Earth Is Headed For Its Sixth Mass Extinction - Study

Photo Credit:Earthobservatory.nasa.gov

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The rapid depletion of Earth’s biodiversity indicates that the planet is in the early stages of its sixth mass extinction of life since becoming habitable 3.5 billion years ago, according to a new study published in Science.

Human activity, including a doubling of its population in the past 35 years, has driven the decline of animal life on Earth, the researchers concluded.

There has been a 25 percent average decline rate of remaining terrestrial vertebrates, and a 45 percent decline rate in the abundance of invertebrates. These losses will continue to have innumerable impacts on species that depend on the delicate balance of life on Earth for their own survival.

“We tend to think about extinction as loss of a species from the face of Earth, and that’s very important, but there’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well,” said Rodolfo Dirzo, lead author of the study and a biology professor at Stanford University.

“Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is non-cryptic because of the increasingly obvious consequences to the planet and to human wellbeing.”

The “Anthropocene defaunation,” as some researchers have dubbed this era, is hitting large animals such as elephants, polar bears, and rhinoceroses the hardest, as these megafauna are the subject of some of the highest rates of decline on Earth. This trend matches previous mass die-offs of the Big Five extinction periods.

Megafauna usually have lower population growth rates that need larger habitat areas to maintain their populations, thus they are particularly affected by human growth and desire for their meat mass. Losses among these animals often mean dire impacts for other species that depend on them within an ecosystem.

Past studies have found that the loss of larger animals means a spike in rodents, as grass and shrubs proliferate and soil compaction decreases, all while the risk of predation also declines, Futurity.org notes. As rodent populations increase, so do the disease-transporting ectoparasites that come with them.

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