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We're slowly creeping towards levels of mass extinction (see lines to the right), according to a recent study. Only five mass extinctions have occurred in the Earth's history and this one would the first caused directly by man.  (Source: Nature/The University of California, Berkley)

Some species, like tigers, are expected to die off entirely within the next few decades, thanks to human hunting and habitat destruction.  (Source: ZME Science)

Americans are more concerned with debating global warming than destruction of the rainforests, the planet's greatest biodiverse locations.  (Source: Google Images)
Evolution will likely overcome the role of humanity, but pressure is unlike any in history

mass extinction is a world-changing event.  In order to qualify, 75 percent of species must be eliminated within a "short" period (between a few hundred thousand years to a few million years).

This has only happened five times in history, and according to researchers at the University of California, Berkley, it's happening a sixth time. This time, they claim humans are to blame.

The worst mass extinction in history occurred during the Permian Period, when most land species perished.  While that won't likely happen, the majority of non-domesticate large land species may perish over the next a thousand years if mankind doesn't change its behavior, according to the researchers.

Anthony Barnosky, the curator of the Museum of Paleontology at UC Berkeley and another co-author of the study, comments that species go extinct today just as they have always. However, the real question is, "Is the pace of extinction we're seeing today over these short time intervals usual or unusual?"

To try to answer that question, Professor Barnosky and his student Elizabeth Ferrer had to comb both the fossil record and modern conservation biology for clues.  This wasn't easy as the fossil record has plenty of holes and the best source for modern data -- the International Union for the Conservation of Nature Red List of threatened and endangered species -- only has examined 2.7 percent of the planet's 1.9 million named species (which is likely far from the total species count). 

Comparing to historically-known times of normal extinction rate, the pair says that current extinction rates are conservatively estimated to be 3 to 12 time higher, with the actual multiplier possibly being as high as 80.  Even under the "best case" 3x scenario, within 22 centuries the world would reach a "mass extinction" scenario.

The team says we're just on the cusp of causing this.  Over the last 200 years we've caused approximately 1 to 2 percent of species to go extinct -- much higher than normal extinction rates.  As invertebrate data was still too week to draw strong comparisons, the study focused its efforts largely on vertebrate extinction.  Its findings were that man is driving the Earth towards a mass extinction.

The results will likely be the evolutionary mechanism being kicked into overdrive due to less species, more resources, and smaller populations of surviving species (allowing for random gene drift).  

In an interview with LiveScience, David Jablonski, a paleontologist at the University of Chicago who did not participate in the study, states, "If the fossil record tells us one thing, it's that when we kick over into a mass extinction regime, results are extreme, they're irreversible and they're unpredictable. Factors that promote success and survival during normal times seem to melt away."

The study was published [abstract] in what is arguably the science field's most prestigious journal -- Nature.  The article is drawing a great deal of attention for its comprehensive review and the startling perspective it provides.

Ms. Ferrer morosely remarks on the attention the study is drawing, "It's bittersweet, because we're showing that we have this crisis."

Some reacted to the study with prophesies of doom and gloom.  Comments Paul Ehrlich, the president of the Center for Conservation Biology at Stanford University and author of "The Population Bomb" (Sierra Club-Ballantine, 1968), "Everything we're doing in Washington [D.C.] today is working in the wrong direction. There isn't a single powerful person in the world who is really talking about what the situation is … It's hard to be cheery when you don't see the slightest sign of any real attention being paid."

Others, like Stuart Pimm, a professor of conservation ecology at Duke University, were more optimistic.  He comments, "If we have a business-as-usual scenario, it is pretty grim, but it isn't yet written. I hope that this will alert people to the fact that we are living in geologically unprecedented times. Only five times in Earth's history has life been as threatened as it is now."

Regardless of whether the trend continues or reverses, some of the extinction event's most noticeable changes may be coming soon.  Several large land predator species, including the tiger are on the verge of extinction in the wild and may vanish within a few decades.

Interestingly, while rainforest destruction continues at a break-neck pace threatening mass extinction of millions of species, mankind's attention remains largely wrapped around debating "climate change" a shift in the Earth's temperatures due to carbon dioxide -- a change which would contribute far less to the loss of biodiversity (and could even promote biodiversity in some areas).

 





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