Massive human activity extinctions

Massive human activity extinctions

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Scientists have long believed that Earth is on the verge of a sixth mass extinction that will obliterate as many as three-quarters of all species on the planet. But now new research says that timeframe has been dramatically shortened to just 100 years.

The study doesn’t make for cheerful reading either—in fact, the lead author says that “our study clearly indicates that the sixth mass [species] extinction is already underway.”

The research, published in the peer-reviewed journal Proceedings of the National Academy of Sciences (PNAS), was led by Gerardo Ceballos of Mexico’s Universidad Nacional Autónoma de México and included five other scientists from institutions across the globe.

They reached their conclusion by assessing changes in the abundance of vertebrates, finding that even “globally common species” have undergone a notable decline in recent years. One-third of animals experience population declines greater than 80 percent, while more than 40 percent have experienced severe population drops greater than 90 percent.

“In the last few decades, habitat loss and degradation as well as overexploitation (for example, through hunting) of many taxa by humans have led to devastating population declines and extirpations,” the study’s abstract reads.

“Although we list a number of contributing factors…several causal links in the causal chain leading to global extinction of vertebrates remain either implicit or wholly untested.”

The study’s abstract cites human activities such as deforestation and pollution, particularly those that impact climate change. Other factors mentioned include “diminishing prey sizes,” invasive species and diseases, and loss of genetic biodiversity.

“This is very sad and very scary,” Duke University conservation biologist Stuart Pimm, who was not involved in the study, told The Washington Post. “We are sawing off the limb that we are sitting on.”

The loss of biodiversity has long been seen as a grave threat to humanity’s survival because ecosystems provide valuable services by purifying water, maintaining air quality, filtering soil, regulating climate, and more.

“As goes vertebrates, so goes a life,” the study’s abstract reads. “This is especially true for forest dwellers like amphibians (the most threatened group), birds, and mammals.”

The authors note that humans are causing the extinction of approximately 2,000 species each year via “defaunation,” and the study refers to other research showing that habitat loss has already caused a 25 percent decline in biodiversity since the beginning of the 20th century.

“Our data say: We are now entering the sixth extinction,” Ceballos said to Phys.org. “Whether we avoid it or not depends on our actions.”

So far, there is no consensus as to what could reverse the current extinction cycle. Some have suggested that “medical solutions” such as reviving extinct species from DNA fragments might help at least some animals weather the crisis intact. The study’s authors suggest a few realistic measures that might be taken immediately, including protections for habitat and stronger regulations against poaching and illegal wildlife trade.

“If we don’t do anything now, the sixth mass extinction will happen,” Ceballos said to Phys.org. “Species of our planet are disappearing as a consequence of human activity.”