes, sudden changes in climate and massive volcanic eruptions, the current mass extinction is largely caused by humans.

"The massive loss of populations and species reflects our lack of empathy to all the wild species that have been our companions since our origins," Ceballos said. "It is a prelude to the disappearance of many more species and the decline of natural systems that make civilization possible."

Consequences That Can Impact Humans

The researchers warned that the declining population of animal species has unwanted effects on humans. Fish, considered as commercially extinct, for instance, have damaged local economies of fishing communities. The decline in the elephant's population in Africa due to poaching is also blamed for millions of revenue loss from tourism.

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