Animal Extinction - the greatest threat to mankind
By the end of the century half of all species will be extinct. Does that matter?
By Julia Whitty
Published: 30 April 2007
In the final stages of dehydration the body shrinks, robbing youth from the young as the skin puckers, eyes recede into orbits, and the tongue swells and cracks. Brain cells shrivel and muscles seize. The kidneys shut down. Blood volume drops, triggering hypovolemic shock, with its attendant respiratory and cardiac failures. These combined assaults disrupt the chemical and electrical pathways of the body until all systems cascade toward death.
Such is also the path of a dying species. Beyond a critical point, the collective body of a unique kind of mammal or bird or amphibian or tree cannot be salvaged, no matter the first aid rendered. Too few individuals spread too far apart, or too genetically weakened, are susceptible to even small natural disasters: a passing thunderstorm; an unexpected freeze; drought. At fewer than 50 members, populations experience increasingly random fluctuations until a kind of fatal arrhythmia takes hold. Eventually, an entire genetic legacy, born in the beginnings of life on earth, is removed from the future.
Scientists recognise that species continually disappear at a background extinction rate estimated at about one species per million per year, with new species replacing the lost in a sustainable fashion. Occasional mass extinctions convulse this orderly norm, followed by excruciatingly slow recoveries as new species emerge from the remaining gene-pool, until the world is once again repopulated by a different catalogue of flora and fauna.
From what we understand so far, five great extinction events have reshaped earth in cataclysmic ways in the past 439 million years, each one wiping out between 50 and 95 per cent of the life of the day, including the dominant life forms; the most recent event killing off the non-avian dinosaurs. Speciations followed, but an analysis published in Nature showed that it takes 10 million years before biological diversity even begins to approach what existed before a die-off.
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http://news.independent.co.uk/environment/article2494659.ecehttp://www.commondreams.org/archive/2007/04/30/862/
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