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Sixth Extinction Imminent: Humans Poised To Obliterate Most Of Earth's Species

<p> Pen Waggener/Flickr </p>

A gloomy analysis of the world's species has found that the heralded "sixth extinction" may come a lot sooner than scientists thought.

The report, compiled by the journal Nature, found that a whopping 41 percent of all amphibian species are threatened with extinction, while 26 percent of mammal species and 13 percent of bird species are threatened with extinction over the next 100 years.

The looming mass extinction - during which the planet could lose 75 percent of species or more - is attributed to habitat loss due to the expansion of agriculture and development, invasive species edging out native ones, pollution and overfishing.

This wouldn't be the first time Earth's species have seen such a loss - over the past 3.5 billion years, more than 95 percent of species have vanished. This die-off is alarming because of both its speed and its attribution to humans (the other five extinctions were caused by astronomical or geological events).

But scientists don't know enough about species, in general, to anticipate the effects of this die-off is that. The Nature report says that estimates of the total number of species of animals, plants and fungi alive right now vary from 2 million to more than 50 million. And the added uncertainty of the effects of climate change presents another variable, according to Nature:

Looking forward, the picture gets less certain. The effects of climate change, which are hard to forecast in terms of pace and pattern, will probably accelerate extinctions in as-yet unknown ways.

"In general, the state of biodiversity is worsening, in many cases significantly," Derek Tittensor, a marine ecologist with the United Nations Environment Programme's World Conservation Monitoring Centre, told Nature.

The analysis urges governments and scientists to create a more accurate count of the number of species using computer models to predict how ecosystems will change in the future. These could alert scientists to problems they would otherwise not predict. And movement on this is needed urgently, according to the analysis. As science writer Elizabeth Kolbert writes in her book "The Sixth Extinction: An Unnatural History," time is running out.

"Right now, we are deciding, without quite meaning to, which evolutionary pathways will remain open and which will forever be closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy."