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NYT on Genyornis Story



Here's the New York Times' take on the Genyornis story.
Copyright 1999 The New York Times; acknowledged.

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Extinction, Ancient Style
By HENRY FOUNTAIN

As a protector of fellow creatures, modern humans' record is spotty at
best. The steamroller of progress has put some species on the
endangered list, and even flattened some to extinction. But now comes
word that not-so-modern humans didn't do so well either. 

A team of Australian and American researchers has concluded that the
earliest humans in Australia may have inadvertently wiped out most of
the large animal species on the continent 50,000 years ago. 

Like other parts of the world, Australia was at one time home to a
diverse assortment of so-called megafauna. In Australia's case, these
included a marsupial that weighed as much as a linebacker, a horned
tortoise that was about the size of a compact car, and a flightless
ostrich-like bird, Genyornis newtoni, that tipped the scales at 200
pounds. 

Many of these large animals became extinct around the same time, but
exactly when has been unclear. The reason has been unclear as well,
with some scientists blaming climate change and others, human
activity. The researchers, who wrote about their work in a recent
issue of the journal Science, used a variety of newer dating
techniques on fossilized eggshells of Genyornis to calculate that the
birds suddenly disappeared 50,000 years ago. This was a time of only
mild climate change, the researchers note. 

But it was about 5,000 years after the first humans arrived on the
continent. So the researchers speculate that systematic burning of
vegetation by these aboriginal Australians disrupted the food chain
enough that Genyornis and other shrub- and tree-loving species became
extinct. 


Tracking Temperatures 


ack to modern times for a moment. Much has been made of the fact that
human activity is causing global temperatures to rise. But the picture
is more complex than that: In land areas, average annual minimum
temperatures (that is, nighttime temperatures) are increasing at twice
the rate of average annual maximum (daytime) temperatures. 

Three Colorado State University researchers, studying the growth of
vegetation on range land since 1970, have discovered that there appear
to be ecological consequences to this phenomenon. The researchers,
writing in Science, found that higher minimum temperatures have cut
the production of buffalo grass, a prime food source for grazing
cattle, and increased the abundance of invasive, nongrassy plants. 

The researchers speculate on several reasons for this. For one thing,
they say, the warmer nights extend the growing season, which would
primarily benefit cool-season plants (like the nongrasses) that grow
most rapidly. These plants would rob the hot-season (and slower
growing) grasses of nutrients and water. Warmer nights also increase
plant respiration, which will speed up loss of carbon by the plant
(thus slowing growth) if there is not a corresponding increase in
photosynthesis during the day. 





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