Early Days Of A New Mass-Extinction Event ?

[Hum]

Earth is apparently on the verge of another great biological extinction, and humans are solely to blame.

Scientists have previously classified five large-scale losses of animal life as mass-extinction events, all of which occurred millions of years ago. In recent years, the planet has seen the loss of hundreds of species of animals, and according to a new analysis from an international team, the planet may be in the early days of its sixth mass-extinction event.

As part of the study, researchers analyzed previous studies and scientific data to draw their conclusion that human activities and population surges worldwide -- not a catastrophic event, like an asteroid impact, for example -- are responsible for the drastic decline of animal life. Lead author Rodolfo Dirzo, a biology professor at Stanford University, cites actions like overexploitation of resources and habitat destruction as examples of harmful human activities.

Since 1500, 322 terrestrial vertebrates have become extinct, the authors said in their analysis, published Friday in the journal Science. Of the remaining land-dwelling species of vertebrates, there has been a 25 percent average decline in abundance. The situation also appears to be dire for invertebrates, with a 45 percent decline in monitored species.

There may be unforeseen consequences, aside from the possible extinction of threatened species.

"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," Dirzo said in a statement.

Dirzo pointed to potential trickle-down effects, such as threats to ecosystems that are currently stable and even risks to human health.

"Where human density is high, you get high rates of [animal decline], high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission," Dirzo said in the statement, adding, "It can be a vicious circle."

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